组织对差温轧制Al-Zn-Mg-Cu合金厚板晶间腐蚀性能的影响

Effect of Microstructure on Intergranular Corrosion of Differential Temperature Rolled Al-Zn-Mg-Cu Aluminum Alloy Thick Plate

采用光学金相显微镜(OM)、扫描电子显微镜(SEM)、电子背散射衍射器(EBSD)和透射电子显微镜(TEM)对差温轧制(DTR)和常规轧制(CTR)Al-Zn-Mg-Cu合金厚板各层试样的微观组织进行了分析测试,并利用电化学实验平台测试了差温轧制(DTR)和常规轧制(CTR)试样的极化曲线以及IGC实验。结果表明,通过采用差温轧制(DTR)工艺可以改善厚板各层晶粒尺寸的均匀性,通过抑制再结晶率可以减少大角度晶界占比,并使各层的晶界析出相细小及形貌差别变小,沉淀无析出带宽度变窄和差别减少;从而导致DTR试样的耐晶间腐蚀性能普遍要优于CTR试样。电化学曲线测试也表明,DTR工艺能改善Al-Zn-Mg-Cu合金板沿厚度方向的腐蚀性能均匀性,沿厚度方向各层的点蚀电位和腐蚀电位等电化学参数变化减小。

The microstructures of different layers of Al-Zn-Mg-Cu aluminum alloy thick plate rolled by Differential Temperature Rolling(DTR)and conventional temperature rolling(CTR)are analyzed and tested by means of Metallographic Microscope(OM),Scanning Electron Microscopy(SEM),Electron Backscatter Diffractometer(EBSD)and Transmission Electron Microscopy(TEM).The corrosion resistance of DTR and CTR specimens are verified by polarization curves and intergranular corrosion test.The results show that the uniformity of grain size of each layer can be improved by Differential Temperature Rolling(DTR).By significantly decreasing the fraction of High Angle Boundaries(HAB)and recrystallized grain boundaries,and the precipitation phase at grain boundaries of each layer becomes smaller,the width of Precipitation-Free Zones(PFZs)becomes narrower and thus the microstructure of Al-Zn-Mg-Cu aluminum alloy thick plate becomes more uniform.As a result,the Intergranular Corrosion(IGC)resistance of DTR samples is generally better than that of CTR samples.The results of polarization curves also show that DTR process can improve the uniformity of corrosion resistance along the thickness direction of Al-Zn-Mg-Cu aluminum alloy thick plate,and pitting potential as well as corrosion potential along the thickness direction become more stable.