THERMALLY STABLE ALUMINUM ALLOYS DESIGNED FOR LASER POWDER BED ADDITIVE MANUFACTURING

Constellium has developed novel additive manufacturing (AM) aluminum alloys, specifically designed for Laser Powder Bed Fusion (LPBF) additive manufacturing and bringing improved properties, higher AM productivity and simplified post-processing. The alloys are based on rapid solidification metallurgy, using the laser to quench in the alloying elements and resulting in very fine microstructures. This approach eliminates the need for the solution heat treat and quench operation used for conventional alloys, which brings a risk of residual stresses and potentially distortion of the complex geometries targeted by LPBF. With the new rapid solidification alloys, straightforward post-build heat treatments are used to tune the desired component properties. The main alloying elements quenched in by the laser diffuse slowly in aluminum, giving the alloys much higher thermal stability than conventional systems and bringing new possibilities for lightweight aluminum components with service temperatures up to around 500°F (260°C). The alloy designs avoid volatile elements such as Mg or Zn, reducing generation of fumes which may impact laser absorption and process stability, particularly in the case of the new high power multilaser systems. The absence of more volatile elements than aluminum may also help to stabilise the melt pool – the new alloys are showing robust AM performance with higher productivity and quality levels than conventional Aluminum-Silicon systems. The fine microstructures bring improved surface treatment and corrosion performance. In addition, the Mg-free designs lead to a more stable oxide, designed to improve consistency of powder behaviour during multiple build cycles. Looking towards scale-up and sustainability, the alloys are based on input materials used in Constellium’s conventional aerospace casthouses, avoiding rare earths or other critical raw materials. Next steps include civil aviation qualification studies as well as shorter-term developments for applications in heat exchangers and satellites.