块体超细晶Fe-Ni-Cr合金的腐蚀行为

摘要

利用等通道转角挤压方法制备块体超细晶Fe-Ni-Cr合金，对其在0.25 mol/L Na2SO4+0.05 mol/L H2SO4溶液中的耐蚀性进行研究。与粗晶合金相比，超细晶合金表现出加速的活性溶解过程，钝化区间缩小，维钝电流密度更大。对表面钝化膜进行 Mott-Schottky 曲线测试并结合点缺陷模型分析，结果表明，超细晶合金钝化膜内载流子的扩散系数较粗晶合金显著提高一个数量级，载流子密度略有降低。%The corrosion behavior of bulk ultra-fine grained (UFG) Fe-Ni-Cr alloy prepared by equal-channel angular pressing technique was investigated in 0.25 mol/L Na2SO4+0.05 mol/L H2SO4 solution by electrochemical measurements. As compared to the coarse grained (CG) counterpart, the UFG alloy exhibits an acceleration of the active dissolution and a shrunk passive region with a higher passive current. The Mott-Schottky analysis in conjunction with the point defect model indicates that the donor diffusion coefficient in the passive films of the UFG sample increases greatly to one magnitude order higher and the donor density is slightly lower than that of the CG sample.