Initial Softening in Some Aluminium Base Precipitation Hardening Alloys

Abstract

It has been reported by previous workers that some extent of softening is observed before setting in of the usual hardening process when ageing is carried out on the AI-Cu- and AI-Mg precipitation hardening alloys. The possible reason for the initial softening has been sugg-ested as relief of thermal strain. Present work was undertaken to make systematic study of initial softening in certain Al-Cu and Al-Mg alloys. The phenomenon. of initial softening was studied as a funct-ion of solute concentration, quenching medium, and temperature of ageing. Hardness measurements were carried out to follow the process of softening and relief of thermal strain was studied by analysing X-ray line profile.