First-Principles Study of Mechanical Property and Electronic Structure of Quenching and Aging U-Ti Alloy

We use the first principles plane wave pseudopotential method calculated the mechanical property with respect to the quenching and aging process of uranium-1.3 wt.% titanium alloy, including the elastic modulus, bulk modulus, Young’s shear modulus and the ideal tensile strength, meanwhile deeply research on the mechanical property mechanism changes through t-he electronic structure. The results show that t-he elastic modulus and ideal tensile strength of quenching state are 198GP and 21.2GP, respectively, and slightly improving through aging treatment. The variation of energy and electronic structure of uranium-titanium solid solution in process of quenching indicate the phase transition from γ phase (cubic structure) to α′ phase (orthorhombic structure) lead to improve to the mechanical property. In process of aging, at the beginning the metastable supersaturated solid solution appears Guinier-Preston (G.P) zones, which are aggregate of solute atoms in the uranium matrix, further improving the tensile strength. Then U₂Ti (hexagonal structure) precipitates present in over-aged process as a result of decomposition of metastable α′ phase and reduce the tensile strength. The result shows that the G.P/matrix and precipitate/matrix interfaces have ideal work of adhesion are 15.2eV and 12.5eV, respectively. Our results demonstrate theoretically quenching and aging heat treatment strengthening effect of uranium-titanium alloy.