搅拌头停留时间对2524铝合金FSSW焊接头组织与性能的影响

Effect of stirring head dwell time on microstructure and properties of FSSW joint for 2524 aluminum alloy

对2524铝合金薄板进行直插式搭接FSSW(搅拌摩擦点焊)试验,探究搅拌头停留时间对接头的成型、组织状态与力学性能的影响.结果 表明:随着搅拌头停留时间增加,焊核区宽度显著增大;接头显微硬度从焊核区到母材区逐渐降低;焊核区硬度随停留时间增加逐渐减小.在剪切拉伸试验中,接头最大剪切载荷随停留时间的增加先增大后减小,在16s时达到最大值4246N.接头存在三种断裂模式:在4s时平行于搭接面断裂;在8s^12s时剪切断裂;在16 s^20 s时剪切断裂并撕裂焊点上表面.接头断口存在大量韧窝,韧窝底部有细小弥散分布的第二相粒子,部分区域存在解理面,接头为韧-脆混合型断裂.

The FSSW(friction stir spot welding)test of direct insersion and lap joint was carried out on 2524 aluminum alloy sheet to investigate the effect of stirring head dwell time on joint forming,microstructure and mechanical properties?The results show that the width of weld core increases significantly with the increase of stirring head dwell time?The microhardness of the joint decreases gradually from the core area to the base material area?The hardness of weld core decreases with the increase of dwell time.In the shear tensile test,the maximum shear load of the joint increases first and then decreases with the increase of dwell time,reaching the maximum value of 4246N at 16 s.There are three fracture modes in the joint,i.e.the joint break parallel to the lap surface at 4 s;the shear fracture at 8 s-12 s;the shear fracture and the tear on the top surface of the welding spot at 16 s-20 s.There are a large number of dimples in the joint fracture,and the second phase particles with small dispersion distribution are found at the bottom of the dimple,and cleavage surface exists in some areas.The joint is a mixture of tough-brittle fracture.