Thermal‐Stress Fracture of a Thermomechanically Strengthened Aluminosilicate Ceramic

Abstract

The thermal‐stress fracture behavior of an aluminosilicate ceramic thermomechanically strengthened by surface compression was investigated using quenching in silicone oil. Comparison with the behavior of the unstrengthened ceramic showed that the strengthening increased the critical quenching‐temperature difference required to initiate fracture and also increased the strength retained. The room‐temperature strength was not increased further when the strengthened material was quenched from temperatures above the softening point. On the basis of a simple mechanical model, the observations of the critical quenching‐temperature difference and strength retained in the temperature range of brittle behavior were verified theoretically. It is concluded that, to improve thermal‐stress resistance of ceramics and to avoid catastrophic failure, strengthening by surface compression is to be preferred to increasing the inherent strength of the material.