| 1. |
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| 2. |
- Payandeh, Mostafa, 1981-, et al.
(författare)
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Solidification and re-melting phenomena during slurry preparation using the RheoMetal™ process
- 2017
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 48:6
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Tidskriftsartikel (refereegranskat)abstract
- The melting sequence of the enthalpy exchange material (EEM) and formation of a slurry in the RheoMetal™ process was investigated. The EEM was extracted and quenched, together with a portion of the slurry at different processing times before complete melting. The EEM initially increased in size/diameter due to melt freezing onto its surface, forming a freeze-on layer. The initial growth of this layer was followed by a period of a constant diameter of the EEM with subsequent melting and decrease of diameter. Microstructural characterization of the size and morphology of different phases in the EEM and in the freeze-on layer was made. Dendritic equiaxed grains and eutectic regions containing Si particles and Cu-bearing particles and Fe-rich particles were observed in the as-cast EEM. The freeze-on layer consisted of dendritic aluminum tilted by about 30 deg in the upstream direction, caused by the rotation of the EEM. Energy dispersion spectroscopy analysis showed that the freeze-on layer had a composition corresponding to an alloy with higher melting point than the EEM and thus shielding the EEM from the surrounding melt. Microstructural changes in the EEM showed that temperature rapidly increased to 768 K (495 °C), indicated by incipient melting of the lowest temperature melting eutectic in triple junction grain boundary regions with Al2Cu and Al5Mg8Si6Cu2 phases present. As the EEM temperature increased further the binary Al-Si eutectic started to melt to form a region of a fully developed coherent mushy state. Experimental results and a thermal model indicated that as the dendrites spheroidized near to the interface at the EEM/freeze-on layer reached a mushy state with 25 pct solid fraction, coherency was lost and disintegration of the freeze-on layer took place. Subsequently, in the absence of the shielding effect from the freeze-on Layer, the EEM continued to disintegrate with a coherency limit of a solid fraction estimated to be 50 pct.
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| 3. |
- Bjurenstedt, Anton, 1979-
(författare)
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On the influence of imperfections on microstructure and properties of recycled Al-Si casting alloys
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are great energy savings to be made by recycling aluminium; as little as 5% of the energy needed for primary aluminium production may be required. Striving to produce high quality aluminium castings requires knowledge of microstructural imperfections, which is extra important when casting recycled aluminium that generally contains higher levels of imperfections compared to primary aluminium. Imperfections include amongst others Si, Fe, and Mn as well as oxides. Si is needed for castability, but it may also initiate fracture. There are different types of Fe-rich intermetallics influencing properties of castings, generally in a negative direction. Oxides constitute cracks and they are elusive because they are difficult to quantify.This thesis aims to increase knowledge about imperfections in recycled aluminium castings originating from alloying elements and the melt. Experiments were performed in advanced laboratory equipment, including X-radiographic imaging during solidification and in-situ tensile testing in a scanning electron microscope. Experiments were also performed at industrial foundry facilities.The experiments showed that the nucleation temperature of primary α-Fe intermetallics increased with higher Fe, Mn, and Cr contents. Primary α-Fe are strongly suggested to nucleate on oxides and to grow in four basic morphologies. Lower nucleation frequency of α-Fe promoted faster growth and hopper crystals while higher nucleation frequency promoted slower growth rates and massive crystals. Results also showed that a decrease in the size of the eutectic Si and plate-like β-Fe intermetallics improved tensile properties, foremost the elongation to fracture. In β-Fe containing alloys the transversely oriented intermetallics initiated macrocracks that are potential fracture initiation sites. In alloys with primary α-Fe foremost clusters of intermetallics promoted macrocracks. In fatigue testing, a transition from β-Fe to α-Fe shifted the initiation sites from oxides and pores to the α-Fe, resulting in a decrease of fatigue strength. Oxides in Al-Si alloys continue to be elusive; no correlations between efforts to quantify the oxides and tensile properties could be observed.
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| 4. |
- Borkar, Hemant, et al.
(författare)
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Microstructure, texture and mechanical properties of al alloy a380 prepared by directional solidification method
- 2019
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Ingår i: Manufacturing Sciences and Technologies IX. - : Trans Tech Publications. - 9783035713886 - 9783035733884 ; , s. 18-23
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Konferensbidrag (refereegranskat)abstract
- The mechanical properties of Al-Si alloys are affected by several microstructural features such as secondary dendrite arm spacing (SDAS), size and shape of eutectic Si-particles, presence of intermetallics as well as by porosity. In the current study, Al-Si-Cu alloy A380 was prepared by a unique directional solidification method to produce samples with two different SDAS of 9 μm and 27 μm. The lower solidification rate resulted in larger SDAS, larger grain size, larger eutectic Si and larger intermetallics including Fe-rich β phase. The microstructure with higher solidification rate was found to be finer and more homogeneous with smaller eutectic Si and intermetallics. The specimen with larger SDAS exhibited stronger texture than the one with smaller SDAS. The specimen with smaller SDAS showed improved mechanical properties including YS, UTS and ductility.
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| 5. |
- Ceschini, Lorella, et al.
(författare)
-
Aluminum and Magnesium Metal Matrix Nanocomposites
- 2017
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- The book looks into the recent advances in the ex-situ production routes and properties of aluminum and magnesium based metal matrix nanocomposites (MMNCs), produced either by liquid or semi-solid state methods. It comprehensively summarizes work done in the last 10 years including the mechanical properties of different matrix/nanoreinforcement systems. The book also addresses future research direction, steps taken and missing developments to achieve the full industrial exploitation of such composites. The content of the book appeals to researchers and industrial practitioners in the area of materials development for metal matrix nanocomposites and its applications.
