SUBSURFACE STRUCTURE OF ALUMINA ASSOCIATED WITH SINGLE-POINT SCRATCHING

The mechanisms of macroscopic ductile deformation of brittle ceramics during grinding operations are still unclear although the microcrackin g-free processes of grinding have been used widely in industry. This p aper analyses the dislocation structure in the plastic zones of scratc hed alumina. It is shown that there exist three independent slip syste ms (two basal and one prism) and two twin systems even far below the c ritical onset temperatures of these systems that is usually expected. This new finding explains the formation mechanism of the macroscopic d eformation induced by scratching and indicates that it is the stress f ield around the cutting edge which plays an important role in the acti vation of the slip systems. The present study offers a new insight int o the mechanism understanding of material removal in ductile-regime gr inding of ceramic materials. (C) 1998 Chapman & Hall.