Design of metastable β-Ti alloys with enhanced mechanical properties by coupling αS precipitation strengthening and TRIP effect

Nana Chen, Hongchao Kou, Zhihong Wu, Fengming Qiang, Ke Hua, Chuanyun Wang, Bin Tang, Jinshan Li, J. M. Molina-Aldareguia

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

A strain-transformable microstructure was successfully designed in a metastable β Ti–7Mo–3Nb–3Cr–3Al alloy with enhanced mechanical properties, by introducing ∼28% α precipitates coupled with the TRIP effect, overcoming the traditional trade-off dilemma between strength and ductility in most metastable β-Ti alloys. The as-designed lamellar microstructure was predominantly deformed by stress-induced martensitic (SIM α") phase transformations, martensitic twinning and dislocation slip of the parent β grains and α laths. The β→α" transformation followed the [113]β//[112]α"//[-310]α"//[1-21]α" orientation relationship, with the {133}β habit plane predicted by the Phenomenological Theory of Martensite Crystallography (PTMC). A novel <211>α" type II martensitic twinning mode was also found, in addition to the {111}α" type I mode at SIM α"/α impinging region. The results show that, not only the lamellar α precipitates play a major role in precipitation strengthening, but they can also effectively block SIM α" propagation at the initial stages of deformation. However, SIM α" transmission across the α laths was also observed for large strains. Moreover, <c+a> pyramidal slip and shear of the α laths also contributed to the accommodation of internal stresses. Therefore, the origin of the enhanced tensile mechanical properties can be attributed to the combined effects of α precipitation strengthening coupled with the TRIP softening effect and the extra interaction stresses introduced by the α laths and other deformation products, validating the design concept. The current investigation may provide a novel strategy for designing new high-performance metastable β-Ti alloys.

Original languageEnglish
Article number142696
JournalMaterials Science and Engineering: A
Volume835
DOIs
StatePublished - 17 Feb 2022

Keywords

  • Metastable β-Ti alloy
  • Precipitation strengthening
  • Stress-induced α" martensitic twinning
  • Tensile deformation behavior
  • TRIP effect

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