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Indexed by:Journal Papers

Date of Publication:2015-08-01

Journal:METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE

Included Journals:SCIE

Volume:46A

Issue:8

Page Number:3440-3447

ISSN No.:1073-5623

Abstract:Structural stabilities of beta-Ti alloys are generally investigated by an empirical Mo equivalent, which quantifies the stability contribution of each alloying element, M, in comparison to that of the major beta-Ti stabilizer, Mo. In the present work, a new Mo equivalent (Mo-eq)(Q) is proposed, which uses the slopes of the boundary lines between the beta and (alpha + beta) phase zones in binary Ti-M phase diagrams. This (Mo-eq)(Q) reflects a simple fact that the beta-Ti stability is enhanced, when the beta phase zone is enlarged by a beta-Ti stabilizer. It is expressed as (Mo-eq)(Q) = 1.0 Mo + 0.74 V + 1.01 W + 0.23 Nb + 0.30 Ta + 1.23 Fe + 1.10 Cr + 1.09 Cu + 1.67 Ni + 1.81 Co + 1.42 Mn + 0.38 Sn + 0.34 Zr + 0.99 Si - 0.57 Al (at. pct), where the equivalent coefficient of each element is the slope ratio of the [beta/(alpha + beta)] boundary line of the binary Ti-M phase diagram to that of the Ti-Mo. This (Mo-eq)(Q) is shown to reliably characterize the critical stability limit of multi-component beta-Ti alloys with low Young's moduli, where the critical lower limit for beta stabilization is (Mo-eq)(Q) = 6.25 at. pct or 11.8 wt pct Mo. (C) The Minerals, Metals & Materials Society and ASM International 2015