CALCULATION OF THE STRENGTH OF SNOEK RELAXATION IN DILUTE TERNARY BCC ALLOYS

The distortion around a pair of an interstitial solute atom and a substitutional solute atom in the b.c.c. lattice has been calculated by the method of molecular statics. The model crystal consists of a finite number of atoms forming a b.c.c. crystallite and an elastic continuum surrounding the crystallite. The atoms are assumed to interact through pairwise interatomic potentials. The atomic displacements in the vicinity of an interstitial-substitutional solute pair and the elastic displacements at large distances have been calculated for the first to the fifth neighbour configurations. To describe the elastic distortion of the outer region, two elastic displacement fields of isotropic and cylindrical symmetry are employed and are utilized to estimate the Volume expansion and the uniaxial distortion due to the pair. Internal friction profiles expected for dilute ternary alloys are calculated by using the results of the simulation. The observed effect of manganese on the Snoek relaxation of carbon in cc iron has been discussed in terms of the trapping of carbon to manganese and an associated decrease of the uniaxial distortion.