Relationship between phase stability and mechanical properties on near/metastable beta-type Ti-Cr-(Mn) cast alloys

摘要

The phase stability of near/metastable beta-type Ti-Cr-(Mn) alloys with 4.06-13.46 wt% molybdenum equivalent fabricated by rapid solidification process were evaluated using several parameters, i.e. bond order, metal d-orbital energy level and molybdenum equivalent. The microstructural evolution of the near/metastable beta-type Ti-Cr and Ti-Cr-Mn alloys was systematically investigated by using optical and transmission electron microscopies. With increasing molybdenum equivalent value in the Ti-Cr-(Mn) alloys, alpha '' martensitic transformation and precipitation of athermal omega phase were strongly suppressed during rapid cooling. Based on microstructural investigation, the beta phase stability of the alloys was evaluated using the phase stability index diagram using bond order, metal d-orbital energy level parameters. Moreover, the microstructural evolution depending on the phase stability of Ti-Cr-(Mn) alloys strongly affected to mechanical properties and trade-off behavior between strength and plasticity. Based on these microstructural evolutions and mechanical properties of the Ti-Cr-(Mn) alloys, the phase stability and a relationship between phase stability and mechanical properties of near/metastable beta-type titanium alloys were systemically investigated. (C) 2019 Elsevier B.V. All rights reserved.