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| 6. |
- Dini, Hoda, 1984-
(författare)
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As-cast AZ91D magnesium alloy properties : Effects of microstructure and temperature
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, there is an essential need for lightweight, energy-efficient, environmentally benign engineering systems, and this is the driving force behind the development of a wide range of structural and functional materials for energy generation, energy storage, propulsion, and transportation. These challenges have motivated the use of magnesium alloys for lightweight structural systems. Magnesium has a density of 1.74 g/cm3, which is almost 30% less than that of aluminium, one quarter of steel, and almost identicalto polymers. The ease of recycling magnesium alloys as compared to polymers makes them environmentally attractive, but their poor mechanical performance is the primary reason for the limited adoption of these alloys for structural applications.The Mg-Al-Zn alloy AZ91D exhibits an excellent combination of strength, die-castability, and corrosion resistance. However, its mechanical performance with regard to creep strength, for example, at evaluated temperatures is poor. Moreover, very little is known about the correlation between its mechanical properties and microstructural features. This thesis aims to provide new knowledge regarding the role played by microstructure in the mechanical performance of the magnesium alloy. The properties/performance of the material in relation to process parameters became of great interest during the investigation.An exhaustive characterisation of the grain size, secondary dendrite arm spacing (SDAS) distribution, and fraction of Mg17Al12 was performed using optical and electron backscatter diffraction (EBSD). These microstructural parameters were correlated to the offset yield point (Rp0.2), fracture strength, and elongation to failure of the material. It was proposed that the intermetallic phase, Mg17Al12, plays an important role in determining the mechanical and physical properties of the alloy in a temperature range of room temperature to 190°C by forming a rigid network of intermetallic. The presence of this network was confirmed by studying the thermal expansion behaviour of samples of the alloy containing different amounts of Mg17Al12.A physically based constitutive model with a wide validity range was successfully adapted to describe the flow stress behaviour of AZ91D with various microstructures. The temperature-dependent variables of the model correlated quite well with the underlying physics of the material. The model was validated through comparison with dislocation densities obtained using EBSD.The influence of high-pressure die-cast parameters on the distortion and residual stress of the cast components was studied, as were distortion and residual stress in components after shot peening and painting. Interestingly, it was found that intensification pressure has a major effect on distortion and residual stresses, and that the temperature of the fixed half of the die had a slight influence on the component's distortion and residual stress.
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| 7. |
- Dini, Hoda, 1984-, et al.
(författare)
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Effect of process parameters on distortion and residual stress of high-pressure die-cast AZ91D components
- 2018
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Ingår i: International Journal of metalcasting. - : Springer. - 1939-5981 .- 2163-3193. ; 12:3, s. 487-497
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study of distortion and residual stress within a high-pressure die-cast AZ91D component, cast under different processing conditions. The influence of process parameters, i.e., die temperature, cooling time, intensification pressure and first-phase injection speeds, was examined. Distortions were measured using the in-house standard analog quality control fixture. Residual stress depth profiles were measured using a prism hole-drilling method. It was found that the most important process parameter affecting the distortion was intensification pressure and the second most important was temperature difference between the two die halves (fixed and moving side). Tensile residual stresses were found very near the surface. Increasing the intensification pressure resulted in an increased level of tensile residual stresses.
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| 8. |
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| 9. |
- Dini, Hoda, 1984-, et al.
(författare)
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Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn
- 2018
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Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 710, s. 17-26
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Tidskriftsartikel (refereegranskat)abstract
- A dislocation density-based constitutive model, including effects of microstructure scale and temperature, was calibrated to predict flow stress of an as-cast AZ91D (Mg-9%Al-1%Zn) alloy. Tensile stress-strain data, for strain rates from 10-4 up to 10-1 s-1 and temperatures from room temperature up to 190 °C were used for model calibration. The used model accounts for the interaction of various microstructure features with dislocations and thereby on the plastic properties. It was shown that the Secondary Dendrite Arm Spacing (SDAS) size was appropriate as an initial characteristic microstructural scale input to the model. However, as strain increased the influence of subcells size and total dislocation density dominated the flow stress. The calibrated temperature-dependent parameters were validated through a correlation between microstructure and the physics of the deforming alloy. The model was validated by comparison with dislocation density obtained by using Electron Backscattered Diffraction (EBSD) technique.
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| 10. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Atmospheric Corrosion of Mg Alloy AZ91D Fabricated by aSemi-Solid Casting Technique: The Influence of Microstructure
- 2015
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 162:7, s. C311-C321
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Tidskriftsartikel (refereegranskat)abstract
- The atmospheric corrosion behavior of alloy AZ91D produced by a semi-solid metal (SSM) technique and by conventional high pressure die casting (HPDC) was investigated for up to 1176 hours in the laboratory. Alloy AZ91D in the SSM state was fabricated using a rheocasting (RC) technique in which the slurry was prepared by the RheoMetal process. Exposures were performed in 95% RH air at 22 and 4 degrees C. The RC alloy AZ91D exhibited significantly better corrosion resistance than the HPDC material at two temperatures studied. The effect of casting technology on corrosion is explained in terms of the microstructural differences between the materials. For example, the larger number density of cathodic beta phase particles in the HPDC material initially causes relatively rapid corrosion compared to the RC material. During later stages of corrosion, the more network-like beta phase particles in the RC alloy act as a corrosion barrier, further improving the relative corrosion resistance of the RC material.
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| 11. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Effect of Rheocasting on Corrosion of AM50 Mg Alloy
- 2015
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 162:3, s. C85-C95
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion behavior of magnesium-aluminum (Mg-Al) alloy AM50 produced by a rheocasting (RC) technique was examined in the presence and absence of CO2 at three temperatures -4, 4 and 22 degrees C. The slurry preparation in the RC material was performed with the newly developed RheoMetal process. For reference, 99.97% Mg was included in the corrosion exposures. The influence of the microstructure on the atmospheric corrosion of alloy AM50 produced by RC and high pressure die casting (HPDC) was investigated. The RC AM50 alloy showed better corrosion resistance than HPDC AM50 in all the exposure environments studied. For both materials, there was a strong positive correlation between temperature and the atmospheric corrosion rate. The superior atmospheric corrosion behavior of RC AM50 compared to HPDC AM50 is carefully discussed in relation to differences in the as-cast microstructure. This study demonstrates that producing the alloy AM50 by this type of RC technique opens the door to Mg-Al alloys as a promising candidate for various applications where corrosion resistance is of importance.
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| 12. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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On the microstructure and corrosion behavior of AZ91/SiC composites produced by rheocasting
- 2016
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 180, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure and atmospheric corrosion behavior of two types of SiC (10 vol%)-reinforced magnesium alloy metal matrix composites (Mg alloy AZ91D-based MMCs) produced by rheocasting (RC) were investigated and compared to the monolithic alloy. Micron-sized and nano-sized SiC particles were used for fabrication of the MMCs. Microstructural studies using a broad range of analytical techniques showed the formation Al carbides and MgO at the alpha-Mg/SiC interface. The higher corrosion rate of the MMCs than RC AZ91D was attributed to a lesser degree of connectivity of the beta phase, the high impurity level of SiC-reinforced MMCs and also the higher fraction of casting pores in the MMCs as compared to the RC alloy.
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| 13. |
- Ghasemi, Rohollah, 1983-, et al.
(författare)
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Abrasion resistance of lamellar graphite iron : Interaction between microstructure and abrasive particles
- 2018
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 120, s. 465-475
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on abrasion resistance of Lamellar Graphite Iron (LGI) using microscratch test under constant and progressive load conditions. The interactions between a semi-spherical abrasive particle, cast iron matrix and graphite lamellas were physically simulated using a sphero-conical indenter. The produced scratches were analysed using LOM and SEM to scrutinise the effect of normal load on resulting scratch depth, width, frictional force, friction coefficient and deformation mechanism of matrix during scratching. Results showed a significant matrix deformation, and change both in frictional force and friction coefficient by increase of scratch load. Furthermore, it was shown how abrasive particles might produce deep scratches with severe matrix deformation which could result in graphite lamella's coverage and thereby deteriorate LGI's abrasion resistance.
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| 14. |
- Ghasemi, Rohollah, 1983-, et al.
(författare)
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Load effect on scratch micro-mechanisms of solution strengthened Compacted Graphite Irons
- 2019
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 133, s. 182-192
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the scratch load effect, from 100 to 2000 mN, on micro-mechanisms involved during scratching. A pearlitic and three ferritic Compacted Graphite Irons (CGI) solution strengthened through addition of 3.66, 4.09, and 4.59 Si wt% were investigated. Good correlation was observed between hardness measurements, tensile testing, and scratch results explaining the influence of matrix characteristics on scratch behaviour for investigated alloys. A significant matrix deformation, change in frictional force and scratch coefficient of friction was observed by increase in scratch load. In all cases, microscratch depth and width increased significantly with load increasing, however pearlitic CGI showed most profound deformation, while the maximum and minimum scratch resistances were observed for high-Si ferritic and pearlitic CGI alloys, respectively.
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| 15. |
- Ghasemi, Rohollah, 1983-, et al.
(författare)
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Scratch behaviour of silicon solid solution strengthened ferritic compacted graphite iron (CGI)
- 2018
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 318-325
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Tidskriftsartikel (refereegranskat)abstract
- The present study focuses on scratch behaviour of a conventional pearlitic and a number of solid solution strengthened ferritic Compacted Graphite Iron (CGI) alloys. This was done by employing a single-pass microscratch test using a sphero-conical diamond indenter under different constant normal load conditions. Matrix solution hardening was made by alloying with different contents of Si; (3.66, 4.09 and 4.59 wt%. Si) which are named as low-Si, medium-Si and high-Si ferritic CGI alloys, respectively. A good correlation between the tensile and scratch test results was observed explaining the influence of CGI’s matrix characteristics on scratch behaviour both for pearlitic and fully ferritic solution strengthened ones. Both the scratch depth and scratch width showed strong tendency to increase with increasing the normal load, however the pearlitic one showed more profound deformation compared to the solution strengthened CGI alloys. Among the investigated alloys, the maximum and minimum scratch resistance were observed for high-Si ferritic CGI and pearlitic alloys, respectively. It was confirmed by the scratched surfaces analysed using Scanning Electron Microscopy (SEM) as well. In addition, the indenter’s depth of penetration value (scratch depth) was found as a suitable measure to ascertain the scratch resistance of CGI alloys.
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| 16. |
- Ghassemali, Ehsan, 1983-, et al.
(författare)
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On the Formation of Micro-Shrinkage Porosities in Ductile Iron Cast Components
- 2018
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- A combination of direct austempering after solidification (DAAS) treatment and electron backscatter diffraction (EBSD) method was used to study the formation of micro-shrinkage porosities in ductile iron. Analyzing the aus-ferritic microstructure revealed that most of micro-shrinkage porosities are formed at the retained austenite grain boundaries. There was no obvious correlation between the ferrite grains or graphite nodules and micro-shrinkage porosities. Due to the absolute pressure change at the (purely) shrinkage porosities, the dendrite fragmentation rate during the DAAS process would be altered locally, which caused a relatively finer parent-austenite grain structure near such porosities.
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| 17. |
- Ghassemali, Ehsan, 1983-, et al.
(författare)
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Revisiting the graphite nodule in ductile iron
- 2019
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Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 161, s. 66-69
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Tidskriftsartikel (refereegranskat)abstract
- The growth mechanism of graphite nodules in ductile iron was experimentally investigated using high-resolution 3D tomography of an individual graphite nodule in a near-eutectic ductile iron. The dual beam scanning electron microscopy (FIB-SEM) technique was used for this purpose. Iron particles elongated in the radial direction were observed inside a graphite nodule. Some micro-voids were detected inside the nodule, mostly located at the end of the iron particles. These observations were compared with established theories about the growth of graphite nodules and iron entrapment/engulfment in between the graphite sectors during solidification of ductile iron.
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| 18. |
- Jarfors, Anders E.W. 1963-, et al.
(författare)
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Recent advances in commercial application of the rheometal process in China and Europe
- 2019
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Ingår i: Semi-Solid of Alloys and Composites. - : Trans Tech Publications. - 9783035713732 - 9783035733730 ; , s. 405-410
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Konferensbidrag (refereegranskat)abstract
- Recent advances in rheocasting have resulted in significant expansion in the types of products currently in full commercial production. The current paper gives an overview of components in production in Europe and in China produced using the RheoMetal™ process, that has taken the lead in a strong drive towards new heavy-duty applications made from aluminium alloys. In China, the dominating applications are found in the telecom industry. The trend in Europe is more towards marine and automotive applications commonly in fatigue loaded applications. The reason for the choice of rheocasting for complicated shape thin-walled electronics components with requirements is dominated by process yield and by the ability to improve thermal conductivity. The heavy-duty truck chassis thick walled components target weight reduction through design and to sustain fatigue load normally requiring forged components. Common in all applications are seen in production yield, reduced tool wear and reduction of die soldering.
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| 19. |
- Kasvayee, Keivan Amiri, 1986-, et al.
