2219-T87厚板搅拌摩擦焊沿厚度方向的性能差异

Through-thickness diversity of properties in friction stir welded 2219-T87 thick aluminum alloy plate

采用搅拌摩擦焊方法对35mm厚的2219-T87高强铝合金进行了单道对接焊。结果表明,焊缝的抗拉强度可达274MPa,且断裂于焊核区。用螺旋形搅棒焊接厚板时,焊接速度较慢,焊核区上部组织因温度较高,同时在螺旋产生的向下泵吸作用下,会产生比较粗大的疏松组织;而焊核区中下部组织则因温度较低,并在螺旋推力作用下形成比较细小的致密组织。焊核区上部的显微硬度存在一个下陷区,而中下部的显微硬度变化较为平缓。焊接厚度过大时,螺旋搅棒的泵吸作用引起焊核区上部组织疏松,并使其显微硬度下陷,是造成厚板搅拌摩擦焊缝强度不高且断裂于焊核区的原因。

Friction stir welding of 2219-T87 high-strength aluminum alloy plate in 35 mm thickness was completed with a single pass. The results demonstrate that the tensile strength of weld reaches 274 MPa, and the fracture happens in the WNZ(welding nugget zone). Because the welding speed was slow for welding thick plate, and the temperature of the upper WNZ was higher, the microstructure became coarse under the pumping action of screwed stirrer. While the temperature of the bottom WNZ was lower, the microstructure became compact under the crushing action of screwed stirrer. The microhardness of upper WNZ had a decrease zone, while that of bottom changed slowly. When the welding thickness was too large, the microstructure of upper WNZ will become coarse for pumping of screwed stirrer, and it can cause microhardness decrease. It was the reason why the tensile property not high and the fracture was located in the WNZ.