An in-situ high-energy X-ray diffraction study on the hot-deformation behavior of a beta-phase containing TiAl alloy

In engineering materials, microstructural evolution during hot-working critically determines the properties of the finished part. Intermetallic TiAl alloys are no exception and numerous attempts have been made to improve their performance by subjecting them to harmonized hot-working steps. In the current work a novel in-situ diffraction technique along with conventional microscopic methods were employed to characterize the behavior of the individual phases at two different deformation temperatures. A so-called TNM (TM) alloy with a nominal composition of Ti-43.5 Al-4 Nb-1 Mo-0.1 B (in at%), which exhibits an adjustable fraction of disordered beta-phase at elevated temperatures, was deformed isothermally at 1220 degrees C and 1300 degrees C. At 1220 degrees C three phases (alpha,beta,gamma) are present in thermodynamic equilibrium which reduces to two (alpha,beta) at 1300 degrees C. It was possible to observe in-situ the individual behavior of the involved phases during deformation and the phenomena which accommodate the defects generated by hot-working. Results of post-mortem microscopic investigations were used to confirm the findings. The results of the in-situ experiments give unique insights into the hot-deformation behavior of multi-phase TiAl alloys, which can be used for specific process optimization and for further alloy development. (C) 2013 Elsevier Ltd. All rights reserved.