Electron Microscopic Investigation of the Dislocation Structure in Molybdenum Single Crystals Deformed in Tension at 293 and 493 °K

Abstract

The dislocation structure of high purity molybdenum single crystals after weak tensile deformation a t 293 and 493 O K is studied b y transmission electron microscopy. The transition from parabolic stress-strain behaviour to three-stage hardening which occurs between the considered temperatures is associated with a basic change in the deformation substructure. Crystals deformed at 293 OK contain a uniform distribution of long primary and secondary screw dislocations. On the contrary, the dislocation structure in stage I at 493 O K consists mainly of isolated clusters of primary edge dipoles. It is concluded that the effect of temperature on the mobility of screw dislocations is responsible for the change observed both in work-hardening characteristics and related dislocation structures.

Dislocation junctions as indicators of elementary slip planes in body-centered cubic metals

“…Only 96 occur due to reactions between f110g planes only. So far in experiments only the h100i screw orientations have been reported in a-Fe [34] and edge, screw and mixed orientations have been reported in <1 Mo [35,36]. The sessile edge orientation can only result from glide on f110g planes only and the occurrence of a large density of such junctions is a strong indication for elementary slip on f110g planes only.…”

The Influence of Temperature on Slip Behaviour of Molybdenum Single Crystals Deformed in Tension in the Range from 293 to 573 °K .II. Slip Geometry and Structure of Slip Bands

“…For this reason the activation of secondary sources is suppressed giving rise to single slip in work-hardening stage I (e.g. [5]). Furthermore, the observation of heavily wavy slip traces suggests that the increase in mobility of screw dislocations is associated with the operation of large-scale cross-slip.…”

The structural dependence of work hardening in low carbon steels

“…It has been observed in bee metals that the extent of cell formation at a given strain is strongly temperature dependent in certain temperature ranges, with higher temperatures promoting cell development [33,[36][37][38][39][73][74][75]103]. Although designation of a structure as .…”

“…Luft and co-workers for example, have studied instability processes in bee transition metals and alloys, following a temperature change [36,[73][74][75]. Their most extensive work was performed on molybdenum single crystals.…”