强激光冲击对7075铝合金等离子弧焊接头电化学腐蚀行为的影响

发布时间：2019-05-16 08:08

【摘要】：采用极化曲线、电化学交流阻抗谱、X射线衍射仪(XRD)测试残余应力、扫描电镜(SEM)测试腐蚀形貌从实验上研究了强激光冲击对7075铝合金等离子弧焊接头电化学腐蚀行为的影响。研究结果表明,激光冲击后7075铝合金焊接头表面残余应力由拉应力变成压应力,从而使得铝合金等离子弧焊接头的自腐蚀电位和点蚀电位提高,激光冲击4次后自腐蚀电位正移700 m V,点蚀电位正移约为1000 m V,极化曲线上出现了电位范围至712.9 m V的阳极钝化区间。经过激光冲击处理细化晶粒,7075铝合金焊接头的显微孔洞数量和气穴的体积减少,组织致密性提高,溶液中Cl等原子的渗入被有效阻止,从而降低了腐蚀速率,使自腐蚀电流密度降低了1个数量级。激光冲击使焊接头处晶粒沿β相分布变得均匀,β相与α基相构成的微电偶的活性降低,钝化电阻比冲击前提高了近30倍,浓差极化现象大为改善。
[Abstract]:The residual stress was measured by polarization curve, electrochemical impedance spectroscopy and X-ray diffractometer (XRD). The effect of strong laser shock on electrochemical corrosion behavior of 7075 aluminum alloy plasma arc welding joint was studied by scanning electron microscope (SEM). The results show that the surface residual stress of 7075 aluminum alloy welded joint changes from tensile stress to compressive stress after laser shock, which increases the self-corrosion potential and pitting corrosion potential of aluminum alloy plasma arc welding joint. After 4 times of laser shock, the self-corrosion potential shifts positively to 700 MV, and the pitting corrosion potential is about 1000 MV. The anodic passivation range from 712.9 MV to 712.9 MV appears on the polarization curve. After laser shock treatment, the number of micropores and the volume of cavitation in 7075 aluminum alloy welded joint decreased, the microstructure tightness increased, and the infiltration of Cl and other atoms in solution was effectively prevented, thus reducing the corrosion rate. The self-corrosion current density is reduced by an order of magnitude. Laser shock makes the grain distribution along 尾 phase uniform, the activity of microcouple formed by 尾 phase and 伪 base phase decreases, the passivation resistance is nearly 30 times higher than that before shock, and the concentration polarization phenomenon is greatly improved.
【作者单位】：江苏大学机械工程学院;江苏理工学院材料工程学院;东南大学机械工程学院;
【基金】：国家“863”计划子项目(2012AA040104) 国家自然科学基金(51275221,51105182) 江苏省高校自然科学基金(12KJB460002) 江苏省光子制造重点实验室开放基金(GZ201202,GZ201101) 江苏省青蓝工程项目,校科研预研项目(KYY12040)
【分类号】：TG457.14

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