(湖南大學(xué) 汽車車身先進(jìn)設(shè)計(jì)制造國(guó)家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410082)
摘 要: 針對(duì)鋁/鋼焊接的技術(shù)難點(diǎn)，采用鋁表面預(yù)置AlSi12Mg1.5粉、鋁/鋼層間預(yù)置Sn粉的方法，對(duì)1.2 mm厚6016鋁合金和1.4 mm厚DP590雙相鋼進(jìn)行鋁上鋼下搭接、鋁/鋼表面同時(shí)預(yù)置粉末的光纖激光焊接試驗(yàn)，分析接頭成形、連接界面顯微組織及力學(xué)性能；利用ANSYS有限元軟件，建立鋁/鋼激光焊接瞬態(tài)有限元模型，計(jì)算接頭溫度場(chǎng)分布；利用基于密度泛函理論的第一性原理方法，計(jì)算預(yù)置粉末新形成物相FeSn、Fe3Sn及FeAl3、Fe2Al5等化合物的模量和熱力學(xué)性能。結(jié)果表明：在激光頭沿焊接方向偏轉(zhuǎn)10°、激光功率2750 W、焊接速度32 mm/s、離焦量 -2 mm、Ar保護(hù)氣體流量20 L/min條件下，鋁/鋼表面同時(shí)預(yù)置粉末可實(shí)現(xiàn)6016鋁合金與DP590雙相鋼有效連接，無(wú)明顯氣孔、裂紋等缺陷，接頭平均線載荷54.16 N/mm，與鋁表面預(yù)置AlSi12Mg1.5粉、鋁/鋼層間未預(yù)置Sn粉相比，接頭性能提高1.6倍；鋁表面預(yù)置AlSi12Mg1.5粉，焊接元素光譜相對(duì)強(qiáng)度和等離子體的電子密度增大，預(yù)置AlSi12Mg1.5粉增加上層鋁對(duì)激光的吸收率，改善焊縫表面成形；當(dāng)鋁/鋼層間預(yù)置Sn粉時(shí)，鋁、鋼均達(dá)到熔化狀態(tài)，上層鋁液和下層鋼液的熔合寬度加大，鋁/鋼橫向結(jié)合面積增加，焊合率提高；此外，焊縫區(qū)晶粒細(xì)小，接頭界面Fe-Al化合物的層厚度減少，生成高溫下結(jié)構(gòu)穩(wěn)定的FeSn和Fe3Sn等延性新相，因而同時(shí)預(yù)置粉末獲得了較好的鋁/鋼接頭性能。
關(guān)鍵字: 激光焊接；鋁/鋼；預(yù)置粉末；Fe-Al化合物
（State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China）
Abstract:In view of the technical difficulties of aluminum/steel welding, the 1.2 mm-thick 6016 aluminum alloy and 1.4 mm-thick DP590 dual phase steel was laser welded by adding AlSi12Mg1.5 powder to aluminum surface and Sn powder to aluminum/steel interlayer layer with lap joint applied with aluminum sheet on the top and steel sheet at the bottom. The weld appearance, microstructure and mechanical properties of welding joint were studied. The temperature field distribution of aluminum/steel joints was calculated by establishing the transient finite element model of aluminum/steel laser welding based on ANSYS finite element software. The modulus and thermodynamic properties of compounds such as FeSn, Fe3Sn, FeAl3 and Fe2Al5, were calculated by using ？rst–principles method based on density functional theory. The results indicate that 6016 aluminum alloy and DP590 double phase steel can be effectively connected with preset filler powder to aluminum/steel surface, no obvious porosity, cracks, and other defects are seen when the welding power is 2750 W, welding speed is 32 mm/s, the defocus distance is -2.0 mm, Ar gas acts as the protection gas with ？ow rate 20 L/min, and laser deflection is along welding direction 10°. The average linear load of the welding sample with aluminum/steel surface preset filler powder reaches 54.16 N/mm. Compared to that without aluminum/steel interlayer powder addition, the average shear strength of weld joint increases by 1.6 times. The relative intensity of spectra and electron density of plasma increases, which shows that the laser energy absorption rate increases by adding AlSi12Mg1.5 powder to the aluminum surface. Thus, the surface of the weld is improved. When Sn powder is added to aluminum/steel interlayer layer, the aluminum and steel are both melted, the fusion width of the upper aluminum and the lower steel increases, the combined area of aluminum/steel increases, and the welding rate is improved. In addition, grain size of weld zone is ？ne, Fe-Al compound layer thickness decreases. FeSn and Fe3Sn compounds has better ductility and is more stable than that of Fe-Al compounds at high temperature, which can improve the mechanical properties of weld joint.
Key words: laser welding; aluminum/steel; preset filler powder; Fe-Al compounds
