Influence of SiC particles on the microstructure and mechanical behaviors of AlMgScZr alloy processed by laser powder bed fusion

Laser powder bed fusion (LPBF) of AlMgScZr alloy has garnered significant attention as a high-strength aluminum alloy. However, its low modulus, Portevin-Le Chatelier (PLC) behavior, and weak strain hardening capability restrict its application in the aerospace sector. In this study, SiC/AlMgScZr composites with different SiC content have been successfully fabricated using LPBF. The inherent bimodal grain structure of AlMgScZr alloy was not completely altered by the addition of SiC particles. However, with increasing SiC content, heat accumulation increased, and the solidification cooling rate decreased. This led to an increase in the size of α-Al grains in the 5 wt% SiC/AlMgScZr composites. Meanwhile, movable dislocations can be efficiently preserved inside the grains, where they effectively accumulate and become entangled. Consequently, the strain hardening capability of the 5 wt% SiC/AlMgScZr composites improved by approximately 58 % compared to AlMgScZr alloy, with a strain hardening index (n) reaching 0.29. Additionally, the addition of SiC particles led to an increase in the elastic modulus (81.0 GPa). Furthermore, the reaction between Mg atoms and SiC particles resulted in the formation of Mg₂Si, which altered the distribution of Mg elements and initiated the reactive precipitation of a Mg-rich phase. There is no competition between the diffusive migration of solute atoms and the motion of movable dislocations within the composites. The additional SiC particles effectively eliminated the PLC effect in the LPBF of AlMgScZr alloy. This work provides essential guidance for developing high-strength and high-stiffness aluminum matrix composites with excellent processing properties in LPBF technology.