铝钢电磁脉冲焊接接头中性盐雾腐蚀行为

为了获得铝钢电磁脉冲焊接接头中性盐雾介质的腐蚀过程及机理，对5%NaCl腐蚀后的焊接接头进行拉剪试验，并采用带能谱的扫描电子显微镜进行断口微观形貌分析.结果表明，铝钢电磁脉冲焊接接头中性盐雾腐蚀3天后的抗剪强度由原态74 MPa降为33 MPa，为原态的44.6%，腐蚀周期7天时，焊缝完全失效；在焊缝外围，粒子流击碎铝板表面氧化物生成粒状腐蚀物NaAlO₂，焊缝上FeAl₃破碎，露出铝被快速腐蚀为Al(OH)₃；在铝板表面撞击产生凹坑和嵌入钢板表面片状铝的位置最先被腐蚀，NaCl液体堆积并在表层金属下流动腐蚀，且沿着腐蚀坑互连方向扩展，再向焊缝存在FeAl₃相的连接区延伸；当氧化膜或焊缝被NaCl介质腐蚀抬起且破碎后，向着铝基体深层腐蚀，形成多而深的沟壑或凹坑，这成为接头快速失效的主要腐蚀机理.

Corrosion behavior of joints by electromagnetic pulse welding with aluminum to steel in neutral salt spray

In order to obtain the corrosion process and mechanism of joints by electromagnetic pulse(EMP) welded with aluminum to steel in neutral salt spray medium of 5%NaCl, shear test was performed and the shear fracture morphologies were analyzed by scanning electron microscopy. The results showed that the shear strength of the welded joint decreased from 74 MPa to 33 MPa after 3 days in the neutral salt spray corrosion, which was 44.6% of the original shear strength, and the weld failed completely after 7 days in corrosion. At the periphery of the weld, particle flow impacted the oxides at the surface of the aluminum plate to form granular corrosion NaAlO₂, and FeAl₃ at the weld was broken, exposing the aluminum to be rapidly corroded into Al(OH)₃. Where the impact pits at the surface of the aluminum plate and the embedded aluminum metal at the surface of the steel plate was the place first to be corroded, NaCl liquids accumulated and flowed under the metal surface for corrosion, and expanded along the direction of corrosion pits interconnection, and then extended to the joint zone where FeAl₃ phase existed in the weld. When the oxide or the weld was corroded by NaCl liquids and lifted and broken, it would be deeply corroded towards the aluminum matrix, and formed many and deep gullies or pits, which became the main corrosion mechanism of rapid joint failure.