(1. 廣州有色金屬研究院 焊接技術(shù)研究所，廣州 510650；
2. 哈爾濱工業(yè)大學(xué) 先進焊接與連接國家重點實驗室，哈爾濱 150001；
3. 上海鍋爐廠有限公司 技術(shù)部，上海 200245；
4. 南車株洲電力機車有限公司 轉(zhuǎn)向架開發(fā)部，株洲 412001)
摘 要: 使用疲勞試驗機測試A7N01鋁合金焊接接頭的疲勞裂紋擴展速率，采用光學(xué)顯微鏡對焊接接頭的顯微組織進行分析，使用掃描電鏡對疲勞斷口形貌進行研究。結(jié)果表明：母材的顯微組織為時效狀態(tài)的α(Al)基體與粗大一次相、彌散二次強化相以及少量的夾雜物構(gòu)成的軋制狀態(tài)組織；熱影響區(qū)的顯微組織為α(Al)基體以及少量未固溶的一次相組織，焊縫的顯微組織為α(Al)基體與離異共晶組織。焊接接頭的顯微組織以及第二相粒子尺度不同導(dǎo)致了疲勞裂紋擴展特性不同。隨著應(yīng)力比的增加，疲勞裂紋擴展速率均呈增大趨勢。裂紋尖端塑性區(qū)內(nèi)的第二相粒子與基體的不協(xié)調(diào)塑性變形可促進疲勞裂紋的擴展，影響疲勞裂紋的擴展速率。
關(guān)鍵字: 高強鋁合金；焊接接頭；第二相粒子；疲勞裂紋擴展
YANG Jian-guo2, ZHANG Jian2
（1. Institute of Welding Technology, Guangzhou Research Institute of Non-ferrous Metals, Guangzhou 510650, China;
2. State Key Laboratory of Advanced Welding and Jointing, Harbin Institute of Technology, Harbin 150001, China;
3. Technology Department, Shanghai Boiler Works Co., Ltd., Shanghai 200245, China;
4. Bogie Development Department, Southern Zhuzhou Electric Locomotive Co., Ltd., Zhuzhou 412001, China）
Abstract:An experimental set-up was designed for measuring the fatigue crack propagation rate of A7N01 aluminum alloy welded joint using fatigue test system. The microstructure of welded joint was analyzed by an optical microscope, and the morphology of fatigue fracture was studied by an election scanning microscope. The results show that the microstructure of parent metal is the aging rolled structure by the α(Al) matrix, coarse first phase, secondary disperse strengthening phase and some inclusions. The microstructure of HAZ is the α(Al) matrix with some un-soluble microstructure. The microstructure of weld seam is the α(Al) matrix with divorced eutectic phase. The fatigue crack propagation characteristic is different due to different microstructures and different scale second phase precipitates of welded joint. The fatigue crack propagation rate increases with the increase of stress ratio. The discordant plastic deformation between the second phase precipitate and matrix in the crack tip plastic region can promote the propagation of fatigue crack and affect growth rate of it.
Key words: high strength aluminum alloy; welded joint; secondary phase precipitate; fatigue crack propagation
