Abstract

The microstructure and mechanical properties of chromium–nickel austenitic stainless steel fabricated by selective laser melting using a Realizer SLM100 3D printer have been investigated in this work. The structure of the studied specimens has been formed by the complete melting of the initial powder and high-speed cooling of the melt. Cooling of the melt initially leads to the formation of δ ferrite, and then, polymorphic δ → γ transformation results in the formation of the final austenitic structure. The structure of δ ferrite which formed during melt crystallization has been found to exhibit a clear pattern of periodicity. The periodicity depends on the parameters of the melting process, such as the distance between neighboring bands formed during laser-beam traveling (intertrack distance) and the step of platform feeding (distance between layers). The polymorphic δ → γ transformation takes place by a disordered mechanism and no austenite texture forms. However, some structural heredity remains. It can be seen in the orientational relationship between some austenite grains and δ-ferrite grains. The steel fabricated by laser melting is shown to have high mechanical properties such as the yield strength, the ultimate tensile strength, and the tensile elongation at a strain rate of 10^–2 s^–1, which are 320, 765 MPa, and 50%, respectively. The yield strength and ultimate tensile strength of the specimens under dynamic compression by the Hopkinson–Kolskii technique at an average strain rate of 10³ s^–1 are 550 and 945 MPa, respectively.

中文翻译：

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选择性激光熔化制备奥氏体不锈钢的组织和力学性能

摘要

在这项工作中已经研究了使用 Realizer SLM100 3D 打印机通过选择性激光熔化制造的铬镍奥氏体不锈钢的微观结构和机械性能。研究样品的结构是由初始粉末完全熔化和熔体高速冷却形成的。熔体的冷却最初导致δ铁素体的形成，然后多晶型δ→γ转变导致最终奥氏体组织的形成。已发现在熔体结晶过程中形成的 δ 铁素体结构表现出清晰的周期性模式。周期取决于熔化过程的参数，如激光束行进过程中形成的相邻波段之间的距离（道间距离）和平台进料的步骤（层间距离）。多晶型 δ → γ 转变是通过无序机制发生的，没有形成奥氏体组织。然而，一些结构遗传仍然存在。从一些奥氏体晶粒和δ-铁素体晶粒的取向关系可以看出。通过激光熔化制造的钢具有较高的机械性能，如屈服强度、极限抗拉强度和应变速率为 10 时的拉伸伸长率。^–2 s ^–1，分别为 320、765 MPa 和 50%。Hopkinson-Kolskii 技术在平均应变速率为 10 ³ s ^{–1 时}动态压缩下试样的屈服强度和极限拉伸强度分别为 550 和 945 MPa。