准连续钨/铜功能梯度材料的激光选区熔化3D打印制备及其热疲劳性能研究

W/Cu functionally gradient materials (FGMs) combine high melting point of W and high thermal conductivity of copper, which make them possible to operate in extreme environments repeatedly. Therefore, it is very suitable for high-power integrated circuit, electronics heat sink material and high heat fusion device component material. However, the big challenge to applying the quasi-continuous distribution of W/Cu FGMs is the extreme difficulty in manufacturing. Selective Laser Melting (SLM) 3D printing technique developed in recent years seems to be a promising method to solve the problems. The project intends to design several typical models according to the principle of thermal stress reducing during the simulation process by the ANASYS. Then it chooses the tailored particle size distribution of W and Cu powders, using the innovative SLM process which outputs multilayered continuous forming data integrated by process parameters of singer layer forming, combining the self-developed online process of powder mixing and feeding, intends to achieve an integral forming of W/Cu FGMs with quasi-continuous components. It will study the influence of microstructure, phase boundary and interface on the thermal fatigue property and illustrate the failure behavior and its mechanism. It will be envisaged that the success of the present research can provide theoretical and technical base for application of the W/Cu FGMs.

钨/铜（W/Cu）功能梯度材料兼具钨的高熔点和铜的高导热性能，非常适合用作高功率集成电路和电子器件热沉材料以及聚变装置高热流部件材料。然而，准连续W/Cu功能梯度材料难以制备是制约这类材料工程应用的瓶颈。近年来发展起来的激光选区熔化（SLM）3D打印技术有望解决该类材料成形制造难题。本项目拟首先采用ANASYS有限元软件根据热应力降低的原则优化设计几种典型梯度材料成分分布及其结构（梯度层厚、层数）的模型，然后选择粒度级配优化的W、Cu粉末，利用创新的SLM技术：即将单层成形工艺参数集成为多层连续成形数据输出，结合自主研制的在线混粉送粉工艺，辅以基板预热和激光重熔扫描策略，实现一体化、致密化的准连续W/Cu功能梯度材料成形。探索梯度材料微观组织结构、相界、宏观层界面与热疲劳性能的内在关系，阐明层间界面失效行为及机理。项目研究成果将为W/Cu梯度材料的应用提供理论与技术基础。

钨/铜（W/Cu）功能梯度材料兼具钨的高熔点和铜的高导热性能，非常适合用作高功率集成电路和电子器件热沉材料以及聚变装置高热流部件材料。本项目针对SLM成形钨基材料的致密度不高、存在裂纹缺陷等关键问题展开研究，通过进行SLM工艺参数优化、组织性能对比研究以及引入第二相纳米颗粒进行性能调控等方法，获得了高致密度且热力学性能良好的SLM钨基材料。同时采用辐射预热结合成形腔预热的创新方式成形了致密的Cu材料。最后成形了强度较好的W/Cu多材料，初步测试了其热冲击性能。主要研究进展、重要结果及关键数据等如下：.首次获得了致密度高达98.7％的纯钨试样，并系统阐述了SLM纯钨表面缺陷的形成原因。SLM成形试样的最大抗压强度、显微硬度和导热系数分别为1523 MPa、428 HV3和148 W/m·K，均优于传统粉末冶金工艺制备的试样。对比SLM钨和商业热轧钨的组织和热力学性能的结果表明， SLM钨的强度抗拉强度、硬度和导热性均差于目前的商业热轧钨。研究发现SLM纯钨存在三类晶粒，纵向晶粒、横向晶粒和S形晶粒，它们为晶界提供了裂纹扩展路径。添加纳米ZrC颗粒后发现钨中的裂纹密度减少了64%。研究为抑制SLM钨中的微裂纹提供了新的途径，即通过引入第二相粒子增加形核质点，有利于改善SLM钨中典型的各向异性微结构，从而提升其强韧性。阐述了SLM成形Cu合金的热导性能各向异性机理。通过合适的热处理可以调节Cu合金的硬度和热导率二者综合性能，成形了结合强度较好的W/Cu多材料，初步测试了其热冲击性能。本项研究为将SLM成形W/Cu材料的成形工艺及成形理论应用于未来的核聚变堆奠定了基础。