(författare)
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Characterization and modeling of the mechanical behavior of high silicon ductile iron
- 2017
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Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 708, s. 159-170
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the effect of the solidification conditions and silicon content on the mechanical properties of ductile iron and presents empirical models for predicting the tensile behavior based on the microstructural characterizations. Two ductile iron grades of GJS-500-7 and GJS-500-14 were cast with silicon content of 2.36% and 3.71%, respectively. The cast geometry consisted of six plates with different thicknesses that provided different cooling rates during the solidification. Microstructure analysis, tensile and hardness tests were performed on the as-cast material. Tensile behavior was characterized by the Ludwigson equation. The tensile fracture surfaces were analyzed to quantify the fraction of porosity. The results showed that graphite content, graphite nodule count, ferrite fraction and yield strength were increased by increasing the silicon content. A higher silicon content resulted in lower work hardening exponent and strength coefficient on the Ludwigson equation. The results for 0.2% offset yield and the Ludwigson equation parameters were modeled based on microstructural characteristics, with influence of silicon content as the main contributing factor. The models were implemented into a casting process simulation to enable prediction of microstructure-based tensile behavior. A good agreement was obtained between measured and simulated tensile behavior, validating the predictions of simulation in cast components with similar microstructural characteristics.
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| 20. |
- Kasvayee, Keivan Amiri, 1986-, et al.
(författare)
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Effect of Boron and Cross-Section Thickness on Microstructure and Mechanical Properties of Ductile Iron
- 2018
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 925, s. 249-256
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Tidskriftsartikel (refereegranskat)abstract
- Eeffect of Boron addition on the microstructure and mechanical properties of ductile iron, GJS-500-7 grade was studied. Three cast batches with the Boron content of 10, 49 and 131ppm were cast in a casting geometry containing plates with thicknesses of 7, 15, 30, 50 and 75mm. Microstructure analysis, tensile test, and hardness test were performed on the samples which were machined from the casting plates. Addition of 49 ppm Boron decreased pearlite fraction by an average of 34±6% in all the cast plates. However, minor changes were observed in the pearlite fraction by increasing Boron from 49 to 131 ppm. Variation in the plate thickness did not affect the pearlite fraction. The 0.2% offset yield and ultimate tensile strength was decreased by an average of 11±1% and 18±2%, respectively. Addition of 49 ppm Boron decreased Brinell hardness by 16±1%, while 11±2% reduction was obtained by addition of 131ppm Boron.
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| 21. |
- Kasvayee, Keivan Amiri, 1986-, et al.
(författare)
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Microstructural strain mapping during in-situ cyclic testing of ductile iron
- 2018
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Ingår i: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; 140, s. 333-339
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Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on local strain distribution in the microstructure of high silicon ductile iron during cyclic loading. In-situ cyclic test was performed on compact-tension (CT) samples inside the scanning electron microscope (SEM) to record the whole deformation and obtain micrographs for microstructural strain measurement by means of digital image correlation (DIC) technique. Focused ion beam (FIB) milling was used to generate speckle patterns necessary for DIC measurement. The equivalent Von Mises strain distribution was measured in the microstructure at the maximum applied load. The results revealed a heterogeneous strain distribution at the microstructural level with higher strain gradients close to the notch of the CT sample and accumulated strain bands between graphite particles. Local strain ahead of the early initiated micro-cracks was quantitatively measured, showing high strain localization, which decreased by moving away from the micro-crack tip. It could be observed that the peak of strain in the field of view was not necessarily located ahead of the micro-cracks tip which could be because of the (i) strain relaxation due to the presence of other micro-cracks and/or (ii) presence of subsurface microstructural features such as graphite particles that influenced the strain concentration on the surface.
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| 22. |
- Kasvayee, Keivan Amiri, 1986-
(författare)
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On the deformation behavior and cracking of ductile iron; effect of microstructure
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the effect of microstructural variation on the mechanical properties and deformation behavior of ductile iron. To research and determine these effects, two grades of ductile iron, (i) GJS-500-7 and (ii) high silicon GJS-500-14, were cast in a geometry containing several plates with different section thicknesses in order to produce microstructural variation. Microstructural investigations as well as tensile and hardness tests were performed on the casting plates. The results revealed higher ferrite fraction, graphite particle count, and yield strength in the high silicon GJS-500-14 grade compared to the GJS-500-7 grade.To study the relationship between the microstructural variation and tensile behavior on macroscale, tensile stress-strain response was characterized using the Ludwigson equation. The obtained tensile properties were modeled, based on the microstructural characteristics, using multiple linear regression and analysis of variance (ANOVA). The models showed that silicon content, graphite particle count, ferrite fraction, and fraction of porosity are the major contributing factors that influence tensile behavior. The models were entered into a casting process simulation software, and the simulated microstructure and tensile properties were validated using the experimental data. This enabled the opportunity to predict tensile properties of cast components with similar microstructural characteristics.To investigate deformation behavior on micro-scale, a method was developed to quantitatively measure strain in the microstructure, utilizing the digital image correlation (DIC) technique together with in-situ tensile testing. In this method, a pit-etching procedure was developed to generate a random speckle pattern, enabling DIC strain measurement to be conducted in the matrix and the area between the graphite particles. The method was validated by benchmarking the measured yield strength with the material’s standard yield strength.The microstructural deformation behavior under tensile loading was characterized. During elastic deformation, strain mapping revealed a heterogeneous strain distribution in the microstructure, as well as shear bands that formed between graphite particles. The crack was initiated at the stress ranges in which a kink occurred in the tensile curve, indicating the dissipation of energy during both plastic deformation and crack initiation. A large amount of strain localization was measured at the onset of the micro-cracks on the strain maps. The micro-cracks were initiated at local strain levels higher than 2%, suggesting a threshold level of strain required for micro-crack initiation.A continuum Finite Element (FE) model containing a physical length scale was developed to predict strain on the microstructure of ductile iron. The material parameters for this model were calculated by optimization, utilizing the Ramberg-Osgood equation. The predicted strain maps were compared to the strain maps measured by DIC, both qualitatively and quantitatively. To a large extent, the strain maps were in agreement, resulting in the validation of the model on micro-scale.In order to perform a micro-scale characterization of dynamic deformation behavior, local strain distribution on the microstructure was studied by performing in-situ cyclic tests using a scanning electron microscope (SEM). A novel method, based on the focused ion beam (FIB) milling, was developed to generate a speckle pattern on the microstructure of the ferritic ductile iron (GJS-500-14 grade) to enable quantitative DIC strain measurement to be performed. The results showed that the maximum strain concentration occurred in the vicinity of the micro-cracks, particularly ahead of the micro-crack tip.
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| 23. |
- Kasvayee, Keivan Amiri, 1986-, et al.
