碳纳米管复合增韧难熔高熵合金的激光增材制造及其强韧化机理研究

Refractory high-entropy alloys have superior high-temperature properties, which is of crucial importance to the technology progress in the advanced aerospace industry, however, the prominent obstacles of application are their poor ductility and limited traditional preparation process. This project introduces the carbon nanotubes (CNTs) toughening effects into the refractory high-entropy alloys fabrication to increase their ductility, and the laser metal deposition (LMD) process to induce quick solidification and 3D additive manufacturing. In this project, interfacial mechanical performance between the CNTs and refractory high-entropy alloy matrix under rapid solidification condition will be researched with composition designing, structure optimization, deposition parameters control. The effects of LMD and CNTs on the composition structure will be investigated, and interaction among the composites’ elements after thermal treatment and compression as well as the physical and chemical effects of the fracture surface, will be investigated. The design principles of the composition and structure of CNTs-refractory high-entropy alloys composites fabricated by LMD, as well as the control methods of preparation technology will be demonstrated. We expect the following significant beneficial results from this proposal: (1) development of the theoretical foundation in advanced the fabrication and toughing of refractory high-entropy alloys; (2) development of the corresponding technical support for research and development of new high -temperature structural material.

难熔高熵合金具有高温性能优异的突出优势，对促进航空航天用新型高温合金材料的发展有重要意义，但存在室温塑性差和传统制备工艺受限等突出问题。本项目将碳纳米管(CNTs)的强韧化效应引入高熵合金制备以改善其塑性，同时利用激光熔化沉积(LMD)技术实现CNTs增强难熔高熵合金复合材料的3D快速成形。项目拟通过成分设计、结构优化、成形参数控制等手段，解决快速凝固条件下碳纳米管与难熔高熵合金基体的界面结合问题；探索LMD工艺、CNTs添加对复合材料结构形貌、相组成、织构特征的影响规律；揭示热处理及室温压缩、高温热变形过程中合金各元素之间的相互作用规律以及断裂表面的物理化学本质，提出高性能CNTs复合难熔高熵合金的设计原则和制备工艺控制方法。本项目的研究将丰富难熔高熵合金的制备技术及其强韧化方法，为其作为新一代高温结构材料的研发与应用提供理论依据和技术支撑。

难熔高熵合金具有高强度、良好的热稳定性等特点，在航空航天等高温环境领域表现出广泛的应用前景，通过碳纳米管作为增强相可望改善合金的强韧性。本项目聚焦难熔高熵合金室温塑性差和传统制造工艺受限等问题，采用基于碳纳米管/原位碳化物作为增强相，CoCrMoNiTi系难熔高熵合金为基质，通过激光增材制造技术实现难熔高熵合金性能的有效提升，开展了CNTs增强难熔高熵合金复合粉体的制备、激光增材制造CNTs增强难熔高熵合金成形件的成分设计、物相组成、微观结构、室温/高温力学行为、成形机理、强韧化机制及高温热变形行为等关键科学问题研究。主要成果有：1.开发了超声分散结合机械合金化法制备CNTs增强难熔 高熵合金粉末的制备新技术，解决了CNTs在粉末中的均匀分散、界面结合问题，实现了不同含量CNTs/难熔高熵合金的可控制备；2. 利用激光熔化沉积技术制备了不同含量CNTs增强难熔高熵合金薄壁件，优化了成形工艺和CNTs含量，当激光能量密度为3.6 J/mm，CNTs含量为0.8wt%时，LMD成形CNTs-0.8/CoCrMoNbTi0.4合金显微硬度可达1015 HV0.5，断裂强度2110.50 MPa和断裂应变2.39%，明显优于传统铸态同成分合金的性能；3. 高温热处理工艺能够显著提高成形件的强韧性，通过热处理温度的调控实现固溶体相BCC和HCP相的转变，更多细小TiC析出相均匀分布，加强强韧化作用；4. 揭示了成形件的强韧化机制和高温热变形行为，高熵合金的固溶强化、CNTs的“桥接”作用、碳化物析出相的弥散强化以及LMD的细晶强化等多种强化机制共同作用使得该合金具有优异的室/高温力学性能和高温热稳性。以上成果对于促进先进制造高熵合金及其复合材料的进一步应用产生积极的作用。