On the transformation between micro-concave and micro-convex in nanosecond laser ablation of a Zr-based metallic glass

Understanding the physical mechanism of laser-material interaction is significant and meaningful in both pure science and engineering applications. Laser ablation induced micro-concave is a commonly-observed phenomenon, but the formation of micro-convex by laser ablation is rarely reported. In this study, the transformation in surface microstructure from micro-concave to micro-convex, then to micro-concave again was reported for the first time in laser ablation of a typical Zr-based metallic glass (MG). The experimental results indicated that such transformations strongly depended on the peak laser power intensity and number of laser pulses. The coupling effects of the recoil pressure and Marangoni flow were proposed to explain the observed transformation. By locally overlapping adjacent micro-convexes, various surface patterns could be fabricated on the MG surface, which could tune its surface wettability. This study would not only enhance the understanding of laser-MG interaction but also provide new methods for patterning MG surface.