【正文】 時 ,當轉(zhuǎn)速為 600rpm,焊速為 60mm/min,攪拌針偏移量為 1mm,鋼置于返 回邊時 ,焊縫成形較好 ,鎂 /鋼連接緊密 。鋼側(cè)熱力影 響區(qū)板厚方向由上至下組織轉(zhuǎn)變?yōu)?:不均勻板條狀鐵素體 +先共析鐵素體 +珠光體 →不均勻板條狀鐵素體 +珠光體→細小針狀鐵素體 +珠光體 ,鋼側(cè)熱影響區(qū)和母材 區(qū)組織為先共析鐵素體 +珠光體 。接頭橫截面硬度呈高 ?不均勻 ?低變化 ,焊核局部區(qū)域硬度值很高 ,昀 高值達 。接頭抗拉強度分布不 均 ,接頭中部抗拉強度昀高 , 抗拉強度高于接頭整體抗拉強度 ,昀高值達 , 達鎂合金母材強度的 %,接頭上部和接頭底部抗拉強度低于接頭整體抗拉強 度 。 鎂 /鋼 FSW 搭接焊時 ,當軸肩下壓量為 ,攪拌轉(zhuǎn)速為 950rpm,焊速為 60mm/min 時接頭成形昀好 ,焊核與鋼界面呈“鉗形” 。各區(qū)域的鎂晶 粒較母材晶粒都發(fā)生了長大 ,焊核底部近鎂 /鋼界面晶粒長大昀明顯 。 關(guān)鍵詞 :攪拌摩擦焊 ,鎂合金 ,低碳鋼 ,工藝 ,接頭性能 IAbstract Magnesium alloys is one of the lightest structure material which is widely used in 、 , automotive aerospace and munication fields and the steel is the widely used , , structure material at currently thus it is inevitable to face the dissimilar metal joining . problem between magnesium alloys and steels in project fields Due to the great , differences in physical and chemical properties of the two kinds of metals it is difficult , to obtain a good joint by using the conventional fusion welding methods and the . magnesium will be lossed easily during fusion welding process As a new joining , technology friction stir welding FSW has a great advantage to solve the joining . problem of dissimilar materials with high performance differences And FSW is an ideal weld method for joining dissimilar materials which has a great significance to realizing . a well joining between the magnesium alloys and steels , In this paper the 4mm thick AZ31B magnesium alloy and Q235 steel were . selected as experimental materials for friction stir lap welding and butt welding The impact of process parameters on the weld formation and the joint performance were . investigated The transition of microstructure of joints was observed by optical , microscope and the elements distribution of the interface and interface characteristics , of magnesium and steel were examined by scanning electron microscopy SEM Xray . energy dispersive spectroscopy EDS and electron probe microanalysis The results show that, the butt welding and lap welding of the magnesium and steel were success welded by friction stir welding, For the friction stir butt welding, when the rotating speed was 600rpm,welding speed was 60mm/min,the pin offset is 1mm toward steel and steel was put on return side,the well weld was formed and the connection of magnesium/steel was upper part of the weld nugget is constituted of magnesium,the grains of this part are coarse pared with the base material,the lower part of the weld nugget has larger number of steel particles,The grains of heataffected zone HAZ on the magnesiumside was growing significantly。The hardness of the cross section of joint was showing a highnonuniformedlow distribution,the hardness of some area in nugget is quite high,the imum hardness value reaches to rotating speed was 600rpm,welding speed was 60mm/min,the pin offset was 1mm toward steel,the imum tensile strength is about ,which was about % of the tensile strength of magnesium matrix. The tensile strength of joint is nonuniformed, the imum tensile strength appeared in the central of joints,and it is higher than the overall joints tensile strength,which was about % of the tensile strength of magnesium matrix,the tensile strength of the upper and the lower part of joint was lower than the overall joints tensile joint usually fractured along the interface between the weld nugget and steel. In the lap welding,when the plunge depth of shoulder was ,rotating speed was 600rpm,welding speed was 60mm/min, the formation of joint is the best,the interface between weld nugget and steel like a“pincer”. The microstructure of the TMAZ on the steel side is including of ferrite side plate and pearlite, the grains was refine pared to the base material,the HAZ on the steel side is not obviouspared with magnesium matrix,the grains in magnesium side were