Hybrid-heat effects on electrical-current aided friction stir welding of steel, and Al and Mg alloys

Electrical current aided friction stir welding (EFSW) is based on increasing heat generation during welding by adding a resistant heat source. The influence of current intensity to surface shaped features on welding seam was discussed. The comparison between AZ31B joints and Al 7075 joints was conducted. For the AZ31B joints, the resistant heat source promoted significant grain refinement and hardness improvement in the weld nugget zone (WNZ). It also increased plastic deformation during welding. For the Al 7075 joints, the grain size in the WNZ and heat affected zone (HAZ) increased slightly with the increase in electric current intensity. EFSW was proven to be suitable for joining high-strength alloys, such as 2Cr13Mn9Ni4 and Q235B. High microhardness values were obtained at both sides of the mechanical interlock zone.