Ab initio systematic description of thermodynamic and mechanical properties of binary bcc Ti-based alloys

Abstract

The effects of the dissolution of 3d, 4d and 5d metals and Al, Ga, Ge, In and Sn in the bcc Ti lattice (β-phase) were studied within the framework of first-principles calculations. Lattice parameters, mixing enthalpies, single-crystal elastic constants C11, C12, C44 and C′, polycrystalline elastic moduli E, G, and plasticity characteristics of bcc Ti-based solid solutions in a wide concentration range up to 50 at% were investigated using the EMTO-CPA method. The PAW-SQS method was used to study the effects of alloying and local atomic relaxations on the indicated properties of Ti-X bcc alloys, where X is a series of 4d elements Nb, Mo, Tc, Ru, Rh, and 5d elements Ta, W, Re, Os, Ir for the set of concentrations: 6.25, 25 and 50 at%. The effect of concentration and periodic dependences on the properties of alloys and the dependence of elastic properties on the electronic structure were analyzed. It is shown that the calculated elastic constant C′ is a convenient and useful parameter for ranking chemical elements according to the relative strength of the stabilizing effect on the β-phase, in addition, the concentration dependences of C′ demonstrate softening with concentration increasing in the case of late transition metals, thereby reflecting the tendency of these metals to form intermetallic compounds with titanium, while early transition metals show a linear grow in stability with increasing concentration.