Flow stress behavior and deformation characteristics of Ti-3Al-5V-5Mo compressed at elevated temperatures

Samples of Ti-3Al-5V-5Mo alloy were compressed in both beta and alpha + beta phase region on a Gleeble 1500 Simulator. Compression tests were carried out in the temperature range of 700-1000 degreesC and strain rate range of 0.05-15 s(-1). Experimental results show that the flow stress of Ti-3Al-5V-5Mo alloy decreases with the increase of temperature and the decrease of strain rate. At high strain rate, typically 5 and 15 s(-1), discontinuous yielding followed by flow oscillations was observed in both beta phase region and alpha+beta phase region; at low strain rate, the flows display single peak stress. The flow stress at a strain of 0.2 was analyzed with a stand constitutive equation. Activation energy parameters were obtained, and they are 133.46 kJ/mol for the beta phase region and 661.90 kJ/mol for the alpha + beta phase region. Microstructures of the compressed specimens in water-quenched conditions were critically observed. High temperature deformation mechanisms have been elucidated. In the beta phase region, the operative deformation mechanisms are dynamic recovery at high strain rates and grain boundary sliding at low strain rates. In alpha + beta phase region, the alpha phase undergoes dynamically recrystallization at both high and low stain rates. (C) 2002 Elsevier Science Ltd. All rights reserved.