Effects of alumina nanoparticles, number of stirring pass and rotational speed on the mechanical behavior of friction stir welded (FSW) magnesium alloy (AM60)

In this study, effects of alumina nanoparticles and stirring pass in mechanical behavior of friction stir welded AM60 magnesium alloy were studied. Microscopic analysis showed occurrence of dynamic recrystallization during plastic deformation in weld area and mechanical tests revealed optimum condition for hardness and tensile strength could be produced in 1200 rpm rotational speed not only in absence of reinforcing alumina nanoparticles but also in presence of them. Opposing effects of higher temperatures in grain growth and greater strains in lowering grain size should be considered. In lacking of alumina nanoparticles, grain size diminished with increasing stirring pass but in being nanoparticles, predominant mechanism in depressing grain size came from nanoparticles and negligible effect of stirring pass in grain size was found. XRD results showed increasing solubility of γ-Mg phase as a result of stirring operation. Better toughness performance of weldment was produced via decreasing size of agglomerated alumina particles. Higher hardness and greater ultimate tensile strength were achieved in specimens with alumina nanoparticle with increasing rotational speed. In a constant rotational speed, higher hardness and greater ultimate tensile strength achieved in samples having alumina nanoparticles in contrast with free alumina nanoparticle samples