Interfacial investigation of AISI 321 / Al in compound casting: Casting temperature and melt to solid ratio

Joining two metals with distinct properties through compound casting is highly effective for numerous industrial applications. This method offers advantages such as reduced processing time, flexibility in producing complex and large parts, and the absence of the need for costly equipment. The goal of this research is to join Al and steel using the compound casting process. Initially, an AISI 321 core was prepared and placed in a mold, into which Al was cast around the core at four different temperatures: 770, 810, 840, and 870 °C. The microstructure of the interface between the two metals was examined using optical microscopes (OM) and scanning electron microscopes (SEM) with EDS. To assess the mechanical properties, the hardness of the samples was evaluated using a Vickers microhardness tester. The microstructure of the samples revealed that the casting process resulted in a composite material. Compared to other methods, this approach is more cost-effective for producing the mentioned materials. EDS analysis further indicated that the bimetallic interface contains various intermetallic compounds, including FeAl3, Fe2Al5, Fe2Al7, FeAl2, FeAl, and Fe3Al. The comparison of the results revealed that as the melt temperature increased, the thickness of the interface also grew. In all four samples, the hardness of the interface was significantly higher than that of the base metals—steel and Al —due to the presence of hard and brittle intermetallic compounds.