不扎透上板对2024-T4铝合金搅拌摩擦搭接焊力学性能的影响

Mechanical properties of friction stir lap welded 2024-T4 aluminum alloy joints for pin not plunging into lower sheet

钩状缺陷是影响搅拌摩擦搭接焊接头性能的重要因素.为了尽可能的避免钩状缺陷的产生,利用不扎透上板的方式对2024-T4铝合金进行焊接,重点分析不同转速下的接头横截面形貌及力学性能.结果表明,利用不扎透上板的方式所得搭接界面保持连续且主要呈水平方向分布.由于搅拌针长度较小,焊核区底部的宽度远大于搅拌针尖端直径,使有效连接宽度增加,导致搭接接头在承受拉剪载荷时呈拉伸断裂模式.与转速为500 r/min相比,600 r/min下接头的有效连接宽度与剪切拉伸强度均有小幅度地增加,最大剪切拉伸载荷为17 215.11 N.

Hook defect is the key factor on the mechanical properties of friction stir lap welded(FSLW)joints.In order to avoid the hook defect as much as possible,the tool pin did not plunge into lower sheet during the FSLW process of 2024-T4 aluminum alloy.The cross sections and mechanical properties of FSLW joints at different rotational speeds were studied.The experimental results show that when the pin does not plunge into lower sheet,the lap interface is continuous and presents the horizontal distribution.The width of stir zone bottom is greater than the diameter of pin tip due to the small pin length,which leads to the increase of effective lap width(ELW).Tensile fracture model is obtained during tensile test.Compared with the rotational speed of 500 r/min,the ELW and lap shear failure load at 600 r/min are both slightly increased.In this study,the maximum lap shear failure load is about 143 MPa.