Influence of aging heat treatment on the microstructure and mechanical properties of Co29Cr31Cu4Mn15Ni21 high-entropy alloys strengthened by nano-precipitates

Abstract

Nanoprecipitation strengthening represents a highly effective strategy for enhancing the mechanical properties of high-entropy alloys (HEAs). While existing research primarily concentrates on elucidating the strengthening mechanisms, comparatively limited attention has been paid to the processing technologies, which are equally vital for the industrial application of these materials. In this study, we systematically investigate the effects of aging heat treatment at various temperatures (300-800 °C) and durations (0.5-12 h) on the microstructure and mechanical properties of Co29Cr31Cu4Mn15Ni21 HEA, which is reinforced by nanoprecipitates. Our findings indicate that aging the alloy at 700 °C for 4 h increases the yield strength from 323 MPa to 440 MPa compared to the as-cast alloy, representing a substantial enhancement in strength of 36%. However, this improvement is accompanied by a slight reduction in plasticity. This enhancement is attributed to successfully forming uniformly distributed coherent nanoprecipitates within the alloy matrix. Furthermore, an evaluation of the strengthening contribution based on dislocation pinning theory suggests that nanoprecipitation is the predominant mechanism responsible for this increase in strength. These results underscore the critical role of processing parameters in optimizing the mechanical performance of HEAs, thereby facilitating their broader industrial applications.