On the strain‐enhanced diffusion of α‐iron

Abstract

I n order to explain the origin of strain-enhanced diffusion in a-iron, the concentration of excess vacancies generated by non-conservative motion of jogs on screw dislocations during creep deformation was estimated under various creep conditions. I n the estimation the values of activation volume for high temperature creep obtained by the stress-relaxation test during creep were used. It was concluded that the reported strain-enhanced diffusion is well explained by the excess vacancies due to the non-conservative motion of jogs on screw dislocations.Um die Ursache der Erhohung der Diffusion durch plastische Verformungen von cc-Eisen festzustellen, wurde die Konzentration der uberschussigen Leerstellen, die wahrend des Kriechens durch nichtkonservative Wanderung der Sprunge an den Schraubenversetzungen gebildet werden, bei verschiedenen Kriechzustanden abgeschiitzt. Bei der Berechnung wurden die Werte des Aktivierungsvolumens fur Hochtemperaturkriechen benutzt, die durch die Spannungsrelaxation wahrend des Kriechens erhalten wurden. Es wird geschlossen, daD die berichtete Erhohung der Diffusion durch plastische Verformungen auf uberschiissige Leerstellen, die durch nichtkonservative Bewegung der Sprunge an Schraubenversetzungen gebildet werden, zuriickgefuhrt werden kann.

Development of microstructure and texture of medium carbon steel during heavy warm deformation

“…The formation of spheroidized cementite particles along the former pearlite lamellae can be seen. According to Chattopadhyay and Sellars [4], an excess of vacancies, which formed during the deformation, promotes carbon diffusion, especially near lamellae kinks, which are characteristic of severely deformed pearlite [2,5]. An important factor for the acceleration of the spheroidization process can be a local difference between the equilibrium carbon concentrations in ferrite near the surface of a deformed lamella with different curvature radii, according to the GibbsThompson equation.…”

Effect of deformation and annealing temperatures on ultrafine microstructure development and yield strength of pearlitic steel through continuous recrystallization

“…2(b) and the dissolution of pearlite lamellae, as shown in Fig. 2(c) [24]. After spheroidization, the coarsening of cementite particles took place through the diffusion of carbon atoms during annealing.…”

In-situ nuclear magnetic resonance investigation of strain, temperature, and strain-rate variations of deformation-induced vacancy concentration in aluminum

“…[5] indicates thermal equilibrium, and additional vacancies can be formed by various processes such as quenching, irradiation, plastic deformation, etc. We are concerned here with the excess nonequilibrium vacancies due to deformation ( ), and these ε C v additional vacancies resulted in increased rates of atomic jumps (Eq.…”

“…[2][3][4][5][6]24] While theoretical analyses [23] clearly point to the strain-enhanced diffusion due to the excess vacancies produced during plastic deformation, experimental studies (tracer diffusion, creep, etc.) failed to yield consistent results, [25,26,27] and Ruoff [4] and Ruoff and Balluffi [23] cited experimental data on creep, which exhibited no such presence of excess vacancies.…”

“…Moreover, the excess vacancies resulting in enhanced diffusion have strong influence on the creep behavior of metals and ceramics in that the activation energy for creep decreases with increased stress or strain rate if the concentration of these nonequilibrium vacancies is significant. [4][5][6][7] The dynamical behavior of point defects in metals is usually characterized by investigating annealing kinetics following extensive cold work. The recovery of induced plastic deformation is monitored using various techniques such as electrical resistivity, [8] positron lifetimes, [9] perturbed-angular correlation, [10] Mossbauer spectroscopy, [11] ultrasonic attenuation, [12] etc.…”