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Author Shulumba, Nina ♦ Hellman, Olle ♦ Rogström, Lina ♦ Raza, Zamaan ♦ Tasnádi, Ferenc ♦ Odén, Magnus ♦ Abrikosov, Igor A.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS ♦ AGE HARDENING ♦ ALLOYS ♦ ANISOTROPY ♦ ANNEALING ♦ ELASTICITY ♦ MATERIALS RECOVERY ♦ TEMPERATURE DEPENDENCE ♦ THERMAL EXPANSION ♦ X-RAY DIFFRACTION
Abstract Ti{sub 1−x}Al{sub x}N is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the symmetry imposed force constant temperature dependent effective potential method, which include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C{sub 11} decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy.
ISSN 00036951
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-12-07
Publisher Place United States
Journal Applied Physics Letters
Volume Number 107
Issue Number 23


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