Powder plasma arc additive manufacturing (PPA-AM) is a promising method for fabricating high-entropy alloys (HEAs). However, the characteristics of thermal cycling during the PPA-AM process and the mechanism of subsequent heat treatment on the microstructure and mechanical properties are unclear. In this study, an Al_1.2CoCrFeNi_2.1 HEA with dual-phase (FCC + B2) was fabricated via PPA-AM. The microstructure and mechanical properties of the as-built and heat-treated samples were explored. The crystallographic orientations of the FCC and B2 phases were also determined. Because the alloy in the bottom region was affected by thermal cycling, B2 particles precipitated in the FCC phase, and FCC particles precipitated in the B2 phase. During the tensile test, the phase boundary between B2 matrix and FCC particles produced cracks preferentially. These cracks reduced the strength and elongation of the alloy. After heat treatment at 1200 °C, the FCC and B2 precipitates formed globular shapes inside the B2 and FCC grain matrix, respectively. The alloy showed a uniform structure and the ductility of the alloy was improved significantly. This work elucidates the mechanisms of thermal cycling and heat treatment on the microstructure and mechanical properties of the alloy.

粉末等离子弧增材制造 (PPA-AM) 是一种很有前途的制造高熵合金 (HEA) 的方法。然而，PPA-AM工艺过程中的热循环特性以及后续热处理对微观结构和力学性能的作用机制尚不清楚。在这项研究中，Al _1.2 CoCrFeNi _2.1通过 PPA-AM 制造具有双相 (FCC + B2) 的 HEA。研究了完工和热处理样品的微观结构和机械性能。还确定了 FCC 和 B2 相的晶体取向。由于底部区域的合金受到热循环的影响，B2颗粒在FCC相中析出，FCC颗粒在B2相中析出。在拉伸试验中，B2基体和FCC颗粒之间的相界优先产生裂纹。这些裂纹降低了合金的强度和伸长率。在 1200 ℃热处理后，FCC 和 B2 析出物分别在 B2 和 FCC 晶粒基质内形成球状。合金呈现出均匀的组织结构，合金的延展性显着提高。