Laser powder bed fusion fabrication and characterization of crack-free aluminum alloy 6061 using in-process powder bed induction heating

A parameter development study for pre-alloyed aluminum alloy 6061 (AA6061) was carried out using an open-architecture powder bed laser melting (LM) technology with capabilities of induction heating for raising the powder bed temperature. Cube specimens (10 mm on each side) were used for parameter development with variation in laser power and scanning speed, whereas layer thickness, hatch spacing and powder bed temperature were empirically determined. While higher relative densities were achieved when using induction heating (as compared to specimens fabricated without induction heating), the key difference in the experiments was the ability to fabricate specimens without cracks when using induction heating. That is, crack-free AA6061 parts were fabricated with the highest relative density measured of 98.7%. Micrographs of specimens fabricated with the induction heating demonstrated the lack of melt pool and melt track features, which are normally only achieved with post-processing heat treatments. This research was important in its approach of using high temperature heating of the powder bed prior to laser scanning to produce crack-free AA6061 parts. Further investigations are ongoing to explore and optimize this fabrication process.