Optimization of Microstructure and Mechanical Properties of Co-Cr-Mo Alloys by High-Pressure Torsion and Subsequent Short Annealing


Creative Commons License

Isik M. , Niinomi M., Liu H., Cho K., Nakai M., Horita Z., ...More

MATERIALS TRANSACTIONS, vol.57, no.11, pp.1887-1896, 2016 (Journal Indexed in SCI) identifier

  • Publication Type: Article / Article
  • Volume: 57 Issue: 11
  • Publication Date: 2016
  • Doi Number: 10.2320/matertrans.m2016112
  • Title of Journal : MATERIALS TRANSACTIONS
  • Page Numbers: pp.1887-1896
  • Keywords: cobalt-chromium-molybdenum alloys, biomaterials, high-pressure torsion, grain refinement, short annealing, INDUCED MARTENSITIC-TRANSFORMATION, GRAIN-REFINEMENT, DYNAMIC RECRYSTALLIZATION, CO-29CR-6MO ALLOYS, EVOLUTION, DEFORMATION, METALS, TITANIUM, BEHAVIOR, COPPER

Abstract

The main target of this study is to optimize the microstructure and to achieve an optimization for the mechanical properties in a biomedical Co-Cr-Mo (CCM) alloy with the nominal composition of Co-28Cr-6Mo (mass%) subjected to high-pressure torsion (HPT) and subsequent short annealing. The gamma ->epsilon phase transformation and grain refinement occur in the CCM alloy subjected to HPT processing at an equivalent strain (epsilon(eq)) of 2.25 (CCMHPT). The HPT processing causes a decrease in the elongation due to the formation of an excessive amount of epsilon phase. For removal of the excessive amount of e phases, the CCMHPT was subjected to a short annealing (CCMHPTA). The effect of the short annealing temperature (1073 K, 1273 K, and 1473 K; annealing time was fixed at 0.3 ks) on CCMHPT was investigated. In addition, the effect of the length of duration for the short annealing (0.06 ks, 0.3 ks, and 0.6 ks;) for a fixed annealing temperature of 1273 K on CCMHPT was studied. CCMHPTA(1273 K) annealed for 0.3 ks shows a good optimization of mechanical properties that include high strength and large elongation owing to its ultra fine-grained microstructure, and removal of excessive e phases.