Influence of laser shock peening on Residual stress and microhardness of AA2219 friction stir weld

Abstract

This work focuses on the effect of Laser Shock Peening (LSP) on residual stress (RS) and microhardness of AA2219 T87 Friction Stir Weld (FSW). FSW plate was laser peened, covering all the regions of the weld and RS measurement was carried out before and after peening. RS distribution across the weld is non-uniform, and the profile is M shaped with tensile RS near to weld center and compressive RS away from the center. The maximum tensile RS is + 123.5 MPa and + 96.7 MPa on the top and bottom surfaces, respectively. LSP has reversed the tensile RS to compressive with a single pass of peening, and the subsequent passes increased the compressive RS further. Peak tensile RS changes to compressive RS of −20 MPa, −130.2 MPa, and −195.5 MPa with single, three and six passes of peening, respectively, on the top surface. It is due to plastic deformation and strain-hardening effect induced on the surface during LSP. An increase in hardness due to LSP on the surface and subsurface levels is noticed, and increased number of passes affected higher depth.