钎焊在电子、医疗、航空航天等领域的元器件和零部件制造中有广泛应用。提高液态钎料对母材表面的润湿铺展性是高钎焊质量的关键之一。超快（皮秒和飞秒）激光与物质作用时具有非线性吸收、多材料适应、极低热效应等显著优点并成为微纳加工研究热点。本项目提出在不影响非辐射区母材性能、不改变其表面成分及不增加涂层前提下，制备可控、有序微纳米表面结构，实现对钎料润湿铺展性的调控，提高钎焊质量。利用皮秒激光、飞秒激光、皮秒和飞秒激光复合分别制备微米有序、纳米有序、微米-纳米多尺度有序的表面结构并实现优化控制，研究揭示有序微纳米结构对润湿铺展性的调控机制、其尺寸和尺度效应在润湿铺展中的作用，及有序表面结构影响钎焊接头强度的规律。同时建立时域有限差分和有限元模型，分析阐明有序微纳米表面结构形成机理及其提高钎焊接头强度的影响机理。推动钎焊发展并特别适合难钎焊材料或要求钎着率高、长距离润湿铺展的场合，理论和工程意义重大。

Brazing has been widely applied in electronics, aerospace, energy, and medical industries. The wettability and spreadability of liquid filler metal on the base metal are essential factors affecting the brazement quality. Ultrafast lasers, including picosecond and femtosecond laser, possess prominent features derived from their interaction with materials, such as non-linear energy absorption, multi-material adaptability, and ultra-low thermal effects. Based on the above reasons, the ultrafast lasers were used to induce micro/nano Periodic Surface Structures (PSS), which would enhance the wetting and spreading of the filler metal and also improve the brazement strength. In the present project, picosecond laser, femtosecond laser and their hybrid will be used to produce micro scale PSS, nano scale PSS and micro-nano multi-scale PSS. Effects and mechanisms of PSS on the reacting/dissolving driven wetting and spreading will be systematically studied. The size effects and multi-scale effects of PSS on the wetting and spreading of filler metal will be investigated. The mechanisms of brazement strength improvement by inducing PSS will be conducted. Finite Difference Time Domain (FDTD) model and finite element model will be built up in order to simulate the PSS formation and brazement strength improvement, respectively. This project is expected to drive the development of brazing, especially for materials having bad brazability, braze components requiring high brazed rate and long spreading distance. This is meaningful for both theoretical development and engineering significance.