Demonstration of Shear Localization in Ultrafine Grained Tungsten Alloys via Powder Metallurgy Processing Route

Report No. ARL-TR-6214
Authors: Brady Butler, Eric Klier, Daniel Casem, Ajmer Dwivedi*, Micah Gallagher**, and Judy Hays**
Date/Pages: September 2012; 36 pages
Abstract: Mechanical properties and deformation characteristics are very closely linked to the underlying microstructure of a material. As the grain size of a metal is pushed to ultrafine (<1000 nm) and nano (<100 nm) length-scales, there is often a fundamental shift in the deformation mechanisms of these materials. In particular, tungsten and tungsten alloys have been shown to deform by shear localization as opposed to stable plastic flow when their grain size approaches 100 nm. While this failure mechanism is not ideal for many structural applications, it does provide an opportunity for improving the ballistic performance of tungsten in kinetic energy penetrator applications. This report analyzes the deformation characteristics of bulk, ultrafine grained tungsten and tungsten alloys produced via a powder metallurgy. In addition to grain size, the ability to shear localize is a strongly dependent on the overall ductility of the material. This research represents the first bulk demonstration of shear localization in a high density (>18 cm3) tungsten based alloy tested in the as-sintered state.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2012