【摘要】 对2.5 mm 7050-T7451铝合金搅拌摩擦焊接头进行自然时效处理,时效时间分别为72 h和17 520 h.对时效处理的接头进行拉伸试验、显微硬度测试和微观组织观察,确定自然时效时间对接头的力学性能、硬度分布、微观组织以及析出物的影响规律.结果表明,自然时效17 520 h接头的屈服强度、抗拉强度和断后伸长率较自然时效72 h的接头分别提高了20%,12%和25%;自然时效17 520 h接头的焊核区和热力影响区的硬度相应的提高了约60 MPa;随着自然时效时间的延长,焊核区和热力影响区的溶质原子富集区(GP区)所占的比例升高、η’和η析出相增多,它们能够钉扎位错,使位错运动消耗更多的能量,从而提高了接头的强度和塑性.更多还原

【Abstract】 Natural aging of 2. 5 mm thick 7050-T7451 aluminum alloy friction stir welded joints was conducted for 72 h and 17 520 h,respectively. The tensile test,Vickers microhardness test and microstructure observation on the joints were carried out to investigate the effect of natural aging time on the mechanical properties,microhardness profile,microstructure and precipitation. The results show that the yield strength,tensile strength and elongation of the joint subjected to 17 520 h natural aging were about 20%,12% and 25% higher than those of joint natural aged for 72 h. Moreover,the microhardness values were 60 MPa higher in the nugget zone and thermal-mechanical-affected zone in the joint natural aged for 17 520 h. More GP zone,η’ andη phases emerged in nugget zone and thermal-mechanical affected zone with increasing the natural aging time,which effectively pinned the dislocations and consequently enhanced the strength and plasticity of the joint.更多还原