In this work, 20-mm-thick aluminum-alloy plates were joined via friction stir welding. The temperature gradient was reduced by reducing the surface welding heat input to achieve uniformity of the mechanical properties...In this work, 20-mm-thick aluminum-alloy plates were joined via friction stir welding. The temperature gradient was reduced by reducing the surface welding heat input to achieve uniformity of the mechanical properties across the thick plate joints. The welding temperature was measured using thermocouples. The microstructures were observed via electron backscatter diff raction and transmission electron microscopy. The tensile properties of the samples sliced along the thickness direction of the joint were evaluated. The results show that the highest welding peak temperature is 430℃ on the advancing side on the top surface of the joint. The grain size gradually decreased along the thickness direction, and grain refi nement was due to the combination of continuous, discontinuous, and geometric dynamic recrystallization. The tensile properties of the sliced samples were found to be uniform, and the ultimate tensile strength reached 62% of that of the base metal. The main strengthening mechanism of the Al–Zn–Mg–Cu alloy joints consists of precipitation strengthening. In addition, the η ` → η phase transition and grain coarsening in the heat-affected zone were found to be responsible for the fracture of the joints.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U1760201,51974220,52034005)the Innovation Capacity Support Project of Shaanxi Province(No.2020KJXX-077)+4 种基金the National Key Research and Development Program of China(No.2017YFB0306202)the Key Research and Development Program of Shaanxi Province(Grant No.2020ZDLGY13-06)the Key Industrial Research Program of Shaanxi Province(Grant No.2017ZDXM-GY-037)the Natural Science Basic Research Program of Shaanxi Province(Grant Nos.2019JQ-111,2019JQ-769)the Xi’an Science and Technology Project(Grant No.201805033YD11CG17(8))。
文摘In this work, 20-mm-thick aluminum-alloy plates were joined via friction stir welding. The temperature gradient was reduced by reducing the surface welding heat input to achieve uniformity of the mechanical properties across the thick plate joints. The welding temperature was measured using thermocouples. The microstructures were observed via electron backscatter diff raction and transmission electron microscopy. The tensile properties of the samples sliced along the thickness direction of the joint were evaluated. The results show that the highest welding peak temperature is 430℃ on the advancing side on the top surface of the joint. The grain size gradually decreased along the thickness direction, and grain refi nement was due to the combination of continuous, discontinuous, and geometric dynamic recrystallization. The tensile properties of the sliced samples were found to be uniform, and the ultimate tensile strength reached 62% of that of the base metal. The main strengthening mechanism of the Al–Zn–Mg–Cu alloy joints consists of precipitation strengthening. In addition, the η ` → η phase transition and grain coarsening in the heat-affected zone were found to be responsible for the fracture of the joints.
