Accession Number:

ADA523968

Title:

Ab-initio Simulations of Molten Ni Alloys

Descriptive Note:

Journal article (preprint)

Corporate Author:

AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE

Report Date:

2010-04-01

Pagination or Media Count:

28.0

Abstract:

Convective instabilities responsible for misoriented grains in directionally solidified turbine airfoils are produced by variations in liquid-metal density with composition and temperature across the solidification zone. Here, fundamental properties of molten Ni-based alloys, required for modeling these instabilities, are calculated using ab-initio molecular dynamics simulations. Equations of state are derived from constant number-volume-temperature ensembles at 1830 and 1750 K for elemental, binary Ni-X, X Al, W, Re, and Ta and ternary Ni-Al-X, X W, Re, and Ta Ni alloys. Calculated molar volumes agree to within 0.6-1.8 of available measurements. Predictions are used to investigate the range of accuracy of a parameterization of molar volumes with composition and temperature based on measurements of binary alloys. Structural analysis reveals a pronounced tendency for icosahedral short-range order for Ni-W and Ni-Re alloys and the calculations provide estimates of diffusion rates and their dependence on compositions and temperature.

Subject Categories:

  • Metallurgy and Metallography
  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE