Influence of gradual stress relieving on the microstructure, texture development, grain structure and orientation of the hot-rolled Ti6Al4V–5Cu alloy

Abstract

In order to investigate the influence of gradual stress relieving treatment on the microstructure, texture evolution, grain structure, and misorientation distribution of the hot-rolled Ti6Al4V–5Cu (α+β) alloy deformed in various thickness reduction ratios (TRR's) of 15%, 58%, and 73% to maintain the burger orientation relationship (BOR), different stress reliving treatment was specially designed for relieving the residual stresses occurred due to the hot deformation process. Using IPF maps, the majority of the α grains, specifically the elongated ones were found nearly at 45 ° with respect to the rolling and transverse direction. The study also show that the heat treatment schedule on the 58% deformed alloy significantly promote the transformation of β to α phase and a special microstructure with an equiaxed grains is produced. The local misorientation angle distribution due to stress reliving treatment has also discussed. Using EBSD analysis, the alloy processed under highest TRR's (i.e., 73%) and subsequent stress relieving treatment could result a serious internal crystalline instability with various degree of element diffusion rate, which promote a severe and ease of alloy coarsening. Thus, coarsening encourage the formation of grains with the highest softening potential, comparatively. It is obvious that the stress-relived treatment does not result a change in microstructure. However the internal residual stresses on the hot deformation were relieved, the texture intensity had increased quietly. A significant textural behavior could be achieved on the 73% hot-rolled alloys by the stress-relieving process to align the α/β fiber texture interface in parallel coincidence to maintain the BOR.

Keywords

• Ti6Al4V–5Cu alloy
• Hot-rolling
• Stress reliving treatment
• Microstructure
• Texture evolution
• Burger orientation relationship (BOR)