熱處理對氣體霧化法製備Al0.5CoCrFeNi2高熵合金粉末之相變化、微結構與機械性質之影響

Effects of heat treatment on the phase transformation, microstructure and mechanical properties of gas-atomized Al0.5CoCrFeNi2 high-entropy alloy powders

高熵合金主要由五元以上之溶質元素組成，以高亂度及多元固溶相使結構發展傾向簡單固溶體，再依據不同元素調配可獲得優異之機械、物理和化學性質。本研究以氣體霧化法製備Al0.5CoCrFeNi2之高熵合金粉末為研究對象，主要探討熱處理對於相變化、微結構和機械性質之影響。氣體霧化法與其他製程相比，可使元素成份均勻分佈，且保持高溫原始狀態之相。從相圖可發現原始粉末為FCC結構，經熱處理後析出富含Cr之析出相，母相仍保持FCC之AlNi3晶格結構，本研究再進一步探討熱處理之時間與溫度，對於此合金系統之相變化及晶體結構影響。

A High-entropy alloy is composed of at least five solute elements generally. Its structure tends to become simple solid solution with high randomness and multi-solid solution phases. Moreover, it possesses excellent mechanical, physical and chemical properties depending on the different compositions. In this study, Al0.5CoCrFeNi2 high-entropy alloy powders were prepared by gas atomization. The effects of heat treatment on phase transformation, microstructure and mechanical property were investigated. Comparing with other processes, the gas atomization process can make the distribution of elements uniformly and keep in the phase produced in high temperature. From phase diagram, it can be known that the phase of original powders could be transformed from FCC into FCC/BCC. After heat treatment, the Cr-rich phase was precipitated and the matrix phase still maintained FCC phase of AlNi3 lattice structure. Furthermore, this research will discuss how the temperature and time of heat treatment influence the phase transformation and crystal structure of this high-entropy alloys system.