High-entropy alloys : a new concept for exceptional mechanical properties

Details

Supervisors

Jacques, Pascal

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien

Abstract

High-entropy alloys constitute a completely new family of metallic alloys and were proposed less than 10 years ago. These new alloys are constituted by the mixing of large quantities of different elements. Which is quite different from the classical alloys based on one dominant element together with the addition of minor levels of alloying elements. Furthermore, these alloys present exceptional properties, particularly a level of fracture toughness that is larger than any other level reported up to now which also increases when the temperature decreases. Thus, those alloys are expected to be used for cryogenic applications. The present master's thesis is focused on the processing of two alloys, a stainless steel 304L and an alloy made of iron and nickel, the Invar steel. The aim is to characterize the toughness of thin sheets of ductile conventional alloys using the essential work of fracture method. The results will be used to compare HEAs and conventional alloys. The facture toughness' determination is based on the essential work of fracture method. The obtained results show a high strength for medium entropy alloy only studied with a very low elongation, thus, a less ductility than expected. The SS 304L has the best elongation at room and low temperature with a high strain in both cases. The fracture toughness is higher for the SS 304L at both temperatures. This alloy is the best compromise between all the alloys studied here. So high-entropy alloys did not prove, in this study, their exceptional mechanical properties, namely a high ductility combined with a high ultimate tensile strength as promised in other studies.