| 1. |
- Ali, Sharafat, 1976-, et al.
(författare)
-
Hardness, elastic modulus and refractive index of oxynitride glasses prepared from woody biofuel ashes
- 2017
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Ingår i: European Journal of Glass Science and Techology. Part B. Physics and Chemistry of Glasses. - : Society of Glass Technology. - 1753-3562 .- 1750-6689. ; 58:6, s. 231-236
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports the hardness, elastic modulus and refractive index values of the oxynitride glasses prepared from woody biofuel ashes. The glasses were prepared in nitrogen atmosphere at 1350-1500°C with addition of Ca metal as a precursor to the extra addition of this modifier. The glasses were homogenous, but appeared translucent grey to black. They contained up to 23 eq% of Ca and 5 eq% of N. The glass densities vary slightly between 2·76 to 2·92 g/cm3. The molar volume and compactness values vary between 8·01 cm3/mol to 8·31 cm3/mol and 0·446 to 0·462 respectively. Mechanical properties like hardness and reduced elastic modulus show values, up to 10 and 105 GPa, respectively. These properties are strongly correlated with the amount of N in the glass. The refractive index (1·54-1·75) increases with increasing N and Ca contents.
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| 2. |
- Bjurenstedt, Anton, 1979-
(författare)
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On the influence of imperfections on microstructure and properties of recycled Al-Si casting alloys
- 2017
-
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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| 3. |
- Bjurenstedt, Anton, 1979-, et al.
(författare)
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The effect of Fe-rich intermetallics on crack initiation in cast aluminium : an in-situ tensile study
- 2019
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 756, s. 502-507
-
Tidskriftsartikel (refereegranskat)abstract
- To evaluate the role of Fe-rich intermetallics on crack initiation, two fully modified Al-Si alloys, one containing plate-like β-Fe and the second containing primary α-Fe intermetallics, were investigated by in-situ tensile testing in the scanning electron microscope. In the first alloy, large plate-like β-Fe intermetallics oriented parallel to the test direction were the first to crack at an elongation of about 1.8%. More transversely oriented intermetallics caused crack initiation in the matrix which linked up with the final fracture. In the second alloy, the cracking of α-Fe intermetallics initiated at an elongation of about 0.9%. It is concluded that large α-Fe intermetallics crack first and that clusters of α-Fe are the most potent crack initiation sites.
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| 4. |
- Bogdanoff, Toni, et al.
(författare)
-
On the combined effects of surface quality and pore size on the fatigue life of Al–7Si–3Cu–Mg alloy castings
- 2023
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 885
-
Tidskriftsartikel (refereegranskat)abstract
- This study has aimed to determine the effects of surface quality and pore size, obtained by different levels of hydrogen content of the liquid metal, on the fatigue behavior of an Al–7%Si–3%Cu–Mg casting alloy. Three surface conditions have been studied: as-cast rough, as-cast smooth, and standard machined and polished surface. The S–N curves have shown that surface roughness and hydrogen content individually impact fatigue strength. Surprisingly, the fatigue strength of machined and polished samples, which aligns with standard testing practices, is significantly reduced, compared to other conditions. Fatigue cracks have been observed to initiate at the pores just below the as-cast surface or on the machined surfaces. In all cases, pores have been observed to be surrounded by bifilms. Moreover, hydrogen content and roughness of the as-cast surface have been found to interact to determine the fatigue performance. These findings necessitate a re-evaluation of fatigue testing procedures for cast aluminum components.
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| 5. |
- Bogdanoff, Toni, et al.
(författare)
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On the Effectiveness of Rotary Degassing of Recycled Al-Si Alloy Melts : The Effect on Melt Quality and Energy Consumption for Melt Preparation
- 2023
-
Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 15:6
-
Tidskriftsartikel (refereegranskat)abstract
- The effectiveness of rotary degassing on the defect formation and mechanical properties of the final casting of aluminium alloy EN AC 46000 was investigated, along with its impact on the energy consumption in the casting furnace. In the melt preparation prior to casting, the molten metal is usually transported from the melting furnace to the casting furnace with rotary degassing as a cleaning procedure. Under the conditions of this specific study, negligible degradation was observed in the mechanical properties of the final cast component in an aluminium EN AC 46000 alloy after removing the rotary degassing step in the process. Furthermore, removing the rotary degassing step led to a reduced temperature drop in the melt, thus minimizing the need for reheating (energy consumption) by up to 75% in the casting furnace. The reduced energy consumption was up to 124,000 kWh in yearly production in a 1500 kg casting furnace. The environmental impact showed a similar to 1500 kg reduction in CO2 for one 1500 kg electrical casting furnace in a year.
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| 6. |
- Bogdanoff, Toni, et al.
(författare)
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On the secondary cracks during crack propagation in an Al-Si-Cu-Mg alloy : An in-situ study
- 2023
-
Ingår i: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; 203
-
Tidskriftsartikel (refereegranskat)abstract
- During in situ cyclic testing of hot isostatically pressed and heat-treated Al-5Si-0.5 Mg-1Cu alloy castings, cracks were observed to open up in places far away from the area of stress concentration. Cyclic testing was interrupted to assess these cracks. Analysis showed that these cracks originated from oxide bifilms that were entrained in the liquid state. Moreover, Si and Fe-rich intermetallics were observed to have precipitated on these bifilms. These finding makes it necessary to re-evaluate how damage is interpreted in mechanical studies. Entrainment damage, which takes place in the liquid state, may remain invisible in non-destructive inspection and can significantly affect fatigue properties when bifilms open up under low tensile stresses and present the propagating crack a path of low resistance during propagation.
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| 7. |
- Bogdanoff, Toni, et al.
