Many metallic medical devices needing specific properties such as superelasticity or shape memory effect are made from NiTi alloys. These properties are due to a thermal-induced or a stress-induced martensitic transformation (SIMT). However, the poor biocompatibility of nickel can lead to some medical issues. Beta titanium alloys are then promising Ni-free candidates to replace NiTi alloys for biomedical applications, but SIMT in these alloys is still not completely understood. This project aims to characterize SIMT in beta titanium alloys during cyclic tensile tests. Evolution of volume fraction of martensite during straining and the effect of type and content of alloying elements will be particularly investigated, as well as influence of SIMT on twinning. Expected results aims then to correlate the part of SIMT on total deformation as a function of alloying elements (type and/or content) to better understand the role of this deformation mechanism.