Publication

Obstacle strength of binary junction due to dislocation dipole formation: An in-situ transmission electron microscopy study

Seyed Masood Hafez Haghighat
2015
Journal Articles

Abstract

We report the experimental observation of the 1/2 < 111 > edge dislocation dipole formation and annihilation in ultra-high purity Fe using transmission electron microscopy (TEM) in-situ straining. The observation is confirmed by TEM image simulations. The edge dipole is formed by the interaction of a moving screw dislocation with an obstacle of dislocation character. It results from the glide of the two arms of the dislocation on two different glide planes, which stabilizes the dipole that is closed by a jog. The dipole is later released from the obstacle and disappears, presumably by gliding of the dipole's edge segments along their Burgers vector and freeing the mobile screw dislocation from the jog. This mechanism. leads to enhanced obstacle strength of the immobile dislocation well above Orowan critical stress, promoting forest strength. (C) 2015 Elsevier B.V. All rights reserved.

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https://infoscience.epfl.ch/entities/publication/f4f23b02-be6d-47db-8850-c76571890484

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Seyed Masood Hafez Haghighat
2015
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/f4f23b02-be6d-47db-8850-c76571890484

About this result

Related concepts (26)

Dislocation

In materials science, a dislocation or Taylor's dislocation is a linear crystallographic defect or irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms. The movement of dislocations allow atoms to slide over each other at low stress levels and is known as glide or slip. The crystalline order is restored on either side of a glide dislocation but the atoms on one side have moved by one position. The crystalline order is not fully restored with a partial dislocation.

Transmission electron microscopy

Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a sensor such as a scintillator attached to a charge-coupled device.

Creep (deformation)

In materials science, creep (sometimes called cold flow) is the tendency of a solid material to undergo slow deformation while subject to persistent mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods and generally increase as they near their melting point. The rate of deformation is a function of the material's properties, exposure time, exposure temperature and the applied structural load.

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Obstacle strength of binary junction due to dislocation dipole formation: An in-situ transmission electron microscopy study

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