Single-step process of microstructural functionally graded Ti6Al4V by laser powder bed fusion additive manufacturing

The objectives of this study are: (1) to verify whether using linear heat input alone is sufficient to predict the resulting microstructure of Ti6Al4V and (2) to demonstrate the potential of single-step process of functionally graded material using powder bed fusion. In laser powder bed fusion, linear heat input is defined as the ratio of laser power to scan speed. It is a key process variable that describes the unit energy input. Therefore, linear heat input has been extensively linked with the resulting microstructure. However, review of existing studies shows that when similar linear heat input was used, a marked difference in mechanical properties exists. Using proportionally changed laser power and scan speed in five zones, functionally graded specimens were fabricated in this study. All other parameters remain the same for these zones. Variation of microstructure and hardness across the five zones were obtained. This implies that linear heat input is not sufficient to determine the resulting microstructure and mechanical properties. The amplitude of laser power and scan speed has an effect on the resulting microstructure, so they need to be separately considered in future studies.