Phase stability and mechanical properties of the six-principal element TiVNbCrCoNi alloys

This study designed a series of six-principal element TiVNbCrCoNi alloys according to the maximum entropy principle under the constraint of valence electron concentration (VEC). The phase stability and mechanical properties were investigated. It was showed that at VEC levels below 5.2, the body-centered cubic (BCC)-structured solid-solution phase remained stable at room temperature. As VEC exceeded 8.0, the face-centered cubic (FCC)-structured solid-solution phase stabilized. In the VEC range of 5.2–8.0, (Co, Ni)Ti and Ni3Nb intermetallic compounds formed combining with the solid-solution phases. Both yield strength and ductility increased with increase of VEC in the BCC-structured solid-solution alloys. The phase stability was elucidated through First-principle and thermodynamic calculations, while the evolution of mechanical properties of solid-solution alloys was evaluated in terms of multiple parameters. The thermodynamic calculation achieved satisfactory accuracy after being adjusted to utilize atomic bond enthalpy instead of atomic electronegativity difference.