Characterization of ballistically deformed tungsten [100]-, [111]-, and [110]-oriented single crystal penetrators by opt
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W.J. Bruchey, Jr. and P.W. Kingman United States Army Ballistic Research Laboratory, Aberdeen Proving Ground, Maryland 20005-5066 (Received 23 February 2004; accepted 11 June 2004)
Single-crystal penetrators of tungsten having orientations of [100], [111], and [110] were ballistically deformed into targets of standard armor material and characterized by optical metallography, x-ray diffraction, and transmission electron microscopy (TEM) methods, which showed significant differences in their deformation mechanisms and microstructures corresponding to their deformation performance as measured by the penetration of the target. The [100] single-crystal penetrator, which produced the most energy efficient deformation, provided a new, alternative mechanism for ballistic deformation by forming small single-crystal blocks, defined by {100} oriented cracks, which rotated during extrusion from the interior to the side of the penetrator while maintaining their single crystal integrity. The [111] single-crystal penetrator transferred mass along allowed, high-angle deformation planes to the penetrator’s side where a buildup of mass mushroomed the tip until the built-up mass let go along the sides of the penetrator, creating a wavy cavity. The [110] penetrator, which produced the least energy-efficient deformation, has only two allowed deformation planes, cracked and rotated to invoke other deformation planes.
I. INTRODUCTION
Various high-density materials are currently in use by the military for long rod kinetic energy (KE) projectiles. These materials include tungsten–nickel–iron composites with 90% or more tungsten, and uranium alloys such as uranium 3/4 titanium (U–0.75Ti). Within the United States, the penetrator material of choice is U–0.75Ti alloy. Many attempts have been made over the years to find a more environmentally friendly replacement for the uranium alloy, which would also alleviate other handling and safety issues and still maintain performance. The U–0.75Ti material selectively fails at the penetrator– target interface by local adiabatic shear. This process prevents the formation of a bulbous, mushroomed head on the penetrator and enhances its penetrating efficiency. Many attempts have been made to alter the properties of tungsten alloys and tungsten composites to mimic this
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0464 J. Mater. Res., Vol. 19, No. 12, Dec 2004
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behavior. These efforts to improve penetrator performance have centered on improving the tensile or compressive strengths of tungsten materials. These performance improvement attempts have been less than fully successful, partially due to a lack of understanding of the basic high deformation rate failure mechanisms of the materials. A starting point to understanding the behavior of these alloy or composite systems is to first fully understand the individual component high rate deformation behavior (the relative contribution of the tungsten si
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