超声辅助激光沉积原位铝基纳米复合材料的机理研究

In-situ aluminum matrix nanocomposites fabricated by laser deposition have wide application prospect in the field of light weight for railway transportation. But the non-uniform szie and distribution of in-situ nano-particles limits the application of the technology because the temperature field is not evenly distributed during laser deposition process. Therefore, based on the strong mechanical shock effect and cavitation effect generated by ultrasonic vibration, the in-situ nano-particles with uniform szie and distribution during laser deposition process can be obtained. A new type of ultrasonic assisted laser deposition technology for in-situ aluminum matrix nanocomposites is presented in the project. The temperature variation during ultrasonic assisted laser deposition process, formation mechanism of in-situ nano-particles, microstructure evolution mechanism and strengthening and toughening mechanism of in-situ aluminum matrix nanocomposites will be investigated in the project, which is in favor of understanding the mechanism of ultrasonic assisted laser deposition for in-situ aluminum matrix nanocomposites.The project helps to catch the physical mechanism of ultrasonic assisted laser deposition of in-situ aluminum matrix nanocomposites. The new fabricating method of in-situ aluminum matrix nanocomposites can be obtained after finishing the project, which is very important to investigate the scientific problem and apply laser deposition technique.

激光沉积原位铝基纳米复合材料在轨道交通领域轻量化方面具有广阔的应用前景，但激光沉积层各区域的温度场分布不均匀，将降低原位纳米相尺寸和分布的均匀性，从而限制了该技术的广泛应用。本项目充分利用超声振动产生的强烈机械冲击效应和空化效应，实现激光沉积过程中原位纳米相尺寸均匀和分布均匀，提出了超声辅助激光沉积制备原位铝基纳米复合材料的方法。探索超声辅助激光沉积过程中的温度变化规律，分析原位纳米增强相的形成机制，阐明原位铝基纳米复合材料的微观结构演化机理及强韧化机制，揭示原位铝基纳米复合材料的超声辅助激光沉积机理。本项目的顺利实施，将有助于进一步认识超声辅助激光沉积原位铝基纳米复合材料的物理机制，为原位铝基纳米复合材料的制备提供了新思路，对科学问题的探索和加快激光沉积技术的应用具有重要的意义。

激光沉积原位铝基纳米复合材料在轨道交通领域轻量化方面具有广阔的应用前景，但激光沉积层各区域的温度场分布不均匀，将降低原位纳米相尺寸和分布的均匀性，从而限制了该技术的广泛应用。本项目充分利用超声振动产生的强烈机械冲击效应和空化效应，实现激光沉积过程中原位纳米相尺寸均匀和分布均匀，提出了超声辅助激光沉积制备原位铝基纳米复合材料的方法。本项目研究了激光沉积原位Mg2Si/Al铝基复合材料，其反应动力学机制为：熔化、扩散、反应、分解、冷却，得出了原位合成Mg2Si的动力学方程。随着激光功率的增加，原位生成Mg2Si的的速率和程度加大，随着富镁层厚度、Si颗粒大小和铝浓度的增大，反应速率和反应程度下降。随着激光功率和扫描速度的增加，Mg2Si含量增加，Mg2Si晶粒尺寸先减小后增大，Mg2Si的含量影响组织中Mg2Si的形态和分布。当激光功率为1000W，扫描速度为350mm/min时，Mg2Si/Al铝基的硬度最高，耐磨性和耐腐蚀性最好。研究了激光沉积原位TiC-TiB2/Al-12Si复合材料，发现TiC为细小弥散分布的多边形状、TiB2 为短棒状，两者均可作为 Al 的异质形核核心而细化晶粒。当复合材料中TiC-TiB2含量从0wt.%增加到12wt.%时，平均维氏硬度也在增加，8wt.%及以上相较于0wt.%约增加了1倍。复合材料中TiC-TiB2含量为8wt.%时，摩擦系数和磨损率最低，比0wt.%约减少了50%，耐磨性能提升。TiC-TiB2/Al-12Si复合材料的平均纳米硬度和弹性模量最大约为Al-12Si复合材料的2倍。复合材料中TiC-TiB2含量为8wt.%时，自腐蚀电流密度最小和自腐蚀电位最大，耐蚀性能最好。本项目的实施为进一步认识超声辅助激光沉积制备原位铝基纳米复合材料的物理机制，为原位铝基纳米复合材料的制备提供了新思路，对科学问题的探索和加快激光沉积技术的应用具有重要的意义。