Selective laser melting of titanium parts: Influence of laser process parameters on macro- and microstructures and tensile property

The laser process parameters play an important role in the macro- and microstructures and tensile property of titanium samples fabricated by selective laser melting (SLM). In this study, the effect of laser process parameters on the density, surface morphology, dimensional accuracy, microstructure and tensile property of SLMed Ti6Al4V parts was investigated. With the increase of laser power and decrease of scan speed, the densification increased and the relative density showed reduced sensitivity to laser power under higher laser power (>175 W). The morphology of scan tracks on the top surface changed from clear and uniform mode to disordered mode with the increase of scan speed. The marks of melt flow, molten pool overlap and adhered powder could be observed obviously on the side surface. In the analysis of dimensional accuracy, the size shrinkage effect in the building direction (z-axis) was discussed and the “periphery spreading effect” in horizontal direction (x-axis and y-axis) was presented. Martensite α’ was the main constituent phase in SLMed Ti6Al4V samples. With the increase of scan speed, the width of prior β grains decreased gradually and the formed α’ phase changed into a relatively refined acicular shape. Conclusively, the relationship between microstructure and tensile property was discussed and a relative high tensile property was obtained.