A calculation of dislocation densities in quenched α-iron from internal friction experiments

Abstract

Slightly nitrided iron samples are quenched from the α or γ phase at different cooling rates. After quenching from the α phase, tensile and internal friction experiments show respectively a decrease of the lower yield stress and an increase of the Köster peak height, when the cooling rate is varied from 300 to 4000 K s−1. Quenching from the γ phase also makes the Köster peak higher. In both cases, the number of dislocations increases. Dislocation densities are estimated by means of the Schoeck theory.

Isothermal Transformation of a CMnSi Steel Below the MS Temperature

“…[16,17] A pure Snoek-type relaxation peak for carbon at the position of the peak P3 generally is not observed in high-carbon iron martensite as the octahedral interstitial site is not equivalent in the tetragonal lattice. [20] Peak P3 in martensite is related to the Dislocation-Enhanced Snoek relaxation, or the migration of kinks along nonscrew dislocations in an atmosphere of point defects that retard dislocation motion. [17,21] The peak P3 had the same intensity in both transformation products and occurred at the same peak temperature of 370 K (97°C).…”