Accession Number : AD0813542

Title :   PLASTIC DEFORMATION OF BODY-CENTERED CUBIC METALS. VOLUME I. PLASTIC DEFORMATION OF TANTALUM.

Descriptive Note : Technical rept. 15 Feb 63-30 Jun 66,

Corporate Author : LIVERPOOL UNIV (UNITED KINGDOM) DEPT OF METALLURGY AND MATERIALS SCIENCE

Personal Author(s) : Owen, Walter S. ; Hull, Derek ; Formby, Christopher L. ; Byron, John

Report Date : FEB 1967

Pagination or Media Count : 140

Abstract : The effects caused by the segregation of interstitial atoms to dislocations have been investigated by tensile tests of polycrystalline tantalum. The dislocation friction stress, sigma sub i, was relatively unaffected by the segregation but the dislocation locking parameter, k sub y, increased continuously up to a maximum value during strain aging and quench aging. The interstitial element responsible for locking dislocations in tantalum was identified as oxygen, and the binding energy of oxygen atoms to dislocations has been determined. The effect of the introduction of hydrogen into polycrystalline tantalum has been investigated. The friction stress, sigma sub i, was unaffected by hydrogen but k sub y was found to depend on the aging treatment. The variation of k sub y with aging treatment has been correlated with the precipitate size as determined by electron microscopy. In addition, an order-disorder transformation occurred which could be observed directly in the electron microscope. Single crystals of tantalum with orientations around the edge of the standard stereographic triangle were deformed in tension and compression. The plastic deformation phenomena associated with yielding were investigated as a function of orientation at two temperatures. The variation of the yield stress with orientation was studied to determine whether yielding is controlled by a critical resolved shear stress law. The yield stress only obeyed a critical resolved stress criterion under certain conditions of temperature, orientation and deformation process. (Author)

Descriptors :   (*TANTALUM ALLOYS, DEFORMATION), PLASTIC PROPERTIES, STRESSES, FRICTION, STRAIN(MECHANICS), AGING(MATERIALS), HYDROGEN, ELECTRON MICROSCOPY, SHEAR STRESSES, PROCESSING, OXYGEN, CARBON, QUENCHING, IMPURITIES, HARDENING, TUNGSTEN ALLOYS, SINGLE CRYSTALS, MOLYBDENUM ALLOYS, BRITTLENESS, HEAT TREATMENT, ANNEALING.

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE