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#13926, Structure of Shock Waves and Inelasticity in Shock-Compressed Cemented Tungsten Carbides

Cemented WCs are metal matrix composites in which a large fraction of hard grains of tungsten carbide are embedded in a soft transition metal matrix (also referred to as the binder). A compromise of high hardness and toughness originates from the composition of the tungsten carbide grains and the binder and is also a function of microstructure. By systematically controlling the microstructural parameters including grain size, cobalt content, dotation (e.g., alloy carbides) and carbon content, the cemented carbide performance can be tailored to specific applications.
Due to their high density and hardness, cemented tungsten carbides have attracted attention from both military and industry. As such, the response of these composites to high-rate mechanical loading is an important factor, but perhaps surprisingly, there is little data on dynamic mechanical properties of these materials in the open literature.

The objective of the present investigation is to understand the structure of shock waves and inelasticity in shock-compressed cemented WC with 3% and 6% Co binder. In both cases the carbides are processed to yield microstructures with grain size in a narrow range of 1 to 2 microns. A series of plate impact wave transmission experiments are conducted to investigate the effects of material composition and microstructure on shock-induced compression response of cemented tungsten carbides using plate impact wave transmission experiments. The measured elastic-plastic wave profiles are analyzed to obtain the elastic and plastic shock wave speeds, elastic precursor wave amplitude (decay) with propagation distance, time dependent structure of the wave just behind the elastic precursor, Hugoniot Elastic Limit, shock speed versus particle velocity relationship, longitudinal stress vs. specific volume, and an estimate of material strength at the measured Hugoniot states in the cemented tungsten carbide samples. Release properties of the WC samples are determined from the arrival time and structure of the release wave immediately following the peak plateau in the wave profile. In particular, the release profiles provide critical high-pressure elasticity data needed to properly model finite compressibility of the WC samples. In addition, dispersion (spreading) in the release wave profiles is analyzed to better understand elastic nonlinearity as well as the reverse inelastic deformation characteristics of the shocked samples.

Bingsen Wang   Washington State University
Vikas Prakash   Washington State University