Mechanical properties of Invar 36 alloy additively manufactured by selective laser melting
Mechanical properties of Invar 36 alloy additively manufactured by selective laser melting
复制标题
选区激光熔化增材制造Invar 36合金的力学性能
DOI：
10.1016/j.msea.2019.138799
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发表时间：
2020-01-20
期刊：
影响因子：
6.4
通讯作者：
Fang, Daining
中科院分区：
文献类型：
--
作者：
Wei, Kai;Yang, Qidong;Fang, Daining
因瓦36合金因其极低的热膨胀系数而被广泛应用于航空航天工程。本工作旨在探索工艺参数对Invar 36的微结构和机械性能的潜在影响，该微结构和机械性能通过选择性激光熔化（SLM）与岛扫描策略增材制造。建立了适用于大范围SLM工艺参数序列的全析因设计。对复合材料的密度、硬度、抗拉强度等力学性能以及显微组织、断口形貌进行了表征。结果表明，增加曝光时间和减小点距可显著诱导稳定熔化，并获得上级密度和硬度。激光能量密度对显微组织有显著的影响，因为极低的激光能量密度会导致相当大的熔合孔缺乏、未熔化的粉末颗粒和岛的模糊边界。但是，过高的激光能量密度会导致少量的小孔孔隙，并使激光扫描轨迹和岛状界面过渡变得不规则。最佳激光能量密度为99.2J/mm（3），所制备的Invar 36合金的相对密度为99.5%，维氏硬度为1.8GPa，抗拉强度为480 MPa，与常规方法制备的Invar 36合金相当。在200 ℃和600 ℃的试验温度下，γ相粗化，导致拉伸性能显著退化。SLM工艺与力学性能之间的相关性为Invar 36合金的增材制造提供了实验依据。
Invar 36 alloy is widely used in aerospace engineering, owing to its extremely low coefficient of thermal expansion. This work aims to explore the underlying influence of process parameters on the microstructures and mechanical properties of Invar 36 additively manufactured by selective laser melting (SLM) with island scanning strategy. A full factorial design for a wide range of SLM process parameter sequence was established. Density and the mechanical properties including hardness, tensile strength as well as microstructures, fractography were characterized. The results confirm that the increment of exposure time and the reduction of point distance remarkably induce stable melting and achieve superior density and hardness. The laser energy density shows a pronounced effect on the microstructures, as extremely low laser energy density induces considerable lack-of fusion pores, unmelted powder particles and blurry boundaries of islands. While, very high laser energy density induces a few keyhole pores, and makes the laser scanning tracks and island boundaries transfer to be irregular. The optimal laser energy density is recommended to be 99.2 J/mm(3), and the as-fabricated Invar 36 shows the relative density of 99.5%, Vickers hardness of 1.8 GPa and ultimate tensile strength of 480 MPa those are very comparable to conventionally fabricated one. The testing temperatures of 200 degrees C and 600 degrees C induce the coarsening of gamma phase, and result in a significant degeneration of tensile properties. The correlations between the SLM process and mechanical properties provide experimental basis of the additive manufacturing Invar 36 alloy.