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Wetting and Interface Microstructures of Copper Alloy on Titanium and Steel Surfaces under Cold Metal Transfer Condition

The wetting behavior and interface characteristics of ERCuNiAl copper alloy on the surface of bare steel plate, galvanized steel plate and pure titanium plate are studied under cold metal transfer condition. The results show that the wettability of copper alloy on bare steel, galvanized steel and pure titanium surfaces increase with the increase of wire feeding speed, the wettability of copper alloy on the surface of bare steel is better than that of galvanized steel under the same wire feeding speed. This system is a typical temperature-dependent wetting system. When copper alloy is wetted on the surface of galvanized steel, the temperature of interfacial reaction decreases because the heat was taken away by the volatilization of zinc in the galvanized layer, resulting in weak interfacial reaction and poor wettability. Under the action of arc, zinc-rich zone is formed around the copper droplet, in which aluminum is enriched and AlFeZn8 and Al5Fe2 compounds are formed. When copper alloy is wetted on the surface of bare steel, due to the strong affinity between aluminum and iron, aluminum in the welding wire can easily react on the interface under the action of arc, thus the obvious Cu-Fe-Al interface reaction layers were formed. When copper alloy is wetted on the surface of pure titanium, due to the low solid solubility of Ti in Cu, copper and titanium are mixed to form an obvious interface reaction layer under the action of arc, which is mainly composed of TiCu, Ti2Cu and α-Ti.