Elastic properties and microstructure: study of two fused cast refractory materials

Youngʹs modulus evolutions versus temperature have been studied for two fused cast materials containing 40 or 95 wt.% of zirconia. During the manufacturing process involving cooling from very high temperatures, internal stresses can bring on damage in the microstructure. Youngʹs modulus has been measured by using a high temperature ultrasonic pulse-echo technique. Characteristic phenomena have thus been identified in accordance with chemical and mineralogical compositions, and physico-chemical transformations. Youngʹs modulus is affected by the individual contributions of intrinsic properties of each phase, but also by damage due to thermal expansion mismatch between the phases. Thus, the glassy phase involves changes related to the viscosity evolution at high temperature. Furthermore, the allotropic martensitic transformation of zirconia produces effects on Youngʹs modulus: either direct or induced by the volume change. A simple Hashin and Shtrikman analytical model has been used to bring out some explanations about these effects.