| 1. |
- Zamani, Mohammadreza, et al.
(författare)
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High Temperature Tensile Deformation Behaviour and Failure Process of an Al-Si-Cu-Mg Cast Alloy : The Microstructural Scale Effect
- 2015
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 86, s. 361-370
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Tidskriftsartikel (refereegranskat)abstract
- In this study the high temperature tensile deformation behavior of a commercial Al–Si–Cu–Mg cast alloy was investigated. The alloy was cast with two different cooling rates which resulted in average secondary dendrite arm spacing of 10 and 25 μm, which is typical of the microstructure scale obtained from high pressure die casting and gravity die casting. Tensile tests were performed at different strain rates (10− 4 s− 1 to 10− 1 s− 1) and over a wide temperature range from ambient temperature to 500 °C. The fine microstructure had superior tensile strength and ductility compared to the coarse microstructure at any given temperature. The coarse microstructure showed brittle fracture up to 300 °C; the fracture mode in the fine microstructure was fully ductile above 200 °C. The fraction of damaged particles was increased by raising the temperature and/or by microstructure coarsening. Cracks arising from damaged particles in the coarse microstructure were linked in a transgranular-dominated fashion even at 500 °C. However, in the fine microstructure alloy the inter-dendritic fracture path was more prevalent. When the temperature was raised to 300 °C, the concentration of alloying elements in the dendrites changed. The dissolution rates of Cu- and Mg-bearing phases were higher in the fine microstructure.
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| 2. |
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| 3. |
- Awe, Samuel A., et al.
(författare)
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Development of new Al-Cu-Si alloys for high temperature performance
- 2017
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Ingår i: Advanced Materials Letters. - : VBRI Press. - 0976-3961 .- 0976-397X. ; 8:6, s. 695-701
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Tidskriftsartikel (refereegranskat)abstract
- In a quest to develop new light metal alloys that can perform excellently at elevated-temperatures (from 300°C to 400°C), a ternary eutectic Al-Cu-Si alloy was exploited to gain a deeper understanding of the alloy system and its suitability for high temperature applications. The alloys studied, with chemical composition of Al-27%Cu-5%Si (by weight percent) with Ni addition in the range of 0 to 1.5%wt, were cast in a rapid solidification casting technique. The solidification characteristics of the alloy was studied using the Thermo-Calc software. Microstructures were characterized in a scanning electron microscope coupled with energy dispersive spectrometry (SEM-EDS). Finally, the elevated-temperatures tensile properties of the alloys were investigated. Comparing the microstructures and mechanical properties of these Al-Cu-Si(-Ni) alloys with conventional Al-Si alloy A319, the refined microstructure with dispersed Ni intermetallic particles formed in the as-cast Al-Cu-Si(-Ni) alloys deliver improved elevated temperature properties. In particular, the yield strength and ultimate tensile strength of the new alloy with 1.5% Ni at 400?C were observed to be 220% and 309% higher, respectively, than for conventional A319 alloy.
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| 4. |
- Ceschini, Lorella, et al.
(författare)
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Effect of Microstructure and Overaging on the Tensile Behavior at Room and Elevated Temperature of C355-T6 Cast Aluminum Alloy
- 2015
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 83, s. 626-634
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Tidskriftsartikel (refereegranskat)abstract
- The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature.
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| 5. |
- 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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| 6. |
- Ceschini, Lorella, et al.
(författare)
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Microstructural and Mechanical Properties Characterization of Heat Treated and Overaged Cast A354 Alloy with Various SDAS at Room and Elevated Temperature
- 2015
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Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 648, s. 340-349
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to carry out a microstructural and mechanical characterization of the A354 (Al–Si–Cu–Mg) cast aluminum alloy. The effect of microstructure on the tensile behavior was evaluated by testing samples with different Secondary Dendrite Arm Spacing, (SDAS) values (20–25 μm and 50–70 μm for fine and coarse microstructure, respectively), which were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated both at room and elevated temperature (200 °C), in the heat treated and overaged (exposure at 210 °C for 41 h, after heat treatment) conditions. Optical, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) were used for microstructural investigations.Experimental data confirmed the significant role of microstructural coarseness on the tensile behavior of A354 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Moreover, solidification rate influenced other microstructural features, such as the eutectic silicon morphology as well as the size of the intermetallic phases, which in turn also influenced elongation to failure. Coarsening of the strengthening precipitates was induced by overaging, as observed by STEM analyses, thus leading to a strong reduction of the tensile strength of the alloy, regardless of SDAS. Tensile properties of the alloy sensibly decrease at elevated temperature (200 °C) in all the investigated heat treatment conditions.
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| 7. |
- Dugic, Izudin, 1962-, et al.
