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<p>In this study, the CoCr<sub>1.5</sub>NiTi<sub>1.5</sub>Al<sub>0.2</sub> eutectic high-entropy alloys (EHEA, FCC + BCC), previously determined through thermophysical parameter calculations and phase diagram analysis, was selected to investigate suitable heat treatment process parameters. This study aims to optimize the alloy’s microstructure and mechanical properties while contributing foundational data to the heat treatment process library for EHEAs. The research findings revealed that heat treatment at temperatures of 700&#xa0;°C and below led to the gradual coarsening of needle-like HCP-structured nano-precipitates within the eutectic phase, accompanied by an increase in the content of low-angle grain boundaries (LAGBs) in the alloy. Consequently, the compressive yield strength and fracture strength of the EHEA gradually increased, while the plastic strain progressively decreased. Starting from heat treatment at 900&#xa0;°C, the CoCr<sub>1.5</sub>NiTi<sub>1.5</sub>Al<sub>0.2</sub> EHEA exhibited an increase in recrystallization content, a decrease in LAGB content, a reduction in dislocation density within the spherical FCC-structured nano-precipitates in the eutectic phase, and the dissolution and disappearance of needle-like HCP-structured nano-precipitates in the grain boundary regions. These changes ultimately resulted in a decrease in the alloy's compressive yield strength and fracture strength, along with an increase in plastic strain.</p>

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Heat Treatment-Assisted Optimization of Microstructure and Mechanical Properties of a Novel FCC + BCC-Type CoCr1.5NiTi1.5Al0.2 EHEA

  • 期刊论文

  • 发表日期：

    2025年10月9日

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  • Xin Zhang,
  • Wenxin Feng,
  • Wanhui Liu,
  • Jian Wang,
  • Jing Tian,
  • Yangchuan Cai

摘要

In this study, the CoCr1.5NiTi1.5Al0.2 eutectic high-entropy alloys (EHEA, FCC + BCC), previously determined through thermophysical parameter calculations and phase diagram analysis, was selected to investigate suitable heat treatment process parameters. This study aims to optimize the alloy’s microstructure and mechanical properties while contributing foundational data to the heat treatment process library for EHEAs. The research findings revealed that heat treatment at temperatures of 700 °C and below led to the gradual coarsening of needle-like HCP-structured nano-precipitates within the eutectic phase, accompanied by an increase in the content of low-angle grain boundaries (LAGBs) in the alloy. Consequently, the compressive yield strength and fracture strength of the EHEA gradually increased, while the plastic strain progressively decreased. Starting from heat treatment at 900 °C, the CoCr1.5NiTi1.5Al0.2 EHEA exhibited an increase in recrystallization content, a decrease in LAGB content, a reduction in dislocation density within the spherical FCC-structured nano-precipitates in the eutectic phase, and the dissolution and disappearance of needle-like HCP-structured nano-precipitates in the grain boundary regions. These changes ultimately resulted in a decrease in the alloy's compressive yield strength and fracture strength, along with an increase in plastic strain.