(författare)
-
Strain localization and crack formation effects on stress-strain response of ductile iron
- 2017
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 702, s. 265-271
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Tidskriftsartikel (refereegranskat)abstract
- The strain localization and crack formation in ferritic-pearlitic ductile iron under tension was investigated by in-situ tensile tests. In-situ tensile tests under optical microscope were performed and the onset of the early ferrite-graphite decohesions and micro-cracks inside the matrix were studied. The results revealed that early ferrite-graphite decohesion and micro-cracks inside the ferrite were formed at the stress range of 280–330 MPa, where a kink occurred in the stress-strain response, suggesting the dissipation of energy in both plastic deformation and crack initiation. Some micro-cracks initiated and propagated inside the ferrite but were arrested within the ferrite zone before propagating in the pearlite. Digital Image Correlation (DIC) was used to measure local strains in the deformed micrographs obtained from the in-situ tensile test. Higher strain localization in the microstructure was measured for the areas in which the early ferrite-graphite decohesions occurred or the micro-cracks initiated. © 2017 Elsevier B.V.
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| 24. |
- Malakizadi, Amir, 1983, et al.
(författare)
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Effects of workpiece microstructure, mechanical properties and machining conditions on tool wear when milling compacted graphite iron
- 2018
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 410-411, s. 190-201
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate the tool performance when machining compacted graphite iron (CGI) alloys. A comparison was made between solid solution strengthened CGI including various amounts of silicon (Si-CGI) and the pearlitic-ferritic CGI as a reference material. The emphasis was on examining the influence of microstructure and mechanical properties of the material on tool wear in face milling process. Machining experiments were performed on the engine-like test pieces comprised of solid solution strengthened CGI with three different silicon contents and the reference CGI alloy. The results showed up-to 50% lower flank wear when machining Si-CGI alloys, although with comparable hardness and tensile properties. In-depth analysis of the worn tool surfaces showed that the abrasion and adhesion were the dominant wear mechanisms for all investigated alloys. However, the better tool performance when machining Si-CGI alloys was mainly due to a lower amount of abrasive carbo-nitride particles and the suppression of pearlite formation in the investigated solid solution strengthened alloys.
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| 25. |
- Maryam, Eslami, et al.
(författare)
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Effect of Segregation and Surface Condition on Corrosion of Rheo-HPDC Al–Si Alloys
- 2018
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion properties of two Al–Si alloys processed by Rheo-high pressure die cast (HPDC) method were examined using polarization and electrochemical impedance spectroscopy (EIS) techniques on as-cast and ground surfaces. The effects of the silicon content, transverse and longitudinal macrosegregation on the corrosion resistance of the alloys were determined. Microstructural studies revealed that samples from different positions contain different fractions of solid and liquid parts of the initial slurry. Electrochemical behavior of as-cast, ground surface, and bulk material was shown to be different due to the presence of a segregated skin layer and surface quality.
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| 26. |
- Matsushita, Taishi, et al.
(författare)
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On the thermal conductivity of CGI and SGI cast irons
- 2018
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Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 31:3, s. 135-143
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity of Compacted Graphite Iron (CGI) and spheroidal graphite iron (SGI) was established in the temperature range from room temperature up to 500 °C using the experimental thermal diffusivity, density and specific heat values. The influence of nodularity, graphite amount, silicon content and temperature on the thermal conductivity of fully ferritic high-silicon cast irons was investigated. It was found that the CGI materials showed higher thermal conductivity than the SGI materials. The thermal conductivity tended to increase with increasing temperature until it reached a maximum followed by a subsequent decrease as temperature was increased up to 500 °C. Conventional models were applied to estimate thermal conductivity and the predictive accuracy of each model was evaluated. The thermal conductivity could be estimated by the Helsing model. The Maxwell model, Bruggeman model and Hashin–Shtrikman model were also in fair agreement using the thermal conductivity value of graphite parallel to the basal planes in graphite.
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| 27. |
- Raza, Mohsin, et al.
(författare)
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Effects of process related variations on defect formation in investment cast components
- 2018
-
Ingår i: Archives of Foundry Engineering. - : Polish Academy of Sciences. - 1897-3310 .- 2299-2944. ; 18:1, s. 103-108
-
Tidskriftsartikel (refereegranskat)abstract
- Castability of thin-walled castings is sensitive to variation in casting parameters. The variation in casting parameters can lead to undesired casting conditions which result in defect formation. Variation in rejection rate due to casting defect from one batch to other is common problem in foundries and the cause of this variation usually remain unknown due to complexity of the process. In this work, variation in casting parameters resulting from human involvement in the process is investigated. Casting practices of different groups of casting operators were evaluated and resulting variations in casting parameters were discussed. The effect of these variations was evaluated by comparing the rejection statistics for each group. In order to minimize process variation, optimized casting practices were implemented by developing specific process instructions for the operators. The significance of variation in casting parameters in terms of their impact on foundry rejections was evaluated by comparing the number of rejected components before and after implementation of optimized casting practices. It was concluded that variation in casting parameters due to variation in casting practices of different groups has significant impact on casting quality. Variation in mould temperature, melt temperature and pouring rate due to variation in handling time and practice resulted in varying quality of component from one batch to other. By implementing the optimized casting instruction, both quality and process reliability were improved significantly.
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| 28. |
- Raza, Mohsin, et al.
(författare)
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Effects of Process Related Variations on Fillablity Simulation of Thin-Walled IN718 Structures
- 2018
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Ingår i: International Journal of metalcasting. - Sweden : Springer Science and Business Media LLC. - 1939-5981 .- 2163-3193. ; 12:3, s. 543-553
-
Tidskriftsartikel (refereegranskat)abstract
- Simulation tools have improved significantly and are now capable of accurately predicting mould filling behavior. The quality of prediction is highly dependent on material properties and set-up of boundary conditions for the simulation. In this work material properties were measured and casting conditions were analyzed to accurately replicate the casting process in simulation. The sensitivity of the predictions to minor process variations commonly found in foundries was evaluated by comparing simulation and cast samples. The observed discrepancies between simulation and cast samples were evaluated and discussed in terms of their dependency on process variations. It was concluded that the simulation set-up was capable of reasonable predictions and could replicate the asymmetry of the filling however did not accurately predict the absolute value of the unfilled area. It was discovered that asymmetric flow due to variations in the orientation of the casting mould during filling could have greater influence on the predictions than the actual variation in fill time. The quality of simulation is dependent on equipment and techniques used in the foundry as well as the metallurgical model to simulate the process. © 2017, The Author(s).
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| 29. |
- Salomonsson, Kent, et al.
