|14-068||Marc HUGER||HUGER, M.(Université de Limoges);||
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 improve thermal shock resistance of materials, since it usually involves a significant decrease in elastic properties. Moreover, this network of microcracks can strongly affect the thermal expansion at low temperature and the stress-strain behaviour in tension. Even if these two last tendencies are not very discussed in literature, they constitute for sure key points for the improvement of the thermal shock resistance of refractory materials. Beyond its influence on Young's modulus, this damage also allows to decrease the thermal expansion and to improve the non-linear character of the stress-strain curves determined 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 particular 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. A pertinent combination between specific experimental devices for characterization and advance dedicated modelling tools offer new insight for better understanding of these complex aspects closely related to microstructure evolution. Furthermore the intricate behaviour often observed on industrials refractories can be more easily interpreted with the help of parallel studies managed on simplified model materials.