CHARACTERIZATION OF FRACTURE IN Fe3Al-BASED ALLOY USING THE SMALL PUNCH TEST

Abstract

The small punch tests at constant deflection rate were performed on two Fe 3 Al-based alloys with additions of niobium and carbon. The purpose was to study the effect of carbides on ductility and fracture behaviour. Three main quantities were evaluated: maximum force, deflection at maximum force and fracture energy. Temperature dependence of these quantities was fully corresponding to the microscopic image of the fractured specimens. Radial cracks were observed at low temperatures, the contraction of the disc thickness was negligible and the fracture surface was characterized by cleavage facets. On the other hand, a circumferential crack clearly separated spherical cap from the rest of specimen at the highest temperatures. Reduction of the specimen thickness was observed as well as the volume analogical to necking in tensile test. Fracture surface had a dimpled appearance. It was proved that both the fracture energy and the deflection at maximum load were greater in the alloy with the greater carbon and that the ductility was not reduced by the presence of niobium carbides.