(1. 南昌航空大學(xué) 材料科學(xué)與工程學(xué)院，南昌 330063；2. 江鈴汽車股份有限公司 車架廠，南昌 330001)
摘 要: 采用摩擦點(diǎn)焊對厚度為2 mm的LY12鋁合金進(jìn)行焊接實(shí)驗(yàn)，分析接頭的顯微組織及力學(xué)性能。根據(jù)焊點(diǎn)接頭的組織特征可將其分為塑性區(qū)、動(dòng)態(tài)靜止層、熱影響區(qū)和母材。結(jié)果表明：塑性區(qū)和動(dòng)態(tài)靜止層的晶粒在熱和力作用下發(fā)生動(dòng)態(tài)再結(jié)晶形成細(xì)小的等軸晶，熱影響區(qū)的晶粒在摩擦熱作用下長大變粗；攪拌頭旋轉(zhuǎn)速度為2 500 r/min，焊接時(shí)間為12 s時(shí)，可以獲得力學(xué)性能較好的焊點(diǎn)，焊點(diǎn)的剪切強(qiáng)度達(dá)到9.24 kN；焊點(diǎn)的剪切強(qiáng)度隨攪拌頭旋轉(zhuǎn)速度的增大而增大，隨焊接時(shí)間的延長先增大后減小；塑性區(qū)的顯微硬度較高，但略小于母材，接頭顯微硬度的最小值分布在熱影響區(qū)；焊點(diǎn)熱輸入量較多時(shí)，接頭為Ⅰ型斷裂，焊點(diǎn)的剪切強(qiáng)度較高；焊點(diǎn)熱輸入量較少時(shí)，接頭為Ⅱ型斷裂，焊點(diǎn)的強(qiáng)度較低。
關(guān)鍵字: LY12鋁合金；摩擦點(diǎn)焊；顯微組織；力學(xué)性能
（1. School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063, China;2. JMC Frame Plant, Jiang Ling Motors Corporation Ltd., Nanchang 330001, China）
Abstract:Friction stir spot welding(FSSW) of LY12 aluminum sheet with thickness of 2 mm were investigated, the joint microstructures and mechanical properties were analyzed. Based on the structure character of the joint, the microstructure of the joint can be divided into plasticity zone, dynamically quiescent layer, heat affected zone and base metal. The results show that the plasticity zone and dynamically quiescent layer become fine equiaxed recrystallisation under the thermo-mechanical effect, the grains in the heat-affected zone grow up because of the effect of friction heat. When the rotation speed is 2 500 r/min and the welding time is 12 s, good joint is achieved, and the tensile shear strength of the joint reaches 9.24 kN. The tensile shear strength of spot increases with increasing tool rotation speed, with increasing welding time, the strength increases first, while then reduces. The microhardness of plasticity zone is high, but is slightly lower than that of the base metal, the minimum value of microhardness is in the heat affected zone. When the energy input of joint is high, the fracture type of spot is mode Ⅰ, and the tensile shear strength is high; on the contrary, when the energy input of joint is less the fracture type of spot is mode Ⅱ, and the strength is low.
Key words: LY12 aluminum alloy; friction stir spot welding(FSSW); microstructure; mechanical properties
