High-Temperature Deformation Behavior of Co-Free Non-Equiatomic CrMnFeNi Alloy

TL;DR

This study investigates the high-temperature deformation behavior of a cobalt-free non-equiatomic CrMnFeNi alloy, combining experimental tests and computational simulations to understand its mechanical performance and microstructural evolution.

Contribution

It provides new insights into the deformation mechanisms and microstructural stability of Co-free HEAs at elevated temperatures through combined experimental and molecular dynamics approaches.

Findings

Mechanical strength decreases with temperature due to thermally activated mechanisms.

Dislocation activity, twin formation, and grain boundary behavior are characterized.

Co-free alloy shows enhanced high-temperature strength compared to traditional HEAs.

Abstract

Cobalt-free high-entropy alloys (HEAs) have garnered interest for nuclear structural applications due to their good mechanical performance, thermal stability, and resistance to radiation-induced degradation, while avoiding long-lived Co radioisotopes. This study presents an experimental and computational investigation of the plastic deformation behavior of a non-equatomic CrMnFeNi alloy, designed to maintain a stability of fcc phase in a large domain of temperatures and to balance stacking fault (SF) energies for enhanced strain hardening and ductility. Tensile tests reveal a temperature-dependent reduction in mechanical strength, attributed to thermally activated deformation mechanisms and microstructural evolution. Molecular dynamics simulations of single- and polycrystals capture dislocation activity, SF formation, and twin nucleation as a function of strain and temperature. Electron backscatter diffraction (EBSD) confirms twin formation and grain boundary activity. The Schmid factor mapping is drawn to interpret local slip activity and anisotropic deformation behavior. The absence of Co leads to enhanced high-temperature strength compared to the Cantor alloy.