材料期刊网

The influence of H, C, N and O impurities on the phase stability of titanium was studied by first principles total energy calculations. The occupation energies of the impurities were estimated to identify their site preferences. All impurities considered prefer to occupy the octahedral site except for H, which tends to occupy the tetrahedral site in the beta phase. Electronic structures were analyzed to clarify the intrinsic influence mechanisms of impurity on the stability of martensitic phases. It was found that the density of states around the Fermi energy, which was affected dramatically by impurity, and the bonding interactions between impurity and titanium were connected to the phase stability of Ti. Elastic constants of impurity-containing systems were estimated from curves of energy against strain to evaluate the mechanical stability of these systems. It was shown that the alpha '' phase can not be stabilized by impurities considered here, while the alpha' phase (regardless of the impurities) and H- and C-containing beta phase are thermodynamically stable and also satisfy the mechanical stability criteria.