李朝兴
,
李劲风
,
BIRBILISNick
,
贾志强
,
郑子樵
中国腐蚀与防护学报
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(Al-Mg2Si及Al-Mg2Si-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Mg2Si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Mg2Si中活性较高元素Mg的优先溶解，不活泼元素Si富集，致使Mg2Si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 Mg2Si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Mg2Si和晶界无沉淀带的极性转换，协同促进了Mg2Si边缘无沉淀带的阳极溶解，即腐蚀沿晶界Si粒子及Mg2Si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。
关键词:
Al-Mg-Si合金
,
intergranular corrosion
,
corrosion mechanism
M.Cai
,
G.W.Lorimer
材料科学技术（英文）
The effect of equal channel angular extrusion (ECAE) on the microstructure of two Al-Mg-Si extrusion alloys was investigated by high resolution electron backscattered diffraction (EBSD) using a field emission gun scanning electron microscope (FEG-SEM) and a transmission electron microscope (TEM). Two contrasting alloys: a dilute alloy, based on alloy 6061 and a concentrated alloy, based on alloy 6069 were employed for this research. It has been found that prior ECAE to extrusion promotes high angle grain boundaries (HAGBs) in the extrusions, and the increase in HAGBs ratio is due to the large shear deformation involved in the process of ECAE. Tensile testing results show that a further ageing treatment strengthens the alloys after extrusion and the ECAE processed extrusions are more ductile than conventional extrusions.
关键词:
Equal channel angular extrusion
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