Mechanical properties of refractories: Multi‐scale composite approach from grains to material level
Résumé
Refractory materials exhibit a heterogeneous microstructure consisting in coarse aggregates surrounded by fine grains that form an aggregate/matrix composite. This heterogeneous microstructure often leads to a complex mechanical behaviour during loading. This paper is devoted to the study of thermomechanical properties of several industrial and model refractory materials in relation with the evolution of their microstructure during thermal treatments. The aim is, in particular, to highlight the role of thermal expansion mismatches existing between the different phases which can induce damage at local scale. The resulting network of microcracks is well known to decrease elastic properties. Moreover, this network of microcracks can also strongly affect the thermal expansion at low temperature and the stress-strain behaviour in tension. Indeed, the occurrence of a large quantity of small precracks during the cooling stage after sintering, which enhances the development of a fracture process zone while loading, allows the decrease of the brittleness of the material which becomes in this case flexible. The large increase in strain to rupture, which results from this flexibility, is thus of a great interest for the enhancement of thermal shock resistance.