ER5356焊丝用于7075铝合金MIG焊接头热处理性能

Heat treatment performance of ER5356 welding wire for MIG welding joint of 7075 aluminum alloy

采用MIG焊使用ER5356焊丝进行3 mm厚7075铝合金对接焊,焊后接头进行T6热处理。通过光学显微镜、X射线衍射仪、扫描电镜与能谱仪结合室温拉伸、显微硬度与电化学腐蚀分析接头组织、力学性能与耐蚀性。结果表明:焊接时熔池流动将母材熔化部位的Zn,Cu等合金元素带入焊缝,析出MgZn_(2)与AlCuMg相,成为焊缝进行热处理强化的基础;热处理后,大部分析出相溶入基体形成固溶+时效强化,接头抗拉强度提升20%,焊缝硬度提升18.4%,耐蚀性提高。但由于从母材流入焊缝的合金元素含量有限,焊丝与母材力学性能的差异与热影响区软化现象无法消除。

MIG welding and ER5356 welding wire were used for butt welding of 7075 aluminum alloy with a thickness of 3 mm.The joint was subjected to T6 heat treatment after welding.The microstructure,mechanical properties and corrosion resistance of the joints were analyzed by optical microscope,X-ray diffraction,scanning electron microscope and energy spectrometer combined with room temperature stretching,microhardness and electrochemical corrosion.The results show that the molten pool flow brings Zn,Cu and other alloying elements in the molten part of the base metal into the weld,and precipitates MgZn_(2)and AlCuMg phases during the welding process,which become the basis for the heat treatment and strengthening of the weld.After heat treatment,most of the precipitated phase melts into the matrix to form solid solution+aging strengthening,the joint tensile strength increases by 20%,and the weld hardness increases by 18.4%,the corrosion resistance improves.However,due to the limited alloying element content flowing into the weld from the base metal,the difference in mechanical properties between the welding wire and the base metal and the heat-affected zone softening phenomenon cannot be eliminated.