高速列车用高强A7N01铝合金焊接接头的疲劳性能（英文）

Fatigue Property of Al-5Zn-2Mg Aluminum Alloy Welding Joints Used in High-speed Trains

用IBTC-2000型疲劳机对高速列车用A7N01(Al-5Zn-2Mg)铝合金MIG焊焊接接头、热影响区和母材试样进行疲劳试验,用扫描电子显微镜(SEM)观察疲劳断口以及疲劳表面损伤形貌。结果表明,应力高于0.5σ_b时,焊缝部位会产生棘轮应变,发生了明显的塑性变形,表面有明显滑移带,会降低焊接接头试样的疲劳寿命。焊缝部位发生的塑性变形主要集中发生在疲劳过程的第1循环和最后的失效阶段。当应力低于0.5σ_b时,断口位于热影响区。焊缝和熔合区断口为延性断口,热影响区和母材试样断口为准解理断口。母材的疲劳寿命远远高于热影响区试样的疲劳寿命。

The fatigue property of Al-5Zn-2Mg aluminum alloy Metal-Inert Gas（MIG） welding joints used in high-speed trains was studied by a fatigue machine. Scanning electron microscopy（SEM） was used to observe the fatigue fracture and the surface damage. The results show that uniaxial ratcheting behavior occurs in the welding zone（WZ） when the stress is higher than 0.5σ_b;there are obvious plastic deformations in the WZ and a lot of slip bands on the surface, which reduce the fatigue life of the sample. The uniaxial ratcheting behavior mainly appears in the first cycle and the final failure stage of the fatigue process. When the stress is lower than 0.5σ_b, the fatigue samples crack in the heat affected zone（HAZ）. The fatigue fracture of the WZ and the fusion zone（FZ） is typical ductile fracture pattern while that of the HAZ and the base metal（BM） is quasi-cleavage fracture. The fatigue life of the BM is much longer than that of the HAZ.