Bibi Malmal Moshtaghioun

Recent Insights on the Superplastic Behaviour of Ceramics

Superplasticity is the ability exhibited by some fine-grained materials to be elongated a great deal with no failure. Such phenomenological definition accounts for the engineering view point of this remarkable property. From a fundamental basis, there is a full consensus to admit that it is essentially linked to the grain boundary motion under invariance of microstructure. Despite the great scientific effort carried out during the two last decades, or probably due to that, there is still a gap on the scientific comprehension of the equation describing superplasticity from a basic point of view, not to say about its potential extension to nanostructured materials. This paper presents the essential basis of a new model proposed to account for the main features of structural ceramics.

The Role of a Threshold Stress on the Superplasticity of Ceramics Revisited

This paper is a brief review of the concept of superplasticity, which has been extensively used to explain the superplastic behavior of yttria-tetragonal zirconia polycrystals. The diverse theories develop to account for the origin of this quantity are outlined. In addition to that, a modern approach to this concept is reported. This new contribution can give rise to a revision of the until-now established concept of invariant microstructure associated to superplasticity.

High-Temperature Plasticity in Super Hard Boron Carbide Ceramics

Boron carbide-based ceramics will be probably the most promising materials during the next decades due to their excellent mechanical properties combined with its chemical stability and low-density. Boron carbide itself is a very challenging system because of its complicated but highly-symmetrical crystallographic structure. Room-temperature mechanical properties of pure boron carbide have deserved considerable attention due to its remarkable hardness and resistance to shock-impact; however, its high-temperature plasticity with unsual ductility remains unexplored. The high-temperature creep of pure B4C polycrystals and the microsturctural observation were performed to find the mechanism of deformation in this material.