滚压诱导超细晶纯铁表层及其耐腐蚀性能

Burnishing-Induced Ultra-Fine Grained Pure Iron Surface Layer and Its Corrosion Resistance

通过一种新型表面自纳米化方法——剧烈塑性滚柱滚压(SPRB),在纯铁表面成功制备出最小晶粒尺寸约300 nm的梯度超细晶结构.利用电化学方法,结合透射电镜、X射线衍射、扫描电镜等对这种材料的表面微观组织结构及腐蚀性能进行研究,结果表明:与粗晶铁相比,超细晶纯铁最表层硬度提高1.6倍以上,表层形成较强面织构,表层微观应变为(0.313±0.017)%;超细晶纯铁在3.5%Na Cl溶液中的自腐蚀电位相对于粗晶铁的正向移动24 m V,腐蚀电流密度从粗晶铁的2.371×10-5A/cm2降低到超细晶的7.547×10-8A/cm2;超细晶纯铁在6%Fe Cl3溶液中的点蚀腐蚀速度约为粗晶铁的一半;超细晶纯铁的耐腐蚀性能与粗晶铁相比有显著的提高,表层晶粒的细化和滚压形成的强织构是超细晶纯铁耐腐蚀性能提高的原因.

In the investigation,by means of a new surface self-nanocrystallization technique named SPRB（Severe Plasticity Roller Burnishing）,a gradient ultra-fine grain（UFG） surface layer of a minimum grain size of about 300 nm was fabricated on pure iron.Then,the microstructure and the corrosion behavior of UFG surface layer were analyzed by means of TEM,XRD,SEM and electrochemical methods.The results show that（1） the outermost layer hardness of UFG iron is improved by more than 1.6 times in comparison with that of coarse grain（CG） iron;（2） a strongly basal-textured grain orientation forms on the UFG surface and its micro strain is（0.313 ± 0.017） %;（3） in3.5% Na Cl solution,the open circuit corrosion potential of UFG Fe is 24 m V more than that of CG Fe in the positive direction,and the corrosion current density decreases from 2.371 × 10^-5A / cm^2 of CG Fe to 7.547 × 10^-8A / cm^2 of UFG Fe;（4） in 6% Fe Cl3 solution,the pitting rate of UFG Fe is about half as much as that of CG Fe;（5） the corrosion resistance of UFG Fe is remarkably improved in comparison with that of CG Fe;and（6） the corrosion resistance improvement of UFG Fe is attributed to the surface grain refinement and the formation of the strongly basaltextured grain orientation.