Effect of Cold Rolling on Precipitates Evolution in Al-5.5Zn-2.0Mg-2.4Cu Alloy

Abstract

In this work, the evolution and sequence of precipitates in a pre-deformed Al-Zn-Mg-Cu alloy during ageing were investigated by means of differential scanning calorimetry (DSC) measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that cold rolling alters the precipitation sequence due to the large density of deformation induced dislocations which were introduced during cold rolling, resulting in annihilation of excess vacancies and suppression of the formation of GP-zones. Also, large density of dislocations by cold rolling acts as heterogeneous nucleation sites for precipitates and then accelerated the formation of η precipitates making non-uniformly distributed size of precipitates either in matrix and grain boundary which strongly affects fracture surfaces.