Simultaneous strength and ductility enhancement in Co₂₉Cr₃₁Cu₄Mn₁₅Ni₂₁ high entropy alloy through fully coherent nano-precipitates

High strength and high ductility are fundamental goals for metallurgists in developing metal structural materials. However, enhancing material strength often leads to a corresponding reduction in ductility, a phenomenon known as the trade-off effect. This study has successfully introduced fully coherent nano-precipitates into the Co₂₉Cr₃₁Cu₄Mn₁₅Ni₂₁ high-entropy alloy (HEA) through an optimized aging heat treatment process at 500 °C for 4 h. The results of tensile mechanical tests indicate that the strength and ductility are improved after incorporating these nano-precipitates. The yield strength increased from 315 MPa to 400 MPa, representing a 27 % enhancement. Significantly, this enhancement in strength was attained without compromising ductility, as evidenced by an increase in elongation from 53 % to 56 %. These findings effectively challenge the conventional trade-off effect between strength and ductility. Furthermore, the study underscores the critical importance of the aging heat treatment parameters in enhancing the mechanical properties. It was observed that excessive heat treatment duration or elevated temperatures can lead to the formation of detrimental σ phases, which adversely affect the mechanical performance. This research contributes valuable insights for further enhancing the mechanical properties of HEAs, thereby promoting their potential applications in industrial settings.