(författare)
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Three-dimensional microstructural characterization of cast iron alloys for numerical analyses
- 2018
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 427-435
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we aim at characterizing three different cast iron alloys and their microstructural features, namely lamellar, compacted and nodular graphite iron. The characterization of microscopic features is essential for the development of methods to optimize the behavior of cast iron alloys; e.g. maximize thermal dissipation and/or maximize ductility while maintaining strength. The variation of these properties is commonly analyzed by metallography on two-dimensional representations of the alloy. However, more precise estimates of the morphologies and material characteristics are obtained by three-dimensional reconstruction of microstructures. The use of X-ray microtomography provides an excellent tool to generate high resolution threedimensional microstructure images. The characteristics of the graphite constituent in the microstructure, including the size, shape and connectivity, were analyzed for the different cast iron alloys. It was observed that the lamellar and compacted graphite iron alloys have relatively large connected graphite morphologies, as opposed to ductile iron where the graphite is present as nodules. The results of the characterization for the different alloys were ultimately used to generate finite element models.
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| 30. |
- Santos, Jorge
(författare)
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Al-7Si-Mg semi-solid castings – microstructure and mechanical properties
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The vehicles industry is facing increasing demands for fuel efficiency and cost reduction due to environmental legislation, sustainability and customer demands. Therefore, there is a great need to develop and produce lightweight components by using materials and processes that offer higher specific strength and/or design optimization. Semi‐solid aluminium casting offers design freedom and castings with lower shrinkage and gas entrapment defects compared to high pressure die castings. The lack of understanding of microstructure and defect formation, and design data, for semi‐solid castings is a barrier for foundries and designers in the vehicles industry to use semi‐solid castings.In this study, the effect of two grain refiners on slurry formation and surface segregation of semi‐solid Al‐7Si‐0.3Mg castings produced by the Rheometal™ process was evaluated. The influence of grain refinement on primary α‐Al grain size, shape factor and solid fraction was analysed in addition to the solute content of the surface segregation layer.The influence of magnesium on the formation of intermetallic phases during solidification and the heat treatment response of Al‐7Si‐Mg semi‐solid castings was investigated. The magnesium content was varied from 0.3 to 0.6wt.% and the semi-solid castings were analysed in the T5 and T6 conditions. Energy dispersive spectroscopy was used to identify the intermetallic phases formed during solidification. Tensile testing was performed and the results were correlated to the magnesium and silicon concentration measured in the interior of the α‐Al globules formed during slurry preparation.The results suggest that the addition of grain refiner decreases the solid fraction obtained in the Rheometal™ process. However, no significant effect was observed on the α‐Al grain size and shape factor.A good correlation was obtained between the magnesium concentration in the interior of the α‐Al globules formed during slurry preparation and the offset yield strength for all alloys. The low magnesium solubility in α‐Al at temperatures in the solidification range of the Al‐7Si‐Mg alloys is suggested to be the reason for the low hardening response for the T5 heat treatment compared to the T6 condition.
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| 31. |
- Santos, Jorge, et al.
(författare)
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Formation of Iron-Rich Intermetallic Phases in Al-7Si-Mg : Influence of Cooling Rate and Strontium Modification
- 2019
-
Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 50:9, s. 4148-4165
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of cooling rate on the formation of iron-rich intermetallic phases during solidification of unmodified and strontium-modified Al-7Si-0.3Mg alloys has been investigated. The effect of strontium on the intermetallic phases was evaluated in unquenched and quenched samples. Samples were quenched before the start of the Al-Si eutectic reaction, along the Al-Si eutectic reaction and just after the end of solidification. The results show that the addition of strontium increased the size of both β-Al5FeSi and π-Al8FeMg3Si6 at low cooling rates. For unmodified and strontium-modified alloys, an increase of cooling rate resulted in a decrease in size of the intermetallic phases, particularly in the strontium modified alloy. In the strontium modified alloy quenched before the start of the Al-Si eutectic reaction, π-Al8FeMg3Si6 appeared as thin platelets at the eutectic cell boundaries. Chinese script-like π-Al8FeMg3Si6 and platelet-like β-Al5FeSi intermetallic phases were observed uniformly distributed in the eutectic regions in the unmodified alloy quenched before the start of the eutectic reaction. Strontium modified semi-solid Al-7Si-0.3Mg castings were produced and the type of intermetallic phase, morphology, size, area fraction and distribution were similar to that observed in the strontium modified alloy quenched before the start of the Al-Si eutectic reaction.
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| 32. |
- Santos, Jorge, et al.
(författare)
-
Influence of grain refinement on slurry formation and surface segregation in semi-solid Al-7Si-0.3Mg castings
- 2018
-
Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 49A:10, s. 4871-4883
-
Tidskriftsartikel (refereegranskat)abstract
- This study aims to evaluate the effect of grain refinement on slurry formation and surface segregation in semi-solid castings produced by the Rheometal™ process. The effect of two grain refiners, Al-8B and Al-5Ti-1B, on the slurry α-Al grain size, shape factor and solid fraction was evaluated. The results suggest that the addition of a grain refiner can affect the solid fraction obtained in the RheometalTM process and, consequently, reduce the solute content near the casting surface. Grain refiner addition resulted in a larger fraction of α-Al grains ≤ 60 µm for the refined alloys compared with the unrefined alloy. Additionally, the growth of α-Al slurry globules was greater for the unrefined alloy compared with the refined alloy during solidification in the die-cavity. A more homogeneous and finer microstructure was observed near the surface in the grain-refined castings compared with the unrefined castings. Evidence of significant liquid penetration was identified in some α-Al globules, indicating that disintegration of α-Al globules may occur during the Rheometal™ casting process.
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| 33. |
- Santos, Jorge, et al.
(författare)
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Variation of properties in the cross-section of semi-solid al-7si-0.3mg castings
- 2019
-
Ingår i: Semi-Solid of Alloys and Composites. - : Trans Tech Publications. - 9783035713732 - 9783035733730 ; , s. 81-86
-
Konferensbidrag (refereegranskat)abstract
- In semi-solid casting, a slurry consisting of primary α-Al crystals and liquid is injected into the die cavity. The solidification in the die-cavity occurs by the growth of the primary α-Al crystals formed during slurry preparation and in the shot sleeve, nucleation and growth of in-cavity solidified crystals and ends with the eutectic reaction. During solidification in the die cavity, the cooling rate near the die wall is higher in comparison to the centre of the casting, particularly for thick-walled castings. The solidification conditions for the slurry α-Al crystals that are closer to the die wall can be very different compared to the slurry α-Al crystals located at the casting centre. This can result in different solute concentration in the interior of the α-Al globules in different regions of the semi-solid casting cross-section and consequently, different response to heat treatament. The RheoMetal™ process was used to produce thick-walled semi-solid castings. Semi-solid castings in the as-cast and T6 conditions were investigated. Indentation tests for hardness measurements in the nano-range were performed in the interior of α-Al globules near the surface and at the casting cross-section centre. The hardness variation across the casting cross-section was evaluated by low-force Vickers hardness. The castings in the as-cast condition showed more uniform properties in the cross-section compared to the T6 condition. Additionally, the results suggest that microsegregation in the interior of α-Al globules is very low in castings in the as-cast and T6 conditions.
