2A12铝合金筋板件T型搅拌摩擦焊工艺及焊后热处理

Friction stir welding and successive heat treatment of T-shaped rib-web parts of 2A12 aluminim alloy

为评价2A12铝合金筋板件搅拌摩擦焊工艺并探寻提高接头强度的途径,进行了2A12铝合金筋板件的T型搅拌摩擦焊焊接工艺试验,并对不同人工时效热处理下焊接接头的微观组织及性能进行了研究.研究表明:采用T型搅拌摩擦焊即可实现2A12铝合金筋板件的成形,当搅拌头旋转速度为750 r/min、焊接速度60 mm/min时,接头的抗拉强度达到了315 MPa,为母材强度的70.1%;断裂出现在前进侧热机影响区,硬度的最低处也在该区域,说明2A12铝合金搅拌摩擦焊接头的薄弱点在热机影响区.采用退火+固溶+分级时效热处理的方法能显著改善焊接接头的强度,接头的抗拉强度可达387 MPa,为母材的86.3%;焊接接头的薄弱点仍在前进侧的热机影响区.

To evaluate the friction stir welding （FSW） technique of rib-web parts and to explore the ways of improving the joint strength, the T-shaped FSW process was conducted for the rib-web parts of 2A12 aluminum alloy, and the relative microstructure and mechanical property of welded joints were investigated before and after a series of aritificieal aging processes. Results show that the T-shaped FSW technique alone can realize the formation of 2A12 aluminum alloy rib-web parts. And when the rotating speed of stirring joint is 750 r/rain and the welding speed is 60 mm/min, the welded joints have a better tensile strength of 315 MPa that is 70. 1% of that of the base metals, which are regarded as an ideal parameters under the experimental conditions. The fracture and the lowest hardness appear in the same location in the thermo-mechanically affected zone （TMAZ） of advancing side of joints, which is the weak point of friction stir welding joints for 2A12 aluminum alloy. The welded joints after heat treatment show that a significant improvement upon tensile strength can be observed by using a combined aging process of annealing, solution and step aging. The tensile strength of joints can reach 387 MPa, 86.3% of that of the base metals. However, the weak point of joints is still located in the thermo-mechanically affected zone （TMAZ） of advancing side.