Resistance element welding（REW）with a concealed rivet cover was used to join steel and aluminum alloy.The intermetallic compound（IMC）of FeAl

3

is formed at the Q235/Al interface.The IMCs of Fe

2

Al

5

and FeAl

3

are formed at the DP780/Al interface.The welding current has significant influence on the nugget size

peak load

average hardness of aluminum heat affected zone（HAZ）as well as the bearing area of the aluminum plate.Three major failure modes were identified:interfacial failure model

nugget pullout failure model and aluminum HAZ fracture model.At the welding current of 18kA

the desirable mechanical properties of the joint can be obtained at 5 712N with nugget pullout failure model.