Study on the effects of friction stir welding process parameters on the microstructure and mechanical properties of 5086-H34 aluminum welded joints

摘要

In this study, the effects of tool rotational and traverse speeds on the mechanical properties and the microstructure of the friction stir welded joints from Al 5086-H34 were studied. Insufficient heat generation and inadequate metal transportation at very low rotational speed and high turbulence in the plasticized metal at very high rotational speed emerged tunnel and worm hole defects into the weldment. It was discovered that as rotational and traverse speed increased, the average grain size of the weldment decreased due to more dynamic recrystallization and amplified stirring effect. An increase in the rotational speed increased the ultimate tensile strength and microhardness of the specimens. At the best welding condition, by employing the rotational and traverse speeds of 1250 rpm and 80 mm/min, respectively, 51 % enhancement in the elongation and 8 % increase in the microhardness of the welded samples were obtained. Moreover, the ultimate tensile strength of this welded joint reached to 85 % of the base metal.