(1. 湖南大學(xué) 汽車車身先進設(shè)計制造國家重點實驗室，長沙 410082；
2. 湖南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410082)
摘 要: 采用光纖激光器作為焊接熱源，對1.4 mm厚DP600雙相鋼和1.8 mm厚AZ31鎂合金平板試件進行鋼上、鎂下搭接、鋼/鎂層間添加Sn箔的激光熱傳導(dǎo)焊試驗，通過試驗調(diào)整優(yōu)化焊接工藝參數(shù)，獲得最佳焊縫成形，采用臥式金相顯微鏡、帶有能譜儀(EDS)的掃描電鏡、X射線衍射儀(XRD)等觀察添加Sn箔鋼/鎂接頭的顯微組織、界面元素分布和相結(jié)構(gòu)組成；利用ANSYS有限元軟件，考慮材料物性參數(shù)的溫度相關(guān)性、初始條件、邊界條件等因素影響，建立鋼/鎂異種金屬激光焊接非線性三維傳導(dǎo)有限元模型，模擬計算鋼/鎂焊接接頭的溫度場分布。結(jié)果表明:添加Sn箔可實現(xiàn)鋼/鎂之間的有效連接，焊接模式為激光熱傳導(dǎo)焊，模擬計算獲得熔池形狀、尺寸與實際焊縫基本吻合，驗證采用高斯體熱源模型用于模擬雙相鋼/鎂合金焊接接頭溫度場的合理性；由于添加Sn箔減緩從上層鋼板向下層鎂合金的熱量傳遞，起到一定程度的隔熱效果，利于熔沸點差異大的鋼、鎂同時熔化，此外上層鋼側(cè)冷卻速度降低，延長鋼板與Sn箔中Fe、Sn元素的相互擴散時間，導(dǎo)致鋼/鎂界面中鋼側(cè)過渡區(qū)域生成FeSn、Fe1.3Sn、Fe3Sn等Fe-Sn相，鎂側(cè)過渡區(qū)域生成Mg2Sn相。因此，添加Sn箔有助實現(xiàn)雙相鋼/鎂合金異種金屬的有效連接。
關(guān)鍵字: 鋼/鎂異種金屬；Sn箔；激光熱傳導(dǎo)焊；數(shù)值模擬；溫度場
（1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,
Hunan University, Changsha 410082, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:Laser welding test with Sn foil addition was carried out on DP600 double steel with thickness of 1.4 mm and AZ31 magnesium alloy with thickness of 1.8 mm by using fiber laser beam and the method of laser heat-conduction welding in an overlap steel-on-magnesium configuration. The best welding was achieved based on the optimization of welding parameters, and microstructure, elements distribution and phase compositions of the welding joint were studied by the horizontal microscopy, SEM with EDS and XRD. Considering the temperature dependence of material properties, initial conditions, boundary conditions and other factors, the nonlinear 3-D conduction finite element model of the steel/magnesium dissimilar metal laser welding was established by ANSYS finite element software. The results show that the effective connection between steel and magnesium can be realized in the heat-conduction welding mode with addition of Sn foil. The simulation calculation results of the weld pool shape, size are basically consistent with those of the actual weld, which verifies the rationality of the Gauss body heat source model for simulating the temperature field of the dual phase steel/magnesium alloy welded joints. Because of the addition of Sn foil to slow down the heat transfer from steel to the magnesium alloy, the effect of heat insulation of Sn foil is beneficial to the steel and magnesium plates melting at the same time. In addition, the cooling speed of the upper steel decreases and prolongs the diffusion time of Fe and Sn element, resulting in FeSn, Fe1.3Sn, and Fe3Sn phases in the transition zone of steel and Mg2Sn phase in transition region of magnesium. Therefore, the addition of Sn foil can help to realize the effective connection of dissimilar metals between double phase steel and magnesium alloy.
Key words: steel/magnesium dissimilar metal; Sn foil; laser heat-conduction welding; numerical simulation; temperature field
