时效状态对Al-1.63Mg-1.01Si-0.1Mn-0.12Cr-0.1Zr-0.1Ti合金组织及晶间腐蚀性能的影响

Effect of aging state on microstructure and intergranular corrosion behavior of Al-1.63Mg-1.01Si-0.1Mn-0.12Cr-0.1Zr-0.1Ti alloy

采用硬度测试,扫描电子显微镜(SEM),动电位极化测量和高分辨率透射电子显微镜(HRTEM)研究了时效状态对Al-1.63Mg-1.01Si-0.1Mn-0.12Cr-0.1Zr-0.1Ti合金微观组织及晶间腐蚀行为的影响。结果表明:在欠时效状态下,合金表现为局部腐蚀;在峰时效状态下,合金具有最高的强度,晶间腐蚀最为严重;在过时效状态下,合金导电率最大,表现为轻微的晶间腐蚀和点腐蚀。晶界析出相大小和分布的改变是导致合金腐蚀形式转变的主要原因。欠时效状态的合金发生点腐蚀是由于粗大结晶相和周围贫溶质原子区导致的。峰时效状态的合金的高晶间腐蚀敏感性源于连续分布的β'相和宽化的无沉淀析出带(PFZ)。过时效状态的合金是通过晶界β'相溶解周围基体析出相进一步长大而提高耐腐蚀性能。

The effect of aging state on the microstructures and intergranular corrosion behavior of Al-1.63 Mg-1.01 Si-0.1 Mn-0.12 Cr-0.1 Zr-0.1 Ti alloy were studied by means of hardness test, scanning electron microscope(HRSEM), potentiodynamic polarization measurement and high-resolution transmission electron microscope(HRTEM). The results show that in under-aging condition, the alloy shows local corrosion. The alloy in peak aging state has the highest strength, and the intergranular corrosion is the most serious. In the over aging state, the conductivity of the alloy is the highest, showing slight intergranular corrosion and pitting corrosion. The change of size and distribution of the precipitates at the grain boundary is the main reason for transformation of corrosion form of the alloy. Point corrosion of the under-aged alloy is caused by coarse crystalline phase and surrounding solute-poor atomic zone. The high intergranular corrosion sensitivity of the peak-aged alloy results from the continuous distribution of β′ phases and widened precipitation-free zone(PFZ). The reason why the corrosion resistance of the over-aged alloy is improved is that the β;phase at the grain boundary grows further by dissolving the precipitated phase in the surrounding matrix.