| In this paper,the thickness of 10 mm plates of 1060 pure aluminum,5A06 and7075 aluminum alloys were welded by friction stir welding used a cylindrical tool designed independently with left-hand thread.Through the same mechanical properties of the material to be welded,study effect of material properties and welding parameters on joint performance and mechanical properties.Through the different materials and the same materials with different condition of heat treatment to be welded and laminated experiment,study effect of material properties on plastic metal flow behavior.The results shows that the influence of the tool’s rotational speed and welding speed is growing stronger with increasing of the material’s strength and hardness.Low-strength and hardness of aluminum alloy friction stir welding,in a wide tool head rotation speed and welding speed can get a good joint performance without welding defects.The material with high-strength and hardness can only get excellent joint performance in a narrow range of process parameters.The nugget showed a different rule in the condition of same welding parameters when the material properties are unequal.Increasing tool’s rotational speed or decreasing welding speed will increase the weld nugget within a certain range.When the same material is butted,the constraint of metal around the weld decreases with the decrease of the strength and hardness of the material,the size of the welding nucleus increases and bigger than the material which strength and hardness is higher.When the different material is butted,in the case of same welding heat input,the thread on the pin is contacted with weld metal which strength and hardness is lower in a sliding friction state prematurely resulting in insufficient driving force,the size of nugget is smaller and the center of seam is near to the material which strength and hardness is higher.It is showed different morphology at different cross-section through the laminated experiment,shoulder affected zone occurred the greatest degree of deformation and defect happened in the turbulent zone which dissimilar material convergence fully.The metal layer of the pin at both sides of weld showed a great degree of deformation,the thickness of the metal layer at both sides will thin,and the metal which strength andhardness is lower thins more. |
