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Metallurgical and Materials Transactions B-Process Metallurgy and Materials Processing Science


The effects of artificial aging time on the mechanical properties of Al-Si-Mg cast alloys were investigated as a function of Si content and morphology. Five alloys with Si ranging from 1 to 13 pct, unmodified and Sr-modified, were tested systematically in as-cast, T4, and T61 conditions with different aging times. The results indicated that the ultimate tensile strength (UTS) and the yield strength (YS) increased with increasing aging time, and that the YS increased more than the UTS. The increase was low during the first 2 hours, significantly increased after 2 hours, and slowed down at similar to 10 hours; after 10 hours of aging, both UTS and YS remained nearly constant. The elongation decreased with increasing aging time. The decrease was observed from similar to 2 hours to similar to 14 hours, and no significant change was observed after similar to 14 hours. In T61 conditions with different aging times, UTS increased up to 24 pct, whereas YS increased up to 88 pct. The Si level had significant effects on UTS, YS, and elongation. For all aging conditions, alloys with a higher Si level had higher UTS and YS. Si content increased alloys' response to aging. Si modification also increased YS. The changes in mechanical properties were correlated to the fundamentals of the formation and evolution of Mg2Si phase from forming clusters of Si atoms, GP zones, rod-like β' precipitates, and equilibrium Mg2Si platelets.





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Copyright 2011, ASM International. This paper was published in Metallurgical and Materials Transactions B-Process Metallurgy and Materials Processing Science Vol. 42 Iss. 1 pp. 181-188 and is made available as an electronic reprint with the permission of, ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited.