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CRITICAL EVALUATION OF THE MECHANICAL BEHAVIOR OF BERYLLIUM.
FRANKLIN INST RESEARCH LABS PHILADELPHIA PA
Data available in the literature on the mechanical behavior of beryllium were evaluated to ascertain the operative dislocation mechanisms. These suggest that the deformation dynamics of polycrystalline beryllium in the range of 78 K to 800 K is related to the motion of dislocation on the first order prism planes. Above 800 K, the yield stress exhibits a stronger temperature dependence than that for prism slip and the deformation dynamics may be associated with either the operation of C a pyramidal slip or perhaps some diffusion-controlled mechanism. Insufficient data are presently available to positively identify the rate controlling dislocation mechanisms. The effect of hydrostatic pressure on the ductile-to-brittle transition temperature is in accord with the concept that the transition is associated with the operation of c a pyramidal slip. As a first step in the study of the anisotropy of bonding in beryllium the elastic shear constant C C11 C12 2 C33 - 4 C13 has been calculated for beryllium using Jones model and was found to be in good accord with the experimental value. Using this model, the effect of the addition of monovalent and polyvalent alloying elements on the elastic constant was calculated and found to be significant. Author
Final rept. 17 Jan-31 Aug 66,