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The effect of quench rate on the β-α″ martensitic transformation in Ti-Nb alloys

DOI: 10.1016/j.msea.2021.141240 DOI Help

Authors: E. L. Pang (University of Cambridge) , E. M. Hildyard (University of Cambridge) , L. D. Connor (Diamond Light Source) , E. J. Pickering (University of Manchester) , N. G. Jones (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Materials Science And Engineering: A , VOL 88

State: Published (Approved)
Published: April 2021
Diamond Proposal Number(s): 15420

Abstract: While Ti-Nb binary alloys have been extensively studied over the years, there are discrepancies in the literature relating to the β-α″ martensitic transformation that indicate an incomplete understanding. In particular, there are inconsistencies regarding the phase constitution of as-quenched material and the ability for α″ phase to be thermally-induced. To resolve these issues, the β-α″ phase transformation is studied in a Ti-24Nb (at.%) alloy subjected to two different water quench conditions. It is demonstrated that only the fastest quench rates (≳500˚C/s) result in the formation of α″ phase, and these materials exhibit a reversible thermally-induced β-α″ transformation at low temperatures. In contrast, slightly slower water quench procedures lead to a β+ω microstructure, and these samples do not exhibit a thermally-induced β-α″ transformation, even when cooled to -168˚C. Despite this, room temperature mechanical testing results indicate that α″ can be induced by stresses as low as 200 MPa. To explain these results, it is proposed that quenching stresses play a role in the competition between α″ and athermal ω phases at rapid quench rates. The present results are then reconciled with the body of literature and a broader understanding of phase stability in metastable β-titanium alloys.

Journal Keywords: titanium alloys; phase transformations; omega phase; martensite; quench sensitivity

Diamond Keywords: Alloys

Subject Areas: Materials, Engineering

Instruments: I11-High Resolution Powder Diffraction

Discipline Tags:

Engineering & Technology Materials Engineering & Processes Material Sciences Metallurgy

Technical Tags: