Microstructure and mechanical behavior of additively manufactured CoCrFeMnNi high-entropy alloys: Laser directed energy deposition versus powder bed fusion
Microstructure and mechanical behavior of additively manufactured CoCrFeMnNi high-entropy alloys: Laser directed energy deposition versus powder bed fusion
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DOI：
10.1016/j.actamat.2023.118884
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发表时间：
2023-03-31
期刊：
影响因子：
9.4
通讯作者：
Chen, Wen
中科院分区：
文献类型：
--
作者：
Liu, Yanfang;Ren, Jie;Chen, Wen
CoCrFeMnNi 高熵合金 (HEA) 通过激光定向能量沉积 (L-DED) 和激光粉末床熔合 (L-PBF) 工艺增材制造。对L-DED和L-PBF样品的显微组织和变形机制进行了对比研究。在这两种类型的样品中，都会形成高度异质的微观结构，由柱状晶、凝固单元和位错网络组成。然而，在晶体结构、晶胞尺寸和元素分布方面存在显着差异。 L-DED 样品中较深的熔池促进了 / 的混合晶体结构，这与 L-PBF 样品中沿着构建方向相反。 / 纹理提高了流动应力并促进 L-DED 样品中变形孪晶的激活。此外，它们较大的凝固单元尺寸和相关的单元壁化学偏析增加了位错存储能力和对位错运动的抵抗力，导致塑性变形过程中产生大量的平面滑移带和微带。与 L-PBF 样品相比，L-DED 样品增强的塑性变形能力可产生更持久的应变硬化，从而具有更高的延展性。我们的工作不仅提供了对增材制造 HEA 变形机制的基本见解，而且还强调了加工条件对增材制造的凝固微观结构和材料设计的关键影响。
CoCrFeMnNi high-entropy alloys (HEAs) are additively manufactured by laser directed energy deposition (L-DED) and laser powder bed fusion (L-PBF) processes. Comparative studies are conducted for the microstructures and deformation mechanisms of L-DED and L-PBF samples. In both types of samples, highly heterogeneous microstructures are formed, consisting of columnar grains, solidification cells, and dislocation networks. However, substantial differences are measured in the crystallographic texture, cell size, and elemental distribution. Deeper melt pools in the L-DED samples promote a mixed crystallographic texture of / as opposed to along the build direction in the L-PBF samples. The / texture elevates the flow stresses and facilitates the activation of deformation twins in the L-DED samples. Moreover, their larger solidification cell sizes and associated chemical segregation across cell walls increase the dislocation storage capability and resistance to dislocation motion, leading to profuse planar slip bands and microbands during plastic deformation. The enhanced plastic deformation capabilities in the L-DED samples give rise to more sustained strain hardening and thus higher ductility compared to the L-PBF samples. Our work not only provides fundamental insights into the deformation mechanisms of additively manufactured HEAs, but also underscores the critical impact of processing conditions on the solidification microstructure and material design by additive manufacturing.