The Temperature Dependences of Mechanical Properties, Deformation Hardening, and Fracture of FeMnNiCoCr Heterophase Alloy

Abstract

It is established that the temperature dependence of the mechanical properties and deformation behavior of a heterophase multicomponent Cantor alloy (FeMnNiCoCr) and the mechanisms of its fracture under uniaxial static tension in the temperature range 77–300 K are determined by the mechanism of formation and distribution of dispersed phases in it. The heterogeneous formation of chromium-enriched σ‑phases and phases with an fcc crystal lattice,mainly at grain boundaries in the course of annealing of homogenized samples (when particles are inhomogeneously distributed over the structure) and at deformation defects in the course of annealing of preliminarily strained samples (when particles are distributed uniformly over the structure), takes place in the Cantor alloy as a result of annealing. It is found that the grain-boundary phases slightly affect the temperature dependence of yield stress σ0.2, the deformation behavior of the heterophase alloy and its mechanism, but contribute to a decrease in the plasticity and to the formation of brittle secondary cracks on fracture surfaces under low-temperature deformation. The complex effect of the dispersion and the grain boundary hardenings in samples with a uniform distribution of particles that are formed in the course of aging of pre-strained samples leads to a substantial increase in the strength properties of the Cantor alloy in the entire temperature range while maintaining high plasticity and a strong temperature dependence of σ0.2.