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

摘要

Investigations were conducted on the y-TiAl-based alloy Ti-42Al-2.5Cr-lNb-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 α_2 "textured colonies". These textured α_2 are found to be in Burgers orientation relationship with their parent (5 grains. After 1 h of conventional post-weld heat treatment at 1200 °C followed by furnace cooling, the textured colonies are refined. The aj. grains nucleate heterogeneously on borides so that the sharp texture of the weld zone was broken down.