搅拌针形状对搅拌摩擦焊焊缝截面形貌的影响

采用镶嵌异种材料作为标识材料的方法,用不同搅拌针形状的搅拌头,进行了搅拌摩擦焊试验.结果表明,搅拌针形状影响焊缝塑化金属流动的行为,导致焊缝截面形貌发生变化.搅拌针表面的反螺纹使搅拌针周围塑化金属向下流动,迫使搅拌针端部周边金属向上运动,焊核中心处于焊缝横截面下部;正螺纹使搅拌针周围塑化金属向上流动,迫使轴肩下方及周边金属向下运动,焊核中心处于焊缝横截面上部.改变搅拌针形状及长度,可以改变搅拌针下方及附近区域塑化金属的流动形态,从而改变焊缝底部的成形及包铝层进入焊缝的深度.

Influence of pin shape on weld transverse morphology in friction stir welding

Friction stir welding was conducted by using four types of pin and copper foils,piled up with aluminum plate alternately,as a tracer material.The distribution feature of the tracer materials was observed after welding.The results showed that,the flow of the plasticized metal in the weld is influenced by the pin shopes,which results in the variety of the morphology of the weld.If the screw thread on the pin is counter-clockwise,the metal around the pin will move downwards,which drives the metal around the pin tip to move around and upwards.So the center of the nugget is located at the lower part of the tansverse weld section.If the screw thread on the pin is clockwise,the metal around the pin will move upwards to the root of the pin and moves outwards along the shoulder surface,which causes that the center of the nugget will located at the upper part of the weld section.By using the pin with cylindrical shape,the transverse weld section appears onion ring pattern;but the onion ring pattern is not clear in the weld transverse section for the pin with taper shape or cam shape.If the length of the pin and shape at the tip are changed,the flow state of the plasticized metal below the pin and around the tip of the pin will be changed,therefore,the morphology of the weld at the bottom will change and the depth that the aluminum layer on the back surface of the plate enteed into the weld will be larger.