【正文】 鎂 _鋼異種金屬攪拌摩擦焊工藝及性能研究 ? 摘要 鎂合金是目前昀輕的金屬結(jié)構(gòu)材料之一 ,廣泛應用于 汽車、航空航天及通訊 等領(lǐng)域 ,鋼是目前工業(yè)上應用昀廣的結(jié)構(gòu) 材料 ,在工程領(lǐng)域必然面臨兩種材料的 連接問題。由于二者的性能差異較大 ,采用傳統(tǒng)的熔焊方法難以獲得良好的焊接 接頭 ,且熔焊過程中鎂元素易流失。攪拌摩擦焊 (FSW)作為一種新型的連接技 術(shù) ,對克服性能差異大的異種材料難焊接問題具有很大優(yōu)勢 ,是異種材料連接比 較理想的方法 ,對實現(xiàn)鎂和鋼良好連接具有重要的指 導意義。 本課題采用 FSW 技術(shù)對 4mm 厚的 AZ31B 鎂合金和 Q235 低碳鋼進行對接和 搭接試驗 ,研究了焊接工藝參數(shù)對焊縫成形及接頭性能的影響 ,采用光學顯微鏡 觀察了接頭組織轉(zhuǎn)變形態(tài) ,并利用掃描電鏡、能譜分析及電子探針深入分析了鎂 / 鋼界面的元素分布特點及界面形態(tài)。 研究結(jié)果表明 ,采用攪拌摩擦焊能成功實現(xiàn)鎂 /鋼對接和搭接。鎂 /鋼 FSW 對 接焊時 ,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 。焊核區(qū)上部主要由鎂組 成 ,晶粒較母材 晶粒大 ,焊核底部含鋼粒較多 ,鎂側(cè)熱影響區(qū)晶粒發(fā)生了明顯長大 。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 。焊核與鋼側(cè)界面沿板厚方向由不規(guī)則曲線向直線 型轉(zhuǎn)變 ,近焊核與鋼側(cè)界面處存在 Mg 元素向鋼的短程擴散 ,而 Fe 元素并未向鎂 中擴散 。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 。轉(zhuǎn)速為 600rpm,焊 速 60mm/min、攪拌針偏移量 1mm 時 ,接頭 抗拉強度值昀高為 ,達鎂合金母材強度的 %。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 。拉伸試驗中接頭一般斷裂于焊核與鋼界面 ,為脆性斷裂。 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” 。接頭鋼側(cè)熱力影響區(qū)為板 條狀鐵素體 +珠光體組織 ,晶粒較母材晶粒細小 ,熱影響區(qū)不明顯 。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 。焊縫橫截面 硬度整體分布不均 ,接頭承受的昀大拉剪力為 。 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 microstructure of the thermomechanically affected zone TMAZ on the steelside up to down was nonuniformed ferrite side plate+ proeutectoid ferrite + pearlite, nonuniformed ferrite side plate + pearlite,then fine acicular ferrite and pearlite along the thickness microstructure of the HAZ on the steel side and the base IImetal are constituted of proeutectoid ferrite and interface shape between nugget and steel change from irregular