Tuning strain-induced γ-to-ε martensitic transformation of biomedical Co–Cr–Mo alloys by introducing parent phase lattice defects

Manami Mori, Kenta Yamanaka, Shigeo Sato, Shinki Tsubaki, Kozue Satoh, Masayoshi Kumagai, Muneyuki Imafuku, Takahisa Shobu, Akihiko Chiba

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

In this study, we examined the effect of pre-existing dislocation structures in a face-centered cubic γ-phase on strain-induced martensitic transformation (SIMT) to produce a hexagonal close-packed ε-phase in a hot-rolled biomedical Co–Cr–Mo alloy. The as-rolled microstructure was characterized by numerous dislocations as well as stacking faults and deformation twins. SIMT occurred just after macroscopic yielding in tensile deformation. Using synchrotron X-ray diffraction line-profile analysis, we successfully captured the nucleation of ε-martensite during tensile deformation in terms of structural evolution in the surrounding γ-matrix: many dislocations that were introduced into the γ-matrix during the hot-rolling process were consumed to produce ε-martensite, together with strong interactions between dislocations in the γ-matrix. As a result, the SIMT behavior during tensile deformation was accelerated through the consumption of these lattice defects, and the nucleation sites for the SIMT ε-phase transformed into intergranular regions upon hot rolling. Consequently, the hot-rolled Co–Cr–Mo alloy simultaneously exhibited an enhanced strain hardening and a high yield strength. The results of this study suggest the possibility of a novel approach for controlling the γ → ε SIMT behavior, and ultimately, the performance of the alloy in service by manipulating the initial dislocation structures.

Original languageEnglish
Pages (from-to)523-529
Number of pages7
JournalJournal of the Mechanical Behavior of Biomedical Materials
Volume90
DOIs
Publication statusPublished - 2019 Feb

Keywords

  • Biomedical Co−Cr−Mo alloy
  • Lattice defects
  • Strain hardening
  • Strain-induced martensitic transformation
  • Strength
  • Synchrotron diffraction

ASJC Scopus subject areas

  • Biomaterials
  • Biomedical Engineering
  • Mechanics of Materials

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