Initiation of Dislocation Systems in Alumina Under Single-point Scratching

Abstract

This paper aims to investigate the initiation and distribution of dislocations and twins in the subsurface of alumina subjected to single-point scratching and to gain a deeper understanding of the mechanisms of ductile-regime grinding of alumina. It found that there generally exist three regions of dislocation and twin systems in the scratched alumina. The first region contains five independent slip systems so that macroscopic plastic flow is possible there. In the second and third regions, not all the systems can be activated, and then microcracking in the subsurface may occur easily. The distribution of these regions varies with the grain size of alumina. In the 25 μm-grained alumina all three regions appear. Thus, in this case, microcracking is difficult to avoid. In the 1 μm-grained alumina, however, only the first region appears, indicating that the material may be scratched under a real ductile mode without microcracking. A comparison shows that theoretical predictions are in good agreement with experimental observations.