Characterisation of interface formed at 650°C between AISI H13 steel and Al–12Si–1Cu aluminium melt

Abstract

Quenched and tempered, nitrided and oxidised die casting pins were tested in order to evaluate their response to the corrosion imposed by the contact against a molten aluminium alloy. A static immersion apparatus was used to maintain the pin surfaces, and the aluminium alloy melt at 650°C from 5 up to 50 000 s. The pins were characterised by scanning electron microscopy using advanced electron dispersive X-ray spectroscopy capabilities that enable deeper characterisation of the soldering phenomenon occurring in steel/molten aluminium alloy interfaces. The achieved results indicate that nitrided and oxidised surfaces present non-wetting behaviour, whereas the quenched and tempered surface is easily wetted. Mechanical soldering occurs after short immersion times, while chemical soldering takes place for longer immersion periods. Chemically soldered material is composed of four layers. The two nearest layers from steel are the intermetallics Al5(Fe, Mn, Cr)2 and Al12(Fe, Mn, Cr)3Si2. The third layer has a chemical composition that resulted from the aluminium alloy enrichment with Fe, Cr and Mn. The outer layer corresponds to the solidified aluminium alloy. The growth equations for the four layers of the quenched and tempered samples were identified, and a formation mechanism for intermetallic phases is proposed.