(1. 中南大学粉末冶金国家重点实验室，长沙 410083；
2. 厦门五星珑科技有限公司，厦门 361023)
摘 要: 采用选区激光熔化技术(SLM)制备了Fe23.3Co25.1Cr18.8Ni22.6Ta8.5Al1.7共晶高熵合金，研究了工艺参数对凝固组织演化的影响。结果表明：SLM产生的高过冷度是影响共晶高熵合金组织形态变化的主要因素。通过计算共晶和枝晶生长速率与过冷度的关系，发现当过冷度？T＞129 K时，面心立方(FCC)相枝晶的生长速率将超过共晶生长，共晶高熵合金凝固组织转变为以FCC相为主的枝晶生长。共晶高熵合金FCC相生长的绝对稳定性临界速率约为850 mm/s，凝固组织主要通过树枝状生长。SLM工艺特有的热循环特征造成熔池搭接区富Ta，贫Fe、Cr，这是由于Ta元素与Fe、Cr较低的混合焓引起凝固时Ta对Fe、Cr的排斥。
关键字: 共晶高熵合金；选区激光熔化；竞争生长；快速凝固
（1. National Key Laboratory of Powder Metallurgy, Central South
University, Changsha 410083, China;
2. 3D METALWERKS Co., Ltd., Xiamen 361023, China）
Abstract:Fe23.3Co25.1Cr18.8Ni22.6Ta8.5Al1.7 eutectic high entropy alloy was fabricated by selective laser melting (SLM), and the effect of process parameters on the evolution of solidification structure was investigated. The results indicate that the high undercooling produced by SLM is the main parameter affecting the morphological changes of the eutectic high entropy alloy. By calculating the relationship between the microstructural growth rate and the undercooling, it is found that the dendrite growth rate of FCC phase will exceed that of the eutectic when ？T＞129 K. The solidified structure of the eutectic high entropy alloy changes into the dendrite growth dominated by FCC phase. The absolute stability critical rate of FCC phase growth is about 850 mm/s, and the solidification structure mainly forms through dendritic growth. The overlapping area of the molten pool is rich in Ta but poor in Fe and Cr, which is attributed to the thermal cycle characteristics of the SLM. This is due to the low mixing enthalpy of Ta with Fe and Cr which causes the repulsion of Fe and Cr by Ta during solidification.
Key words: eutectic high entropy alloy; selective laser melting; competitive growth; rapid solidification
