Journal of Materials Research and Technology (May 2023)

Temperature dependence of the deformation behavior and mechanical response of CoCrNi medium-entropy alloy: Experiment and simulation

  • H.W. Deng,
  • H.E. Ge,
  • C.Y. Zhan,
  • Y. Liu,
  • Q.S. Ren,
  • Z.Y. Liu,
  • T. Zhang

Journal volume & issue
Vol. 24
pp. 9731 – 9742

Abstract

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Tailoring the microstructure of metallic materials by controlling the fabrication process is crucial to achieving superior mechanical properties. Herein, the mechanism of modifying the microstructure and mechanical properties of medium-entropy CoCrNi alloys was investigated by equal-channel angular pressing (ECAP) at room temperature (RT) and cryogenic temperature (CT) and post-deformation annealing (PDA) and was analyzed by molecular dynamics simulations. It was found that temperature influences the deformation mechanism of the alloy, dislocations, stacking faults, deformation twins, and FCC-HCP phase transitions, which assume different roles at different temperatures. The dislocation density of the ECAP-CT sample is significantly higher than that of the ECAP-RT sample; however, the ECAP-RT sample exhibits unique deformation features of kink bands and hierarchical twin structure, resulting in dynamic grain refinement effects. In addition, the HCP phase strength increment caused by annealing-induced HCP phase transformation is higher in the ECAP-RT sample than in the ECAP-CT sample, thus leading to a substantial increase in strength after PDA. The present study exhibits the strengthening mechanisms and provides a generic approach to obtaining desirable mechanical properties of alloys.

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