Dissimilar Joining of Immiscible Fe–Mg using Solid Metal Dealloying

Abstract

Joining of Mg alloy to steel has received wide attention for design of multi-materials. This letter describes joining of immiscible pure iron and pure magnesium (Fe–Mg), as a simplified model, performed by solid metal dealloying (SMD) between Mg and Fe100−xNix interlayers that were preliminary joined to the Fe part by diffusion bonding. SMD formed an Fe–Mg bicontinuous composite with interconnected morphology at the Fe–Mg weld interface. The effect of Ni composition x in the interlayer on the weld strength was examined. Strong joints were obtained when 30 < x < 50 at.%, which caused Mg base-metal fracture due to a well-interconnected Fe–Mg structure. When too little (x < 30 at.%) or too much (x > 60 at.%) Ni was added, interfacial fracture occurred due to limited dealloying reaction and formation of an isolated Fe product surrounded by a large amount of brittle Mg2Ni.