Structures of intermetallic phases formed during immersion of H13 tool steel in an Al–11Si–3Cu die casting alloy melt

The structures of intermetallic alloy layers formed during immersion of H13 tool steel into an aluminium die casting alloy melt have been studied by X-ray diffraction. Energy dispersive spectroscopy (EDS) analysis on the intermetallic phases was also conducted. A thick composite layer away from the H13 steel substrate consisted of irregular intermetallics and solidified cast alloy. A thin intermetallic layer was present between the thick composite layer and an inner compact layer next to the steel substrate. The intermetallic phase in the composite layer was found to have a cubic structure, αbcc-(FeSiAlCrMnCu). The thin layer was identified to be structurally isomorphous with hexagonal αH-Fe2SiAl8. The compositional difference between αH and αbcc intermetallic phases was mainly that the latter consisted of a higher amount of Cr+Mn+Cu. This is consistent with the suggestion that chromium, manganese and copper stabilise αbcc phase at the expense of αH phase. The inner compact layer next to the steel substrate was identified to be isomorphous with orthorhombic η-Fe2Al5.