Abstract In this study, the process-structure-property relationship for selective laser melting of Invar 36 and stainless steel 316L is discussed. Invar 36 and stainless steel 316L have been used in various industrial applications for their unique properties, especially in the aerospace industry. Invar 36 offers a very low coefficient of thermal expansion while stainless steel 316L offers high corrosion resistance. Since both materials are weldable, but hard to machine, this study is aimed at finding the optimum laser process parameters for producing dense components from both alloys. A full factorial design of experiments was formulated in this paper to study a wide range of process parameters for both materials. The bulk density, tensile mechanical properties, fractography, material composition, and residual stresses of the parts produced were investigated. An optimum process window has been suggested based on experimental work. The induced residual stresses were categorized into two categories: microscopic residual stresses and macroscopic residual stresses. The microscopic residual stresses were measured using X-ray diffraction method and the macroscopic residual stresses were measured using cantilever deflection method and finite element simulations. The paper proposes two laser energy densities for each material: brittle-ductile transition energy density, ET, and critical laser energy density, EC. Below the brittle-ductile transition energy density, the parts exhibited void formation, low density, and brittle fracture. Above the critical energy density, the parts showed vaporization of some alloying elements that have low boiling temperatures. Stable melting ranges were found to occur between these two laser energy densities: 52.1–86.8 J/mm3 for Invar 36 and 62.5–104.2 J/mm3 for stainless steel 316L.

中文翻译：

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因瓦合金 36 和不锈钢 316L 选择性激光熔化的密度和机械性能

摘要 本研究讨论了Invar 36和316L不锈钢选区激光熔化的工艺-结构-性能关系。因瓦 36 和不锈钢 316L 因其独特的性能已被用于各种工业应用，尤其是在航空航天工业中。Invar 36 提供非常低的热膨胀系数，而不锈钢 316L 提供高耐腐蚀性。由于这两种材料均可焊接，但难以加工，因此本研究旨在寻找最佳激光工艺参数，以从这两种合金生产致密部件。本文制定了全因子实验设计，以研究两种材料的各种工艺参数。堆积密度、拉伸力学性能、断口、材料成分、并对所生产零件的残余应力进行了研究。已根据实验工作提出了最佳工艺窗口。诱导残余应力分为两类：微观残余应力和宏观残余应力。微观残余应力采用X射线衍射法测量，宏观残余应力采用悬臂偏转法和有限元模拟法测量。该论文为每种材料提出了两种激光能量密度：脆-韧转变能量密度 ET 和临界激光能量密度 EC。在脆-韧转变能量密度以下，零件表现出空隙形成、低密度和脆性断裂。高于临界能量密度，这些部件显示出一些沸点低的合金元素的汽化。发现稳定的熔化范围出现在这两种激光能量密度之间：因瓦合金 36 为 52.1-86.8 J/mm3，不锈钢 316L 为 62.5-104.2 J/mm3。