高压扭转对GW83K镁合金耐腐蚀性能的影响  

Effect of High-pressure Torsion on Corrosion Behavior of GW83K Magnesium Alloy

作　　者：文道静 赵永好[1] 唐玲玲[1] 宋云云[1] 郑宇希 李鑫[1] 江静华[2,3] 

机构地区：[1]南京理工大学材料科学与工程学院纳米结构材料中心,南京210094 [2]河海大学力学与材料学院,南京210098 [3]江苏省先进微纳米材料及装备协同创新中心,南京210094

出　　处：《材料导报》2016年第10期105-112,共8页Materials Reports

基　　金：江苏省自然科学基金面上项目(BK20131373)

摘　　要：采用高压扭转(HPT)工艺对Mg-8Gd-3Y-0.4Zr(GW83K)合金进行剧烈塑性变形加工,通过显微组织观察、物相分析、显微硬度测定、开路电位测试、动极化曲线测试、交流阻抗谱及扫描开尔文探针分析,对比研究了HPT前后GW83K合金的显微组织和耐蚀性。结果表明:经5圈高压扭转后,GW83K合金的晶粒细化不显著,物相结构亦无变化,晶粒中出现大量孪晶和位错,试样中心区域和边缘区域的晶粒尺寸无明显差异,但边缘区域硬度远高于中心区域。HPT后镁合金在空气中伏打电位较低,在3.5%(质量分数)NaCl溶液中浸泡时开路电位迅速稳定(约1h)但稳定值较负,腐蚀电流密度较大,电化学阻抗较小且随浸泡时间延长而减少,其耐蚀性不及未HPT加工的初始态合金。在0.1mol/L NaOH溶液中,浸泡初期初始态和HPT态合金开路电位较接近,交流阻抗相差不大,浸泡6h后初始态的电化学阻抗容抗弧直径则明显大于HPT态样品。极化曲线显示HPT态合金在碱性溶液中的维钝区间减小,维钝电流密度增大,初次击穿电压负移。HPT加工虽有助于镁合金表面快速形成钝化膜(不能有效保护基体),却使镁基体更活泼(溶解加速),GW83K镁合金耐蚀性下降。Microstructure and corrosion behavior of Mg-8Gd-3Y-0.4Zr（GW83K）alloy fabricated by high-pressure torsion（HPT）was investigated by microstructure observation,X-ray diffraction spectroscopy analysis,microhardness test,open-circuit potential test,potentiodynamic polarization test,electrochemical impedance spectroscopy（EIS）and scanning Kelvin probe test（SKP）.The results showed that the grain size and phase constitution of the GW83 Kalloy after 5 HPT turns changed inconspicuously compared with the unprocessed specimen,but the microhardness on the edge was much higher than that of the center because of plenty of twins and dislocation formed in the fine-grains.After HPT,the GW83 Kalloy had a lower interfacial voltage in air.In 3.5% NaCl solution,the open circuit potential（Eoc）of the HPT-processed specimen came to be steady quickly（about one hour）,but was more negative than the unprocessed specimen.It had a larger corrosion current density and a smaller electrochemical impedance which decreased with the immersion time.In 0.1mol/L NaOH solution,the Eocvalue and the electrochemical impedance of two kinds of specimens differed remotely in the beginning.However after 6hours,the electrochemical impedance of the unprocessed specimen was significantly greater than the HPT-processed specimen.The polarization curves show that the HPT-processed specimen had a smaller stable passivation range,a larger current density and more negative pitting voltage in alkaline solution.HPT contributes to the rapid formation of the passive film which cannot provide the magnesium matrix with an effective protection,but leads to the magnesium matrix more active and dissolve more quickly,resulting in the worse corrosion resistance.

关 键 词：MG合金 高压扭转 组织细化 腐蚀行为 

分 类 号：TG146.4[一般工业技术—材料科学与工程]