Microstructures and mechanical properties of friction stir welded brass/steel dissimilar lap joints at various welding speeds

Abstract

The dissimilar lap joints of commercially brass (Cu–40Zn) to plain carbon steel (S25C) were fabricated using friction stir welding. The relationship between welding speed and heat input during the friction stir welding processes was discussed. The effect of welding speed on microstructures and mechanical properties of brass/S25C dissimilar joints was investigated. The grain size, Vickers hardness at the stirred zone and tensile shear fracture load of the joints varied significantly with the change of welding speed. The transmission electron microscope observations and energy dispersive X-ray spectrometry line analyses at the interface revealed that a mutual diffusion zone of Cu, Zn and Fe, the dominant elements of each plate was formed at the interface. The microstructure evolution and the joining mechanism of the brass/S25C joint are systematically discussed.