Crack Propagation Studies in Beryllium Single Crystals and Calculations of Solubility Limits in Dilute Beryllium Alloys.
Final technical rept. 1 Mar 69-31 Jul 70,
FRANKLIN INST RESEARCH LABS PHILADELPHIA PA
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Crack propagation was studied in three purity levels of beryllium single crystals. Cracks were initiated at the base of a notch and propagated on the 0001 and 11-200 planes. The effect of temperature on the propagation and blunting of cracks was examined. The propagation of cracks on the 0001 plane is less sensitive to purity than propagation on the 11-20 planes. Although cracks on readily propagated on the 0001 planes in high purity beryllium at 350C they are easily blunted at room temperature on the 11-20 plane. The band structure energy was computed as a function of the axial ca ratio for hcp metal such as Be, Mg and Zn and for their dilute alloys with Cu, Ag, Au and Li. A theoretical criterion was obtained for the solubility limits for hcp metals, which is in agreement with experiments. It was found that in order to form a ternary alloy with Be-Cu, the third element should have a very broad form factor such as in thallium or indium. It was demonstrated the stability of hcp phase of Be and Mg and their dilute alloys and shown that fcc structure and at the formation of stacking faults is quite unlikely in Be-Cu alloy. Finally, a method was obtained to judge the validity of the different forms of pseudopotential and thus come closer to the explanation of the observed phase diagrams of metals. Author
- Properties of Metals and Alloys
- Solid State Physics