(författare)
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Prototyping of a high pressure die cast al-si alloy using plaster mold casting to replicate corresponding mechanical properties
- 2019
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Ingår i: Minerals, Metals and Materials Series. - Cham : Springer. - 9783030058630 - 9783030058647 ; , s. 435-442
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Konferensbidrag (refereegranskat)abstract
- Prototyping prior high pressure die casting (HPDC) is used for product/mold design optimization. Plaster mold casting is a cost-efficient prototyping technique providing good surface quality and dimension accuracy, similar to HPDC components. However, the corresponding mechanical properties of a component produced with these two methods are diverging significantly, mainly due to differences in the cooling rate. This work presents a procedure to optimize the plaster mold casting for prototyping to replicate mechanical properties of a commonly used Al-Si alloy (A380). Two commercial alloys with compositions close to the A380 alloy (A356.0 and A360.2) were used. Yield strength was considered as the main design criteria, thus the target mechanical property. Tensile testing results showed that with an optimized T6 heat treatment, not only the yield strength, but also ultimate tensile strength and elongation correspond well to the properties in the HPDC component.
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| 8. |
- Bogdanoff, Toni, et al.
(författare)
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The complex interaction between microstructural features and crack evolution during cyclic testing in heat-treated Al–Si–Mg–Cu cast alloys
- 2021
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 825
-
Tidskriftsartikel (refereegranskat)abstract
- The study aimed to investigate crack initiation and propagation at the micro-scale in heat-treated Al–7Si–Mg cast alloys with different copper (Cu) contents. In-situ cyclic testing in a scanning electron microscope coupled with electron back-scattered diffraction and digital image correlation was used to evaluate the complex interaction between the crack path and the microstructural features. The three-nearest-neighbour distance of secondary particles was a new tool to describe the crack propagation in the alloys. The amount of Cu retained in the α-Al matrix after heat treatment increased with the Cu content in the alloy and enhanced the strength with a slight decrease in elongation. During cyclic testing, the two-dimensional (2D) crack path appeared with a mixed propagation, both trans- and inter-granular, regardless of the Cu content of the alloy. On fracture surfaces, multiple crack initiation points were detected along the thickness of the samples. The debonding of silicon (Si) particles took place during crack propagation in the Cu-free alloy, while cracking of Si particles and intermetallic phases occurred in the alloy with 3.2 wt% Cu. Three-dimensional tomography using focused ion beam revealed that the improved strength of the α-Al matrix changes the number of cracked particles ahead of the propagating crack with Cu concentration above 1.5 wt%.
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| 9. |
- Bogdanoff, Toni
(författare)
-
The effect of microstructural features, defects and surface quality on the fatigue performance in Al-Si-Mg Cast alloys
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Global warming is driving industry to manufacture lighter components to reduce carbon dioxide (CO2) emissions. Promising candidates for achieving this are aluminium-silicon (Al-Si) cast alloys, which offer a high weight-to-strength ratio, excellent corrosion resistance, and good castability. However, understanding variations in the mechanical properties of these alloys is crucial to producing high-performance parts for critical applications. Defects and oxides are the primary reasons cast components in fatigue applications are rejected, as they negatively impact mechanical properties.A comprehensive understanding of the correlation between fatigue performance and parameters such as the α-aluminium matrix, Al-Si eutectic, surface roughness, porosities, hydrogen content, oxides, and intermetallic phases in Al-Si castings has not been reached.The research presented in this thesis used state-of-the-art experimental techniques to investigate the mechanical properties and crack-initiation and propagation behaviour of Al-Si-Mg cast alloy under cyclic loading. In-situ cyclic testing was conducted using scanning electron microscopy (SEM) combined with electron back-scattered diffraction (EBSD), digital image correlation (DIC), and focused ion beam (FIB) milling. These techniques enabled a comprehensive study of parameters affecting fatigue performance, including hydrogen content, surface roughness, oxides, and intermetallic phases. More specifically, we investigated the effect of melt quality, copper (Cu) content, oxide bifilms, surface quality, and porosity.The increased Cu concentration in heat-treated Al-Si alloys increased the amount of intermetallic phases, which affected the cracking behaviour. Furthermore, oxide bifilms were detected at crack-initiation sites, even in regions far away from the highly strained areas. Si- and Iron (Fe)-rich intermetallics were observed to have precipitated on these bifilms. Due to their very small size, these oxides are generally not detected by non-destructive inspections, but affect mechanical properties because they appear to open at relatively low tensile stresses. Finally, Al-Si alloy casting skins showed an interesting effect in terms of improving fatigue performance, highlighting the negative effect of surface polishing for such alloys.
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| 10. |
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| 11. |
- Bogdanoff, Toni, et al.
(författare)
-
The impact of HIP process and heat treatment on the mechanical behavior of an Al-Si-Mg alloy component
- 2023
-
Konferensbidrag (refereegranskat)abstract
- Castings generally contain pores and defects that can have a detrimental impact on mechanical properties. The hot isostatic pressing (HIP) process is usually applied to reduce internal porosities, which improves the mechanical properties because of the closed porosities. Therefore, this study investigates the effect of the HIP process on the mechanical properties of sand casting A356 aluminum alloys. This investigation was performed in collaboration with Unnaryd Modell, Quintus Technologies, and IAC Ankarsrum. Investigation of the complex interaction between the microstructural features on mechanical properties before and after the HIP process was examined using computed tomography scanning, in-situ cyclic testing, and scanning electron microscope. In the absence of large defects, the fatigue performance was improved. However, a significant variation in the result was found between the different conditions, whereas the coarser microstructure with larger porosities before the HIP process showed decreased ultimate tensile strength and elongation to failure. The samples tested under high cycle fatigue showed a reduced fatigue propagation zone in that the coarser microstructure. Moreover, large cleavage areas containing oxides in the fracture surfaces indicated that the HIP process closes all the porosities, but the oxide films are not creating a strong bonding. Furthermore, the samples tested under low cycle fatigue showed a difference in the crack propagation, whereas the coarser microstructure showed large cracks opened up away from the notch that assists the propagation leading to reduced fatigue life.
