Effect of a Zr source addition on the microstructure of Al-SiC composites elaborated by the Laser Powder Bed Fusion (L-PBF) process

The present work focuses on the effect of the addition of a zirconium source on the microstructure of Al-SiC composites produced by Laser Powder Bed Fusion (L-PBF). More specifically, the aim is to address the issue of the SiC decomposition into the water-soluble aluminum carbide Al₄C₃ in Al-SiC composites produced by L-PBF, with the objective of limiting its formation by adding another element to the system. To this end, AlSi₇Mg_0.6-SiC-ZrO₂ composite powders are successfully prepared and printed in a standard L-PBF equipment. The resulting parts are then thoroughly characterized, in order to understand the physico-chemical mechanisms involved during the L-PBF process. The results show a decrease in the Al₄C₃ amount by ZrC formation. Another important result is that bulk composites exhibit a fully equiaxed microstructure attributed to the τ₁ (Al,Si)₃Zr ternary phase, with all the characteristics of a good nucleating agent for aluminum phase. To support these microstructure experimental results, a first version of a quaternary Al-Zr-Si-C thermodynamic database was developed using the Calphad method. These calculations enable to establish a solidification path providing information on the phases that may form after heat treatment of L-PBF materials.