This study investigates the columnar to equiaxed transition (CET) and deformation behavior of a FeCoCrNiMn high entropy alloy (HEA) fabricated by laser-based directed energy deposition (DED). The results show that two kinds of microstructure can be obtained in the as-built HEAs by changing laser scanning speed: one kind of microstructure is formed at a low scanning speed and composed of near fully equiaxed grains; the other is formed at a high scanning speed and composed of columnar grains. These two different microstructures are closely related to the CET, which is decided by the ratio of thermal gradient and solidification rate in the molten pool. Additionally, compared with traditional HEAs, as-built HEAs show a heterogeneous grain-size distribution and high dislocation density, as well as improved tensile properties, one of which (Yield strength = 330 MPa; Ultimate tensile strength = 630 MPa; Fracture elongation = 55%) is similar to the properties of wrought HEAs. Moreover, the as-built HEA with equiaxed grains shows a higher work hardening rate than the as-built HEA with columnar grains and the equiaxed microstructure has the characteristics of intergranular microcracks, the columnar microstructure shows the characteristics of intragranular microcracks. The deformation behavior was investigated using in-situ high-resolution digital image correlation methods, and the result shows that the difference in work hardening rate is closely related to the texture formed during deposition.

这项研究调查了由基于激光的定向能量沉积（DED）制备的FeCoCrNiMn高熵合金（HEA）的柱状至等轴转变（CET）和变形行为。结果表明，通过改变激光扫描速度，可以在建成的HEA中获得两种微观结构：一种是在低扫描速度下形成的，由几乎完全等轴晶的晶粒组成；另一种是在近乎完全等轴的晶粒上形成的。另一个以高扫描速度形成并且由柱状晶粒组成。这两种不同的微观结构与CET密切相关，CET由熔池中的热梯度与凝固速率之比决定。此外，与传统的HEA相比，建成的HEA显示出不均匀的晶粒尺寸分布和高的位错密度，并改善了拉伸性能，其中之一（屈服强度= 330 MPa；极限抗拉强度= 630 MPa；断裂伸长率= 55％）类似于锻造的HEA的性能。此外，等轴晶化后的HEA的加工硬化率高于柱状晶化后的HEA，等轴显微组织具有晶间微裂纹的特征，柱状微结构表现出晶内微裂纹的特征。变形行为使用 柱状组织显示出晶粒内微裂纹的特征。变形行为使用 柱状组织显示出晶粒内微裂纹的特征。变形行为使用原位高分辨率数字图像相关方法，结果表明加工硬化速率的差异与沉积过程中形成的织构密切相关。