铝合金回填式搅拌摩擦点焊组织及力学性能分析

采用回填式搅拌摩擦点焊技术对7075-T6铝合金进行了点焊试验.对接头进行了显微组织、显微硬度、剪切和十字形拉伸测试.结果表明,接头显微组织可分为焊核区、热力影响区、热影响区及母材；在焊缝中发现了钩状缺陷、孔洞、未焊合、未完全回填及粘连韧带等缺陷；焊缝区显微硬度呈W形分布,焊点中心呈V形分布；在旋转频率为1 400 r/min,焊接时间为4s时,接头的抗剪强度达到最大值125.6 MPa,为母材强度的39.6％；接头的十字形拉伸载荷随工艺参数的变化规律比较复杂,最大十字形拉伸强度可达43.9 MPa.

Analysis of microstructure and mechanical properties of refill friction stir spot welded aluminum alloy

7075-T6 aluminum alloy was successfully spot joined by refill friction stir spot welding process. The microstructure, microhardness,tensile/shear strength and cross-tension strength of the joints were tested. Experimental results indicate that the microstructure can be divided into the nugget zone,thermo-mechanically affected zone,heat-affected zone and base material, respectively. Defects such as hook,cavity,incomplete fusion,incomplete refill and bonding ligament were found in the joint. The microhardness profile in the welded zone exhibited Wshaped appearance,but that in the stir zone exhibited V-shaped appearance. When the rotational speed was 1 400 r/min,the highest tensile/shear strength reached 7 916.0 N,which was 39.6% of the base material. The change of the cross-tension strength with the processing parameters was complicated,and the highest cross-tension strength can reach 43.9 MPa.