中文摘要：

采用彩泥对搅拌摩擦焊塑性流动进行观察,据焊缝内部材料受力情况,分析了焊缝各截面流动特征产生的成因。论文将轴肩范围内的焊缝划分为搅拌挤压区和塑性变形区,焊缝中下部搅拌挤压区内,搅拌针周围大部分材料绕搅拌针呈螺旋型搅拌迁移,填充后方瞬时空腔,小部分材料被迫逆时针向后方迁移;塑性变形区内,大部分材料绕搅拌针顺时针由返回边向搅拌针后方迁移,少量前进边的材料被迫逆时针流向搅拌针后方。焊缝上部搅拌挤压区内,搅拌针前方的材料首先绕搅拌针旋转迁移填充后方瞬时空腔,并在轴肩作用下与塑性变形区内彩泥一道经历一种连续＂涂抹式＂迁移运动。

英文摘要：

The plastic flow of friction stir welding was observed by plasticine.According to the interior material stress situation of the joint,the reason for the typical flow characteristics of each cross-section of the weld.was analyzed The area within the shoulder was divided into agitating-extruding region and plastically deforming zone.In the mid-lower portion of the weld,most material in the Agitating-extruding region around the pin was stirred spirally into the transient cavity which was formed behind the pin and the rest was forced to pull counterclockwise into the cavity.In the plastically deforming zone,besides few material was forced to move backward to the cavity.Most material experiences the same change,though it was not so intensely any more.In the upper part of the weld,the material in the Agitating-extruding region was agitated into the cavity until the void was filled out,then experienced a continuous ＂smearing-like＂ movement under the press of the shoulder with the material from the plastically defor mation region