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| 34. |
-
Science and Processing of Cast Iron XI
- 2018
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Proceedings (redaktörskap) (refereegranskat)abstract
- The goal of this book is to present for readers the articles from the 11th International Symposium on the Science and Processing of Cast Iron that was held in September 2017 in Jönköping, Sweden. The content of the book reflects the state of the art, research and development tendencies of cast iron as the main engineering cast material also in the 21st century.
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| 35. |
- Siafakas, Dimitrios, 1982-, et al.
(författare)
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Measurement of Viscosity of SiO2-CaO-Al2O3 Slag in Wide Temperature Range by Aerodynamic Levitation and Rotating Bob Methods and Sources of Systematic Error
- 2018
-
Ingår i: International journal of microgravity science and application. - : Japan Society of Microgravity Application. - 0915-3616. ; 35:2
-
Tidskriftsartikel (refereegranskat)abstract
- Viscosity measurements for SiO2-CaO-Al2O3 based ternary slags with low SiO2 content were performed for a wide temperature range utilizing the aerodynamic levitation and rotating bob methods. Aerodynamic levitation was used for temperatures >= 2229 K and the viscosity was calculated by the sample oscillation decay time. The rotating bob method was used for temperatures <= 1898 K and the viscosity was determined by the variation of the torque at different rotation speeds. Fitting curves were created using Mauro’s viscosity equation. The main sources of systematic error were identified to be the sample weight measurement, the resolution of the high-speed camera, the fitting of the linear trend line in the torque against rpm diagrams and the vertical position of the bob. The combined standard uncertainty from all error sources was calculated for both measurement methods.
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| 36. |
- Siafakas, Dimitrios, 1982-
(författare)
-
On particles and slags in steel casting
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hadfield steel is widely accepted as one of the most important steel alloys utilized in industrial applications where high impact strength and wear resistance is required. Like in most metallic alloys used for component casting, the mechanical properties of Hadfield steel are directly connected with the microstructure of the material. It has been reported that Hadfield steel components with fine microstructure can present up to 30% increased strength and reduced risk of porosity formation during solidification when compared with their coarser microstructure counterparts.In the light-metal alloy and cast-iron industry, one of the most widely used methods for achieving refinement of the microstructure of the material is known as inoculation. As the name implies, inoculation is the practice ofadding selected compounds or alloying elements in a metal melt that have the ability to promote rapid grain nucleation during solidification. Even though it has been proved that inoculation is one of the most efficient methods for the refinement of a wide variety of metallic alloys, it has not yet gained adequate acceptance in the steel casting industry because researchers have not yet been able to identify proper inoculants for steel.The efficiency of the microstructural refinement when inoculating is influenced by several factors like the type of inoculant used and the processing conditions during melting, deoxidation, casting and heat treatment. Following proper deoxidation methods and application of tailored oxidic slags during melting could significantly promote the precipitation of desired inclusions that can act as potent nucleation sites for grains or as grain growth inhibitors.In any case, efficient inoculation is influenced by the complex interaction between the inoculant, the oxide slag, and the melt. The way this interaction happens is in many ways dictated by the chemical and thermophysical properties of the substances involved. Therefore, obtaining accurate values of basic thermophysical properties like viscosity and interfacial tension by improving current and utilizing novel measurement methods could significantly help in the effort of identifying and efficiently utilizing potent inoculants for austenitic steels.Considering the above, this work has a dual objective. The primary aim is to investigate if any of the by-products of deoxidation of Hadfield steel that remain in the material after solidification can act as potent inoculants by examining their qualitative and quantitative characteristics and their influence on the as-cast microstructure of the steel. The secondary aim is to acquire accurate values for oxide slag viscosity and slag-iron interfacial tension at high temperatures using different measurement methods and investigate how thermophysical properties are influenced by thermal and compositional conditions. This type of research is important because not only it can help to identify which substances are potent inoculants for austenitic steels but also pave the way for developing new or improving conventional deoxidation and inoculation processes with the ultimate goal of improving the cast component’s mechanical properties.The work is divided into 3 different stages. The first stage is dedicated to high-temperature oxide slag viscosity measurements. The viscosity of oxide slags with varying composition is measured in a wide temperature range utilizing the rotational bob and aerodynamic levitation methods. The systematic error is defined, and the compositional and thermodynamic dependence of viscosity is explained. In the second stage, the precipitation of particles in aluminum and titanium deoxidized Hadfield steel is investigated. The characteristics of particles, including type, size, morphology, composition, population, and sequence of precipitation are identified. The results are then compared against thermodynamic equilibrium calculations, a particle growth mathematical model is developed and the precipitation mechanism of each type of particle is described. Finally, in the third stage, the as-cast grain size of samples produced with varying deoxidation procedures is measured and the relationship between particle characteristics and grain size is determined. The particles are ranked according to their refining potency and compared to a ranking based on their disregistry with austenite.
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| 37. |
- Siafakas, Dimitrios, 1982-, et al.
(författare)
-
The Influence of Deoxidation Practice on the As-Cast Grain Size of Austenitic Manganese Steels
- 2017
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 7:6
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of in-situ precipitating particles on the grain size of Al-Ti-treated and untreated Hadfield steel cast in a pilot scale environment was studied. Hadfield steel was melted in an induction furnace and cast in Y-Block samples. Light Optical Microscopy (LOM) and the intercept method were utilized for the grain size measurements. Additionally, Thermo-Calc Software TCFE7 Steels/Fe-alloys database version 7 was used for thermodynamic equilibrium calculations of the mole fraction of particles. The planar disregistry values between the austenite and the precipitating particles were calculated. It was observed that increasing oxide content in samples with low Ti(CN) content resulted in a finer microstructure, while increasing the Ti(CN) content under similar oxide content levels led to a coarser microstructure. The potency of each type of particle to nucleate austenitic grains was determined. Spinel (MnAl2O4, MgAl2O4) particles were characterized as the most potent, followed by olivine (Mn2SiO4), corundum (Al2O3, TiO2), and finally Ti(CN), the least potent particle.
