Evolution and Distribution of Geometrically Necessary Dislocations for TA15 Titanium Alloy Sheets During the Hot Tensile Process

Abstract

A thorough understanding of the behavior of geometrically necessary dislocations (GNDs) for titanium alloys during the thermo-mechanical process is very important for effectively guiding the forming process and controlling the property of finial products. The current work seeks to provide valuable insights into the evolution and distribution of GNDs for TA15 titanium alloy sheet during the hot tensile process through the experimental study and numerical simulation. Based on EBSD analyses, the overall GND densities increased with the imposed macroscopic strain and saturated after a true strain of 0.4. A modified model for the prediction of average GND density with the imposed strain was proposed according to the mixed mechanism of texture, crystalline orientation, grain size, dynamic restoration and imposed strain. Moreover, GNDs were commonly distributed near grain boundaries, and some band-liked GND structures took triple junctions as starting points and extended linearly into grains nearly along a 45° angle toward the tensile direction. According to the result of a crystal plasticity finite element model, the mechanism of GND distribution was revealed.