Beryllium Research and Development Program. Volume 5. Metallurgical Factors Affecting the Ductile-Brittle Transition in Beryllium
Technical documentary rept. 1 Oct 1961-31 Mar 1963
LOCKHEED MISSILES AND SPACE CO INC PALO ALTO CA
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An investigation was made of the factors controlling the ductile- brittle behavior of two grades of commercial purity beryllium, Brush QMV and Pechiney CR. Tensile tests were made on randomly oriented samples at temperatures from 23 to 500 deg C. Extrusions were tested in the longitudinal and transverse directions in the range -195 to 200 deg C. Three grain sizes of each material were investigated, and comparisons made between specimens tested in the aged and unaged condition. The aging treatment was 900 deg C for 6 hours followed by 48 hours at 700 deg C. Mechanical properties of both materials were very similar after this heat treatment and no advantage could be claimed for the higher purity Pechiney beryllium. Aging reduced the amount of impurities in solid solution and contributed to improved ductility in certain temperature ranges. The ductile-brittle transition could not be described in terms of the dislocation pileup theories for body-centered-cubic metals. A theory of the ductile-brittle transition based on the thermally activated cross slip of screw dislocations from the basal plane into pyramidal or prismatic planes was proposed. The data could be described reasonably well in terms of this theory.
- Metallurgy and Metallography