Abstract Thermal stability of CoCrFeNi high entropy alloy in as-milled and sintered conditions was investigated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, and atom probe tomography. Composite microstructure consists of FCC and carbide with a fine dispersion of oxide was observed in the sintered condition. Unsolicited contamination of carbon and oxygen in the as-milled powder due to the milling medium had led to the formation of composite microstructure. An exceptional thermal stability was observed upon exposure of sintered compact to higher temperatures (0.56 T m to 0.68 T m ) for the prolonged duration of 600 h. Sintered compact exposed to 700 °C (0.56 T m ) for 600 h showed negligible change in hardness and grain size. Analysis based on the modified Hall-Petch model for two phase alloy indicates the phase boundaries act as a strong obstacle while the major contribution to strengthening comes from grain boundaries.

中文翻译：

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超细晶CoCrFeNi高熵合金复合材料的热稳定性和晶界强化

摘要 使用 X 射线衍射、差示扫描量热法、透射电子显微镜和原子探针断层扫描法研究了 CoCrFeNi 高熵合金在铣削和烧结条件下的热稳定性。复合微观结构由 FCC 和碳化物组成，在烧结条件下观察到氧化物的细分散。由于研磨介质，研磨后的粉末中碳和氧的未经请求的污染导致了复合微结构的形成。在将烧结体暴露于较高温度（0.56 T m 至 0.68 T m ）600 小时的延长时间后，观察到了优异的热稳定性。烧结体暴露于 700 °C (0.56 T m ) 600 小时后，硬度和晶粒尺寸的变化可以忽略不计。