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THE EFFECT OF PRESSURE ON THE STRUCTURE AND PROPERTIES OF METALS,
WATERVLIET ARSENAL N Y
Pagination or Media Count:
Under certain conditions, sufficiently high hydrostatic pressures can induce localized microscopic deformation in polycrystalline metals. Based on the examination of the effect of hydrostatic pressures to 26 kilobars on several cubic metals, the occurrence of such deformation, which in the early stages is localized along grain boundaries and increases in severity with increasing pressure, results from microscopic shear stresses arising from anisotropy in the linear compressibility. Pressure cycling to 20 kilobars slightly increases the flow stress of polycrystalline zine. The tensile strength and ductility are not reproducibly affected. As has been observed in other materials, the ductility of magnesium, tungsten and 1045 steel with an untempered martensitic structure is drastically enhanced when fracture under a superimposed hydrostatic pressure. These materials are also known to undergo abrupt brittle-ductile transitions as a function of temperature, thus indicating that the pressure induced transition may be directly related to the atmospheric pressure phenomenon.
APPROVED FOR PUBLIC RELEASE