Papers by Author: J.W. Morris

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Authors: J.W. Morris, D.C. Chrzan, Shigeru Kuramoto
Abstract: Tensile tests of single crystals of Gum Metal (Ti-36Nb-2Ta-3Zr-0.3O (wt %)) showed, anomalously, that (1) extensive, stress-induced (bcc)”(orthorhombic) transformation occurred in a crystal pulled in the <110> direction, but no transformation was observed in crystals pulled in the <100> or <111> directions and (2) little or no transformation occurred in tensile tests of severely worked rods, which are polycrystals with very strong <110> texture. Analysis of the energetics of the ” transformation offers straightforward explanations for these results. (1) An ” precipitate has very low elastic energy if it forms as a thin plate with a habit near {11√2}. A <110> tensile load significantly decreases the energy of this plate, promoting the transformation; loading along <100> or <111> is much less effective. (2) While cold-swaged rods of Gum Metal have a strong <110> axial texture, their perpendicular planes are severely distorted, increasing the elastic energy of ” and inhibiting the transformation.
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Authors: Velimir Radmilović, U. Dahmen, B. Dracup, Michael K. Miller, D. Mitlin, J.W. Morris
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Authors: J.W. Morris, D.M. Clatterbuck, D.C. Chrzan, C.R. Krenn, W. Luo, M.L. Cohen
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Authors: John E. Sanchez, D.R. Frear, J.W. Morris
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Authors: Takahito Ohmura, A. Minor, Kaneaki Tsuzaki, J.W. Morris
Abstract: Deformation behavior in the vicinity of grain boundary in Fe-0.4wt%C tempered martensitic steel were studied through in-situ nanoindentation in a TEM. Two types of boundaries were imaged in the dislocated martensitic structure: a low-angle lath boundary and a high-angle block boundary. In the case of a low-angle grain boundary, the dislocations induced by the indenter piled up against the boundary. As the indenter penetrated further, a critical stress appears to have been reached and a high density of dislocations was suddenly emitted on the far side of the grain boundary into the adjacent grain. In the case of the high-angle grain boundary, the numerous dislocations that were produced by the indentation were simply absorbed into the boundary, with no indication of pile-up or the transmission of strain.
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