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| 12. |
- Bogdanoff, Toni, et al.
(författare)
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The impact of HIP process and heat treatment on the mechanical behaviour of an Al–Si–Mg alloy component
- 2024
-
Ingår i: International Journal of metalcasting. - : Springer. - 1939-5981 .- 2163-3193.
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the effect of hot isostatic pressing (HIPping) on the static and fatigue properties of sand-casting A356 aluminium alloys. HIPping is a method to improve the fatigue properties in aluminium cast material by reducing or eliminating the inner porosities. Investigation of the complex interaction between the microstructural features on mechanical properties before and after the HIPping process was examined using computed tomography and scanning electron microscopy (SEM). Castings generally contain pores and defects that have a detrimental impact on the fatigue properties. The HIPping process closes the porosities in all investigated samples with an increase in density. Without significant defects, the mechanical performance improved in the finer microstructure. However, a considerable variation in the results was found between the different conditions, whereas the coarser microstructure with larger porosities before HIPping showed remarkably reduced results. The high-cycle fatigue-tested samples showed reduced fatigue propagation zone in the coarser microstructure. Moreover, large cleavage areas containing bifilms in the fracture surfaces indicate that the healing process of porosities is inefficient. These porosities are closed but not healed, resulting in a detrimental effect on the static and dynamic properties.
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| 13. |
- Bogdanoff, Toni, et al.
(författare)
-
The influence of copper addition on crack initiation and propagation in an Al–Si–Mg alloy during cyclic testing
- 2020
-
Ingår i: Materialia. - : Elsevier. - 2589-1529. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of copper (Cu) addition up to 3.2 wt% on crack initiation and propagation in an Al–Si–Mg cast alloy was investigated using in-situ cyclic testing in the as-cast condition. A combination of digital image correlation, electron backscatter diffraction, and scanning electron microscopy was used to investigate crack initiation and propagation behaviour during in-situ cyclic testing. The results showed that Cu-rich intermetallic compounds with the addition of Cu up to 1.5 wt% do not affect the fatigue behaviour of these alloys, and that crack propagation in these cases is trans-granular and trans-dendritic. However, increasing the concentration of the Cu retained in the primary α-Al matrix in solid solution and Cu-containing precipitates delayed crack propagation during cyclic testing. The results showed that strain accumulation was highest at the grain boundaries; however, the crack preferred to propagate along or across primary α-Al dendrites due to the relatively lower mechanical strength of the matrix compared to the eutectic and intermetallic phases. Moreover, the addition of Cu of more than 3.0 wt% to Al-Si-Mg alloys changes the fatigue behaviour that a rapid failure occurs.
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| 14. |
- Bogdanoff, Toni
(författare)
-
The influence of microstructure on the crack initiation and propagation in Al-Si casting alloys
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For reducing the CO2 footprint in many industrial fields, the goal is to produce lighter components. The aluminium-silicon (Al-Si) cast alloys are promising candidates to fulfill these goals with a high weight-to-strength ratio, good corrosion properties, excellent castability, and recyclable material. However, the variations within these components need to be understood to produce high-performance components for critical applications. The main reason for the rejection in these applications is defects and microstructural features that reduce the mechanical properties. The addition of copper (Cu) is one way of increasing the mechanical properties in Al-Si alloys and is commonly used in the automotive industry. Casting defects harm the mechanical properties, and these defects can be reduced by improving the melt quality, the correct design of the component, and the gating system.The study aims to investigate the static mechanical properties and the crack initiation and propagation under cyclic loading in an Al-7Si-Mg cast alloy with state-of-the-art experiments. The main focuses were on the effect of the HIP process and the role of Cu addition. In-situ cyclic testing using a scanning electron microscope coupled with electron back-scattered diffraction, digital image correlation, focused ion beam (FIB) slicing, and computed tomography scanning was used to evaluate the complex interaction between the crack path and the microstructural features.The amount of Cu retained in the α-Al matrix in as-cast and heat-treated conditions significantly influenced the static mechanical properties by increasing yield strength and ultimate tensile strength with a decrease in elongation. The three-nearest-neighbor distance of eutectic Si and Cu-rich particles and crack tortuosity were new tools to describe the crack propagation in the alloys, showing that a reduced distance between the Cu-rich phases is detrimental for the mechanical properties. Three dimensional tomography using a FIB revealed that the alloy with 3.2 wt.% Cu had a significantly increased quantity of cracked Si particles and intermetallic phases ahead of the crack tip than the Cu-free alloy. The effect of Cu and HIP process in this work shows the complex interaction between the microstructural features and the mechanical properties, and this needs to be considered to produce high-performance components.
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| 15. |
- 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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| 16. |
- Ceschini, Lorella, et al.
(författare)
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Effect of Cu addition on overaging behaviour, room and high temperature tensile and fatigue properties of A357 alloy
- 2020
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Ingår i: Transactions of Nonferrous Metals Society of China. - : Elsevier. - 1003-6326 .- 2210-3384. ; 30:11, s. 2861-2878
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the present work are to evaluate the overaging behaviour of the investigated Cu-enriched alloy and to assess its mechanical behaviour, in terms of the tensile and fatigue strength, at room temperature and at 200 °C, and to correlate the mechanical performance with its microstructure, in particular with the secondary dendrite arm spacing (SDAS). The mechanical tests carried out on the overaged alloy at 200 °C indicate that the addition of about 1.3 wt.% Cu to the A357 alloy enables to maintain ultimate tensile strength and yield strength values close to 210 and 200 MPa, respectively, and fatigue strength at about 100 MPa. Compared to the quaternary (Al−Si−Cu−Mg) alloy C355, the A357−Cu alloy has greater mechanical properties at room temperature and comparable mechanical behaviour in the overaged condition at 200 °C. The microstructural analyses highlight that SDAS affects the mechanical behaviour of the peak-aged A357−Cu alloy at room temperature, while its influence is negligible on the tensile and fatigue properties of the overaged alloy at 200 °C.
