冷喷涂/选区激光熔化复合增材制造成形纯铜显微结构与力学性能的研究

Microstructure and mechanical properties of hybrid additively manufactured pure copper based on cold spray and selective laser melting

基于冷喷涂和选区激光熔化复合增材制造技术,以经热处理的冷喷涂沉积纯铜为基体进行选区激光熔化成形,成功制备出具有多重组织结构和优异结合强度的纯铜试样,并通过金相显微镜、扫描电子显微镜和拉伸试验等分析测试方法,系统研究了热处理对其显微结构和力学性能的影响.研究结果表明:以原始态冷喷涂沉积纯铜为基体进行选区激光熔化成形时,试样上下两部分分别由均匀排列的鱼鳞状熔道和扁平化沉积粒子堆积搭接而成,两者界面由于冷喷涂沉积粒子之间的机械结合和局部冶金结合而表现出较低的结合强度;冷喷涂沉积纯铜经热处理之后,其晶粒发生再结晶和长大而形成大量等轴晶和孪晶,有效地愈合了沉积粒子之间的界面;与此同时,由于选区激光熔化成形过程中的定向散热和凝固特性,成形纯铜试样内部晶粒呈柱状生长,部分柱状晶穿过熔池边界并在界面处与冷喷涂沉积纯铜冶金结合,从而使得试样结合强度显著提高,其值高达62 MPa,较冷喷涂沉积纯铜提高了38%.表明,基于冷喷涂和选区激光熔化复合增材制造技术的可行性,为快速实现大尺寸、复杂结构、高精度金属构件指明了新的方向.

A hybrid additive manufacturing technique based on cold spray(CS) and selective laser melting(SLM),in which the CS parts after heat treatment were used as the substrate for SLM process,was proposed to manufacture the pure copper with multiple microstructures and well bonding strength. The effect of heat treatment on the microstructure evolution and mechanical properties was systematically investigated by optical microscope(OM),scanning electron microscope(SEM)and tensile test. The results show that the hybrid additive manufactured pure copper samples were composited of SLMed Cu with semicircle melt tracks(upper part)and CSed Cu with stack particles(lower part). Meanwhile,the interface between CSed and SLMed part shows low bonding strength due to the mechanical bonding and limited local metallurgical bonding. However,the CSed Cu after heat treatment shows a large number of equiaxed crystals and twins,which can effectively heal the interface between the deposited particles and make them metallurgical bonding. At the same time,the grain of SLMed Cu grow as columnar and will pass through the boundary of molten pool due to its directional heat dissipation and solidification characteristics,which result into the metallurgical boding at the interface. The samples show the highest bonding strength of 62 MPa,which is38% higher than the former. The current results demonstrate the feasibility of composite additive manufacturing technology based on cold spraying and selective laser melting forming,and point out a new direction for the rapid realization of large-size,complex structure and high-precision metal components.