R‐Curve Behavior of In Situ Toughened α‐SiAlON Ceramics

Abstract

R-curves of single-phase Y-and Ca-containing ␣-SiAlON ceramics have been measured. They range from flat ones for fine-grain ceramics to pronounced rising ones when large elongated grains are present. The highest toughness measured reached 11.5 MPa⅐m 1/2 over a crack extension of about 1000 m.

Understanding the mechanical properties of hot pressed Ba-doped S-phase SiAlON ceramics

“…It can be pointed out here that R-curves are exhibited by a wide range of SiAlON materials, e.g. Y-␣-SiAlON, 2 in situ toughened Y-␣-SiAlON, Ca-␣-SiAlON, 39 etc. Depending on the amount of seed crystals, a peak toughness of 10 MPa m 1/2 or little higher was recorded in these ceramics.…”

“…see Refs. 35,[37][38][39]. Table 3 presents the summary of the mechanical property data of some selected SiAlON ceramics and such data illustrate a large variation in apparent hardness and toughness properties.…”

Hot pressing of α-sialon powder prepared by SHS method

“…According to Chen and Rosenflanz [1], in order to make elongated α-Sialon grains, it is important to control the nucleation rate and form only a small number of α-Sialon nuclei that grow into elongated grains without hindrance from impingement with other α-Sialon grains. Zenotchkine et al introduced less than 5 % of α-Sialon seeds in the starting powder mixture and obtained elongated α-Sialon grains growing from the seeds [2]. Nordberg et al reported that growth of elongated α-Sialon grains was promoted by the presence of a liquid rich in Al and O [3].…”

“…However, α-Sialon exhibits lower fracture toughness and flexural strength than β-Sialon or β-Si 3 N 4 consisting of elongated grains due to the microstructure consisting of equiaxial grains. Since Chen and Rosenflanz reported that the properties of α-Sialon were improved by establishing a microstructure consisting of elongated grains, there have been many reports on α-Sialon ceramics with elongated grains [1][2][3][4][5]. According to Chen and Rosenflanz [1], in order to make elongated α-Sialon grains, it is important to control the nucleation rate and form only a small number of α-Sialon nuclei that grow into elongated grains without hindrance from impingement with other α-Sialon grains.…”

Fracture Resistance and Contact Damage of TiN Particle Reinforced Si3N4 Ceramics

“…The test bar was next subject to 4-point bending with a gradual increase of load, in small increments, to allow in situ monitoring of crack extension following the method described in Ref. 25.…”