Equal-channel angular extrusion of beryllium
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CTION angular extrusion (ECAE) is a method for introducing large amounts of simple-shear deformation in a material, resulting in a high degree of microstructural refinement (i.e., grain and/or subgrain size). The reader is referred to comprehensive reviews for details of the process and deformation modes.[1,2] Most ECAE studies have been performed on cubic materials, in which a sufficient number of independent slip systems are available to produce homogeneous plasticity. At the grain level, hcp materials exhibit highly anisotropic plastic properties. The implications of this fact on the deformation and texture development during ECAE processing of an hcp metal (Mg) have been investigated previously by one of the authors.[3] In the current investigation, a Be billet was subjected to single-pass ECAE processing. Microstructural characterization of the billet was performed using both optical microscopy and transmission electron microscopy (TEM) techniques to investigate the grain refinement and deformation microstructures. In addition, texture development was characterized by X-ray and electron backscatter diffraction (EBSD) techniques. The experimental results are compared to results from deformation modeling using a viscoplastic self-consistent (VPSC) code.
EQUAL-CHANNEL
II. EXPERIMENTAL PROCEDURE The starting material for this study was powder metallurgy (P/M) source Be, designated as P31664, which was produced R.D. FIELD, Team Leader, and C.T. NECKER, Technical Staff Member, are with the Microstructural Characterization Team, MST-6, Los Alamos National Laboratory, Los Alamos, NM 87545. K.T. HARTWIG, Professor, is with the Mechanical Engineering Department, Texas A&M University, College Station, TX 77843-3123. J.F. BINGERT, Technical Staff Member with the Microstructural Characterization Team, MST-6, Los Alamos National Laboratory, is currently on temporary assignment with the Multifunctional Materials Branch, Naval Research Laboratory, Washington, DC 20375. S.R. AGNEW, formerly with the Oak Ridge National Laboratory, Oak Ridge, TN 37831-6115, is Assistant Professor, Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904-4745. This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee. METALLURGICAL AND MATERIALS TRANSACTIONS A
by the Brush–Wellman Company (Cleveland, OH) by vacuum hot pressing of attrited powder. The BeO content is 0.72 wt pct. Cylinders of this material, 0.75 inches in diameter by 5.5 inches long (19.1 ⫻ 139.7 mm), were removed from the bulk using wire electrodischarge machining (EDM). These were machined to fit into 1-i
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