First-principles study of structural, elastic, and thermodynamic properties of ZrHf alloy

Structural parameters, elastic constants, and thermodynamic properties of ordered and disordered solid solutions of ZrHf alloys are investigated through first-principles calculations based on density-functional theory （DFF）. The special quasi-random structure （SQS） method is used to model the disordered phase as a single unit cell, and two lamella structures are generated to model the ordered alloys. Small strains are applied to the unit cells to measure the elastic behavior and mechanical stability of ZrHf alloys and to obtain the independent elastic constants by the stress-strain relationship. Phonon dispersions and phonon density of states are presented to verify the thermodynamic stability of the considered phases. Our results show that both the ordered and disordered phases of ZrHf alloys are structurally stable. Based on the obtained phonon frequencies, thermodynamic properties, including Gibbs free energy, entropy, and heat capacity, are predicted within the quasi-harmonic approximation. It is verified that there are no obvious differences in energy between ordered and disordered phases over a wide temperature range.

新型ZrHf合金显微组织、力学性能及耐蚀性研究

利用真空自耗电弧熔炼(VAR)制备了一种Zr、Hf质量比为1∶1的新型ZrHf合金,研究了该合金的显微组织、力学性能及其在沸腾硝酸溶液中的耐蚀性能。结果表明,该合金由密排六方结构相构成,其晶格常数介于α-Zr与α-Hf之间;在固溶强化机制下,该合金具有较高的室温屈服强度、抗拉强度和延伸率,分别达到641 MPa、714 MPa和51%。该ZrHf合金在6 mol/L的沸腾硝酸溶液中腐蚀192 h后,腐蚀速率低于0.002 mm/a,具有高强度、耐腐蚀的优异性能。