转速对水下搅拌摩擦焊接7A04-T6铝合金组织与性能的影响

对7A04-T6铝合金板进行水下搅拌摩擦焊接(FSW),研究转速对水下FSW接头组织和力学性能的影响。结果表明:水下FSW接头的硬度最小值均位于热机械影响区。高转速条件下(950r/min)接头的硬度分布呈现"W"形,焊核区平均硬度值高于低转速条件下(475,600,750r/min)接头的硬度值。当焊速恒定为235mm/min,转速从475r/min提高到750r/min时,接头焊核区的析出相随转速的增大逐渐粗化,接头抗拉强度系数从89.71%降低到82.33%;当转速升高到950r/min时,析出相发生固溶时效,呈现细小弥散的分布特征,接头的强度系数提高到89.04%。接头具有较高的应变硬化能力,塑性伸长率较高。水下FSW接头的拉伸断口均呈现微孔聚合和解理混合断裂特征。

Effect of Rotation Rate on Microstructure and Properties of Underwater Friction Stir Welded 7A04-T6 Aluminum Alloy

Underwater friction stir welding (FSW)on 7A04-T6 aluminum alloy plates was carried out, and the effect of rotation rate on microstructure and mechanical properties of joints was investigated. The results show that the minimum hardness of underwater FSW joints is located in the thermo-me-chanically affected zone.The hardness of welded joints at the high rotation rate of 950r/min exhibits W-shaped distribution,and the average hardness value in the nugget zone is higher than that of wel-ded joints at the low rotation rate of 475,600,750r/min.When the rotation rate increases from 475 r/min to 750r/min with a constant welding speed of 235mm/min,the precipitated phases in the nugget zone gradually become coarse,and the ultimate tensile strength coefficient of the joint decreases from 89.71% to 82.33%;when rotation rate increases to 950r/min,the precipitated phases dissolve into aluminum matrix during welding,and age after welding.This produces the fine and homogeneous dis-persed phases,which results in an increase of the strength coefficient to 89.04% and a certain en-hancement of strain hardening capacity and elongation for the joints.All the tensile fracture surfaces exhibit the mixed characteristics of microporous polymerization and cleavage fracture.