Modeling the mechanical behavior of tantalum
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INTRODUCTION
TANTALUM possesses several desired properties that makes it well suited for a number of engineering and structural applications, such as high density, good ductility, high melting point, and excellent corrosion resistance. Most commercially produced tantalum used in electrical capacitors does not require close control of grain size, impurity content, or crystallographic textures. The potential use of tantalum for ballistic applications requires a knowledge of its plastic behavior at large deformations and high strain rates. In penetration applications, the combined effects of large strains, high-strain-rate deformation, and an adiabatic temperature rise can significantly modify the plastic behavior of tantalum compared with its quasi-static, isothermal behavior. An experimental study of the temperature and strain-rate dependence of the flow stress of tantalum was conducted by Hoge and Mukherjee in 1977.[1] However, considerable differences now exist between the melting practices and thermomechanical processing methods for tantalum used in the 1970s and current practices. These changes, such as triple-electron-beam melting, cross rolling, and upset forging, allow much tighter control of interstitial content, grain size, and initial crystallographic textures of tantalum products. Thermomechanical processing and forming operations of tantalum require controlled impurity levels and crystallographic textures, to allow predictable final product shape and consistent mechanical properties. In many engineering applications, texture development resulting from deformation history plays an important role in subsequent mechanical response. Initial crystallographic texture is particularly important in deep drawing and related sheet-forming operations, where textures can influence the final product shape and surface finish. Clark et al.[2,3] have studied the influence of initial ingot breakdown and transBING-JEAN LEE, Associate Professor, is with the Department of Civil Engineering, Feng Chia University, Taichung, Taiwan, Republic of China 40724. KENNETH S. VECCHIO, Associate Professor, is with the Materials Science Group, Department of Applied Mechanics and Engineering Sciences, University of California-San Diego, La Jolla, CA 92093. SAID AHZI, Assistant Professor, is with the Department of Mechanical Engineering, Clemson University, Clemson, SC 29634. SCOTT SCHOENFELD, Project Scientist, is with the Army Research Laboratory, Aberdeen Proving Ground, MD 21005. Manuscript submitted April 15, 1996. METALLURGICAL AND MATERIALS TRANSACTIONS A
verse rolling on the development of the {111} fiber components in tantalum plates, which is the texture favorable for deep drawing of body-centered cubic (bcc) metals.[4] Their results indicate that the {111}^uvw& orientations can be enhanced by upset forging of the initial ingots, or by the introduction of a transverse rolling operation in the production of plate products. Accurate modeling of deformation processes of tantalum over a wide range of strain rates and temperatures
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