Ultrashort pulse laser shows good potential for heat control improvement in metal additive manufacturing. The challenge of applying ultrashort pulse laser as the heat source is to form a fully melted and dense microstructure. In this study, a picosecond pulse laser is introduced for fabricating single layer Ti6Al4V samples. The results, by examining through X-ray computed tomography (X-CT), scanning electron microscopy (SEM), show that highly dense Ti6Al4V samples were fabricated with optimized process parameters. The analysis of the cross section presents a three-zones structure from top to bottom in the sequence of the fully melted zone, the partially melted zone, and the heat-affected zone. A semi-quantitative study is performed to estimate the thermal efficiency of melted pool formation. The mechanical properties of the samples are tested using nano-indentation, showing an elastic modulus of 89.74 ± 0.74 GPa. The evidence of dense melted pool with good mechanical properties indicates that the picosecond laser can be integrated as the heat source with the current metal additive manufacturing to fabricate parts with accuracy control for the smaller size of thermal filed.
Keywords: heat effect; laser additive manufacturing; laser-matter interaction; molten pool formation; nano–indentation; picosecond pulse laser.