Papers by Keyword: Grain Boundary Fracture

Abstract: First-principles grain boundary (GB) tensile deformation simulations were performed to investigate the atomic-scale mechanism of GB fracture of the Σ13 pyramidal twin GB in α-Al2O3. It was found that the specific Al-O bond broke at the GB core in the early stage of tensile deformation. From chemical bonding analyses, the first breaking bond was the weakest bond in the GB core. However, when the catastrophic GB fracture started, initially strong Al-O bond broke. This indicates that local atomic bonds should determine the microscopic GB fracture behavior.

Abstract: Plane honing machining of aluminum nitride (AlN) was investigated in this study. AlN has advantageous thermal and dielectric characteristics and is in great demand as a semiconductor mounting board or packaging parts material. However, as AlN is a sintered material, the AlN grains readily detach during machining making it difficult to obtain fine surface roughness at high efficiency. In previous studies, we have developed a new plane honing method that makes it possible to grind hard and brittle materials. In this paper, plane honing experiments of AlN were carried out using a resinoid or vitrified bond wheel. Fine surface roughness could be obtained using the resinoid bond wheel but there was low-machining efficiency due to burying and detachment of abrasives. The vitrified bond wheel, however, enabled high efficiency grinding but resulted in traces of detached AlN grains forming at the machined surface. Highly efficient mirror grinding of AlN could be achieved by using a vitrified bond wheel for semi-finishing and a resinoid bond wheel for finishing.