Grain-boundary relaxations in an Fe-Ni-Cr alloy

Abstract

Grain boundary internal friction spectra have been studied in a stabilized and an unstabilized Fe-20 pct Cr-25 pct Ni alloy. The effect of grain size and of prior creep on the relaxation phenomena have been studied. It has been found that the spectrum consists of three constituent peaks occurring in the temperature regions of 630°, 690°, and 770°C at 1 Hz. The relaxation strength and the width (seen through the β factor) of each of the peaks have been observed to decrease and the peak temperature to increase with increasing grain size. It has been suggested that the relaxation processes at the grain boundaries are associated with the solvent iron, solute chromium, and solute nickel atoms, respectively. Deformation by creep increases the peak height, width, and temperature of the peaks in the stabilized alloy, but has no effect on the grain-boundary relaxation spectrum of the unstabilized alloy. From the study of stabilized and unstabilized alloys it can be implied that the dislocation structure at the grain boundaries influences the relaxation strength of the grain-boundary peaks.