This paper aims to investigate the influence of different post-annealing cooling conditions, i.e. furnace cooling (heat treatment (HT) 1 – slow cooling) and air cooling (HT 2 – fast cooling), on the microstructure and mechanical properties of selective laser melting (SLM) built austenitic 316L stainless steel (SS).,Three sets of 316L SS samples were fabricated using a machine standard scanning strategy. Each set consists of three tensile samples and a cubic sample for microstructural investigations. Two sets were subsequently subjected to annealing HT with different cooling conditions, i.e. HT 1 and HT 2, whereas one set was used in the as-built (AB) condition. The standard metallographic techniques of X-ray diffraction, scanning electron microscopy and electron back-scattered diffraction were used to investigate the microstructural variations induced by different cooling conditions. The resultant changes in mechanical properties were also investigated.,The phase change of SLM fabricated 316L was observed to be independent of the investigated cooling conditions and all samples consist of austenite phase only. Both HT 1 and HT 2 lead to dissolved characteristic melt pools of SLM. Noticeable increase in grain size of HT 1 and HT 2 samples was also observed. Compared with AB samples, the grain size of HT 1 and HT 2 was increased by 12.5% and 50%, respectively. A decreased hardness and strength, along with an increased ductility was also observed for HT 2 samples compared with HT 1 and AB samples.,From previous studies, it has been noticed that most investigations on HT of SLM fabricated 316L were mainly focused on the HT temperature or holding time. However, the post-HT cooling rate is also an equally important factor in deciding the microstructure and mechanical properties of heat-treated components. Therefore, this paper investigates the influence of different post-annealing cooling conditions on microstructure and mechanical properties of SLM fabricated 316L components. This study provides a foundation for considering the post-HT cooling rate as an influential parameter that controls the properties of heat-treated SLM components.

中文翻译：

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热处理后冷却对选区激光熔化奥氏体316L不锈钢组织和力学性能的影响

本文旨在研究不同的退火后冷却条件，即炉冷（热处理（HT）1 - 缓慢冷却）和空冷（HT 2 - 快速冷却）对选择性激光熔化的组织和机械性能的影响。 (SLM) 制造奥氏体 316L 不锈钢 (SS)。使用机器标准扫描策略制造三组 316L SS 样品。每组由三个拉伸样品和一个用于微观结构研究的立方体样品组成。两组随后在不同的冷却条件下进行 HT 退火，即 HT 1 和 HT 2，而一组用于竣工 (AB) 条件。X射线衍射的标准金相技术，使用扫描电子显微镜和电子背散射衍射来研究由不同冷却条件引起的微观结构变化。还研究了由此产生的机械性能变化。观察到 SLM 制造的 316L 的相变与研究的冷却条件无关，并且所有样品仅由奥氏体相组成。HT 1 和HT 2 都会导致SLM 的溶解特征熔池。还观察到HT 1 和HT 2 样品的晶粒尺寸显着增加。与AB样品相比，HT 1 和HT 2 的晶粒尺寸分别增加了12.5%和50%。与 HT 1 和 AB 样品相比，还观察到 HT 2 样品的硬度和强度降低，同时延展性增加。，根据之前的研究，已经注意到，大多数关于 SLM 制造的 316L HT 的研究主要集中在 HT 温度或保持时间上。然而，HT 后冷却速度也是决定热处理部件的微观结构和机械性能的一个同样重要的因素。因此，本文研究了不同的退火后冷却条件对 SLM 制造的 316L 部件的微观结构和机械性能的影响。该研究为将 HT 后冷却速率视为控制热处理 SLM 部件性能的影响参数提供了基础。在决定热处理部件的微观结构和机械性能方面，HT 后冷却速度也是同样重要的因素。因此，本文研究了不同的退火后冷却条件对 SLM 制造的 316L 部件的微观结构和机械性能的影响。该研究为将 HT 后冷却速率视为控制热处理 SLM 部件性能的影响参数提供了基础。在决定热处理部件的微观结构和机械性能方面，HT 后冷却速度也是同样重要的因素。因此，本文研究了不同的退火后冷却条件对 SLM 制造的 316L 部件的微观结构和机械性能的影响。该研究为将 HT 后冷却速率视为控制热处理 SLM 部件性能的影响参数提供了基础。