Mishra Pragya, Åkerfeldt Pia, Forouzan Farnoosh, Svahn Fredrik, Zhong Yuan, Shen Zhijian James, Antti Marta-Lena
Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, 97187 Luleå, Sweden.
GKN Aerospace, 46130 Trollhättan, Sweden.
Materials (Basel). 2021 Oct 6;14(19):5856. doi: 10.3390/ma14195856.
Laser powder bed fusion (L-PBF) has attracted great interest in the aerospace and medical sectors because it can produce complex and lightweight parts with high accuracy. Austenitic stainless steel alloy 316 L is widely used in many applications due to its good mechanical properties and high corrosion resistance over a wide temperature range. In this study, L-PBF-processed 316 L was investigated for its suitability in aerospace applications at cryogenic service temperatures and the behavior at cryogenic temperature was compared with room temperature to understand the properties and microstructural changes within this temperature range. Tensile tests were performed at room temperature and at -196 °C to study the mechanical performance and phase changes. The microstructure and fracture surfaces were characterized using scanning electron microscopy, and the phases were analyzed by X-ray diffraction. The results showed a significant increase in the strength of 316 L at -196 °C, while its ductility remained at an acceptable level. The results indicated the formation of ε and α martensite during cryogenic testing, which explained the increase in strength. Nanoindentation revealed different hardness values, indicating the different mechanical properties of austenite (γ), strained austenite, body-centered cubic martensite (α), and hexagonal close-packed martensite (ε) formed during the tensile tests due to mechanical deformation.
激光粉末床熔融（L-PBF）在航空航天和医疗领域引起了极大的关注，因为它能够高精度地制造复杂且轻量化的部件。奥氏体不锈钢合金316L因其良好的机械性能和在较宽温度范围内的高耐腐蚀性而被广泛应用于许多领域。在本研究中，对采用L-PBF工艺加工的316L在低温服役温度下在航空航天应用中的适用性进行了研究，并将其在低温温度下的行为与室温下的行为进行了比较，以了解该温度范围内的性能和微观结构变化。在室温及-196°C下进行拉伸试验，以研究其力学性能和相变。使用扫描电子显微镜对微观结构和断口表面进行表征，并通过X射线衍射分析相组成。结果表明，316L在-196°C时强度显著增加，而其延展性仍保持在可接受的水平。结果表明，在低温测试过程中形成了ε和α马氏体，这解释了强度的增加。纳米压痕显示出不同的硬度值，表明在拉伸试验过程中由于机械变形而形成的奥氏体（γ）、应变奥氏体、体心立方马氏体（α）和六方密排马氏体（ε）具有不同的力学性能。
