Etude de l'interaction dislocation défauts ponctuels par méthode ultrasonore sous contrainte quasi statique

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Abstract
The method is also applied to the study of the transversal or longitudinal stress-induced motion of pinning points: an analysis of the experimental results shows that the first kind of diffusion appears above 270 K in competition with the breakaway, in the case of extrinsic pinning points; the second kind of diffusion is observed around 140 K in the case of interstitial-type pinning points, and is related to the low-frequency internal friction peak PB. STUDY OF THE INTERACTION BETWEEN DISLOCATIONS AND POINT DEFECTS BY AN ULTRASONIC METHOD UNDER QUASI-STATIC STRESS An analysis of the ultrasonic attenuation changes Δα induced by a bias stress σ in aluminium leads to a precise statement of the interaction between dislocations and point defects. When the activation energy for unpinning (or repinning) is less than a critical value U 1c, the motion of dislocations is attributed to a modification of the equilibrium thermodynamics between the pinned and the unpinned loops. This phenomenon can be observed through reversible curves Δα = f(σ) when there is a low density of pinning points on the dislocation line. On the other hand, if the activation energy is larger than U lc the breakaway is ' out of equilibrium '; in this case the hysteresis of the cycle Δ α = f(σ) may be related to the low–frequency internal friction peak Pc.STUDY OF THE INTERACTION BETWEEN DISLOCATIONS AND POINT DEFECTS BY AN ULTRASONIC METHOD UNDER QUASI-STATIC STRESS An analysis of the ultrasonic attenuation changes Δα induced by a bias stress σ in aluminium leads to a precise statement of the interaction between dislocations and point defects. When the activation energy for unpinning (or repinning) is less than a critical value U 1c, the motion of dislocations is attributed to a modification of the equilibrium thermodynamics between the pinned and the unpinned loops. This phenomenon can be observed through reversible curves Δα = f(σ) when there is a low density of pinning points on the dislocation line. On the other hand, if the activation energy is larger than U lc the breakaway is ' out of equilibrium '; in this case the hysteresis of the cycle Δ α = f(σ) may be related to the low–frequency internal friction peak Pc.STUDY OF THE INTERACTION BETWEEN DISLOCATIONS AND POINT DEFECTS BY AN ULTRASONIC METHOD UNDER QUASI-STATIC STRESS An analysis of the ultrasonic attenuation changes Δα induced by a bias stress σ in aluminium leads to a precise statement of the interaction between dislocations and point defects. When the activation energy for unpinning (or repinning) is less than a critical value U 1c, the motion of dislocations is attributed to a modification of the equilibrium thermodynamics between the pinned and the unpinned loops. This phenomenon can be observed through reversible curves Δα = f(σ) when there is a low density of pinning points on the dislocation line. On the other hand, if the activation energy is larger than U lc the breakaway is ' out of equilibrium '; in this case the hysteresis of the cycle Δ α = f(σ) may be related to the low–frequency internal friction peak Pc.STUDY OF THE INTERACTION BETWEEN DISLOCATIONS AND POINT DEFECTS BY AN ULTRASONIC METHOD UNDER QUASI-STATIC STRESS An analysis of the ultrasonic attenuation changes Δα induced by a bias stress σ in aluminium leads to a precise statement of the interaction between dislocations and point defects. When the activation energy for unpinning (or repinning) is less than a critical value U 1c, the motion of dislocations is attributed to a modification of the equilibrium thermodynamics between the pinned and the unpinned loops. This phenomenon can be observed through reversible curves Δα = f(σ) when there is a low density of pinning points on the dislocation line. On the other hand, if the activation energy is larger than U lc the breakaway is ' out of equilibrium '; in this case the hysteresis of the cycle Δ α = f(σ) may be related to the low–frequency internal friction peak Pc.