The observation of a dislocation ‘Climb’ source

Abstract

Abstract It has been found, using thin film electron microscopy, that aluminium 3.5 and 7.3 atomic per cent magnesium alloys quenched into silicone oil contain concentric diamond-shaped dislocation loops lying upon the cube planes. An examination of the various dislocation interactions which occur together with the electron diffraction contrast behaviour shows that these loops have alternate Burgers vectors of the (a/2)⟨110⟩-type lying in the cube face perpendicular to that in which the loops lie. The source is believed to be a dislocation of the a⟨001⟩-type which accepts vacancies during the quench, but dissociates during climb into two component dislocations. This dissociation can occur with the new Burgers vectors lying in either of two possible cube planes and evidence of both types is frequently seen. The origin of the source is discussed.