Microstructure and texture evolution of stationary shoulder friction stir welded Ti6Al4V alloy

Abstract

Microstructure evolution and texture evolution in the weld zones during stationary shoulder friction stir welding of Ti6Al4V alloy of 7 mm thickness have been investigated by optical microscopy and electron backscatter diffraction method. A unique method was developed to differentiate the heat affected zone (HAZ) and the thermomechanically affected zone (TMAZ). The weld zones are characterised by equiaxed structure in the base material (BM), bimodal structure in the HAZ, coarse lamellar structure in the TMAZ and fine lamellar structure in the stir zone (SZ). Prismatic texture {110} < 0001> and {110} < 100> were developed in the BM and the HAZ, the SZ is dominated by the simple shear texture component D1 (11)[111] and the TMAZ has intermediate shear texture D1.