镶嵌铸造-变形制备Mg/Mg层状复合材料的界面结合机制与演变规律

Under the big background of weight reduction of weapon system, magnesium alloys are becoming an optimal selection. However, for the normal magnesium alloys (NM), the strength is low and the creep resistance is poor. For the rare earth magnesium alloys (RM), the strengths at both room temperature and elevated temperature are relatively high. The creep resistance at elevated temperature is also excellent. The disadvantages such as high production cost, low deformation ability and difficult processing feature, however, still exist. To utilize their advantages and overcome their disadvantages from the NM and RM, NM/RM laminated composites, which can keep the light weight and meet the demands from armor materials, are suggested to be fabricated in this proposal. The good interface bonding cannot be achieved for the traditional fabrication methods such as solid-solid bonding and liquid-solid bonding due to the influence of oxide layer on the surface of magnesium alloys. A novel method of insert molding combined with deformation proposed by the current applicant can solve the technical problems mentioned before. However, some underlying scientific issues for this kind of new fabrication method still have to be faced. .To aim at solving these scientific issues, the interfacial bonding mechanism for the insert molding method can be explored based on understanding the microstructure formation and the evolution rule of oxide layer at the interface. The interfacial evolution rule during the heat deformation and heat treatment can be studied based on constructing the relationship among parent metal selection, processing parameters, microstructure, and properties. Moreover, a new type of NM/RM laminated composite with good properties and independent intellectual property will be fabricated. After finishing the project, the theory on interface formation between the same types of metals can be updated. Moreover, it can lay a foundation for the industrial fabrication of the NM/RM laminated composites.

武器系统减重迫切需求的大背景使得镁合金成为理想的“瘦身良药”。常规镁合金强度不高、抗蠕变性能差；稀土镁合金强度和高温性能优异，但成本高、塑形差、难加工。利用复合技术制备常规镁合金/稀土镁合金层状复合材料，充分发挥两种镁合金的“相补效应”，在保持轻量化同时改善组元镁合金的缺点，满足装甲材料性能需求。受限于镁合金表面氧化层，现有固-固和液-固制备技术无法实现界面牢固的冶金结合。申请人提出的镶嵌铸造-变形新方法解决上述难题的同时，其涉及的一些基础科学问题亟待解决。本项目以此为目标，将在理解复合界面微观组织形成与氧化层演变规律的基础上，掌握镶嵌铸造复合界面结合机制；在建立母材配置-工艺参数-显微组织-性能关联性基础上，掌握复合铸锭变形热处理过程中界面的演变规律，并制备自主知识产权的新型常规镁合金/稀土镁合金层状复合材料。项目的实施，可丰富目前同种金属复合界面的形成理论，也可为其工业制备奠定基础。

镁合金具有密度低、比强度和比刚度高、电磁屏蔽和阻尼性好等优点，是最轻的金属结构工程材料之一，具有广阔的应用前景。常规镁合金室温强度较低、高温性能差；稀土镁合金室温强度和高温性能优异，但成本高、塑形差、加工成形困难，限制了它们的广泛应用。利用复合技术制备常规镁合金/稀土镁合金层状复合材料，充分发挥两种镁合金的相补效应，在保持轻量化同时，提高了镁合金的塑性和强度。但是，现有的材料复合制备技术存在结合强度低、工艺复杂、成本高等缺点。. 本课题以常规镁合金（AZ31、AZ91和ZK60）与稀土镁合金（WE43）为研究对象，首先利用镶嵌铸造的方法制备出常规镁合金/常规镁合金（AZ31/AZ91）和常规镁合金/稀土镁合金（AZ31/WE43、ZK60/WE43）复合铸锭，在理解复合界面微观组织形成与氧化层演变规律的基础上，掌握了镶嵌铸造复合的制备工艺和界面结合机制。之后，建立了母材配置-工艺参数-显微组织-性能的关联性并筛选出两种性能突出的常规镁合金/稀土镁合金复合铸锭（AZ31/WE43、ZK60/WE43）进行热处理研究。在掌握了复合铸锭热处理工艺的基础上，阐明了热处理过程中界面的演变规律和强化规律。最后利用复合挤压制备了高性能AZ31/WE43复合棒材和具备界面增强结构的ZK60/WE43复合棒材，并对复合棒材的界面微观组织、力学性能和强化机理进行了分析，着重研究了两种界面结构在压缩过程中组织演变的规律，揭示了复合材料中的界面特征和两组元的加工硬化行为对混合法则的影响。本课题的执行，不但制备出了性能优异的常规镁合金/稀土镁合金复合材料，使得该材料具备工程应用的前景，而且首次通过在界面结构中引入强化相，解决了界面的弱化问题，这对于强化对复合材料学科界面形成理论的理解具有重要的科学意义。