Solid -state flow, mechanical alloying, and melt-related phenomena for [001] single -crystal W ballistic rod penetrators interacting with steel targets

Carlos Pizana, University of Texas at El Paso

Abstract

This research program consists of a detailed microstructural investigation of in-target, single-crystal [001], clad (with Inconel 718) and unclad, W long-rod, ballistic penetrators. The rods were shot into rolled homogeneous armor (RHA) steel targets approximately 76 mm in thickness at impact velocities ranging from 1100 m/s to 1350 m/s. A comprehensive microstructural overview of the penetration process was obtained from this investigation. Solid-state flow/erosion, solid-state target/rod mixing as well as influencing factors such as strain rate, penetration performance, cladding interference and the interaction between target and projectile were emphasized. ^ Some of the microstructural features observed, including deformation twins, cleaving, adiabatic shear bands and DRX support an overall solid-state penetration process. Furthermore they provide for a unifying perspective for the applicability of the hydrodynamic paradigm (DOP ≈ l&j0;rp/rt ) and earlier mechanistic erosion approaches. DRX and grain growth within adiabatic shear bands observed at specific high strain/strain-rate zones within the rods suggest that the projectile erodes by means of these microstructures in a solid-state form. This erosion process contributes to the performance of the rod by either allowing optimum flow of rod material which would increase penetration depth, or by maximizing rod material consumption which would reduce it. Since flow and/or erosion are also necessary in the target for perforation to occur, it is not surprising that the erosion process in the target was observed to mirror the one in the projectile. That is both target and projectile developed erosion zones with DRX facilitating the extreme deformation via dense overlapping shear band formation. ^ Mechanical alloying and/or mixing of the target (steel) and rod (W, or W-Inconel 718) was also observed and investigated. Selective etching techniques as well as energy-dispersive x-ray mapping revealed unambiguous evidence of the latter. Considerable mixture (target/rod) material was observed to intercalate into vehicles of erosion including shear bands. These mixtures, which included some isolated melt regimes, differ in composition for clad and unclad samples. The Inconel 718 alloy clad material which is used in order to prevent fragmentation of the projectile during launch, also contributed to the penetration deformation and to the projectile/target interaction. The cladding material appears to influence the solid-state flow by functioning as the principal flow interaction regime between the target and penetrator at the penetrating interface. Since material flow efficiency at the target/rod interface and erosion initiation zones was found to be a necessary condition for increasing penetration depth, a penetrator design strategy can include the careful selection of cladding material. That is the cladding can function first as a solid-state lubricant at the penetrating target/rod interface and secondly as an intercalated mixture in vehicles of erosion allowing for optimum flow. ^

Subject Area

Engineering, Materials Science

Recommended Citation

Pizana, Carlos, "Solid -state flow, mechanical alloying, and melt-related phenomena for [001] single -crystal W ballistic rod penetrators interacting with steel targets" (2006). ETD Collection for University of Texas, El Paso. AAI3223773.
http://digitalcommons.utep.edu/dissertations/AAI3223773

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