Selective laser melting of pure tantalum: Densification, microstructure and mechanical behaviors
Selective laser melting of pure tantalum: Densification, microstructure and mechanical behaviors
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DOI：
10.1016/j.msea.2017.09.083
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发表时间：
2017-11
期刊：
影响因子：
6.4
通讯作者：
Li-bo Zhou;Tiechui Yuan;Rui-di Li;Jianzhong Tang;Guohua Wang;Guo Kaixuan
中科院分区：
文献类型：
--
作者：
Li-bo Zhou;Tiechui Yuan;Rui-di Li;Jianzhong Tang;Guohua Wang;Guo Kaixuan
本文系统地研究了纯钽的选区激光熔化工艺，重点研究了钽试样的致密化、显微组织和力学性能。高的激光扫描速度导致微孔和不连续的扫描轨迹，由于马兰戈尼对流和球化效应引起的液体的不稳定性升高。然而，由于热应力和球化效应，在低扫描速度下产生层间热微裂纹。最佳SLM处理的Ta零件的显微硬度和抗拉强度分别提高到445 HV和739 MPa，这是相当高的比通过铸造（110 HV和205 MPa）或粉末冶金（120 HV和310 MPa）方法处理的试样，由于细晶强化。拉伸失效的SLM处理的试样的断裂形貌表明，孔隙和不完全熔化的颗粒是负责多孔样品的断裂。而致密试样的断裂主要是解理断裂和轻微的韧性断裂。并对其破坏机理进行了探讨。在干滑动磨损试验中，最佳制备工艺的钽零件由于硬化摩擦膜的形成而使摩擦系数降低到0.3，磨损率最低为7.1×10−3mm3N−1m− 1。
In this study, selective laser melting (SLM) of pure tantalum (Ta) was systematically investigated, with emphasis on densification, microstructure and mechanical properties of Ta specimen. The high laser scanning speed resulted in micropores and discontinuous scan tracks, owing to the elevated instability of the liquid induced by Marangoni convection and the balling effect. However, the interlayer thermal microcracks were produced at a low scanning speed, due to the thermal stress and balling effect. The microhardness and tensile strengths of the optimally SLM-processed Ta parts were improved to 445 HV and 739 MPa, respectively, which were considerably higher than specimens processed by cast (110 HV and 205 MPa) or powder metallurgy (120 HV and 310 MPa) method, due to the fine-grain strengthening. The fracture morphology of the tensile-failed SLM-processed specimens showed that the porosities and incompletely melted particles are responsible for the fracture of porous sample. While for dense sample, cleavage fracture and minor ductile fracture both account for the fracture. And the failure mechanisms were discussed. The reduced coefficient of friction of 0.3 and lowest wear rate of 7.1×10−3mm3N−1m−1in dry sliding wear tests were obtained for the optimally prepared Ta parts due to the formed adhesion of hardened tribolayers.