Effect of different Ni interlayers on interfacial microstructure and bonding properties of Al/Mg bimetal using a novel compound casting

In this work, the Al/Mg bimetal was manufactured using a novel lost foam compound casting (LFCC) process, and the effect of different Ni interlayers prepared by electronickelling (EN), electroless nickel plating (ENP) and plasma sprayed nickel (PSN) methods on the interfacial microstructure and bonding properties of the Al/Mg bimetal was systematically investigated. The surface roughness of the Al insert with PSN coating was much higher than those of the inserts with EN and ENP coatings, improving the wettability between the solid insert and liquid metal and enhancing the reaction of Ni and Mg. The interfaces of the Al/Mg bimetals with EN coating and ENP coating consisted of Ni solid solution layer, Al3Ni layer and Al + Si + Al3Ni layer, while one more Mg2Ni layer was generated in the Al/Mg bimetal with PSN coating. The Al/Mg bimetal with PSN coating obtained a superior bonding property, which was 69 % higher than that of the Al/Mg bimetal without Ni coating. The fractures of the Al/Mg bimetals with EN and ENP coatings occurred in the mechanical joint zone of the Ni solid solution layer and Mg base, while the fracture of the Al/Mg bimetal with PSN coating passed through whole interface layer.