Development of α precipitates in metastable Ti-5Al-5Mo-5V-3Cr and similar alloys

Present work describes the development of the alpha phase in beta WQ specimens of Ti-5Al-5Mo-5V-3Cr (A1), Ti-5Al-3.5Mo-7.2V-3Cr (A2), Ti-5Al-5Mo-8.6V-1.5Cr (A3) and Ti-5Al-3.5Mo-5V-3.94Cr (A4) alloys as function of different ageing temperatures and time intervals. The alpha phase formed during ageing display different morphologies namely, thin film on prior beta grain boundaries, sub boundary and islands of the a phase within the beta matrix. Mechanism of the formation of these morphologies has been explained. The fine and even distribution of the alpha phase in beta matrix exhibit two distinct features i.e. uniform distribution of alpha laths with two variants and clusters of parallel alpha laths. The a phase presents in all morphologies is transformed to Widmanstatten type morphology on further increase in ageing temperature and time. The development of the alpha phase in these alloys at 300 and 400 degrees C results in significant increase in hardness which is attributed to typical precipitation hardening. (C) 2016 Elsevier Inc. All rights reserved.