Effect of alloy temper on surface modification of aluminium 2624 by laser shock peening

Abstract

We have investigated the hardening response, residual stress generation and microstructural changes in aluminium alloy 2624 owing to laser shock peening. The alloy was studied in two heat treatment conditions, T351 and T39, that have 20% difference in yield strength: hence the effects of laser power density and multiple peen impacts on materials with nominally identical physical properties but with different hardening responses has been studied. Hardness was characterised by nanoindentation, and residual stresses were measured by incremental hole drilling.The magnitude and the depth of the peak compressive residual stresses increase with increasing power densities as well as the number of laser impacts, before reaching a saturation point above which loss of surface compression occurs. Maximum compressive residual stresses were around −350 MPa, and maximum hardness increase was around 22%. The treatment has a noticeable effect in changing the microstructures of the T351 temper while the T39 remained almost unchanged.