With great mechanical properties, high-entropy alloys (HEAs) are an attractive new class of materials. Initially referring to an alloy made of at least five multiprincipal elements forming a solid solution, “HEA” is nowadays more widely used for alloys that have fewer elements, or display multiple phases. Therefore we propose an investigation of the HEA concept limits based on the bcc HEA Ti20Zr20Hf20Nb20Ta20. First, the study of the structure/microstructure (XRD, SEM, EPMA) evolution of binary, ternary and quaternary Nb-based alloys will be done using pure Nb and Ti20Zr20Hf20Nb20Ta20 as the two end references. Then, a tensile mechanical study of Ti35Zr27.5Hf27.5Nb5Ta5 , linking the domain of HEA with the Ti-based alloys (with additional TRansformation Induced Plasticity (TRIP) effect), will demonstrate the impact of HEA on “traditional alloys”, conferring them remarkable properties such as, here, a work hardening of 3200 MPa.
 L. Lilensten et al., Materials Letters 132 (2014) 123-125