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E. Silva, L. Batista, B. Callegari, V. Ferrinho, R. Buzolin, R. Coelho, F. Warchomicka, G. Requena, A. Ramirez, H. Pinto:
"Microstructure and Residual Stress Formation during Friction-Stir Welding of Semi-Solid Cast ZK60-RE Magnesium Alloy";
Talk: THERMEC 2013, Las Vegas; 2013-12-02 - 2013-12-06; in: "THERMEC 2013", (2013).

In this work, we report on the friction stir weldability of a semi-solid cast ZK60 alloy modified with 1.5 wt% mischmetall in the lap-joint configuration using a 120WV4 steel tool with concave shoulder and conical pin. The coarser solidification microstructure in the semi-solid cast ZK60-1.5%RE alloy requires low strain rates and increased heat input to produce lap-joints without inner defects. This was achieved with 250 rpm tool rotation and 50 mm/min welding speed. Friction stir welding results in a very fine grained microstructure in the stir zone probably due to dynamic recrystallization. In the thermomechanically affected zones dynamic recrystallization seems to occur within the solute enriched intergranular zones. The distribution of longitudinal residual stresses exhibit stress maxima at both thermomechanically affected zones. A compression peak is observed at the retreating side, whereas a tensile stress maximum occurs at the advancing side.