Initial softening in some Aluminium base precipitation hardening Alloys

IT has been reported by previous workers1'2 that some
extent of softening is observed before setting in of
the usual hardening process when ageing is carried
out on the Al-Cu and Al-Mg precipitation hardening
alloys. The possible reason for the initial softening
has been suggested as relief of thermal strain. No experimental evidence in support of this postulate has
been reported so far.