以45#钢为研究对象,采用波长1064 nm的脉冲激光在45#钢表面进行微凸起造型,利用扫描电子显微镜和三维形貌仪表征形貌。试验得到球冠状、墨西哥帽状和M状形貌三种典型微凸起形貌。结合温度场以及气化反冲压力数值估算,系统研究了激光脉宽和峰值功率密度对微凸起形貌的影响规律,提出了一种火山口形貌形成的新机理。结果表明:微凸起形貌是激光与材料作用过程中热、力耦合作用的结果。中心凸起形貌由熔池内对流形成,峰值功率密度低,脉宽短,形成球冠状形貌。峰值功率密度越高、脉宽越大,所得中心凸台越高越细,演变为墨西哥帽状。当熔池中心温度超过材料沸点,材料气化形成的反冲压力,在熔池中心凸起顶端反压出凹陷,形成M状形貌。该结论有助于控制脉冲激光毛化制造微凸起的微观形貌。 Taking 45 # steel as the research object, the micro-convex shape was made on the surface of 45 # steel by pulsed laser with wavelength of 1064 nm, and the morphology was characterized by scanning electron microscope and three-dimensional topograph. Three types of typical microprotrusions, spherical cap, Mexican cap and M shape, were obtained. Combining with the temperature field and the numerical value of gasification backwashing pressure, the influences of laser pulse width and peak power density on the microprotrusion morphology were systematically studied, and a new mechanism for the formation of crater topography was proposed. The results show that the micro-convex morphology is the result of the coupling of heat and force during the interaction between the laser and the material. The center convex shape is formed by the convection in the weld pool with low peak power density and short pulse width, forming a spherical crown-like appearance. The higher the peak power density, the larger the pulse width, the higher the center boss is, the thinner it becomes. When the center of the molten pool temperature exceeds the boiling point of the material, the recoil pressure formed by the material gasification bulges out to form a M-shaped top in the center of the molten pool. This conclusion helps to control the pulsed laser texturing of micro-convex micro-topography.