Microstructural evolution and hardness of rapidly solidified hypereutectic Al-Si surface layers by laser remelting

Selective laser melting technique is used to manufacture Al-25 wt.%Si and Al-30 surface layers with a thickness of 0.5–0.6 mm followed by rapid solidification process refine the silicon nano-size increase hardness. The as-produced alloyed were heterogeneous composed clustered aggregates primary Si crystals size 5–7 µm, decorated α-Al cells/dendrites, embedded in matrix consisting dendritic Al-Si eutectic. However, after several remelting scanning treatments at fast speed low power, significant refinement all phases was achieved, dramatic proportion interwoven nano-sized fibrous sizes reduced ≤1 while eutectic spacing decreased approached as 10–15 nm highest cooling rate. high rate significantly amount cells/dendrites especially those surrounding Si, thereby stimulating ultrafine grow adjacent spread massively, which turn contributed Transmission electron microscopy revealed block-like worm-like nanoscale internally nano-twinned.