Variation of proprties of Al-Mg2Si alloys on aging and reversion

Abstract

This paper studied aging processes of Al-1.1-1.6%Mg2Si alloys by hardness and electrical resistivity measurements and on electron microscopy. After solution treatment at 580°C, specimens were quenched into water at 1±0.2°C and aged at 20-90°C. Reversion treatment was performed at 285, 320 and 380°C, as determined by preliminary experiments. The results obtained are as follows:(1) Both hardness and resistivity increased on aging.(2) Hardness increase, attained by aging, was recovered nearly completely by reversion when reversion time was within a certain period. This period depended on aging and reversion temperatures. Resistivity increase due to aging was recovered completely by reversion at 285, 320 and 380°C, whatever the aging stage was. Thus, the time required for complete reversion was determined by the resistivity and the hardness on re-aging at the initial aging temperature. At 380°C, the complete reversion time determined by the resistivity measurement agreed with that determined by the hardness measurement. However, on 285°C and 320°C reversion treatment, there was a difference between the reversion time determined by hardness measurement and that by resistivity measurement.(3) When aging was arrested in the early stage at the initial aging and reversion was performed at 285°C, hardening at re-aging progressed very slowly.