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| 17. |
- Ceschini, Lorella, et al.
(författare)
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Effect of Fe content and microstructural features on the tensile and fatigue properties of the Al-Si10-Cu2 alloy
- 2012
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 36, s. 522-528
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Tidskriftsartikel (refereegranskat)abstract
- As the automotive industry has to meet the requirements of fuel efficiency and environmental concerns, the use of aluminium alloys is steadily increasing. A number of papers have been published about the correlation between microstructure and mechanical properties of the widely used A356/A357 aluminium alloys, while relatively few data are available on others hypoeutectic Al-Si alloys, such as Al-Si-Cu alloys with higher Si content. In this work the effect of different amounts of Fe and Mn on the tensile and fatigue behaviour of the AlSi10Cu2 casting alloy was studied. The reason of this study comes from the fact that cast components are mostly made by secondary Al alloys that inevitably contain Fe, which in turn forms intermetallic compounds, negatively affecting the mechanical behaviour of the alloy. Fatigue specimens were subjected to hot isostatic pressing (HIP) before tests, in order to eliminate the internal pores (gas pores and interdendritic shrinkages) and therefore to solely investigate the effect of microstructural features, rather than solidification defects, on the fatigue propagation stage. The microstructural characterization of the alloy was carried out by optical and scanning electron microscopy. Proof and ultimate tensile strength, as well as fatigue life of the investigated alloy were greatly enhanced by high Fe and Mn content, which reduced the micro-crack propagation rate; on the contrary Fe, without Mn, negatively affected the elongation to failure.
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| 18. |
- Ceschini, Lorella, et al.
(författare)
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High temperature tensile behaviour of the A354 aluminum alloy
- 2014
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Ingår i: Materials Science Forum. ; 794-796, s. 443-448
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Tidskriftsartikel (refereegranskat)abstract
- The high temperature tensile behaviour of the A354 casting aluminum alloy was investigated also evaluating the influence of secondary dendrite arm spacing (SDAS). Cast specimens were produced through a gradient solidification equipment, obtaining two different classes of SDAS, namely 20-25 µm (fine microstructure) and 40-50 µm (coarse microstructure). After hot isostatic pressing and T6 heat treatment, the samples underwent mechanical characterization both at room and high temperature (200 °C). Results of tensile tests and hardness measurements were related to the microstructural features and fractographic characterization, in order to investigate the effect of microstructure and high temperature exposure on the mechanical behaviour of the alloy.
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| 19. |
- Ceschini, Lorella, et al.
(författare)
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Influence of sludge particles on the fatigue behavior of Al-Si-Cu secondary aluminium casting alloys
- 2018
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- Al-Si-Cu alloys are the most widely used materials for high-pressure die casting processes. In such alloys, Fe content is generally high to avoid die soldering issues, but it is considered an impurity since it generates acicular intermetallics (β-Fe) which are detrimental to the mechanical behavior of the alloys. Mn and Cr may act as modifiers, leading to the formation of other Fe-bearing particles which are characterized by less harmful morphologies, and which tend to settle on the bottom of furnaces and crucibles (usually referred to as sludge). This work is aimed at evaluating the influence of sludge intermetallics on the fatigue behavior of A380 Al-Si-Cu alloy. Four alloys were produced by adding different Fe, Mn and Cr contents to A380 alloy; samples were remelted by directional solidification equipment to obtain a fixed secondary dendrite arm spacing (SDAS) value (~10 µm), then subjected to hot isostatic pressing (HIP). Rotating bending fatigue tests showed that, at room temperature, sludge particles play a detrimental role on fatigue behavior of T6 alloys, diminishing fatigue strength. At elevated temperatures (200◦C) and after overaging, the influence of sludge is less relevant, probably due to a softening of the α-Al matrix and a reduction of stress concentration related to Fe-bearing intermetallics.
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| 20. |
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| 21. |
- Ghassemali, Ehsan, 1983-, et al.
(författare)
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Hall-Petch Equation in a Hypoeutectic Al-Si Cast Alloy : Grain Size vs. Secondary Dendrite Arm Spacing
- 2017
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Ingår i: Procedia Engineering. - : Elsevier. ; , s. 19-24
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Konferensbidrag (refereegranskat)abstract
- The Al-Si cast alloy family is widely used in the production of complex castings for various applications and known for its very good castability and high strength-to-weight ratio. However, early cracking under tensile loading is sometimes a limiting factor. Among other parameters, it is yet controversial whether grain boundaries are dominant strengthening factor in cast alloys, instead of dendrite/eutectic boundaries. This study presents the effect of secondary dendrite arm spacing (SDAS) and grain size on crack initiation and propagation of Al-Si cast alloys under tensile loading. The Al-10Si (wt.%) alloy with modified Si morphology was cast using inoculants (Al-5Ti-B master alloy) under different cooling rates to obtain a range of grain sizes (from below 138 μm to above 300 μm) and SDAS (6, 15 and 35 μm). Conventional tensile test as well as in-situ tensile test in a scanning electron microscope, equipped with an electron backscatter diffraction (EBSD) was carried out to understand the deformation mechanisms of the alloy. Observation of slip bands within the dendrites showed that in modified Si structure, the interdendritic (eutectic) area takes more portion of the strain during plastic deformation. Besides, only a few cracks were initiated at the grain boundaries; they were mostly initiated from dendrite/eutectic interface. All cracks propagated trans-granularly. Hall-Petch calculations also showed a strong relationship between SDAS and flow stress of the cast alloy. Although statistically correct, there was no physically meaningful relationship between the grain size and the flow stress. Nevertheless, formation of identical slip bands in each grain could be an evidence for the marginal effect of the grain size on the overall strength development of the alloy. Consequently, among other effects, the combinational dominant effect of SDAS and modest effect of grain size shall be considered for modification of the Hall-Petch equation for precise prediction of mechanical properties of cast alloys.
