The effect of heat treatment on crack control and grain refinement in laser beam welded β-solidifying TiAl-based alloy

Investigations were conducted on the γ-TiAl-based alloy Ti-42Al-2.5Cr-1Nb-0.7Si-0.5B (at. %) to assess the influence of in situ and conventional post-weld heat treatment on the microstructure and microtexture transformations induced by laser beam welding. It was found that in situ post-weld heat treatment at 800 °C was important to inhibit weld seam cracking. EBSD and HEXRD results indicated that the welding zone mainly consisted of coarse α2 “textured colonies”. These textured α2 are found to be in Burgers orientation relationship with their parent β grains. After 1 h of conventional post-weld heat treatment at 1200 °C followed by furnace cooling, the textured colonies are refined. The α2 grains nucleate heterogeneously on borides so that the sharp texture of the weld zone was broken down.