扩散蠕变理论的基础问题研究  

Fundamental Problems of Diffusional Creep Theory

作　　者：陈永翀[1] 

机构地区：[1]中国科学院电工研究所,北京100190

出　　处：《稀有金属》2012年第2期171-177,共7页Chinese Journal of Rare Metals

基　　金：国家自然科学基金(50601016;51041008);中国科学院电工研究所创新人才计划(O960131C41)资助项目

摘　　要：Nabarro-Herring蠕变模型一直被认为是解释合金高温扩散蠕变的经典理论模型。然而,在20世纪末,Ruano等在分析当时几乎所有已知合金高温低应力条件下的蠕变试验数据后发现,按Nabarro-Herring扩散蠕变模型计算的蠕变速率数据与实验结果吻合度都很不理想,有的甚至相差1×103倍。研究认为,由于Nabarro-Herring扩散蠕变模型仅仅考虑了几乎不可能存在的空位扩散流,忽略了不均匀力化学势场导致的原子扩散流,因此在定量处理多晶材料的高温低应力蠕变数据时有很大偏差。在高温低应力条件下,由于位错、晶界等非平衡缺陷的存在,实际晶体材料中原子的力化学势并非处处相等,因此导致原子扩散流的产生,材料发生扩散蠕变。多晶材料高温低应力条件下的扩散蠕变可以认为是静水应力作用下的体积蠕变和非静水应力作用下的形状蠕变的叠加。本研究将重新审视Nabarro-Herring扩散蠕变模型的理论基础,初步建立能够合理解释多晶材料高温蠕变时晶界形成无沉淀区的定性模型,为有关问题的解决提供新的思路。Nabarro-Herring creep model was generally considered as the classic model for understanding the diffusional creep behavior of polycrystalline materials at high temperatures.However,the experimental works by Ruano and co-workers in 1982 indicated that the calculation results of Nabarro-Herring model were not in agreement with the experimental data of many alloys creeping at low stresses and high temperatures.The discrepancy even reached 3 orders of magnitude.It was considered in the present article that,since Nabarro-Herring model considered only the plausible vacancies flux and it neglected the atomic flux induced by the inhomogeneous distribution of the mechano-chemical potentials,the model could not deal well with the experimental datum of many alloys creeping at low stresses and high temperatures.Actually,the mechano-chemical potentials of atoms were not homogeneous within the polycrystalline alloy because of the existence of dislocations and grain boundaries.This inhomogeneity would result in the atomic flux from the high potential area to the low potential area and the diffusional creep happens.Therefore,the theoretical foundation of Nabarro-Herring model was critically investigated and a primary new model was proposed to describe the diffusional creep behavior of the crystalline materials and to explain the formation mechanism of denuded zones at grain boundaries.

关 键 词：晶体材料 扩散蠕变 无沉淀区 力化学势 理论模型 

分 类 号：TG111.6[金属学及工艺—物理冶金] TG111.8[金属学及工艺—金属学]