β-Al_2O_3固体电解质的“电解—应力腐蚀”裂纹生长

Crack Growth in βAl_2O_3 Solid Electrolyte under Electro-stress Corrosion

当电解质隔板在使用中出现裂纹时,重要的问题是探求出,在工作应力下,该裂纹通过扩展,达到引起灾难性断裂的临界长度所需的时间。本工作研究了电解电流 Q_(?)对处于受力状态下的β-Al_2O_3电解质中裂纹生长速率 da/dt 的影响。探讨了电解条件下的持久断裂时间 T_(?)对起始应力强度因子 K_(?)的依赖关系。分析了裂纹尖端区域的钠流和钠沉积加速“电解—应力腐蚀”断裂过程的机理。指出,钠沉积对于裂纹扩展可能起着两种相反的作用。一方面,在主裂纹尖端钠尖积诱发微裂纹的合并,有可能加速裂纹扩展的进程;另一方面,当裂纹尖端的温度由于长时间的电解而升高,沉积钠可能软化并起着抑制裂纹生长的韧性相作用。

When a crack is presented in an electrolytic insulator during its service,it isobviously important to explore the time for reaching its critical length of causingits catastrophic propagation.In this work,the influence of electrolytic current density on the crack growthrate in β-Al_2O_3 electroyte under stress has been studied,and the dependence of thedelayed fracture time under the condition of electrolysis on the initial stressintensity factor has also been studied.A mechanism of accelerating electro-stresscorrosion fracture affected by Na flow and the deposition of Na at the front ofthe crack tip has been analysized.It is suggestsd that there may be existing twoopposite effects on crack growth due to Na deposition.Namely,Na deposition atthe front of the crack tip induces the cracks to link,promoting the propagation ofthe crack;on the other hand,Na deposited may suppress the crack growth,becauseof the softening of Na deposited for a long time due to its temperature rising.