Powder-Route Synthesis and Mechanical Testing of Ultrafine Grain Tungsten Alloys

Abstract

We report a W-rich alloy (W-7Cr-9Fe, at%) produced by high energy ball milling, with alloying additions that both lower the densification temperature and retard grain growth. The alloy's consolidation behavior and the resultant compacts' microstructure and mechanical properties are explored. Under one condition, a 98% dense compact with a mean grain size of 130 nm was achieved, and exhibited a hardness of 13.5 GPa, a dynamic uniaxial yield strength of 4.14 GPa in Kolsky bar experiments, and signs of structural shear localization during deformation.

Sub-scale ballistic testing of an ultrafine grained tungsten alloy into concrete targets

“…The pre-factor c in Eqn 1a is a constant that depends on the incident velocity, V S , as follows: (2) where m is the penetrator's mass.…”

“…We also prepared sub-scale rounds from an ultrafine-grained W-Cr-Fe alloy whose chemistry and processing schedule were based on Ref. [2]. The material used in this study was prepared by 6 hours of attrition milling of elemental feedstock powders of W and Cr (99.95 pct W -100 mesh;…”

“…We consolidated the as-milled powder using a Dr. Sinter SPS-515S hot press, a graphite punch and die having a diameter of 24 mm, and the preferred consolidation parameters identified in Ref. [2]: a ramp rate of 100 K/min, a consolidation pressure of 100 MPa, a soak time of 1 min, and a soak temperature of 1200 °C. We then centerless ground samples electro-discharge machined from the center of these compacts into ogive nose rounds with the dimensions given in Figure 1b.…”

“…High-density alloys with ultrafine and nanocrystalline grain sizes possess a unique set of mechanical properties that make them very attractive kinetic energy penetrator materials for rigid body penetration into concrete and geomaterials. Their high strengths, for instance, suggest that they should remain elastic at incident velocities where penetrators made from softer materials, e.g., high strength steels, start to deform plastically [1][2][3].…”

Grain Boundary Character Distributions in Nanocrystalline Metals Produced by Different Processing Routes

“…[2] Other current or near-term applications include more environmentally benign industrial hard coatings, [3] and alternatives to depleted uranium munitions. [4] To facilitate these advances, processing scientists have developed many techniques to synthesize nanocrystalline metals in a variety of forms and compositions. Bulk parts can be manufactured by the top-down refining of a coarse grained alloy into a nanocrystalline one by severe plastic deformation (SPD).…”