(江蘇科技大學(張家港校區(qū)) 冶金與材料學院，張家港 215600)
摘 要: 采用蔡氏顯微鏡(OM)、拉伸力學性能測試、超聲殘余應力測試、透射電鏡(TEM)、X射線衍射(XRD)以及差熱分析實驗(DSC)研究深冷前后車用6005A合金焊接接頭的顯微組織和力學性能，揭示制約嚴寒地區(qū)鋁合金車體材料規(guī)模化使用的技術問題。結(jié)果表明：3次冷熱循環(huán)深冷處理能促使焊接熱影響區(qū)晶內(nèi)的沉淀相均勻析出與彌散分布，其強化相平均尺寸由200 nm減小至50 nm。同時，焊縫區(qū)域粗大柱狀晶低溫“碎化”為超細等軸晶粒，產(chǎn)生大量的位錯纏結(jié)，提升合金抗拉強度至234 MPa；加之冷熱循環(huán)深冷處理可有效消除因焊接熱輸入而產(chǎn)生的大量殘余應力，無相變深冷工藝能提高6005A鋁合金焊接材料的結(jié)構穩(wěn)定性。
關鍵字: 6005A鋁合金；冷熱循環(huán)處理；顯微組織；拉伸性能；殘余應力
（School of Metallurgy and Materials, Zhangjiagang Campus,
Jiangsu University of Science and Technology, Zhangjiagang 215600, China）
Abstract:The microstructural evolution and mechanical properties of welded joint of 6005A Al alloy for vehicle were studied by metallographic microscope, tensile test, residual stress measurement by ultrasonic method, transmission electron microscope, X-ray diffraction and differential scanning colourimeter, and some technical problems of the scale of application in aluminum alloys for car bodies were revealed. The results show the precipitated phase of welding heat affected zone can be dispersively distributed by three times cooling-thermal cycling treatment, and the average sizes of strengthening phase decreases from 200 nm to 50 nm. Meanwhile, the fragmentation mechanisms of transformation happen from dendritic crystal to ultra-fined equiaxed crystal during solidification at the welded joints of 6005A Al alloys, and a large number of dislocation twins form as well as its tensile strength is above 234 MPa. Besides, the cooling-thermal cycling treatment is effective to relieve the welding residual stress, the deep cryogenic treatment without phase-change can improve the dimensional stability of 6005A Al alloy welding materials.
Key words: 6005A Al alloy; cooling-thermal cycling treatment; microstructure; tensile property; residual stress