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| 38. |
- Siafakas, Dimitrios, 1982-, et al.
(författare)
-
Viscosity of SiO2–CaO–Al2O3 slag with low silica – Influence of CaO/Al2O3, SiO2/Al2O3 ratio
- 2018
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 58:12, s. 2180-2185
-
Tidskriftsartikel (refereegranskat)abstract
- The viscosity of low SiO2 (10–20 mass%)-CaO-Al2O3 slag system was measured in a wide temperature range (1 623–2 800 K) using the rotational bob method and the aerodynamic levitation method. The influence of SiO2/Al2O3 ratio and CaO/Al2O3 ratio on the viscosity was examined. It was concluded that the SiO2/Al2O3 ratio did not affect the degree of polymerization of the aluminosilicate network in the composition range of the present study. An abnormal behaviour of the viscosity was observed at a CaO/Al2O3 ratio of 1.57 which was attributed to the formation of 12CaO·7Al2O3-like clusters. It was concluded that the overall influence on the viscosity could be expressed as the summation of the influence from the aluminosilicate network and the influence from the cluster formation of the primary precipitating solid phase. The temperature dependence of the cluster formation was coupled to the driving force of precipitation of the 12CaO·7Al2O3 phase.
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| 39. |
- Stolt, Roland, 1970-, et al.
(författare)
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Challenges and Support when Introducing AM in HPDC Tooling
- 2019
-
Ingår i: Transdisciplinary engineering for complex socio-technical systems. - Amsterdam : IOS Press. - 9781643680200 - 9781643680217 ; , s. 147-156
-
Konferensbidrag (refereegranskat)abstract
- When manufacturing tooling inserts for HPDC (High Pressure Die Casting), several manufacturing steps such as milling, heat treatment, electro discharge machining and finally surface treatment are involved. By instead manufacturing the insert by SLM (Selective laser melting), the process is expected to be quicker and with less material waste compared to the traditional manufacturing. Examples of other expected advantages is higher product variant flexibility and the possibility of making conform cooling channels, extending the die life. However, the insert is part of a die system involving many components. The insert cannot be designed and manufactured without considering the complete die system. This paper seeks how to integrate the insert design in the die assembly design. This is done via an example component and in cooperation with die manufacturing firms. The result is that the printing is a minor step of the total manufacturing process and that special design considerations needs to be taken for an SLM insert. New die concepts are needed that will minimise the amount of material, reduce the tolerance and surface demand and support the subdivision of the die into several printed parts.
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| 40. |
- Sujakhu, S., et al.
(författare)
-
On the fatigue damage micromechanisms in Si-solution-strengthened spheroidal graphite cast iron
- 2018
-
Ingår i: Fatigue & Fracture of Engineering Materials & Structures. - : John Wiley & Sons. - 8756-758X .- 1460-2695. ; 41:3, s. 625-641
-
Tidskriftsartikel (refereegranskat)abstract
- Graphite nodules in spheroidal graphite cast iron (SGI) play a vital role in fatigue crack initiation and propagation. Graphite nodules growth morphology can go through transitions to form degenerated graphite elements other than spheroidal graphite nodules in SGI microstructure. These graphite particles significantly influence damage micromechanisms in SGI and could act differently than spheroidal graphite nodules. Most of the damage mechanism studies on SGI focused on the role of spheroidal graphite nodules on the stable crack propagation region. The role of degenerated graphite elements on SGI damage mechanisms has not been frequently studied. In this work, fatigue crack initiation and propagation tests were conducted on EN-GJS-500-14 and observed under scanning electron microscope to understand the damage mechanisms for different graphite shapes. Crack initiation tests showed a dominant influence of degenerated graphite elements where early cracks initiated in the microstructure. Most of the spheroidal graphite nodules were unaffected at the early crack initiation stage, but few of them showed decohesion from the ferrite matrix and internal cracking. In the crack propagation region, graphite/ferrite matrix decohesion was the frequent damage mechanism observed with noticeable crack branching around graphite nodules and the crack passing through degenerated graphite elements. Finally, graphite nodules after decohesion acted like voids which grew and coalesced to form microcracks eventually causing rapid fracture of the remaining section.
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| 41. |
- Tan, He, et al.
(författare)
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Fuzzy Logic Based Modelling of Cast Component Properties
- 2019
-
Ingår i: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 52:13, s. 1132-1137
-
Tidskriftsartikel (refereegranskat)abstract
- Digitalization of manufacturing requires building models to represent accumulated data and knowledge on the products and processes. The use of formal knowledge models allows for increase of the automation level leading to more sustainable manufacturing. Casting is important for different industries because it offers a great freedom of designing for weight reduction. This paper presents an approach to modelling of cast component properties that is based on fuzzy logic. The approach includes learning of the fuzzy inference rules from the data. The constructed fuzzy logic models can be used to tune the manufacturing process to produces cast components with desired properties. The evaluation of the results demonstrates that the accuracy of the two created models are 3.58% and 3.15% respectively with the learned fuzzy inference rules being identical to the manually created ones. The presented approach can help to automate the management of cast component manufacturing.
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| 42. |
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| 43. |
- Zhu, Bai, et al.
(författare)
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A study of anodising behaviour of al-si components produced by rheocasting
- 2019
-
Ingår i: Solid State Phenomena. - : Trans Tech Publications. - 1012-0394 .- 1662-9779. - 9783035713732 ; 285, s. 39-44
-
Tidskriftsartikel (refereegranskat)abstract
- This paper aims to investigate the anodising behaviour of Al-Si components produced by rheocasting, to understand the effect of the surface liquid segregation (SLS) on the anodising response. The material investigated was EN AC 42000 Al-alloy with an addition of 150 ppm Sr. The component was rheocast and conventionally liquid cast for benchmarking. The RheoMetal™ process was used to prepare slurry and subsequently cast using a vertical pressure die casting machine. Prior to anodising, mechanical grinding was used as pre-treatment method for selected samples as comparison with components in the as-cast state. Anodising was performed on the components using a constant controlled voltage at 25 V, in 1 M H2 SO4, at room temperature. The duration of anodising was varied from 30 mins to 120 mins to examine the relationship between oxide layer thickness and the anodising time. The oxide layer was investigated and characterised. The results demonstrated that the presence of the SLS layer, which was enriched with alloying elements, had a significant influence on the anodising behaviour of the cast component. The oxide layer thickness of the components produced by rheocasting and fully liquid casting was measured and compared. The relations between the oxide layer thickness and anodising time, as well as the casting methods are presented and discussed in this paper..
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