(1. 湖南大學(xué)材料科學(xué)與工程學(xué)院，長沙 410082；2. 南車青島四方機車車輛股份有限公司，青島 266111)
摘 要: 采用電子顯微學(xué)方法和力學(xué)性能測試，探究180℃下焊后時效處理工藝對Al-Mg-Si-Cu合金激光焊接接頭微觀結(jié)構(gòu)和力學(xué)性能的影響。結(jié)果表明：經(jīng)過焊后熱處理的焊件焊接接頭的力學(xué)性能得到一定程度的提升，但焊縫處由于在焊接過程中形成大量的第二相顆粒，消耗了大量的溶質(zhì)原子，因此，焊接接頭硬度最低。對于焊前處理為欠時效的焊件，熱影響區(qū)硬度經(jīng)過焊后熱處理后完全恢復(fù)母材硬度水平；而對于焊前處理為峰值時效和過時效的焊件，熱影響區(qū)硬度不能完全恢復(fù)，會出現(xiàn)一個硬度谷，即軟化區(qū)。通過對軟化區(qū)進行透射電鏡表征后發(fā)現(xiàn)，該區(qū)域內(nèi)析出相出現(xiàn)明顯的粗化。
關(guān)鍵字: Al-Mg-Si-Cu合金；析出相；焊后熱處理；微觀結(jié)構(gòu)；力學(xué)性能；熱影響區(qū)；軟化區(qū)
（1. College of Materials Science and Engineering, Hunan University, Changsha 410082, China;
2. CSR Qingdao Sifang Locomotive and Rolling Stock Co., Ltd., Qingdao 266111, China）
Abstract:The effect of post-weld artificial aging at 180℃ on the microstructure and mechanical properties of laser-beam welded Al-Mg-Si-Cu alloy was investigated. The results show that the mechanical properties of the joint after post-weld heat treatment can be enhanced to some extent compared to the as-welded joint, while the hardness of the weld seam is still the lowest region because the formation of massive second particles during the welding process consumes many solute atoms needed to form strengthening precipitates. The hardness of heat-affected zone in the joint under-aged before welding can be fully recovered to that of base metal after post-weld heat treatment. While the hardness of heat-affected zones in the joint peak-aged and over-aged before welding can not be fully recovered after post-weld heat treatment, in these heat-affected zones, the hardness grooves, typical of softening zones, occur in the hardness profiles. The precipitates in the softening zone coarsen apparently as revealed by transmission electron microscopy (TEM).
Key words: Al-Mg-Si-Cu alloy; precipitate; post-weld heat treatment; microstructure; mechanical property; heat affected zone; softening zone
