Segregation of Atomic Probes and Interstitial Impurities in the Grain Boundary Core and Outside Grain Boundaries in 3d, 4d and 5d Metals

Abstract

The 57 Co atomic probe introduced by diffusion in polycrystalline metals enriches grain boundaries in polycrystalline Cr and W, depletes grain boundaries in Ta, and does not segregate at grain boundaries in Pd, Pt and Au. The isomer shift δ and the width Γ of two components of nuclear gamma-resonance (NGR) spectra used for investigation of segregation of residual interstitial impurities in the grain boundary core (segregation-1) and outside the grain boundary core (segregation-2). In segregation-2 residual interstitial impurities do not have the cubic symmetry and cause formation of similar complexes of point defects. In tungsten interstitial impurities possess the cubic symmetry in segregations-1. The change in the isomer shift δ 1 and the width Γ 1 of components- of NGR spectra in Ta, Cr, W, Pd, Pt and Au depends on the difference in valences of the atomic probe 57 Co and the matrix. The interaction energy in segregations of different types was determined.