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David P. Pope
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Ph.D., Materials Science, California Institute of Technology,
1967.
M.S., Materials Science, California Institute of Technology,
1962.
B.S., Applied Science, University of Pennsylvania, 1961.
Current Research Projects
Deformation and Fracture of Intermetallic Compounds
The ductility of most intermetallics is quite low due either to grain boundary or cleavage failure. In this program we are investigating the deformation and fracture mechanisms in a number of singlecrystalline intermetallics, including TiAl and V2Hf.
Dislocation Generation and the Brittle-to-Ductile Transition
Most crystalline materials undergo a transition from brittle failure at low temperatures to ductile failure at higher temperatures. The temperature of this transition can be quite low for metals and much higher for covalently or ionically bonded materials. We believe this transition is caused by temperature and stress driven dislocation nucleation, without the need for pre-existing dislocations to act as sources.
Grain Boundary Failure
The fracture path in many polycrystalline materials follows the grain boundaries, e.g. in Ni3Al and in certain iron-based alloys with impurities. Since the structure of these boundaries varies with crystallographic misorientation across the boundary and with the orientation of the boundary plane, the strengths of the boundaries are also expected to vary. We are studying the relative strengths of boundaries using the coincidence site lattice model to describe the boundaries. We have found that high coincidence boundaries (Òlow sigmaÓ) are not stronger than random boundaries, but twin boundaries and low angle boundaries are substantially stronger
Selected Publications
F. Chu, D. P. Pope, J. Mater. Sci. Technol., 9, #5, 313-321 (1993).
"Twinning in Intermtallic Compounds - the Dilemma of Shears vs. Shuffles."
F. Chu, D. P. Pope, Acta Met. et Mat. 42, 225-238 (1993).
"A Combined Experimental and Analytical Investigation of Creep Damage Development in Copper."
Z. L. Wu, V. Vitek, D. P. Pope, Phil. Mag. A, 70, 159-169 (1994).
"Plasic Deformation of Cr-Modified L12Al3Ti: (I) Flow Behavior."
Z. L. Wu, V. Vitek, Phil. Mag. A, 70, 171-183 (1994).
"Plastic Deformation of Cr-Modified L12Al3Ti: (II) Weak Beam TEM Study of Dislocation Structures."
M. Khanta, V. Vitek, D. P. Pope, Phys. Rev. Let., 73, 684-687 (1994).
"Dislocation Screening and the Brittle-to-Ductile Transition: A Kosterlitz-Thouless Type Instability."