Laser Stirring Technique for Laser Powder Bed Fusion of High Strength Aluminum Alloys

Recently, much of the focus in developing AM processes has been towards producing fully dense and crack-free deposits that make epitaxial deposits with the texture oriented parallel to the build direction. The thought is that epitaxial deposits would be ideal for maximizing the mechanical properties of AM-built parts as they occur in directionally solidified high strength aluminum alloys loaded along the solidification direction. However, epitaxial growth does not necessarily correlate to enhanced mechanical performance in all situations.

Through the AM process, as build microstructure has the potential to be controlled to produce functionally equiaxed microstructure and crystallographic texture throughout an AM part that, in theory, could perform better under complex mechanical loadings than epitaxial microstructure. A new era of engineering design is possible with crystallographic texture control combined with equiaxed, fine grain microstructure as materials engineering concepts. Within this work, a demonstration of microstructure control and mechanical properties through the variations in the scan strategy by laser stirring was illustrated for A205 and AlSc alloys. Both alloys were successfully deposited crack-free with high density and more refined as build microstructure using stirred hatches. When compared directly, a higher number of parameter combinations using stirred hatches yielded higher density than those using linear hatches.