(1. 上海工程技術(shù)大學(xué) 材料工程學(xué)院，上海 201620；
2. 南車青島四方機(jī)車車輛股份有限公司 技術(shù)中心，青島 266111)
摘 要: 對(duì)高速列車車體用新型A6N01鋁合金進(jìn)行MIG焊接，使用光學(xué)金相(OM)、掃描電鏡(SEM)、透射電鏡(TEM)、顯微硬度計(jì)和拉伸試驗(yàn)機(jī)對(duì)焊接接頭的顯微組織與力學(xué)性能進(jìn)行觀察與分析。結(jié)果表明：焊縫金屬為等軸晶狀的鑄態(tài)組織，焊縫邊緣的熔合區(qū)形成柱狀晶組織。在熱影響區(qū)(HAZ)，過時(shí)效區(qū)的晶粒比淬火區(qū)的更為粗大，形成HAZ軟化區(qū)。A6N01鋁合金母材析出短棒狀β′(Mg2Si)過渡強(qiáng)化相。HAZ析出粗大的短棒狀穩(wěn)定強(qiáng)化相β(Mg2Si)。焊縫顯微硬度最低，約為65 HV。焊接接頭的抗拉強(qiáng)度為270 MPa，斷后伸長率為6.0%。
關(guān)鍵字: 鋁合金；焊接接頭；微觀組織；力學(xué)性能
（1. School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China;
2. Technology Center, Sifang Locomotive and Rolling Stock Co., Ltd., Qingdao 266111, China）
Abstract:The new type A6N01 aluminum alloy used in the high-speed vehicles was welded by MIG welding. The microstructures and mechanical properties of the welding joints were observed and analyzed by OM, SEM, TEM, microhardness and tensile testers. The results show that equiaxial as-cast microstructures exist in the welding metal. The columnar grains are formed in the fusion zone next to the welding seam. In the heat-affected zone (HAZ), the grains of over-aging zone are coarser than those of quenching zone. The softening region exists in the over aging zone of HAZ. The β′(Mg2Si) transitional strengthening phases precipitate in A6N01 aluminum alloy base metal. The β′ phase presents claval shape. The β(Mg2Si) stable strengthening phases precipitate in HAZ, which present coarse claval shape. The microhardness of welding seam is the lowest in the joint, which is about 65 HV. The tensile strength of the joint is 270 MPa, and the elongation after fracture is 6.0%.
Key words: aluminum alloy; welding joint; microstructure; mechanical property
