First-principles prediction of solute effects on thermal properties of nickel alloys

• The effects of Cr and W on high-temperature properties of Ni-based alloys are predicted by first principles calculations combined with a quasi-harmonic Debye model. The modeling procedure integrates all contributions from electronic excitations, magnetic fluctuations and lattice vibrations. The predicted lattice parameter and thermal expansion coefficient agree well with available reference values. The temperature dependence of elastic moduli for Ni-Cr alloys can be described satisfactorily. Debye temperature has been analyzed to show a strong volume dependence but weak temperature dependence. It was found that the concentration dependence of elastic moduli has a close relationship with the volume dependence of Debye temperature and thus the vibrational free energy. Besides, the softening of elastic moduli with increasing temperature is a result of thermal expansion which mainly comes from lattice vibrations. Therefore, lattice vibrations produce effects on both temperature and concentration dependencies of elastic properties at elevated temperatures. With the help of Labusch–Nabarro model, solid solution hardening caused by Cr and W impurities has been analyzed. Moreover, the presence of solute atoms gives rise to a higher elastic anisotropy. The effects of Cr or W additions on the thermodynamic properties are found to be small compared to the effect of temperature.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Ni-Cr solid solutions; Ni-W solid solutions; thermodynamic properties; elastic anisotropy; quasi-harmonic Debye model; ab initio calculations.

Teknisk materialvetenskap

Materials Science and Engineering

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)