(中南大学 机电工程学院, 长沙 410083)
摘 要: 采用搅拌摩擦焊方法对厚度为25 mm的7A52铝合金板进行了单道焊实验。结果表明： 在焊接25 mm板时, 工艺参数可调范围较窄, 在旋转速度为1500 r/min, 且焊接速度为40 mm/min时, 可以获得较好的焊接性能, 抗拉强度可以达到330 MPa, 延伸率可以达到9.6%； 焊缝中存在3个组织变化区, 其中焊核区内是细小均匀的等轴晶, 平均晶粒大小在4 μm左右；焊缝两侧热机影响区组织存在较大差异, 前进侧为窄条状组织, 回退侧为扁平块状组织；热影响区组织发生了回复、 再结晶和粗化； 焊缝显微硬度的最低值出现在前进侧, 说明前进侧是焊缝的薄弱环节； 厚板焊接时, 沿板厚方向的热机作用梯度过大, 造成焊缝金属难以获得优良焊接性能, 这是厚板焊接较困难的原因。
关键字: 7A52铝合金；厚板； 搅拌摩擦焊； 单道焊
7A52 aluminum alloy
（School of Mechanical and Electrical Engineering,
Central South University, Changsha 410083, China）
Abstract: Friction-stir welds of 7A52 aluminum plate of 25 mm thickness were completed in a single pass. The experiment results demonstrate that the adjusting scope of process parameters is very narrow when welding the plate of 25 mm thickness. When the rotating speed is 1 500 r/min and the welding speed is 40 mm/min, the good weld is achieved, and the tensile strength of the weld reaches 330 MPa, and the elongation reaches 9.6%. The welds consist of three different zones. The weld nugget zone consists of fine equiaxed grains which size is about 4 μm. Regarding to the thermo-mechanically affected zone on the two sides, the advancing side consists of narrow slate grains, while the retreating side consists of flat and nubby grains. The grains of heat affected zone have showed some reversion, recrystallization and growth characteristics. The min micro-hardness occurs on the advancing side. For the grads of thermo-mechanical action at the thickness direction is very large, it is difficult to achieve good welds as welding thick plate.
Key words: 7A52 aluminum alloy; thick plate; friction stir welding; single pass welding
