Effect of Fe and Si on Age Hardening Properties of Supersaturated Solid Solutions of Al-Zr Alloy by Rapid Solidification

Abstract

It has been well known that the supersaturated solid solutions of Al-Zr alloys produced by rapid solidification shows remarkable age hardening, so the effect of Fe and Si as common impurities in Al on age hardening and mechanical properties of these alloys were investigated by means of microscopic observation, the resistmetric method and microhardness and tensile tests.The maximum solubility of Zr in solid Al was extended by rapid solidification to about 1∼1.2 wt%Zr which is equivalent to about four times as the equilibrium maximum solubility, and was scarecely affected by a small quantity of Fe and Si involved. The concentration of Zr which allowed the alloys to harden appreciably during aging could be lowered by the addition of these impurities and subsequently the mechanical properties were improved. It might be shown that the precipitation temperature of Zr from the solid solutions was lowered about 300°C to 250°C, especially by the addition of Si and the precipitation rate of Zr was accelerated by a small quantity of these impurities to promote the age hardening of the alloys.