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| 22. |
- Keller, Christina, 1961-, et al.
(författare)
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Teacher roles in a blended learning materials engineering master program : "It's not a new role, it's a new way!"
- 2017
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Konferensbidrag (refereegranskat)abstract
- Engineering education are characterized by laboratories, mathematical foundations and design tools. These pillars of engineering education do not seem to be ideal for online education as the field lags behind other fields in adopting online education. Laboratories are for instance hard to implement online due to the need of direct operation of instruments. Likewise, course materials requiring use of mathematics have traditionally not been as easy to implement as topics that require only text-based instructions (Bourne et al., 2005). Real laboratory sessions have also shown to be more motivated for engineering students than virtual simulations (Stefanovic, 2013). In spite of this, there are increasing evidence of use of blended and online learning in engineering education. For example, online self-study environment to supplement the classroom instruction in engineering courses in graphical communication (Sun et al., 2014), virtual laboratories and simulation environments (Balamuraithara & Woods, 2007; Bourne et al., 2005) and online platforms for developing learning networks for global engineering (Meikleham et al. 2015). The School of Engineering at Jönköping University, the Swedish foundry association, the research institute Swerea/SWECAST and twelve foundry industries cooperate to develop a blended learning one-year master program in product development in materials and manufacturing. As previously performed courses have been given on campus, teachers needed to take on new roles as blended learning teachers. In this paper, we present the initial results from a study that aims to investigate the perceived roles of university teachers in a blended learning materials engineering master program.
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| 23. |
- Olofsson, Jakob, 1980-, et al.
(författare)
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On the effects of defects and imperfections on tensile toughness of a secondary aluminium alloy
- 2019
-
Ingår i: SHAPE CASTING:7th International Symposium CelebratingProf. John Campbell’s 80th Birthday. - Cham : Springer International Publishing. - 9783030060336 - 9783030060343 ; , s. 131-141
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Konferensbidrag (refereegranskat)abstract
- In order to design and produce high-quality castings with reliable performance, the effect of the melt handling and melt quality during different processing stages needs to be understood and controlled, and numerical methods to provide correct input data to structural analyses of castings enabled. This paper aims to investigate tensile properties, in particular tensile toughness, of a secondary high-pressure die casting (HPDC) aluminium alloy with different levels of defects and imperfections. The melt, which was transported in liquid state from the smelter to the foundry, has been sampled after different holding times by casting into Y-blocks. Tensile testing was performed, and the levels of defects and imperfections were characterized using measurements of porosity, bifilm index, density index, sludge factor and the amount of iron-rich intermetallics. Two different quality indices have been evaluated, and a method to apply the results in simulations of damage in a casting, containing defects, subjected to load is demonstrated.
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| 24. |
- Riestra, Martin, 1985-
(författare)
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High performing cast aluminium-silicon alloys
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need to produce lighter components due to environmental aspects and the development of electrical vehicles represents an opportunity for cast aluminium-silicon alloys. With high specific strength, good castability, high corrosion resistance and recyclability, these alloys offer an attractive combination of properties as an alternative to steel, cast iron and titanium-based components in certain applications. To take advantage of such a combination of properties, there is a need to ensure that they can be reliably achieved. In other words, high performing components need to be produced. For that, the production cycle, from alloy selection and melt preparation, to the casting and heat treatment of the component must be understood and controlled as a whole. The different steps in the production cycle will affect the microstructure of the components and hence the resulting mechanical properties. Understanding the relation between the different steps in the production cycle, its consequences on the microstructural features and on the mechanical properties constitutes the aim of this thesis.Experiments applying state-of-the-art knowledge regarding effect of casting process, alloying system and post-process variables were performed aimed at achieving properties similar to those of high pressure die casting (HPDC) components. Different melt quality determination tools were evaluated on three different EN AC-46000 melt qualities. The influence of modification, grain refinement and both treatments together was assessed on an Al-10Si alloy solidified under different cooling rates. The tensile behaviour and the impact of features such as secondary dendrite arm spacing (SDAS) or grain sizes was quantified.It was corroborated that by appropriate selection and control of such alloying system, process and post-process variables it is possible to achieve HPDC EN AC-46000 tensile and fatigue properties through a T5 treated sand cast EN AC-42100 alloy. On the other hand, the available techniques for melt quality assessment are inadequate, requiring further analysis to successfully identify the melt quality. Additionally, it was observed that decreasing the melt quality by additions of 25 wt.% of machining chips did not significantly decrease the tensile properties but slightly increased the variation in them. In relation to the modification and grain refinement of Al-10Si alloys it was concluded that with the slowest cooling rate tested, additions of only grain refiner did not successfully produce equiaxed grains. For cooling rates corresponding to dendrite arm spacings of 15 μm and slower, combined additions of grain refiner and modifier can lead to higher tensile properties compared to the corresponding separate additions. SDAS was observed to describe flow stress through the Hall-Petch equation but grain size did not show a physically meaningful relationship. Furthermore, beginning of cracking was detected in the plastic deformation region at dendrite/eutectic boundaries and propagated in a trans-granular fashion.
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| 25. |
- Seifeddine, Salem, 1978-
(författare)
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Characteristics of cast aluminium-silicon alloys : microstructures and mechanical properties
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Applications of aluminium alloys are spreading in many industrial fields due to the excellent combination of castability, mechanical performance and lightness assured by such material. This project aims to establish a methodology in bringing the foundry process closer to the casting designer, and thereby leading to a more reliable and more optimised design. Improvement in the degree of integration between processing, metallurgical and mechanical properties of cast aluminium alloys will lead to a shorter lead-time from the very first design attempt, and sounder components, both of which strengthen the competitiveness of the material and the foundry industry.The microstructural features and mechanical properties of cast aluminium alloys are sensitive to composition, melt treatment, the casting process and formation of defects during mould filling, solidification and post-solidification treatment. The microstructural characteristics and the mechanical properties of A1-Si based alloys have been investigated by studies on various different commercial cast components and through systematically designed casting experiments with alloys containing various Si, Mg, Cu, Fe and Mn concentrations solidified under a wide range of cooling conditions. In this work, a gradient solidification thechnique has been employed, providing samples with a low content of oxide films and few porosity defects and with a well-fed and homogenous microstructure. In such samples the alloy's mechanical properties are determined by the microstructure constituents and not by any defects. The influence of the casting process on the microstructural formations and tensile properties has been thoroughly elucidated. Furthermore, relationships between microstructure characteristics and mechanical properties are assessed and discussed. The results indicate that Mg and Cu, due to the formation of A12Cu and Mg2Si have a significant role on the alloy strength, especially after thermal treatment. Significant advances have been mead in understanding the relationship between Fe and Mn levels and their contribution to the tensile strength. While Fe and its compounds, particularly the A15FeSi-needles, adversely influence the ultimate tensile strength and ductility, Mn has been found to not fully neutralize the deleterious character of iron, and especially the influence it has on ductility.Algorithms to predict the micorstructural parameters such as porosity, grain size, the volume fraction of different phases, especially A12Cu and Mg2Si, and their influence on the tensile strength, have been developed. The relationships developed between process, microstructure and mechanical properties have been implemented in commercial simulation software.
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| 26. |
- Seifeddine, Salem, 1978-, et al.
(författare)
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Design Education : Now and in the Future!
- 2011
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Konferensbidrag (refereegranskat)abstract
- In Sweden, the design field both within the area of product design as well as in service design has been expanding. In this context, the skills and basic knowledge have to be developed and shared with the surrounding society. It has resulted in developing and establishing a new Master program in the area of Industrial Design at the School of Engineering in Jönköping, Sweden. The aim is to educate industrial designers who understand the demands and design needs of the industry, focusing on the SME-companies, and have good knowledge and competences in the fields of materials, construction, production and market. The paper aims to highlight some ideas about the future classrooms and also how collaborations with the surrounding industries could improve the education. The questions that the paper aims to address are what knowledge should a future designer assess in terms of conventional as well as new materials and processes, environmental and sustainability aspects and the kind of society they live and act within etc. It is where the Cambridge Engineering Selector and its benefits enters the scene.
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| 27. |
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| 28. |
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| 29. |
- Seifeddine, Salem, 1978-, et al.
(författare)
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On the role of copper and cooling rates on the microstructure, defect formations and mechanical properties of Al-Si-Mg alloys
- 2013
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Ingår i: Materials Sciences and Applications. - : Scientific Research Publishing. - 2153-117X .- 2153-1188. ; 4:3, s. 171-178
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to assess the role of Cu on Al-Si-Mg alloys, in a range of 0 - 5 wt%, qualitatively on microstructure, defect formation, in terms of porosity, and strength in the as-cast conditions. The ternary system of Al-Si-Mg, using the A356 alloy as a base material, were cast using the gradient solidification technique; applying three different solidification rates to produce directional solidified samples with a variety of microstructure coarsenesses. Microstructural observations reveal that as the Cu levels in the alloys are increased, the amounts of intermetallic compounds as well as the Cu concentration in the α-Al matrix are increased. Furthermore, the level of porosity is unaffected and the tensile strength is improved at the expense of ductility.
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| 30. |
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| 31. |
- Seifeddine, Salem, 1978-, et al.
(författare)
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Prediction of mechanical properties of cast aluminium components at various iron contents
- 2010
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 31:Supplement 1, s. S6-S12
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Tidskriftsartikel (refereegranskat)abstract
- The simulation of microstructure and mechanical properties is of great importance as a lead in bringing the foundry process and cast materials closer to the casting designer. Prediction of the formation of the microstructure during solidification is a supporting factor for strength optimization of cast aluminium components that allows an improved performance and increased competitiveness of cast engineering components.The deformation behaviour and the integrity of cast components depends mostly on the chemical composition of the material, especially the iron content, solidification behaviour and the resulting microstructural characteristics. This paper aims to demonstrate the capabilities of microstructure and mechanical properties modelling of aluminium cast materials and components. The validation of the models includes investigation of cast cylinder head and measured microstructure and mechanical properties as well as their distributions. The effect of iron-rich compound’s morphology and fraction on the plastic deformation behaviour has been studied and modelled in terms of strain hardening exponent and strength coefficient. This approach enables the prediction of local microstructure and mechanical properties. The developed models have been implemented in a cast simulation software for simulation of the cast cylinder head.The model predictions of microstructural quantities and mechanical properties are in good agreement with experimental measurements.
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| 32. |
- Seifeddine, Salem, 1978-, et al.
(författare)
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The influence of cooling rate and manganese content on the beta-Al5FeSi phase formation and formation and mechanical properties of Al-Si based alloys
- 2008
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 490:39845, s. 385-390
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the influence of manganese level and cooling rate on the formation of iron compounds and mechanical properties of Al–9%Si alloys containing 0.3%Fe. It has been established that high cooling rates and Mn additions are not able to totally nullify the formation of β-Al5FeSi-needles onto α-Al15(Fe,Mn)3Si2-Chinese scripts even at Mn:Fe ratio of 2:1, but produces improvement in tensile strength unlike the ductility which suffers a loss with the increment of Mn concentrations.
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| 33. |
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| 34. |
- Sjölander, Emma, et al.
(författare)
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Influence of Quench Rate on the Artificial Ageing Response of an Al-8Si-0.4Mg Cast Alloy
- 2015
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 828-829, s. 219-225
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study is to present the influence of quench rate on the artificial ageing response of Al-8%Si-0.4%Mg cast alloy in terms of Brinell hardness and yield strength. The investigated material was produced by a gradient solidification technique and exhibited a microstructure that corresponds to the one of gravity die castings, with a dendrite arm spacing of approximately 25 μm. The study comprises two solution treatment temperatures, five quench rates and artificial ageingtimes exceeding 100 hours at 170 and 220 ⁰C. The microstructure and concentration profiles of Mgand Si were evaluated using energy and wavelength dispersive spectroscopy. Microstructural examination reveals an increment of solutes in the Al-matrix when higher solution treatment temperatures accompanied with high quench rates are applied and shows how both Si and Mgatoms have diffused towards the eutectic during quenching. Consequently, i.e. by increasing the levels of solutes and vacancies, the highest strength levels were realized. The study confirmed that quench rates above 2 ⁰C /s do not offer substantial strength improvement while quenching at lower rates resulted in a lower peak hardness and longer times to peak.
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| 35. |
- Sjölander, Emma, 1981-, et al.
(författare)
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Optimisation of solution treatment of cast Al–Si–Cu alloys
- 2010
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 31:suppl. 1, s. 44-49
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Tidskriftsartikel (refereegranskat)abstract
- The influence of solidification rate on the solution treatment response for an Al–8Si–3.1Cu alloy has been investigated. The alloy was cast using the gradient solidification technique to produce samples with three different solidification rates. The samples were solution treated at 495 C for various times between 10 min and 10 h. The concentration of copper in the matrix was measured using the wavelength dispersive spectroscopy technique, WDS. The results show that the coarseness of the microstructure clearly affects the solution treatment time needed to dissolve particles and obtain a homogenous distribution of copper in the matrix. A short solution treatment time of 10 min is enough to achieve a high and homogenous copper concentration for a material with a fine microstructure (secondary dendrite arm spacing, SDAS of 10 μm), while more than 10 h is needed for a coarse microstructure (SDAS of 50 μm). A model was developed to describe the dissolution and homogenisation process. The model shows good agreement with the experimental results.
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| 36. |
- Sjölander, Emma, 1981-, et al.
(författare)
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The heat treatment of Al–Si–Cu–Mg casting alloys
- 2010
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Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 210:10, s. 1249-1259
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Tidskriftsartikel (refereegranskat)abstract
- Heat treatment of gravity cast aluminium components normally involve a solution heat treatment followed by quenching and subsequent ageing, either naturally or artificially. The mechanical properties of aluminium castings containing Cu and Mg are clearly improved by heat treatment but there are still some uncertainties and contradictions about the phase dissolution, formation of precipitates and the influence of natural and artificial ageing parameters such as time and temperature, on the peak strength of these materials. The present paper reviews over 60 papers in attempt to clarify and map out the influence of each and every sequence that is involved in the heat treatment process on the evolution and kind of precipitates, which in turn determines the mechanical properties of cast aluminium components.
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| 37. |
- Svanängen, Patrik, et al.
(författare)
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Life long educaion of foundry employees - A step forward
- 2018
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Ingår i: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings. - : Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association. - 9788390430638 ; , s. 637-637
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Konferensbidrag (refereegranskat)
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| 38. |
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| 39. |
- Tan, He, et al.
(författare)
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A design of fuzzy inference systems to predict tensile properties of as-cast alloy
- 2021
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer. - 0268-3768 .- 1433-3015. ; 113:3-4, s. 1111-1123
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a design of Mamdani type fuzzy inference systems is presented to predict tensile properties of as-cast alloy. To improve manufacturing of light weight cast components, understanding of mechanical properties of cast components under load is important. The ability of deterministic models to predict the performance of a cast component is limited due to the uncertainty and imprecision in casting data. Mamdani type fuzzy inference systems are introduced as a promising solution. Compared to other artificial intelligence approaches, Mandani type fuzzy models allow for a better result interpretation. The fuzzy inference systems were designed from data and experts’ knowledge and optimized using a genetic algorithm. The experts’ knowledge was used to set up the values for the inference engine and initial values for the database parameters. The rule base was automatically generated from the data which were collected from casting and tensile testing experiments. A genetic algorithm with real-valued coding was used to optimize the database parameters. The quality of the constructed systems was evaluated by comparing predicted and actual tensile properties, including yield strength, Y.modulus, and ultimate tensile strength, of as-case alloy from two series of casting and tensile testing experimental data. The obtained results showed that the quality of the systems has satisfactory accuracy and is similar to or better than several machine learning methods. The evaluation results also demonstrated good reliability and stability of the approach.
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| 40. |
- Tan, He, et al.
(författare)
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Fuzzy Logic Based Modelling of Cast Component Properties
- 2019
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Ingår i: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 52:13, s. 1132-1137
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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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| 41. |
- Tarasov, Vladimir, 1966-, et al.
(författare)
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Fuzzy logic-based modelling of yield strength of as-cast A356 alloy
- 2020
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Ingår i: Neural Computing & Applications. - : Springer. - 0941-0643 .- 1433-3058. ; 32:10, s. 5833-5844
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Tidskriftsartikel (refereegranskat)abstract
- Uncertain and imprecise data are inherent to many domains, e.g. casting lightweight components. Fuzzy logic offers a way to handle such data, which makes it possible to create predictive models even with small and imprecise data sets. Modelling of cast components under fatigue load leads to understanding of material behaviour on component level. Such understanding is important for the design for minimum warranty risk and maximum weight reduction of lightweight cast components. This paper contributes with a fuzzy logic-based approach to model fatigue-related mechanical properties of as-cast components, which has not been fully addressed by the current research. Two fuzzy logic models are constructed to map yield strength to the chemical composition and the rate of solidification of castings for two A356 alloys. Artificial neural networks are created for the same data sets and then compared to the fuzzy logic approach. The comparison shows that although the neural networks yield similar prediction accuracy, they are less suitable for the domain because they are opaque models. The prediction errors exhibited by the fuzzy logic models are 3.53% for the model and 3.19% for the second, which is the same error level as reported in related work. An examination of prediction errors indicated that these are affected by parameters of the membership functions of the fuzzy logic model.
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| 42. |
- Wójcik, Natalia A., et al.
(författare)
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Influence of synthesis conditions on glass formation, structure and thermal properties in the Na2O-CaO-P2O5 system doped with Si3N4 and Mg
- 2018
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier. - 0022-3093 .- 1873-4812. ; 494, s. 66-77
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Tidskriftsartikel (refereegranskat)abstract
- Oxynitride phosphate glasses and glass-ceramics were prepared using new synthesis routes for phosphate glasses. Materials were melted from pre-prepared glass samples in the system Na-Ca-P-0 with addition of Mg and/or Si3N4 powders under different preparation conditions. The melting process was conducted at 1000-1500 degrees C either under air or nitrogen atmosphere to obtain materials with different nitrogen content. Their topography and structure were characterized by Confocal Microscopy, Scanning Electron Microscopy, X-ray powder diffraction and Raman and infrared spectroscopy techniques, while their chemical compositions were examined by Energy Dispersive X-ray spectroscopy (EDS). All materials prepared under nitrogen atmosphere were found to contain a relative low quantity of nitrogen and high amount of Nb leached from the crucible. The reaction with the Nb crucible was not previously observed for silicon-based oxynitride glasses. The synthesized materials form two groups: glasses and glass-ceramics. The first ones, were prepared under air and nitrogen atmospheres at temperatures up to 1400 degrees C, and were found to be amorphous and homogeneous. Raman and infrared spectroscopy measurements confirm the presence of amorphous phosphates in the synthesized materials. The samples of the second group were prepared at temperatures above 1400 degrees C and were found to be translucent and partially crystallized. They contain nanocrystallites of calcium and sodium phosphates including hydroxyapatite (HAp). The thermal properties of samples were studied by Differential Scanning Calorimetry (DSC). The obtained glass transition temperatures range from about 360 degrees C to 640 degrees C and exhibit high values for glass-ceramic materials. Stability is improved in the studied glass-ceramics because of the increased degree of network polymerization of the remaining glassy matrix. The approximate fragility index decreases two times for oxynitride materials compared to the primary glass. The synthesized new materials may be competitive to well-known bioactive phosphate glasses thanks to their improved stability by Mg, Si, N and Nb doping.
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| 43. |
- Zamani, Mohammadreza, 1985-, et al.
(författare)
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Optimisation of heat treatment of Al–Cu–(Mg–Ag) cast alloys
- 2020
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Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer. - 1388-6150 .- 1588-2926. ; 139, s. 3427-3440
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Tidskriftsartikel (refereegranskat)abstract
- The optimisation of heat treatment parameters for Al–Cu–(Mg–Ag) cast alloys (2xxx) having different microstructural scales was investigated. Thermo-Calc software was used to design optimal alloy compositions. Differential scanning calorimetry (DSC), scanning electron microscopy and wavelength-dispersive spectroscopy technique were employed to determine proper solution heat treatment temperature and homogenisation time as well as incidence of incipient melting. Proper artificial ageing temperature for each alloy was identified using DSC analysis and hardness measurement. Microstructural scale had a pronounced influence on time and temperature required for complete dissolution of Al2Cu and homogenisation of Cu solute atoms in the α-Al matrix. Refined microstructure required only one-step solution treatment and relatively short solution treatment of 10 h to achieve dissolution and homogenisation, while coarser microstructures desired longer time. Addition of Mg to Al–Cu alloys promoted the formation of phases having a rather low melting temperature which demands multi-step solution treatment. Presence of Ag decreases the melting temperature of intermetallics (beside Al2Cu) and improvement in age-hardening response. Peak-aged temperature is primarily affected by the chemical composition rather than the microstructural scale.
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| 44. |
- Zamani, Mohammadreza, 1985-, et al.
(författare)
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Study on dissolution of Al2Cu in al-4.3cu and a205 cast alloys
- 2020
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- Evolution of microstructure in a binary Al-Cu system (Al-4.3Cu) and a commercially alloyed Al-Cu system (A205) during solution heat treatment was investigated using optical microscopy (OM), scanning electron microscopy (SEM), wavelength-dispersive X-ray spectroscopy (WDS), and differential scanning calorimetry (DSC). The diversified coarseness of the microstructure was initiated by controlling the solidification rate. Different solution treatment temperatures were applied to identify a proper solutioning temperature. The larger microstructural scale required an increased solutioning temperature and prolonged holding time to obtain homogenized solutes in the α-Al matrix. The diffusion of Cu primarily controlled the solution heat treatment process. A diffusion-based model was applied and calibrated to determine the dissolution rate of an Al2Cu particle in the matrix. The model operates on a similar time scale with the experimental results for the Al-4.3Cu and A205 alloys with various microstructural scales, different chemical compositions, and at different solution treatment temperatures. Three-dimensional (3D) reconstructed images from SEM images and energy dispersive spectroscopy (EDS) map of elements showed that TiB2 particles shield the Cu-rich phases in the boundaries of α-Al grains, presumably acting as a physical barrier to the diffusion of Cu solutes toward α-Al grains. The model also suggests that the effective diffusion coefficient of Cu in Al, in the presence of TiB2 particles, reduced by a factor of 2.0–2.5 in the A205 alloy compared with the binary Al-Cu alloy. © 2020 by the authors.
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| 45. |
- Zhu, Bai, et al.
(författare)
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A study of anodising behaviour of al-si components produced by rheocasting
- 2019
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Ingår i: Solid State Phenomena. - : Trans Tech Publications. - 1012-0394 .- 1662-9779. - 9783035713732 ; 285, s. 39-44
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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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