Dislocation Configurations and Work Hardening in Molybdenum Single Crystals Deformed in Tension at 77 and 293 K

Abstract

Ultra high vacuum zone refined molybdenum single crystals oriented at the center of the unit stereo-triangle (Schmid factor of (011) [1\bar11] system is about 0.5) were deformed in tension at 77 and 293 K . Thin foil specimens for transmission electron microscopy (TEM) with desired orientations were prepared from tensile specimens deformed to various strains.
TEM revealed joggy long screw dislocations, debris loops and dark spots for both deformation temperatures. Dense tangles are formed during 293 K deformation, whereas, at 77 K, no tangles are formed, but dense bands corresponding to a few secondary slip systems are formed. The densities of the above mentioned features were measured. Resistive stresses from various origins, contributing to work hardening, were estimated; the stress needed for non-conservative jog motion was found the most predominant and concluded to be the most important component of the flow stress for the low temperature type work hardening of molybdenum single crystals.