Abstract
Relaxation phenomena have been studied in, pure iron, Fe-18.6%Cr, Fe-25%Ni, Fe-25%Cr and a stabilised Fe-25% Ni-20% Cr-Nb alloy over the temperature range 20 C to 1100 C. The individual constituents of the complex internal friction peaks have been separated with the help of computer. A Zener relaxation peak has been identified, for the first time, in the Fe-25% Ni system and a high temperature relaxation peak was observed in some of the alloy systems investigated. Both relaxation processes are discussed in terms of the current theories. The grain boundary relaxation spectrum has been shown to consist of a number of constituent grain boundary relaxation peaks. Each peak is due to one of the solute or solvent elements making up the alloy, A preliminary investigation was also conducted to determine the effect of creep on the grain boundary spectrum of the stabilised and unstabilised ternary alloys. The physical characteristics of these constituent peaks have been shown to be dependent on the alloy composition and grain size. The results are discussed in terms of the "stress induced grain boundary migration model" due to Leak which is extended to explain the additional effects observed in the present work. It has been observed that high temperature background damping is strongly dependent on the grain size and composition of the alloy.