Dislocation mechanisms in a zirconium alloy in the high-temperature regime: An in situ TEM investigation

Abstract : Dislocation mechanisms responsible for the high-temperature mechanical properties of a Zr alloy have been investigated using in situ straining experiments between 250 °C and 450 °C. At 250 °C and 300 °C, the results show a steady and homogeneous dislocation motion in prismatic planes, with little cross-slip in the pyramidal and/or basal planes. At 350 °C, the kinetics of mobile dislocations becomes very jerky and inhomogeneous, in agreement with a dynamic strain aging mechanism. Above this temperature, the motion is again steady and homogeneous. Extensive cross-slip forms super-jogs which are efficient pinning points against the glide motion. These super-jogs move by glide along the Burgers vector direction, never by climb. The glide velocity between super-jogs is linear as a function of the total driving stress (applied stress minus line-tension stress due to dislocation curvature), in agreement with the solute dragging mechanism. The origin of the stress-strain rate dependence with an exponent larger than unity is then discussed. © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Daniel Caillard, Martin Rautenberg, Xavier Feaugas. Dislocation mechanisms in a zirconium alloy in the high-temperature regime: An in situ TEM investigation. Acta Materialia, 2015, 87, pp.283-292. ⟨10.1016/j.actamat.2015.01.016⟩. ⟨hal-01726234⟩

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