In order to resolve reported differences in the compressibility of hexagonal selenium, lattice parameters have been measured at pressures up to 140 kbar. Independent measurements have been made by neutron time-of-flight and by x-ray diffraction. The results from these methods are in good agreement. The a axis is found to contract, but the c axis expands with increasing pressure. Values obtained for the average volume, a-axis, and c-axis zero-pressure compressibilities are 49.7±15, 31.9±7, and −14.3±4×10−4 kbar−1, respectively. These results compare favorably with a correlation of bulk modulus and cohesive energy. The expansion of the c axis under pressure is comparable to the contraction of the c axis with increase of temperature.
Low-cycle fatigue and tensile tests were performed on specimens fabricated from 14-nrci (0.55-in.) cross-rolled tungsten plate which was prepared by a powder metallurgy process. Tests included measurements on both as-received and recrystallized specimens. Oata have been obtained at 108G K (1500°F) in vacuum, and at room temperature. Low-cycle fatigue data at both 1088 K and room temperature are in fair agreement with predictions based on the "universal slopes" equation for the as-received material condition. In contrast, fatigue data for recrystallizeJ specimens at 1008 K fall considerably below prediction, except in the high cycles-to-fail (10 5 cycles) regime. Details of the test procedure as well as modification of the specimen configuration which was required for coon temperature testing are reported.
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