The influence of β phase stability on deformation mode and compressive mechanical properties of Ti-10V-3Fe-3Al alloy

A metastable beta-Ti alloy, Ti-10V-3Fe-3Al (wt.%), was subjected to thermomechanical processing (TMP), where the temperature of isothermal holding in the a alpha+beta phase field was varied in order to change the volume fraction of the alpha phase and, correspondingly, the beta phase stability. Following TMP, compression tests were performed at room temperature to evaluate the deformation mode. Microstructural features induced by compression were identified using transmission electron microscopy. It was found that {3 3 2}< 113 >beta deformation twinning along with stress-induced products (alpha" martensite and omega lamellae) and slip were operational in the least stable beta. The co-existence of {332}<(113 >beta and {112}< 111 >beta twinning was found at intermediate beta stability along with other deformation products. With further increasing of 13 phase stability, no {3 3 2}< 113 >beta twinning was detected whereas other deformation modes remained unchanged. In stable beta phase, dislocation glide was the only deformation mode to be found. It was revealed that triggering stress required inducing the deformation products increases with the beta phase stability. Based on the findings, a modification of the lower portion of the (Bo) over bar-(Md) over bar Md phase stability diagram is proposed. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.