Estimates of internal stresses about interstitials in a bcc lattice

• Published in: Journal of materials science 1990-06, Vol.25 (6), p.2667-2678
• Main Authors: He, Baoping, Rao, Satish, Houska, C. R.
• Format: Article
• Language: English
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF00584865

The atomic volume of interstitial cubic and hexagonal interstitial compounds has been found to correlate with the size of the filled octahedron in corresponding dilute solutions. Data from binary systems containing nitrogen, carbon, and oxygen in vanadium, Nb, Ta, Cr, Mo, tungsten and Fe lattices were examined. Systematic correlations enable estimates to be made of the components of the dipole tensor for interstitials in octahedral sites within selected bcc lattices. The volume change in filling an interstitial site is used to determine the sum of the diagonal tensor components, while their ratio is obtained from the second-neighbour displacement of a lattice atom about a filled site. Estimates from crystallographic data are obtained using either a volume correlation or a common shape factor along with the second-neighbour displacement. A filled octahedron tends to give equal first and second-neighbour distance parameters, making it nearly regular. Estimates are made from isotropic and anisotropic elasticity. Lattice Green function calculations support the use of the second neighbour as a core displacement parameter. As expected, core displacements obtained from lattice theory can differ greatly from those obtained by elastic calculations except for the second-neighbour displacement. The influence of crystal anisotropy on the long range elastic field is examined. In Nb, the first neighbour is displaced along an elastically soft direction and one finds the largest displacements of any system examined. Graphs. 31 ref.--AA