The Influence Of Material Property On The Welding Plastic Metal Flow Of Friction Stir Welding

In this paper, two kinds of aluminum alloys with different condition of heattreatment were friction stir welded in the way of the same heat treatment conditionaluminum alloys butt welding, butt welding and lap welding of aluminum alloys withdifferent heat treatment condition. The flow trajectory and deformation character ofplasticized metal were observed from the distribution of the tracing material on theplane at the weld centerline、the plane perpendicular to the weld direction and thehorizontal plane. The influence of the distance of the thread on pin surface、weldingprocess parameters and material property on the flow behavior of the plasticized matelin weld.The results show that, the mechanic property such as the strength and rigidity andso on are the important factors affecting the transfer of the plasticized metal in weld.The restriction of the metal on both sides will be different with the material propertychanging, then the flow trajectory of plasticized metal in weld will be influenced andthe deformation will be different. Sucking-extruding effect is restricted by the basematerial, and that will be evidence if the strength and rigidity of base material weldedare both greater, the Sucking-extruding effect will be reduced and the extruded areawill be smaller. As to butt welding of dissimilar aluminum alloy, the plasticized metalflows much more to the side that the deformation-resistance is lower when theLY12(M) is placed on the advancing side.The flow of plasticized metal is related with the geometry of stir tool and thewelding process parameters too, Increasing the distance of thread is equivalent towidening the channel of plasticized metal which will result in Sucking-extrudingeffect increasing, onion rings more easily expansion in the weld thickness direction,the width and height of the weld nugget will be increases. But because thedeformation-resistance of dissimilar metals on both sides of weld is different, so thewidth of the weld nugget at retreating side is less than that at advancing side when theLY12(CZ) which have lager deformation-resistance is placed on retreating side usingthe same tool. The diameter and height of the weld nugget increase with the plungedepth of shoulder increasing. The weld process parameters change and the shape andsize of extruded area will change, then the plasticized metal and weld formation will be influenced.The results of three-dimensional flow indicated that, at the different horizontalplane in weld thickness direction or different cross-section of different stages, with thedistance to the center of pin reducing, the thickness of the metal layer at both sides ofweld will gradually thin, and the lower deformation-resistance metal thins more.