Redefining the β-phase stability in Ti-Nb-Zr alloys for alloy design and microstructural prediction

A. Mehjabeen, W. Xu, D. Qiu, M. Qian*

*Corresponding author for this work

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

β-Phase stability is a key consideration for the design of β-titanium (β-Ti) alloys and subsequent heat treatment and/or thermo-mechanical processing. The concept of the Mo equivalence (Mo-Eq), proposed by Molchanova (Phase diagrams of titanium alloys, 1965), has been commonly used as a general guideline to gauge the stability of a β-Ti alloy. A critical literature review has shown that all four existing Mo-Eq expressions deviate substantially from experimental observations and the well-established d-electron theory in predicting the β-phase stability of Ti-Nb-Zr alloys. The reasons are that existing Mo-Eq expressions either completely neglect or significantly overestimate the β-stabilizing effect of Zr. In this study, a new Mo-Eq expression, i.e., (Mo-Eq) Ti-Nb-Zr = 0.238Nb (wt.%) + 0.11Zr (wt.%) + 0.97, has been defined for Ti-Nb-Zr alloys in order to properly address the β-stabilizing effect of Zr. This new Mo-Eq expression showed proven consistency with both experimental observations and the d-electron theory in predicting the β-phase stability of various Ti-Nb-Zr alloys. With necessary modifications, the approach developed is expected to be also applicable to the assessment of the β-phase stability in other Zr-containing Ti alloys.

Original languageEnglish
Pages (from-to)2254-2259
Number of pages6
JournalJOM
Volume70
Issue number10
DOIs
Publication statusPublished - Oct 2018

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