Evolution of interfacial dislocation network during anisothermal high-temperature creep of a nickel-based superalloy

The effect of thermal cycling creep on the dislocation networks at the γ/γ′ interfaces in the MC2 superalloy is investigated. Tensile creep tests were performed under thermal cycling and isothermal conditions at low stress (80 MPa) and high temperature (1150 °C). In these conditions γ′ rafts may dissolve and reprecipitate during thermal cycling creep. The difference between the effects of isothermal and thermal cycling conditions on the γ/γ′ interface dislocation networks, characterized by transmission electron microscopy, is exposed, as well as their evolution during the cycle

Weak-beam study of dislocations in D022-Al3Ti deformed at 400°C

cited By 0International audiencePolycrystalline samples of Al3Ti with the D022-type structure have been plastically deformed at 400°C. Observations using weak-beam transmission electron microscopy show activation of dislocations with <100] or <110] Burgers vectors. The fine structure of [100] and [010] dislocations reveals strong stabilization effect on the pure edge character. [110] superdislocations, resulting from the interactions between [100] and [010] perfect dislocations, are dissociated in two identical superpartials separated by an antiphase boundary (APB). Their segmented shape together with the separation distances between the [110] superpartials point to a large anisotropy of APB energies whose estimated values on (001) and (111) are 13 ± 3 mJ/m2 and 64 ± 5 mJ/m2, respectively. The low mobility of <100] and <110] dislocations is highlighted and related to the low ductility of this material. © 2013 Copyright Taylor and Francis Group, LLC

In situ transmission electron microscopy deformation of the titanium alloy Ti–6Al–4V: Interface behaviour

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Étude d'un alliage d'aluminium pour l'aéronautique par les techniques avancées de microscopie électronique en transmission

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

TEM quantitative characterization of short-range order and its effects on the deformation micromechanims in a Ti-6Al-4V alloy

International audienceLocal order is evidenced in nodules of the duplex microstructure of a Ti-6Al-4V alloy using in situ straining experiments in a transmission electron microscope (TEM). This local order is identified to be short range order (SRO) because of the absence of superlattice diffraction spots, which are associated with alpha(2) (Ti3Al) precipitates and because of the formation of single pairs of mobile dislocations, which are a signature of SRO. The strengthening effect of this SRO is quantitatively evaluated. Qualitatively, the presence of SRO inhibits strongly the cross-slip in nodules in comparison with dislocations gliding in lamellar colonies where no SRO is present. The well-known strengthening effect of the core structure of dislocation in Ti-alloy is revisited here in the presence of SRO to determine its possible influence

Deformation localization during very high temperature notch creep in Ni-based SX

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Long-term stability of René 65 Ni-based superalloy: a methodology to objectively evaluate the impact of TCP on creep and dwell-fatigue properties

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TEM study of structural hardening in a new martensitic steel for aeronautic application

International audienceA new generation of high performance martensitic steel hardened by FeNiAl intermetallic nanoprecipitates has been investigated using conventional and advanced Transmission Electron Microscopy (TEM). Cs-corrected high resolution TEM has been used to provide a fine and accurate microstructural characterization: the shape, size and crystallographic characteristics of the nanoprecipitates have been identified. TEM in situ straining tests have been performed to determine the relevant parameters, which control the deformation. The nanoprecipitates are observed to create anchor lines acting against the propagation of the mobile dislocations and to be crossed by shearing process. In addition, in situ TEM experiments have allowed to measure directly the average distance between these nanoprecipitates along the dislocation lines. This value is of great interest as it is the more accurate data to be used in the calculation of the stress associated with the structural hardening. The strength of the alloy due to these nanoprecipitates has been also determined. It is in good agreement with the value deduced from macroscopic mechanical tests