Microstructure, texture and mechanical studies of an inconspicuous shear band formed during hot compression of Ti-6Al-4V alloy

Abstract

Systematical studies on an inconspicuous shear band formed during hot isothermal forging of Ti-6Al-4V alloy were carried out. During the compression of Ti-6Al-4V alloy in high reduction (>50%), severe shear strain concentrated in the maximum shearing plane in the geometric center of the bulk samples leading to the nucleation of shear band (SB). Grains in SB were refined and elongated with their long axis parallel to the local shearing direction. Electron backscattered diffraction (EBSD) analysis showed that grains in SB were not strongly orientated containing two weak orientations making {0001} planes of α phase parallel to the compression direction, and {101¯0} planes of α phase parallel to the compression direction and, meanwhile, the normal direction of its {0001} planes ~34°away from the compression direction. The observed textures in SB were resulted from slipping and twinning during the hot compression. Pyramidal slip was preferred in SB as well as in its surrounding matrix (M). In addition, {101¯1} <1¯012> twinning was preferentially activated in SB, which is different for M with {101¯2} <1¯011> twinning preferred due to different plastic deformation degrees in SB and M during the hot compression. To evaluate the influence of SB on the mechanical properties of the alloy, micro-hardness and tensile tests were employed. The alloy in SB had been proved to be slightly strengthened compared to M, which was resulted from both the grain refinement and the texture diversity.