(1. 中南大學(xué)粉末冶金國家重點實驗室，長沙 410083；
2. 廈門五星瓏科技有限公司，廈門 361023)
摘 要: 采用選區(qū)激光熔化技術(shù)(SLM)制備了Fe23.3Co25.1Cr18.8Ni22.6Ta8.5Al1.7共晶高熵合金，研究了工藝參數(shù)對凝固組織演化的影響。結(jié)果表明：SLM產(chǎn)生的高過冷度是影響共晶高熵合金組織形態(tài)變化的主要因素。通過計算共晶和枝晶生長速率與過冷度的關(guān)系，發(fā)現(xiàn)當(dāng)過冷度？T＞129 K時，面心立方(FCC)相枝晶的生長速率將超過共晶生長，共晶高熵合金凝固組織轉(zhuǎn)變?yōu)橐訤CC相為主的枝晶生長。共晶高熵合金FCC相生長的絕對穩(wěn)定性臨界速率約為850 mm/s，凝固組織主要通過樹枝狀生長。SLM工藝特有的熱循環(huán)特征造成熔池搭接區(qū)富Ta，貧Fe、Cr，這是由于Ta元素與Fe、Cr較低的混合焓引起凝固時Ta對Fe、Cr的排斥。
關(guān)鍵字: 共晶高熵合金；選區(qū)激光熔化；競爭生長；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
