Abstract This work presents an experimental study of process optimization of the pair of critical parameters (speed function (SF) and focus offset (FO)) for stainless steel 316 L (SS316L) parts additively manufactured by selective electron beam melting (SEBM). Here, there are two sets of optimized SF-FO parameters that could build SS316L parts with high relative densities (>99%) and well-melted top build surfaces. Tensile test results show that most of the SEBM-built SS316L samples exhibit higher tensile strengths than the conventional cast and wrought counterparts, whereas their ductility is lower. In addition, strong anisotropic tensile properties are observed for the SEBM-built SS316L samples, e.g. they generally have better tensile properties when loaded parallel to the build direction as compared to the horizontal direction. However, a large number of σ phase was found to precipitate at grain boundaries in the SS316L samples fabricated under lower SF and larger FO with a higher build temperature, which evidently deteriorates their tensile properties particularly for the horizontal direction. It is suggested that SEBM process parameters for SS316L must be optimized to avoid σ phase precipitation at elevated temperatures apart from a well-melted top build surface and a high relative density.

中文翻译：

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选择性电子束熔化增材制造不锈钢316L零件工艺参数优化及力学性能

摘要 这项工作提出了对通过选择性电子束熔化 (SEBM) 增材制造的不锈钢 316 L (SS316L) 零件的关键参数对（速度函数 (SF) 和焦距偏移 (FO)）进行工艺优化的实验研究。在这里，有两组优化的 SF-FO 参数可以构建具有高相对密度 (>99%) 和熔化良好的顶部构建表面的 SS316L 部件。拉伸试验结果表明，大多数 SEBM 制造的 SS316L 样品表现出比传统铸造和锻造对应物更高的拉伸强度，但它们的延展性较低。此外，观察到 SEBM 构建的 SS316L 样品具有很强的各向异性拉伸性能，例如，与水平方向相比，它们在平行于构建方向加载时通常具有更好的拉伸性能。然而，在较低的 SF 和较大的 FO 下制造的 SS316L 样品中，在较高的构建温度下发现大量 σ 相在晶界处析出，这明显降低了它们的拉伸性能，特别是在水平方向上。建议必须优化 SS316L 的 SEBM 工艺参数，以避免在高温下除了熔化良好的顶部构建表面和高相对密度之外的 σ 相沉淀。