Flow behavior and processing maps of Ti-44.5Al-3.8Nb-1.0Mo-0.3Si-0.1B alloy

The flow behavior of Ti-44.5Al-3.8Nb-1.0Mo-0.3Si-0.1B alloy was investigated by means of uniaxial hot compression tests performed with a Gleeble 3500 simulator within a temperature range of 1100 -1250 degrees C and a strain rate region of 0.01-1 s boolean AND(-1) up to a true deformation of 0.7. The results show that the flow stress increases with increasing strain rate and decreasing temperature. The flow stress curves were composed of three stages: work hardening, softening and steady. Processing maps were developed on the basis of the dynamic materials model. The microstructure of specimens deformed at different conditions was analyzed and connected with the processing map. The predominant flow stability region and instability region mechanism of this alloy were validated by microstructure observation. Based on the constructed processing maps and microstructure analysis, the optimal hot processing window of this alloy corresponds to the temperature range of 1200-1250 degrees C and strain rate range of 0.01-0.5 s boolean AND( -1). The excellent deformability of this alloy is ascribed to soft beta phase and hard alpha(2)/gamma lamellar colonies decomposition at elevated temperature. (C) 2016 Elsevier B.V. All rights reserved.