激光处理非晶化合金表面的结构和性能研究

Metallic glasses are promising corrosion resistant and anti-ware surface and coating materials due to the high corrosion resistance and hardness. In the past two decades, a number of bulk metallic glasses with high glass-forming ability have been developed, which make it possible to synthesize vitrified alloy surface by laser surface treatment. In our recent work, we found that surface vitrification of some alloys by laser surface melting can not only improve the surface properties, but also enables the formation of a structure gradient from the glassy surface to the crystalline substrate. Therefore, the studies on the surface vitrification of alloys by laser surface treatment and the resultant microstructure and properties are of great significance for the fundamentals and applications of metallic glasses. In the proposed project, the effects of glass-forming ability of alloys and laser surface melting parameters on the formation and thickness of glassy surface layer will be studied, and the formation mechanism of the gradient structure from the glassy surface to the crystalline substrate will be clarified. The correlation between the corrosion and tribological behaviors of the laser surface vitrified alloys and the microstructure as well as residual stress will be established. The effects of burnishing process as a new approach for further improving the corrosion resistance as well as other properties of metallic glasses will also be investigated. On the basis, syntheses of metallic glassy coatings with high performance by laser cladding on commercial Al alloys, etc., will be explored. The present research will provide the theoretical and experimental basis for the fabrication of vitrified alloy surface by laser surface treatment and control the surface properties, facilitate the further understanding of the correlation between surface properties and microstructures of alloys and promote the practical applications of metallic glasses.

非晶合金的高耐腐蚀性能和高硬度使其非常适合应用于表面及涂层材料。近二十年来，大量块体非晶合金的发现使采用激光处理获得理想的非晶表面成为可能。我们研究发现，利用激光表面熔化使合金表面非晶化不仅可以改善表面性能，且形成了从非晶表面到晶态基体的层次丰富的结构梯度。因此，针对采用激光表面处理实现合金表面非晶化和所获得的表面结构与性能开展研究在基础和应用方面都具有重要价值。本项目拟系统研究合金的非晶形成能力及激光表面熔化工艺对表面非晶层的形成及厚度的影响，揭示从非晶表面到晶态基体的多层次结构形成机理，建立腐蚀、摩擦磨损行为与合金结构及残余应力的关联，并探索熨压加工等进一步改善非晶合金腐蚀行为等性能的新途径。在此基础上，探索在商用铝合金等表面激光熔覆制备高性能非晶涂层。本项目工作将为利用激光处理制备非晶表面及控制合金表面性能提供理论和实验基础，进一步理解合金表面性能与结构的关系，促进非晶合金的应用。

非晶合金的高耐腐蚀性能和高硬度使其非常适合应用于表面及涂层材料。近二十年来，大量具有高非晶形成能力的块体非晶合金的发现使采用激光处理获得理想的非晶表面成为可能。我们研究发现，利用激光表面熔化使合金表面非晶化不仅可以改善表面性能，而且形成了从非晶表面到晶态基体的层次丰富的结构梯度。因此，针对采用激光表面处理实现合金表面非晶化和所获得的表面结构与性能开展研究在基础和应用方面都具有重要价值。本项目系统研究了合金的非晶形成能力及激光表面熔化工艺对表面非晶层形成的影响，发现非晶形成能力较高的Ti基、Zr基、Fe基、Ni基等合金经激光表面熔化后较容易形成非晶表面，激光表面熔化工艺参数中的加载电压和扫描速度对非晶表面的形成影响较大，并针对上述合金建立了获得非晶表面的激光处理工艺。发现激光表面熔化可以使具有一定非晶形成能力的合金形成从非晶表面到晶态基体的梯度结构，但不同的合金体系具有不同的非晶-晶体过渡层结构；非晶表层厚度与合金的非晶形成能力、激光能量密度及合金对激光能量的吸收率有关，并揭示了该多层次梯度结构的形成机理。在此基础上的实验结果表明，非晶结构有助于获得高耐腐蚀性能，非晶基体中晶体相的出现会导致耐腐蚀性能的降低；通过对合金进行激光表面熔化获得非晶表层可显著提高硬度、改善表面性能，从而进一步揭示了合金的腐蚀行为、硬度等性能与微观结构的关联。在上述研究结果基础上，采用激光表面熔覆技术、利用非晶粉末制备了高硬度、耐腐蚀非晶涂层。此外，通过激光表面熔化工艺设计及熨压加工实现了对非晶合金表面残余应力的调控，显著提高了非晶合金的塑性及耐腐蚀性能，为进一步提高非晶合金的性能提供了新途径。本项目研究成果将为利用激光处理制备非晶表面及调控合金的性能提供理论和实验基础，有助于进一步深入理解合金的性能与结构的关系，促进非晶合金的应用。