Texture analysis and development of ultrafine grained structure during thermo-mechanical treatment in a gamma-TiAl intermetallic

Abstract

Gamma titanium aluminide intermetallic alloys are lightweight heat-resistant materials and their thermo-mechanical properties are affected by hot working. The aim of this study was initially to evaluate the texture developed in a cast Ti-48Al-2Cr alloy during thermo-mechanical treatment at 1000 ℃ at different strain rates of 0.001, 0.01 and 0.1s−1. In addition, development of ultrafine grained microstructure was assessed for different strain rates. The results of pole figures suggested that the amount of the strain rate is one of the most crucial parameter affecting the type of texture developed. So that, when the rate of strain increased from 0.001 to 0.1s−1 the texture changed from Copper to Brass. The results also showed that by increasing the strain rate yield strength, hardness increased substantially. Microstructural study showed that by increasing strain rates, the mean size of the grains reduced even down to nano-range (i.e. <100nm). A high-volume fraction of dynamic recrystallization occurred when strain rate was more than 0.01s−1. Abnormal grain growth is also observed when the samples are hot strained by low strain rates.