Additive manufacturing of a martensitic Co-Cr-Mo alloy: Towards circumventing the strength-ductility trade-off
Additive manufacturing of a martensitic Co-Cr-Mo alloy: Towards circumventing the strength-ductility trade-off
复制标题
马氏体 Co-Cr-Mo 合金的增材制造：避免强度与延展性之间的权衡
DOI：
10.1016/j.addma.2020.101725
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发表时间：
2021-01-01
影响因子：
11
通讯作者：
Prashanth, K. G.
中科院分区：
文献类型：
--
作者：
Wang, Z.;Tang, S. Y.;Prashanth, K. G.
通过选区激光熔化（SLM）制备了一种以马氏体结构为主的 Co-Cr-Mo 合金，其中 SLM 样品中形成的马氏体数量远大于铸造样品，这可归因于位错和 SF 等内部缺陷的高密度。我们观察到跨越不同长度尺度的分层微观结构，由宏观尺度的重熔区和轨道核心区域、微观尺度的细长柱状晶和等轴晶区域、亚微米尺度的马氏体板条以及纳米和原子尺度的高密度位错和堆垛层错组成。分层微观结构导致所制备的SLM和SLM退火样品具有出色的拉伸性能（屈服强度、极限拉伸强度和断裂应变分别接近735 MPa、接近1211 MPa和接近12.8%、接近893 MPa、接近1214 MPa和接近13.8%）。从分级微观结构和内部缺陷的角度讨论了决定强度和延展性的机制。沿其边界具有高密度位错的细胞结构和马氏体结构是强化的原因，而分层微观结构有助于获得适当的延展性。此外，证实了残余FCC板的马氏体相变诱导塑性弯曲，这有助于保持异质结构之间的不同塑性应变。通过 SLM 在这种 Co-Cr-Mo 合金中形成马氏体结构及其特征性的分级显微结构对于材料设计和高强度材料的应用具有改善的强度-延展性权衡而言是有前途的特征。
A Co-Cr-Mo alloy with predominantly martensitic structure was prepared by selective laser melting (SLM), where the amount of martensite formed in the SLM specimens is much larger than in the cast samples which can be ascribed to the high density of internal defects such as dislocations and SFs. We observe a hierarchical microstructure spanning over different length scales, consisting of remelted zones and track core regions at the macro-scale, regions with elongated columnar grains and equiaxed grains at the micro-scale, martensitic laths at the submicron-scale, and a high density of dislocations and stacking faults at the nano- and atomic scale. The hierarchical microstructure leads to the outstanding tensile properties of the as-prepared SLM and SLM annealed samples (with yield strength, ultimate tensile strength and fracture strain of similar to 735 MPa, similar to 1211 MPa and similar to 12.8%, and similar to 893 MPa, similar to 1214 MPa and similar to 13.8%, respectively). The mechanisms determining the strength and ductility are discussed in terms of the hierarchical microstructure and internal defects. The cellular structure with a high density of dislocations along their boundaries and the martensitic structure are the reasons for strengthening, while the hierarchical microstructure helps to obtain appropriate ductility. Furthermore, martensitic transformation induced plastic bending of the residual FCC plates was confirmed, which is helpful to maintain the different plastic strain between the heterogeneous structure. The development of the martensitic structure in this Co-Cr-Mo alloy by SLM and its characteristic hierarchical microstructure are promising features for material design and application of high-strength materials with improved strength-ductility tradeoff.