激光成形颗粒增强镍基高温合金多相复合与梯度界面协同强韧化机理

The incorporation of ceramic reinforcing particles in Ni-based superalloys is an efficient method to improve their high-temperature mechanical performance. However, due to the limited wettability between ceramics and metals and the significant difference in coefficients of thermal expansion, the interfacial residual stress and microcracks are prone to present. Furthermore, the addition of ceramic reinforcing phase in Ni-based superalloys tends to decrease the controllability of compositions and microstructures of γ matrix phase and γ’(γ’’) reinforcing phase. The above factors are responsible for the decrease in the ductility and plasticity of laser formed parts. In the present project, the gradient interface is tailored between ceramic reinforcement and matrix via the control of laser processing parameters and components of composite materials. The interfacial residual stress, interfacial micropores and microcracks can be controlled and eliminated, hopefully resolving the contradiction between strength and ductility of laser formed composites parts. The formation mechanism, microstructure and performance of laser formed gradient interface are studied and the influencing mechanisms of material and process factors are assessed. The microstructural developments of ceramic reinforcing phase, γ’(γ’’) phase, and γ phase at different laser processing parameters are investigated and the control methods of interior metallurgical defects are proposed. The load-bearing properties and mechanical behaviors of the gradient interface under various types of loads and operating temperatures are studied and the transfer and distribution rules of internal stress inside the parts are elucidated. The stress-induced movement and propagation mechanisms of dislocations inside the materials are investigated and the interaction rules of dislocations with reinforcing phases and interfaces are studied, proposing the strengthening and toughening mechanisms of laser formed parts. This project is expected to provide the scientific basis for laser additive manufacturing of high-performance Ni superalloy based composites parts with controlled structures and properties.

在Ni基高温合金中复合陶瓷增强颗粒，是提高其高温力学性能的有效途径，但陶瓷/金属润湿性差、线膨胀系数差异大，易导致界面残余应力及裂纹，且添加陶瓷相使基体相γ和强化相γ’(γ’’)成分和组织可控性变差；这是激光成形件韧性和塑性下降的主因。本项目通过激光工艺参数和复合材料组分调控，可在陶瓷增强体与基体间形成梯度界面层，控制并消除界面残余应力、界面微孔及微裂纹，有望解决复合材料零件“强”与“韧”的矛盾。研究激光作用下梯度界面形成机制、显微结构、界面性能及材料和工艺影响机理；研究陶瓷相、γ’(γ’’)及γ相显微组织随激光工艺参数的演变规律及内部冶金缺陷控制方法；研究各种载荷和温度下梯度界面承载特性、力学行为及内应力传递与分布规律；研究应力作用下材料内部位错运动和增殖机制以及与增强相和界面作用规律，揭示激光成形件强韧化机理。本项目可为高性能Ni基高温合金复合材料零件激光控形控性增材制造提供科学基础。