Effect of plastic strain on the temperature spectrum of internal friction of austenitic and ferritic steels

Abstract

The present work is devoted to temperature dependences of the internal friction of plastically deformed high-alloy ferritic and austenitic steels with different carbon contents and comparable atomic proportions of dissolved interstitial atoms. The effects of composition, carbon content, degree of plastic strain, and aging temperature and time on the relaxation parameters are investigated. A mechanism for the formation of the spectrum of internal friction in strained steels allowing for the migration of atoms into regions of the crystal lattice activated by the presence of"fresh" dislocations is suggested.Alloy ferrite and austenite steels possess relaxation effects caused by diffusion of single (or paired) dissolved interstitial atoms in the stress field. The corresponding relaxation maxima on the temperature or frequency dependences of the internal friction (IF) are described by the known Debye equation for a standard solid body [1], and the dependence of the relaxation time on the temperature is described by the Arrhenius equationwhere H is the activation energy, k is the Boltzmann constant, and % I is the frequency of atomic jumps at temperature T-~ 0.The frequency of elementary atomic jumps in b.c.c, and f.c.c, metals has the same order. In ferrite alloys based on iron the diffusion of interstitial atoms (Snoek or S-relaxation) is described by -I "c s = 3v = 6w I + 12w2,where v is the'frequency of jumps of interstitial atoms over octahedral interstices, w t is the frequency of jumps at a distance of l/2a, w~ is the frequency of jumps at a distance of (1/,/2) a, and a is the lattice parameter. For atomic jumps of pairs of interstitial atoms in an f.c.c, lattice (the Finkel'-shtein -Rosin or FR relaxation) we havewhere v is the frequency of jumps of pairs of interstitial atoms over octahedral interstices; w r is the frequency of rota-I Tula State University, Tula; Russian State Engineering University, Moscow, Russia.tion of a pair of interstitial atoms, and w d is the frequency of diffusion jumps of individual interstitial atoms. The heights of the S and FR peaks depend differently on the content of interstitial atoms. The degree of FR relaxation and the corresponding internal friction in alloys with an f.c.c, lattice is lower because they are determined not only by the redistribution of interstitial atoms in the stress field but also by the probability of the formation of pairs from them. It should be noted that the relaxation maximum in austenite alloys has been determined for the first time by K. Rosin and B. Finkel'shtein in 1953 [2] and not by Ke and Tsin (1956) as is reported in [ 1 ]. In chromium ferritic [3][4][5][6] and chromium-nickel austenitic steels [2] the corresponding Snoek and Finkelshtein-Rosin maxima are formed on the temperature dependences of internal friction (TDIF) in a close temperature range of 200-300~ at a frequency of about 1 Hz, and their position depends on the content and nature of the alloying elements [3]. Cold plastic deformation causes the formation of new scattering-energy c...

On the Stacking Fault Energy of Fe-18 Pct Mn-0.6 Pct C-1.5 Pct Al Twinning-Induced Plasticity Steel

“…[16] This value is about half the value of the activation energy for carbon diffusion in c-Fe. Anelasticity due to the stress-induced reorientation of point-defect complexes in fcc steels has been ascribed to second-neighbor interstitial-interstitial solute pairs, [14,[17][18][19] interstitial-substitutional solute pairs, [14,18,20] and interstitial solute-vacancy pairs. [15,[21][22][23][24] There have been several reports indicating that whereas the nearest-neighbor C-C interaction was repulsive, the C-vacancy interaction [15,[21][22][23][24][25][26] and the C-Mn interaction [25,26] in austenitic alloys were both attractive.…”

Relationship Between Bake Hardening, Snoek-Köster and Dislocation-Enhanced Snoek Peaks in Coarse Grained Low Carbon Steel

“…4d-f). The internal friction spectra are comprised of: (1) carbon Snoek peak [7,[36][37][38][39][40][41], (2) the dislocation-enhanced Snoek peak [27,[51][52][53][54][55][56][57][58][64][65][66][67][68], and (3) Snoek-Köster peak [69][70][71][72][73][74][75][76][77], and typical exponential hightemperature background [70,[75][76][77]. resolved internal friction peaks, obtained after background subtraction, are illustrated in fig.…”

“…A number of excellent reviews exists and the reader is referred to these for background [56,[71][72][73][74][75][76]. The peak temperature of Snoek-Köster relaxation depends on concentration of solute atoms bound in the atmosphere while the relaxation strength is determined by the dislocation density.…”

“…Plastic deformation in iron containing low concentration of solute atoms induces the dislocation-enhanced Snoek peak [51] or equivalently the dislocation-enhanced Snoek effect (DeSe) [52], which occurs exactly at the same temperature as Snoek peak [51][52][53][54][55][56][57][58]. The dislocation-enhanced Snoek peak indicates the presence of Snoek atmosphere in the vicinity of geometrical kinks on fresh non-screw dislocation segments [51][52][53]57,58].…”

Inelastic effects in ordering of Fe−Al alloys

“…Thus, the broadening of the relaxation maximum indicates that the solid solution contains positions for interstitial atoms in the crystal lattice of the solvent metal that are inequivalent from the standpoint of energy. These positions can be interstices near substitutional atoms [3 -5] or dislocations [6]; here the situation becomes very complicated and requires that the actual distribution of the interstitial atoms over the possible types of interstices be taken into account. Although Eq.…”