Influence of thermal damage occurrence at microstructural scale on the thermomechanical behaviour of magnesia-spinel refractories

Many refractory materials exhibit high thermal shock resistance, which is often mostly due to their high flexibility. Understanding the microstructure key points allowing to develop a non-linear mechanical behaviour is of great relevance for future material improvements. The present work aims at optimising the processing of magnesia-spinel refractory materials close to industrial ones with simplified microstructures. The final goal is the investigation of the relationship existing between microstructure evolutions and induced thermomechanical properties. The thermal expansion mismatch which exists between the two phases (spinel inclusions and magnesia matrix) is expected to generate, during cooling, radial microcracks around the inclusions. The development of such microcracks network, closely related to the inclusions content, has been studied and the damage occurrence has been confirmed by several high temperature characterisation techniques. The influence of this thermal micro damage on the evolution of stress-strain law in tension of such materials has also been investigated.