Effects of traverse speed on weld formation,microstructure and mechanical properties of ZK60 Mg alloy joint by bobbin tool friction stir welding  

作　　者：Gaohui LI Li ZHOU Haifeng ZHANG Sanfeng LUO Ning GUO 

机构地区：[1]State Key Laboratory of Advanced Welding ami Joining,Harbin Institute of Technology,Harbin 150001,China [2]Shandong Provincial Key Laboratory of Special Welding Technology,Harbin Institute of Technology(Weihai),Weihai 264209,China

出　　处：《Chinese Journal of Aeronautics》2021年第12期238-250,共13页中国航空学报（英文版）

基　　金：sponsored by the National Science and Technology Major Project(No.2017ZX04005001);the Key Research and Development program of Shandong(No.2018GGX103053)。

摘　　要：ZK60B(Mg-6%Zn-0.6%Zr)alloy joints fabricated by bobbin tool friction stir welding(BTFSW)with various traverse speeds were investigated.The sound joint fabricated by the BTFSW was possible under the appropriate welding parameters.The severe plastic deformation during BTFSW resulted in dispersion and segregation of the Zr-rich particles within the stirred zone(SZ)followed by evolution of a bimodal grain structure with distributed bands of 0.8-1.7μm ultrafine grains and 4.1-7.1μm equiaxed grains.Micro-hardness of SZ is substantially reduced in contrast to that of parent metal(PM)in spite of the finer grain size owing to dissolution of Mg-Zn based precipitates having hardening effects on alpha-Mg matrix.With the decrease in traverse speed,randomization degree of the plasticized metal flow increases,which is evidenced by the randomized arc line pattern at the low traverse speed.Among all defect-free joints,the 200 mm/min joint exhibits the weakest isotropy of texture within SZ and the best tensile properties,which has reduced ultimate tensile strength and yield strength by 5.4% and by 22.2%,respectively,as compared to the PM.The randomized texture hinders the joint fracturing within SZ at low elongation.Therefore,a relatively high elongation of 10.8% was achieved,which corresponded to 72% of the PM value.

关 键 词：Bobbin tool Friction stir welding(FSW) Magnesium alloys Mechanical properties Microstructure evolution Traverse speed 

分 类 号：TG453.9[金属学及工艺—焊接]