Influence of persistent effects of initial microstructure on the evolution of microstructure and mechanical properties in CoCrFeNi-based high entropy alloys

Abstract

Thermomechanical processing is commonly employed to tailor the microstructure and enhance the mechanical properties of high entropy alloys (HEAs). However, the influence of the initial microstructure prior to deformation has received limited attention. In this study, we systematically investigate the influence of initial grain structure on microstructural evolution and mechanical performance in HEAs. Alloys with varying recrystallization degrees and initial grain sizes were fabricated. Results show that smaller initial grains promote finer recrystallized structures due to higher grain boundary density and stored energy. Notably, the recrystallized grain morphology exhibited strong persistence from the initial microstructure. Initial grain size also influenced precipitation behavior. Larger grains favored spherical precipitates and continuous precipitation, while smaller grains promoted lamellar precipitation. Tensile testing at room temperature revealed that the fully recrystallized alloy with the finest initial grains achieved the optimal strength-ductility combination, exhibiting a yield strength of 1567$\pm$$\pm$32 MPa, an ultimate tensile strength of 1844$\pm$$\pm$47 MPa, and a total elongation of (20.4$\pm$$\pm$1.0)%. These findings highlight the pivotal role of initial microstructure in dictating recrystallization and precipitation pathways, offering a practical strategy for optimizing HEA performance through microstructural design.