Thermomechanical characterization and modeling of shape memory alloys - application on 26at%Nb-Ti

The behaviour of shape memory alloys is driven by a first-order solid-solid phase transformation taking place at microscopic scales (grain or sub-grain scale). Thanks to their atypical behaviour (shape memory and pseudo-elastic capacities), they are the privileged candidate for many applications. The family most widely used today is that of binary nickel-titanium alloys in stoichiometric proportions. Their high pseudo-elastic capacity (reversible strain from 5% to 10%) has led to their widespread use in the medical field. Today, studies show that nickel is toxic to humans, with an increased risk of cancer. NiTi alloys exhibit a too high mechanical stiffness. Niobium-titanium binary alloys can be a promising alternative.Micro-macro thermo-mechanical characterisation tests need to be developed to gain a better understanding of their behaviour. The next objective is to propose a suitable model capable of reproducing the behaviour of these alloys as closely as possible, while ensuring simple identification of the material parameters.