CALCULATION OF THE STRENGTH OF SNOEK RELAXATION IN DILUTE TERNARY BCCALLOYS

The distortion around a pair of an interstitial solute atom and a subs titutional solute atom in the b.c.c. lattice has been calculated by th e 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 vici nity of an interstitial-substitutional solute pair and the elastic dis placements at large distances have been calculated for the first to th e fifth neighbour configurations. To describe the elastic distortion o f the outer region, two elastic displacement fields of isotropic and c ylindrical symmetry are employed and are utilized to estimate the Volu me expansion and the uniaxial distortion due to the pair. Internal fri ction profiles expected for dilute ternary alloys are calculated by us ing 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.