In-situ formation and additive manufacturing of nano particulate reinforced metal matrix composites by aser metal deposition

颗粒增强金属基复合材料（PRMMC）由于其综合性能和在航空航天、汽车和其他工业中的许多苛刻应用，在过去的几十年里得到了广泛的研究。近年来的研究表明，当颗粒尺寸缩小到纳米尺度时，纳米颗粒增强MMC （nPRMMC）表现出优异的强度、硬度、耐蚀性、耐热性、抗疲劳性和高温性能，特别是突出的延展性和断裂韧性，是微尺度prmmc无法比拟的。目前，这一研究领域受到了世界各国的广泛关注。然而，仍有三个科学挑战尚未得到很好的理解或解决：(1)纳米陶瓷颗粒由于其强烈的团聚和聚类倾向而难以在基体中均匀分散；（二）纳米级陶瓷颗粒与金属基体之间具有良好的界面结合；（III）成型nPRMMC用于散装结构或涂料的能力和灵活性。对上述问题的清晰认识和可能的解决方案将对探索这些先进的nPRMMC材料具有重大的科学和工程影响。除了文献报道的方法外，我们还提出了一个基于激光金属沉积（LMD）的纳米颗粒增强金属基复合材料原位形成和增材制造的基础研究项目。LMD为设计的宏观/微观结构、成分和几何形状提供了卓越的灵活性和可控性，使其成为新材料开发和成型的有力工具。我们的研究将包括：(1)通过两种新途径在金属基体中形成分散和均匀的纳米级颗粒的机理：(a)在凝固过程中原位形成纳米级颗粒；(b)通过激光金属沉积和激光重熔，将微尺度的陶瓷颗粒溶解到纳米尺度。(2)了解原位形成的纳米颗粒的均匀分布和纳米尺度可调性机制；(3) nPRMMC的表征和性能；(4) LMD对nPRMMC的塑造能力。

Particulate Reinforced Metal Matrix Composites (PRMMC) have been extensively investigated in last decades, due to their comprehensive properties and many demanding applications in aerospace, automobile and other industries. Researches in recent years demonstrate that when the particle size is downsized to nanometer scale, the nanoparticulate reinforced MMC (nPRMMC) show excellent strength, hardness, corrosion resistance, thermal resistance, fatigue resistance, high-temperature performance and especially outstanding ductility and fracture toughness, which is incomparable by the micro-scale PRMMCs. Currently, this research area attracts considerable attention world wide. However, three scientific challenges remain not well understood or solved: (I) the extremely difficult uniform dispersion of nanosized ceramic particles in the matrix due to their strong tendency for agglomeration and clustering; (II) the good interface bonding between the nano-scale ceramic particles and the metal matrix; (III) the capability and flexibility for shaping the nPRMMC for bulk structures or coatings. A clear understanding and possible solutions to above issues will have significantly scientific and engineering impacts to explore these advanced nPRMMC materials. Besides the reported approaches in literature, we propose a fundamental investigation project on the in-situ formation and additive manufacturing of nano particulate reinforced metal matrix composites using laser metal deposition (LMD). LMD offers remarkable flexibility and controllability for designed macro/micro structure, composition and geometry, enabling a strong tool for novel material development and shaping. Our research will cover: (1) Formation mechanism of dispersive and uniform nano-scale particles in a metal matrix by two novel routes: (a) In-situ formation of nano-scaled particulates during the solidification process; (b) Dissolution of micro-scale ceramic particulates into nano-scale by laser metal deposition and laser remelting (2) Understanding the mechanisms on homogenous distribution and nano-scale tunability of in-situ formed nanoparticles); (3) Characterization and performance of the nPRMMC; (4) Shaping capability of the nPRMMC by LMD.