Effect of particle shape of α-Alumina sludge on mechanical strength of sintered body by SPS

Abstract

Alumite sludge is a precipitation that is generated by anodizing of aluminum sash products. The crystal structure of alumite sludge is changed to α-Alumina (α-Alumina sludge) by heat treatment. For effective utilization of alumite sludge, we attempted to improve the sintered body mechanical strength by applying milled α-Alumina sludge to spark plasma sintering. The raw (no milling) material has a cuboid particle shape. By milling the raw material, the particle shape is changed from cuboid to cube, and the particle size is decreased. The changing particle shapes improved flexural strength to a maximum of 403 MPa at low firing temperatures. Observation of the fracture surface using SEM revealed that the fracture originated from a rectangular pore remaining in the sintered body. The shape factor of the rectangular pore (area, pore ratio, inclination angle) decreased with the change in particle shape. In order to ascertain the experimental result, the effect of rectangular pore shape on crack occurrence was investigated by using finite element method. The principal stress value around the rectangular pore decreased with the change in particle shape. Thus, crack occurrence at the fracture origin is inhibited by the change in particle shape.