Mg_2Si及Si粒子在Al-Mg-Si合金晶间腐蚀中协同作用机理的多电极偶合研究  

SYNERGETIC EFFECT OF Mg_2Si AND Si PARTICLES ON INTERGRANULAR CORROSION OF Al-Mg-Si ALLOYS THROUGH MULTI-ELECTRODE COUPLING SYSTEM

作　　者：李朝兴[1] 李劲风[1,2] BIRBILIS Nick 贾志强[1] 郑子樵[1,2] 

机构地区：[1]中南大学材料科学与工程学院,长沙410083 [2]中南大学有色金属材料科学与工程教育部重点实验室,长沙410083 [3]ARC Centre of Excellence for Design in Light Metals,Department of Materials Engineering,Monash University,3800 Australia

出　　处：《中国腐蚀与防护学报》2010年第2期107-113,共7页Journal of Chinese Society For Corrosion and Protection

摘　　要：通过测定Al-Mg-Si合金晶界各组成相的极化曲线及不同Mg/Si比Al-Mg-Si合金晶界组成相(AlMg_2Si及Al-Mg_2Si-Si)间的动态电化学偶合行为,研究了不同Mg/Si比Al-Mg-Si合金的晶间腐蚀机理。研究表明,晶界Si电位比其边缘Al基体正,在整个腐蚀过程中作为阴极导致其边缘Al基体的阳极溶解。晶界Mg_2Si电位比其边缘Al基体负,在腐蚀初期将作为阳极而发生阳极溶解;由于Mg_2Si中活性较高元素Mg的优先溶解,不活泼元素Si富集,致使Mg_2Si电位正移,甚至与其边缘Al基体发生极性转换,导致其边缘Al基体的阳极溶解。Mg/Si>1.73的Al-Mg-Si合金晶界只存在不连续分布的含Mg、Si的析出相,不能在晶界形成连续腐蚀通道,合金不表现出晶间腐蚀敏感性。Mg/Si<1.73的Al-Mg-Si合金晶界同时析出含Mg、Si析出相和Si粒子;腐蚀首先萌生于Mg_2Si相;而后,Si粒子一方面导致其边缘无沉淀带严重的阳极溶解,另一方面通过加速Mg_2Si和晶界无沉淀带的极性转换,协同促进了Mg_2Si边缘无沉淀带的阳极溶解,即腐蚀沿晶界Si粒子及Mg_2Si粒子边缘的无沉淀带发展。Si粒子促进了腐蚀的发展,导致合金表现出严重的晶间腐蚀敏感性。The potentiodynamic scanning curves and the electrochemical coupling behaviors of constituent phases at the grain boundary of Al-Mg-Si alloy were investigated.The corrosion mechanism of Al-Mg-Si alloys different ratio of Mg to Si was analyzed.The results show that the Si particle is cathodic to the Al-base and causes the anodic dissolution of Al-base at its adjacent periphery.At the beginning,the precipitate of Mg_2Si is anodic to the Al-base and corrosion occurs on its surface.However,during its corrosion process,its potential moves to a positive direction with immersion time increasing,due to the preferential dissolution of Mg and the enrichment of Si,which makes Mg_2Si become cathodic to Al-base and leads to the anodic dissolution of the Al-base at its adjacent periphery at a later stage.At the grain boundary of Al-Mg-Si alloys with a ratio of Mg to Si higher than 1.73,the Mg-and-Si contained precipitates are distributed discontinuously,resulting in that they are not sensitive to intergranular corrosion.There exist Mg-and-Si-contained precipitates and Si particles at the grain boundary of Al-Mg-Si alloys with a ratio of Mg to Si less than 1.73,corrosion occurs firstly on the surface of Mg_2Si.Meanwhile,the Si particle leads to the great anodic dissolution of the precipitate-free-zone（PFZ） at its adjacent periphery.The Si particle also accelerates the preferential dissolution of Mg in Mg_2Si precipitate, expediting the polarity transformation between Mg_2Si and the PFZ.As a result,the corrosion development along the PFZ at the adjacent of Mg_2Si particle is enhanced.

关 键 词：AL-MG-SI合金 晶间腐蚀 腐蚀机理 

分 类 号：TG171[金属学及工艺—金属表面处理]