Accession Number : AD0477694

Title :   TWINNING AND THE LOW TEMPERATURE MECHANICAL PROPERTIES OF POLYCRYSTALLINE COLUMBIUM AND MOLYBDENUM.

Descriptive Note : Final technical rept. Feb 65-Jan 66,

Corporate Author : WESTINGHOUSE RESEARCH LABS PITTSBURGH PA

Personal Author(s) : Shaw, Bevil J. ; Harrod, Donald L.

Report Date : JAN 1966

Pagination or Media Count : 36

Abstract : Mechanical properties of Cb and Mo have been investigated over a range of grain sizes from 20 C to minus 269 C. Interpretation of the load elongation curves, in compression and tension, along with detailed metallographic investigation has led to the following conclusions: (1) Twinning can occur more readily in coarse grain than fine grain material, (2) Twins can occur over the entire range of temperature 20 C to minus 269 C in molybdenum but only in the range minus 150 to minus 269 C in columbium at Epsilon = 0.00042/sec; and (3) Enhanced stresses ahead of a crack can cause twinning but there is no definite evidence to show that twins cause cracking. These results have been interpreted in terms of a model independent hypothesis, based on simple considerations of the dissipation of energy by various deformation mechanisms. (Author)

Descriptors :   *TWINNING(CRYSTALLOGRAPHY)), LOW TEMPERATURE, MECHANICAL PROPERTIES, NIOBIUM, MOLYBDENUM, GRAIN SIZE, STRESSES, FRACTURE(MECHANICS), IMPURITIES, ANNEALING, BRITTLENESS, DUCTILITY, MICROSTRUCTURE.

Subject Categories : Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE