Theoretical study on structural transformation and mechanical properties of Ni3Ti1-xNbx

Abstract

Using plane wave pesudopotential method based on density functional theory, we studied the structural transition of intermetallic compounds Ni3Ti1-xNbx (0≤x≤1). By constructing and relaxing various Ni3Ti1-xNbx structures, the most stable configurations were obtained. The variations of the Ni3Ti1-xNbx structures with x were fitted based on the calculated results. It can be seen that the Nb concentration will be in the range of 29.5%∼71.2% in ternary D019 phases if they participate from the system. The structural transitions can induce the change of mechanical and electronic properties of the compounds. It is shown that the elastic constants such as C44 and C66, decrease with the increase of x although the elastic constants such as C11 and C13 as well as the B/G ratio increase evidently. It indicates that the possibility of shear deformation of the system increases with the increase of the Nb concentration. The formation of different stacking-faults becomes favorable with the substitution of Nb for Ti, which results in the structural transition of Ni3Ti1-xNbx. The conclusions are further supported by density of states and charge density differences.

Keywords

• Ni3Ti1-xNbx
• First-principles calculations
• Structural transformation
• Mechanical properties