Influence of Cooling Rate on Primary Silicon Size in Hypereutectic Al–Si Alloy Fabricated by Laser Powder Bed Fusion

Herein, the effects of cooling rate on primary silicon (Si) phases in laser powder bed fusion (PBF‐LB/M) processed hypereutectic Al–Si alloy are investigated. These alloys are particularly in demand for automotive and electronic applications, thanks to their excellent wear and thermal properties. Nevertheless, when processed by conventional methods like casting with comparatively lower cooling rates, the coarse primary Si phases are responsible for increasing brittleness and inducing crack propagation. The refinement of the primary silicon phases is aimed to be achieved through the PBF‐LB/M process, which offers a high cooling rate. The primary Si phases are observed under three different thermal substrate plate conditions—untempered, with cooling and heating, and additionally with varying volume energy density. Furthermore, the impact of primary Si size on the hardness of the fabricated samples is evaluated. The findings show that a faster cooling rate has a notable effect on refining the primary Si size. Then, hardness is directly affected by the primary Si size, with larger Si resulting in decreased hardness.