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Microstructural Evolution and Strain-Hardening in TWIP Ti Alloys

30 Pages Posted: 15 Aug 2019 First Look: Accepted

See all articles by Guo-Hua Zhao

Guo-Hua Zhao

Lancaster University - Department of Engineering

Xin Xu

Imperial College London - Department of Materials

David Dye

Imperial College London - Department of Materials

Pedro E.J. Rivera-Díaz-del-Castillo

Lancaster University - Department of Engineering

Abstract

A multiscale dislocation-based model was built to describe, for the first time, the microstructural evolution and strain-hardening of {332}<113> TWIP (twinning-induced plasticity) Ti alloys. This model not only incorporates the reduced dislocation mean free path by emerging twin obstacles, but also quantifies the internal stress fields present at β-matrix/twininterfaces. The model was validated with the novel Ti-11Mo-5Sn-5Nb alloy (wt.%), as well as an extensive series of alloys undergoing {332}<113> twinning at various deformation conditions. The quantitative model revealed that solid solution hardening is main contributorto the yield stress, where multicomponent alloys or alloys containing eutectoid β-stabilisers exhibited higher yield strength. The evolution of twinning volume fraction, intertwin spacing, dislocation density and flow stress were successfully described. Particular attentionwas devoted to investigate the effect of strain rate on the twinning kinetics and dislocation annihilation. The modelling results clarified the role of each strengthening mechanism and established the influence of phase stability on twinning enhanced strain-hardening. The origin of strain-hardening is owing to the formation of twin obstacles in early stages, whereas the internal stress fields provide a long-lasting strengthening effect throughout the plastic deformation. A tool for alloy design by controlling TWIP is presented.

Keywords: Ti alloys, Twinning-induced plasticity, Strain-hardening, Physical-based modelling

Suggested Citation

Zhao, Guo-Hua and Xu, Xin and Dye, David and Rivera-Díaz-del-Castillo, Pedro E.J., Microstructural Evolution and Strain-Hardening in TWIP Ti Alloys. Available at SSRN: https://ssrn.com/abstract=3436405 or http://dx.doi.org/10.2139/ssrn.3436405

Guo-Hua Zhao (Contact Author)

Lancaster University - Department of Engineering

United Kingdom

Xin Xu

Imperial College London - Department of Materials

South Kensington
United Kingdom

David Dye

Imperial College London - Department of Materials

South Kensington
United Kingdom

Pedro E.J. Rivera-Díaz-del-Castillo

Lancaster University - Department of Engineering ( email )

United Kingdom

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