摘要
时效对Al-7.82Zn-1.99Mg-2.41Cu-0.12Zr合金局部腐蚀模式及过程有重要影响.合金在欠时效状态下,晶界析出相尺寸小,分布连续性高,LGBPs/GB为0.75,主要的腐蚀形式是晶间腐蚀.而在双级时效和回归再时效状态下,晶界析出相尺寸大,分布连续性低,LGBPs/GB小于0.5,晶间腐蚀被抑制,合金主要的腐蚀形式是点蚀.随着浸泡时间的延长,峰时效状态合金的腐蚀模式由点蚀向晶间腐蚀转变.点蚀起始于Al7Cu2Fe粒子,其尺寸越大,与基体的电位差越大,表明较大的Al7Cu2Fe粒子更容易引起点蚀.在腐蚀初期,合金表面发生点蚀,Al和Mg元素在Al7Cu2Fe粒子周围优先溶解.随着浸泡时间的延长,合金表面发生晶间腐蚀.
Abstract
The localized corrosion mode and process dependence on ageing conditions for Al-7.82Zn-1.99Mg-2.41Cu-0.12Zr alloy were investigated.Intergranular corrosion(IGC)is the dominant corrosion mode for UA temper alloy due to the small size(8.48 μm)and low distribution continuity(LGBPs/GB=0.75)of grain boundary precipitates(GBPs),whereas pitting corrosion is the dominant corrosion mode for T74 and T77 temper alloys because the large size(>18.5 μm)and discontinuous distribution(LGBPs/GB<0.5)of GBPs inhibit the occurrence of IGC.The corrosion mode of T6 temper alloy evolves with immersion time from pitting corrosion to IGC.Pitting corrosion is initiated at the site of Al7Cu2Fe particles.Al7Cu2Fe particle with larger size shows a higher potential difference value of 58.4 mV with the matrix,implying that larger Al7Cu2Fe particle is preferred to be the initial sites for pitting corrosion.At the initial stage of corrosion,the surface of T6 temper alloy is attacked by pitting corrosion.Al and Mg elements in the matrix around Al7Cu2Fe particles are preferentially dissolved.As the immersion time prolongs,the surface is attacked by intergranular corrosion.
基金项目
Natural Science Foundation of Shandong Province,China(ZR2021QE136)
Key Research and Development Program of Guangdong Province,China(2020B010186002)
NETL
NSTL
维普
万方数据