Precipitate characteristic and nanoindentation analysis of resistance element welded DP780 steel and 6061 aluminum alloy joint.

• 6061-T6 Al alloy and DP780 steel were successfully joined by REW. • The grain boundary distribution of the Al-NZ of the REWed joint were observed. • Nanoindentation was used to study the local characterization of REWed joint. Resistance element welding (REW) of DP780 steel to 6061-T6 aluminum alloy using a flat Q235 rivet was carried out. The macrostructure, microstructure and nanoindentation hardness of the joint were investigated. The aluminum alloy nugget zone was characterized by high-angle grain boundaries. The elastic modulus and hardness of seven regions of the joint were measured through nanoindentation. The indentation and hardness results exhibited a greater elastic modulus and harness in the steel nugget zone. The elastic modulus and hardness of the heat-affected zone of aluminum alloy depend on the precipitates and grain size. [ABSTRACT FROM AUTHOR]