AN EVALUATION OF THE CREEP-PROPERTIES OF 2 AL-SI ALLOYS PRODUCED BY RAPID SOLIDIFICATION PROCESSING

Tensile creep tests were conducted on two Al-Si alloys produced by rap id solidification: an Al-Si-Ni-Cr alloy and an Al-Si-Cu-Fe alloy, desi gnated alloys A and B, respectively. The creep curves of these two all oys in the temperature range from 493 to 573 K were markedly different , with alloy A exhibiting a normal creep curve with a very short terti ary region and alloy B exhibiting an extended tertiary stage associate d with strain localization. The minimum creep rates varied, with the a pplied stress raised to exponents of similar to 9.0 and similar to 8.5 for the two alloys, respectively. The hardness of alloy B decreased w ith time during:the creep testing, but there was little or no change i n the hardness of alloy A. These differences in the creep and hardness characteristics are attributed to the evolution of precipitates withi n the two alloys during creep testing. A detailed analysis shows that, over the temperature range examined experimentally, alloy A exhibits a creep strength that is superior to conventional Al-based alloys and comparable to, or even higher than, some SiC-reinforced Al composites.