The crack healing effect of scandium in aluminum alloys during laser additive manufacturing

Wrought aluminum alloys are light, strong, and most commonly used in many engineering industries but experienced the hot crack issues during selective laser melting (SLM). A chemical modified aluminum alloy AA6061 is developed and printing process optimization is carried out to obtain nearly dense printed samples. The present study shows that the powders are mostly spherical flow stably. The results also indicate that the addition of a minor amount (0.15 wt%) of scandium is not only able to heal the crack during SLM process but also significantly improve the strength of aluminum alloy, AA6061, to more than 350 MPa with a high elongation of 31 %. Very fine microstructure within a melt-pool is achieved with the formation of the nano-meter to sub-micron meter bundle structure. Scandium and aluminum share similar lattice structures in which many of aluminum atoms can be replaced with Scandium ones acted as the nucleation sites and thus prevented the micro-cracks.