双相镁锂合金表面激光熔覆原位自生陶瓷金属基复合涂层基础研究

Ultra-light biphasic magnesium-lithium alloy is the ideal material to realize lightweight due to its good processibility and comprehesive properties. But its further applications are restricted by the corrosion resistance and wear-resisting property. Consequently, in this project, researches are carried out on the new processing and material system of the in situ synthesis of ceramic particles enhanced metal matrix composite layer on biphasic magnesium-lithium alloy through Laser cladding technology. Aiming at the high chemical reactivity and Easy oxidation of magnesium-lithium alloy, systemic researches on microstructure evolution, physical metallurgy law, rapid solidification behavior and strengthening phase growth mechanism are proposed based on in situ synthesis of ceramic particles enhanced metal matrix composite layer through rectangular flattened laser beam cladding technology; The effect of Uniform heating on the controlling of molten pool local superheating temperature, reducing the burning loss of matrix and chemical metallurgy reaction between alloy composition are studied; Thermodynamics and dynamics conditions for the precipitation of intermetallic compound and ceramic strengthening phase are calculated and analyzed, and the nucleation, growth principle and interface mechanics behavior of binding phase and strengthening phase are revealed, and rapid solidification model of composite layer is build up; Crystallography growth orientation and pattern of the strengthening phase are analyzed, and in-situ precipitation and growth mechanism of strengthening phase are dissed. The research achievement can provide a new way for surface processing of ultra-light magnesium-lithium alloy, and have important theoretical and application value for enlarging the application area of magnesium-lithium alloy and realizing lightweight components.

双相镁锂超轻合金易于成型且具备良好的综合性能，是实现部件轻量化的理想材料，然而耐蚀、耐磨性能差是制约其推广应用的主要因素。为此，本项目将开展双相镁锂合金表面激光熔覆原位自生陶瓷颗粒增强金属基复合层的新工艺、新材料体系研究。针对镁锂合金化学活性高、易氧化的特性，项目拟系统研究基于矩形平顶光束激光熔覆原位自生陶瓷颗粒增强金属基复合层的组织结构演变、物理冶金规律、快速凝固行为、强化相生长机理；研究均匀加热对控制熔池熔体局部过热度、减少基体烧损及合金成分之间化学冶金反应的作用；计算分析金属间化合物、陶瓷强化相析出的热力学与动力学条件，揭示粘结相、强化相的形核、长大规律及其界面力学行为，建立复合层快速凝固模型；辨析强化相晶体学生长取向、模式，探讨增强相的原位析出机制与生长机理。研究成果将为镁锂超轻合金的表面处理方法提供新思路，对扩大镁锂合金的应用范围和实现部件轻量化具有重要的理论价值和应用价值。

镁锂合金作为最轻的金属结构材料，具有较高的比刚度和比强度, 是实现航空、航天、汽车、电子等结构件轻量化的首选材料之一。其中双相镁锂超轻合金易于成型且具备良好的综合性能，是实现部件轻量化的理想材料，然而耐蚀、耐磨性能差是制约其推广应用的主要因素。. 本项目系统开展了双相镁锂合金表面激光原位自生陶瓷颗粒增强金属基复合层的新工艺、新材料体系研究。以激光熔覆、激光熔凝与激光相变硬化为技术总路线，同时开发基于激光熔覆的激光直接沉积成形与选区激光熔化两种新工艺的应用，旨在通过原位自生增强相、组织细化、相变硬化等强化机制制备复合涂层。项目首先对关键元器件与激光加工装备进行了研制开发，提出采用选区激光熔化多层堆积的表面处理新工艺；在此基础上，采用有限元数值计算、试验分析测试等方法深入研究了激光作用材料后加热过程中的熔池形貌与温度场分布特征，以及基体烧损、元素蒸发与迁移、界面结合特征等物理冶金规律，揭示了材料在冷却过程中的结晶凝固行为、晶体生长规律、强化相析出等，以及凝固后冷却过程中相变与元素扩散机制等；最后，针对粉末传输、加热/冷却、相变等现象，分别建立了相应的物理数学模型，进而揭示了不同激光表面处理下的组织演变规律及耐蚀、耐磨性能，重点探讨了微观组织中碳化物熔解、析出机制与性能强化机制。我国作为镁和锂的资源大国，进行镁锂合金的基础理论和应用技术开发具有重要的战略意义。研究成果具有一定的通用性，还可用于汽车制造、模具修复等行业。项目研究成果Optics and Lasers in Engineering、Optics and Laser Technology、Materials Letters、Applied Physics A等重要期刊与会议发表论文17篇，项目研发的原创新关键元器件与技术方法共申请发明专利10余项，研究成果进行了卓有成效的技术推广与成果转化，签订企业委托研发项目1项。.