Influence of eutectic-Si in as-cast and fibrous-eutectic-Si in LPBF-processed AlSi10Mg alloys on wear and corrosion behaviors treated with direct aging route

This study investigates the wear and corrosion performance of AlSi10Mg alloy produced through casting and laser powder bed fusion (LPBF), followed by direct aging (DA) treatment at 180 °C for 6 h. Further, metallurgical characteristics and hardness performance were analyzed to assess the impact of DA heat treatment and to correlate the microstructure and the mechanical performances. Cast samples exhibited dendritic α-Al with eutectic Si, while LPBF samples showed a cellular structure with fibrous eutectic Si owing to the variation in the solidification rates of cast (~ 102 °C/s or less) and LPBF (103–106 °C/s) techniques. Besides, LPBF specimens displayed improved hardness (123.4 HV), a lower wear rate (0.92 × 10−5 g/m), and a coefficient of friction (0.27) compared to their cast counterparts, which exhibit the lowest hardness value of 98.7 HV, highest wear rate of 3.04 × 10−5 g/m and coefficient of friction of 0.395. Meanwhile, the DA treated AlSi10Mg alloy samples processed through LPBF possess the highest hardness of 131.6 HV, lowest wear rate (0.892 × 10−5 g/m) and coefficient of friction (0.26) among all the tested samples under a 10N applied load and 1 ms−1 sliding velocity condition, and this may be attributed to the hard nano-Si particles precipitated inside the cell boundary during the DA treatment. Furthermore, increasing the applied load from 10 to 40N and an increase in sliding velocity from 1 ms−1 to 5 ms−1 resulted in an increase and decrease in the wear rate, respectively. The worn SEM micrographs revealed mild delamination, avulsions, and uniform tribofilms on the worn surface, and the oxide films formed in the LPBF-processed AlSi10Mg alloy acted as a protective layer that reduced the rate of wear.