阳极溶解型应力腐蚀点蚀演化的能量原理

Energy principle for pitting evolution during anodic dissolution stress corrosion

作为一种不可逆的热力学过程,阳极溶解型应力腐蚀点蚀的演化受到表面能、体系应变能和电化学能的影响。基于能量学原理,对应力腐蚀点蚀演化过程中的能量问题进行研究,提出一种双变量半椭球模型描述点蚀的演化过程,推导点蚀形状参数在演化过程中的变化方程,并讨论远场应力等参数对点蚀形状参数以及体系能量变化的影响。结果表明:点蚀的形貌由初始的半球形状逐渐演化为半长椭球;点蚀的演化形貌为体系应变能与点蚀内表面的表面能共同竞争的结果,应变能加速点蚀形状参数的变化,而表面能则抵制点蚀的形状演化;远场应力对体系热力学势能的变化影响显著。

As an irreversible thermodynamics process, the development and evolution of pitting for anodic dissolution stress corrosion is controlled by the combined action of surface energy, elastic energy and electrochemical energy stored in the solid. Based on energy principle, the exploratory study of energy issues for stress corrosion pitting evolution was carried on. A two-variable semi-ellipsoid model was proposed to describe the pitting evolution, and the function of pitting shape parameter was derived in the process of stress corrosion. At the same time, the effects of far-field stress and other parameters on the pit- ting shape parameter and the variation of system energy were discussed. The results show that the pitting morphology initially appears as a hemisphere and evolves into a semi-ellipsoid gradually. The evolution morphology of pitting is controlled by the combined action of strain energy and surface energy stored in the system. The strain energy can accelerate the morphology pitting evolution, while the surface energy resists it. At the same time, the far-field stress has a significant influence on the variation of thermodynamic potential.