ABSTRACT

Corrosion behaviour and intergranular corrosion (IGC) sensitivity of 6061 aluminium alloy were investigated using electrochemical polarisation. A 10% tensile stretching was carried out on as-quenched 6061 alloys to understand the effect of pre-deformation on precipitation during subsequent aging treatments. Grain boundary (GB) TEM micrographs were taken to correlate the relationship between the changes in microstructure and corrosion resistance. For artificially aged 6061 alloys, the introduction of the 10% pre-deformation reduces the corrosion rate, but is unable to change their IGC susceptible nature. Conversely, pre-deformation dramatically reduces the pitting depth and pit distribution of naturally aged 6061 alloys. Needle-like β″ precipitates were found homogeneously distributed in the matrix and the GB areas in the pre-deformed and naturally aged 6061-T3. It is suggested that strain-induced dislocations and misorientation sites cover the lack of vacancies around the as-quenched GBs, therefore promote homogeneous precipitation across the GBs which improves resistance against localised corrosion.

摘要

使用电化学极化研究了 6061 铝合金的腐蚀行为和晶间腐蚀 (IGC) 敏感性。对淬火状态的 6061 合金进行 10% 的拉伸拉伸，以了解预变形对后续时效处理过程中析出的影响。获取晶界 (GB) TEM 显微照片以关联微观结构变化与耐腐蚀性之间的关系。对于人工时效的 6061 合金，引入 10% 的预变形降低了腐蚀速率，但无法改变其 IGC 敏感性质。相反，预变形会显着降低自然时效 6061 合金的点蚀深度和点蚀分布。在预变形和自然时效 6061-T3 的基体和 GB 区域中发现针状 β" 析出物均匀分布。这表明应变引起的位错和错误取向位点覆盖了淬火态 GBs 周围缺乏空位，因此促进了 GBs 上的均匀沉淀，从而提高了对局部腐蚀的抵抗力。