Effect of welding speed on microstructure and mechanical properties of Al−Mg−Mn−Zr−Ti alloy sheet during friction stir welding  

搅拌摩擦焊接过程中焊接速度对Al−Mg−Mn−Zr−Ti合金板材显微组织及力学性能的影响

作　　者：Tian DING Hong-ge YAN Ji-hua CHEN Wei-jun XIA Bin SU 丁天;严红革;陈吉华;夏伟军;苏斌(湖南大学材料科学与工程学院,长沙410082;湖南大学湖南省喷射沉积技术与应用重点实验室,长沙410082)

机构地区：[1]School of Materials Science and Engineering,Hunan University,Changsha 410082,China [2]Hunan Provincial Key Laboratory of Spray Deposition Technology&Application,Hunan University,Changsha 410082,China

出　　处：《Transactions of Nonferrous Metals Society of China》2021年第12期3626-3642,共17页中国有色金属学报（英文版）

摘　　要：Effects of welding speed on the microstructure evolution in the stir zone(SZ)and mechanical properties of the friction stir welding(FSW)joints were studied by OM,XRD,SEM,TEM,EBSD and tensile testing.Compared with the base metal(BM),an obviously fine dynamic recrystallization(DRX)microstructure occurs in the SZ and the DRX grain size decreases from 5.6 to 4.4μm with the increasing of welding speed.Fine DRX microstructure is mainly achieved by continuous dynamic recrystallization(CDRX)mechanism,strain induced boundary migration(SIBM)mechanism and particle stimulated nucleation(PSN)mechanism.Meanwhile,the geometric coalescence and the Burke−Turnbull mechanism are the main DRX grain growth mechanisms.Among all the welding speeds,the joint welded at rotation speed of 1500 r/min and welding speed of 75 mm/min has the greatest tensile properties,i.e.ultimate tensile strength(UTS)of(509±2)MPa,yield strength(YS)of(282±4)MPa,elongation(El)of(23±1)%,and the joint efficiency of 73%.利用OM、XRD、SEM、TEM、EBSD和拉伸测试研究搅拌摩擦焊接过程中焊接速度对焊合区的显微组织以及接头力学性能的影响。与母材相比,焊合区中产生明显的细小动态再结晶显微组织,并且随着焊速的增加,动态再结晶晶粒尺寸从5.6μm降低至4.4μm。细小动态再结晶显微组织主要是通过连续动态再结晶、应变诱导晶界迁移以及粒子激发形核机制获得。与此同时,几何合并和伯克−特恩布尔机制是主要的动态再结晶晶粒生长机制。采用搅拌针转速1500 r/min和焊接速度75 mm/min时,接头具有最佳的拉伸性能,即抗拉强度为(509±2)MPa、屈服强度为(282±4)MPa、塑性为(23±1)%以及接头效率为73%。

关 键 词：friction stir welding mechanical properties dynamic recrystallization nucleation mechanism grain growth mechanism 

分 类 号：TG457.14[金属学及工艺—焊接]