Abstract：The resistance spot welding of an aluminum alloy plate and an aluminum alloy /galvanized steel plate was carried out. In addition,the shear strength and microhardness of the welded are carried out with a testing machine. The microstructures of the joints are analyzed through metallographic microscopy and SEM. The interface composition distribution of a resistance spot welded was tested by electron probe. The formation mechanism of a spot welding joint and a variety of quality problems are discussed. The results indicated that: for an aluminum alloy joint,its melt nuclear size is smaller and its shear strength is bigger,compared with an aluminum alloy / galvanized steel sheet joints; an aluminum alloy spot welding joint microstructure and its heat affected zone have some cracks,incomplete fusion,slag inclusion and porosity,but the defects existing in an aluminum / galvanized steel joint are less.

Keyword：aluminum alloy;galvanized steel;resistance spot welding;