Interfacial microstructures and properties of aluminum alloys/galvanized low-carbon steel under high-pressure torsion

A new composite processing technology characterized by hot-dip Zn-Al alloy process was developed to achieve a sound metallurgical bonding between Al-7 wt% Si alloy (or pure Al) castings and low-carbon steel inserts, and the variations of microstructure and property of the bonding zone were investigated under high-pressure torsion (HPT). During hot-dipping in a Zn-2.2 wt% Al alloy bath, a thick Al5Fe2Znx phase layer was formed on the steel surface and retarded the formation of Fe-Zn compound layers, resulting in the formation of a dispersed Al3FeZnx phase in zinc coating. During the composite casting process, complex interface reactions were observed for the Al-Fe-Si-Zn (or Al-Fe-Zn) phases formation in the interfacial bonding zone of Al-Si alloy (or Al)/galvanized steel reaction couple. In addition, the results show that the HPT process generates a number of cracks in the Al-Fe phase layers (consisting of Al5Fe2 and Al3Fe phases) of the Al/aluminized steel interface. Unexpectedly, the Al/galvanized steel interface zone shows a good plastic property. Beside the Al/galvanized steel interface zone, the microhardnesses of both the interface zone and substrates increased after the HPT process. (C) 2014 Elsevier Ltd. All rights reserved.X111413sciescopu