Tuning strength and plasticity combination on metastable β-Ti-7Mo-3Cr-3Al-3Nb alloy via coupling αs precipitation strengthening and TRIP effect

Xiaoyong Zhu, Baifeng Luan, Huanzheng Sun, An Yan, Fuen Zhang, Zhiqing Zhang, Hongchao Kou

Research output: Contribution to journalArticlepeer-review

Abstract

This study systematically investigates the influence of secondary α (αS) phase fraction on the mechanical properties and deformation behavior of a metastable dual-phase Ti-7Mo-3Cr-3Al-3Nb (wt%) alloy. The microstructural responses of samples with varying αS phase fractions to uniaxial tensile loading were investigated using optical microscopy, electron backscatter diffraction, and transmission electron microscopy. The results indicate that stress-induced martensite and dislocation slip were observed in samples with an αS phase content of 14.6 %-48.4 %. In this range, the yield strength doubles, while the elongation decreases slowly. When the αS content exceeds 48.4 %, dislocation slip becomes the dominant deformation mode, resulting in a sharp decrease in elongation and an increase in strength. Additionally, as the αS phase fraction increases, the work hardening rate curve transitions from a pronounced parabolic shape to a monotonically decreasing trend, indicating a gradual weakening of the work hardening effect. In samples with a low (14.6 %) αS phase fraction, stress induced α′′ martensite coexists with {111}α′′ Type I twins, < 211 >α′′ Type Ⅱ twins, {011}α′′ compound twins, {112}α′′ Type I twins, and {130} < 31̅0 >α′′ compound twins. In samples with moderate (25.8 %) αS phase fraction, {111}α′′ Type I twins induce secondary {111}α′′ Type I twins and {112}α′′ Type I twins. The type and number of martensitic twins decrease as the αS phase fraction increases. Maintaining martensite activation in the residual β of metastable β-titanium alloys containing αS and β mixed phases is considered an effective strategy for optimizing the balance between strength and ductility.

Original languageEnglish
Article number179889
JournalJournal of Alloys and Compounds
Volume1022
DOIs
StatePublished - 10 Apr 2025

Keywords

  • Mechanical properties
  • Metastable β titanium alloy
  • Stress induced α′′ martensite and martensite twins
  • α Precipitation strengthening

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