(författare)
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On the Effects of Alloying Element Range on the Mechanical Properties of Recycled Aluminium Alloy EN AB-46000
- 2016
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Ingår i: Light Metals 2016. - Hoboken, NJ, USA : John Wiley & Sons. - 9781119225799 - 9781119274780 ; , s. 115-120
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Konferensbidrag (refereegranskat)abstract
- Aluminium can be produced from the raw material bauxite or by recycling aluminium scrap. When aluminium is being recycled, the material strength is then depending on the alloying and trace elements in the aluminium scrap. This paper aims to investigate the sole effect of the alloying element range of Si, Cu, Mg, Mn and Fe on the mechanical properties of the recycled aluminium alloy EN AB-46000 by producing directional solidified samples with low defect levels.
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| 8. |
- Ferraro, Stefano, et al.
(författare)
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On the formation of sludge intermetallic particles in secondary aluminum alloys
- 2015
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 46:8, s. 3713-3722
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Tidskriftsartikel (refereegranskat)abstract
- The primary precipitation of Fe-rich intermetallics in AlSi9Cu3(Fe) type alloys is studied for different Fe, Mn, and Cr contents and cooling rates. Differential scanning calorimetry, thermal analysis, and interrupted solidification with a rapid quenching technique were used in combination in order to assess the nucleation temperature of sludge particles, as well as to follow their evolution. The results revealed that the sludge nucleation temperature and the release of latent heat during sludge formation are functions of Fe, Mn, and Cr levels in the molten alloy (i.e., the sludge factor, SF) and cooling rate. Moreover, it can be concluded that sensitivity to sludge formation is not affected by cooling rate; i.e., a decrease in the SF will reduce sludge nucleation temperature to the same extent for a higher cooling rate as for a lower cooling rate. The sludge formation temperature detected will assist foundries in setting the optimal molten metal temperature for preventing sludge formation in holding furnaces and plunger systems.
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| 9. |
- Seifeddine, Salem, et al.
(författare)
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Heat treating of High Pressure Die Cast Components; challenges and possibilities
- 2014
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Ingår i: Light Metals 2014. - Cham : Springer. ; , s. 183-188, s. 183-188
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Konferensbidrag (refereegranskat)abstract
- Improving the mechanical properties of high pressure die-cast (HPDC) components through T6 heat treatment is still a challenge due to surface blistering. In the current study, theoretical formulation of porosity growth in cast aluminum, EN AC 43100, has been developed along with differential scanning calorimetry and wave dispersive spectrometry to determine temperature ranges of phase transformations and Al-matrix enrichment of solutes. Optimal combinations of time and temperature for maximum possible Mg dissolution in the Al-matrix without blistering as well as tensile testing on samples extracted from HPDC components and samples from the gradient solidification technique that offers samples with low porosity levels have been performed. The results demonstrate that even if the Mg level in the Al-matrix increases and no blisters on component surface are apparent, the strength outcome is limited and can be degraded. Consequently no guarantees are granted that with a seemingly well performed T6 treatment, strength improvement will be realized.
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| 10. |
- Sjölander, Emma, 1981-
(författare)
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Heat treatment of Al-Si-Cu-Mg casting alloys
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Environmental savings can be made by increasing the use of aluminium alloys in the automotive industry as the vehicles can be made lighter. Increasing the knowledge about the heat treatment process is one task in the direction towards this goal. The aim of this work is to investigate and model the heat treatment process for Al-Si casting alloys. Three alloys containing Mg and/or Cu were cast using the gradient solidification technique to achieve three different coarsenesses of the microstructure and a low amount of defects. Solution treatment was studied by measuring the concentration of Mg, Cu and Si in the α-Al matrix using wavelength dispersive spectroscopy (WDS) after various times at a solution treatment temperature. A diffusion based model was developed which estimates the time needed to obtain a high and homogenous concentration of alloying elements for different alloys, temperatures and coarsenesses of the microstructure. It was shown that the yield strength after artificial ageing is weakly dependent on the coarseness of the microstructure when the solution treatment time is adjusted to achieve complete dissolution and homogenisation. The shape and position of ageing curves (yield strength versus ageing time) was investigated empirically in this work and by studying the literature in order to differentiate the mechanisms involved. A diffusion based model for prediction of the yield strength after different ageing times was developed for Al-Si-Mg alloys. The model was validated using data available in the literature. For Al-Si-Cu-Mg alloys further studies regarding the mechanisms involved need to be performed. Changes in the microstructure during a heat treatment process influence the plastic deformation behaviour. The Hollomon equation describes the plastic deformation of alloys containing shearable precipitates well, while the Ludwigson equation is needed when a supersaturated solid solution is present. When non-coherent precipitates are present, none of the equations describe the plastic deformation well. The evolution of the storage rate and recovery rate of dislocations was studied and coupled to the evolution of the microstructure using the Kocks-Mecking strain hardening theory.
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