Assessing critical role of iron on microstructure and deformation behaviour of AlSi10Mg processed via laser powder bed fusion additive manufacturing

Iron contamination in Al-Si cast alloy promotes complex intermetallic formation during solidification, which deteriorates the mechanical properties. The present study deals with the laser powder bed fusion additive manufacturing (LPBF-AM) of AlSi10Mg with a maximum allowable iron content of 0.55 wt.%. This study illustrates that the combination of a high base plate temperature (200 degrees C) and a maximum allowable iron content (0.55 wt.%) leads to the formation of coarser 'Chinese-script' intermetallic compounds. These compounds significantly affect both tensile strength and ductility, compared to LPBF AlSi10Mg processed with a lower iron content (0.15 wt.%) under the same base plate temperature. Moreover, conventional post-heat treatment (solution treatment followed by ageing (STA)) disintegrates the fine eutectic network, resulting in coarser globular Si and partial transformation of detrimental Fe-rich intermetallic compounds. This STA cycle slightly improves ductility but substantially reduces strength compared to the as-built (AB) condition with 0.55 wt.% Fe. Therefore, the allowable Fe concentration in LPBF-AM AlSi10Mg should be re-examined in relation to the base plate temperature to achieve superior mechanical properties in the AM parts of this alloy.