Laser polishing is a widely used technology to improve the surface quality of the products. However, the investigation on the physical mechanism is still lacking. In this paper, the established numerical transient model reveals the rough surface evolution mechanism during laser polishing. Mass transfer driven by Marangoni force, surface tension and gravity appears in the laser-induced molten pool so that the polished surface topography tends to be smoother. The AlSi10Mg samples fabricated by laser-based powder bed fusion were polished at different laser hatching spaces, passes and directions to gain insight into the variation of the surface morphologies, roughness and microhardness in this paper. The experimental results show that after laser polishing, the surface roughness of Ra and Sa of the upper surface can be reduced from 12.5 μm to 3.7 μm and from to 29.3 μm to 8.4 μm, respectively, due to sufficient wetting in the molten pool. The microhardness of the upper surface can be elevated from 112.3 HV to 176.9 HV under the combined influence of the grain refinement, elements distribution change and surface defects elimination. Better surface quality can be gained by decreasing the hatching space, increasing polishing pass or choosing apposite laser direction.

4H-SiC (silicon carbide), known as the third-generation semiconductor, has been widely used in high-power electronic devices. However, surface defects on wafers can seriously affect the key parameters and stability of silicon carbide devices. In this work, we pioneered a dual-laser comparative framework to systematically investigate the effects of continuous wave (CW) and femtosecond (FS) pulse laser micromachining on 4H-SiC epitaxial layers. CW laser restructuring optimized lattice integrity at sub-melting thresholds, while ultrafast FS pulse laser achieved submicron roughness control (from 8 μm to <0.5 μm) without obvious thermal collateral damage. To reveal the dynamic mechanism during the laser modification, multi-physics finite element models were adopted that decouple thermal and non-thermal mechanisms. This work expands the feasibility of laser micromachining for next-generation SiC device manufacturing.