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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。
Polarization curves, electrochemical impedance spectroscopy, X-ray diffraction (XRD) testing of residual stress and scanning electron microscopy (SEM) were used to test the corrosion morphology. The effects of intense laser shock on the electrochemical corrosion of 7075 aluminum alloy plasma arc welding The impact of behavior. The results show that the residual stress on the surface of 7075 aluminum alloy after laser shock changes from tensile stress to compressive stress, and the self-corrosion potential and pitting potential of the aluminum alloy plasma arc welding joint increase. After the laser shocks for 4 times, the self-corrosion potential is positive The potential shift of pitting corrosion is about 1000 mV with a displacement of 700 mV, and an anodic passivation range of potential range up to 712.9 mV appears on the polarization curve. After the laser shock treatment of grain refinement, 7075 aluminum alloy welding head of the number of micro-holes and cavities reduce the volume, the organization increased the density of Cl and other atoms in the solution infiltration is effectively stopped, thereby reducing the corrosion rate, so that self-corrosion Current density is reduced by 1 order of magnitude. The laser shock causes the grains at the welding tip to be distributed uniformly along the β phase, the activity of the micro-couples formed by the β-phase and the α-based phase decreases, and the passivation resistance is increased by nearly 30 times compared with that before the impact. improve.