Abstract
The dynamic tensile extrusion (DTE) behavior and microstructural evolution of fine-grained (FG, ~1 μm < d < ~10 μm) Cu fabricated by powder injection molding (PIM) were investigated. The FGM Cu was fabricated by PIM with commercial micro-sized Cu powder sintering at 850 °C for 2 h, while the FGH Cu was developed by the hot isostatic pressing (HIP) of the FGM at 780 °C for 2 h under a pressure of 1000 bar. In order to compare the DTE behavior of the FG Cu manufactured using different methods, the ultrafine-grained-B (UFG, d < ~1 μm) Cu was developed by performing 16 passes of equal-channel angular pressing with route Bc, and the FG-150 Cu was fabricated by annealing the UFG-B Cu bar at 150 °C for 1 h. The DTE tests were performed with identical flyer velocities using an all-vacuum gas gun. The fragments and remnants were carefully recovered after the DTE tests and examined by electron backscattered diffraction measurement and a micro-Vickers hardness test. A strong dual <001> + <111> texture was developed during the DTE for both FGM and FGH Cu. In contrast to the outcome of the UFG-B and FG-150, little evidence of dynamic recrystallization taking place during the DTE in the FGM and FGH was found during analysis of the grain morphology and grain orientation spread. Premature failure based on void coalescence was induced at the vertex region of the FGM fragments due to pre-existing pores. The HIP treatment on the FGM Cu increased the relative density by reducing the pre-existing pores and, as a result, increased the DTE ductility of the FGH Cu.
Highlights
In defense and civilian applications, extreme operating conditions such as supersonic impact, penetration, and explosion accompany the dynamic mechanical behavior of materials
As explosive energy is transmitted to a conical metal sheet called a liner, it deforms forward along the axis, becoming a high-velocity jet of metallic particles which accompany very large plastic deformation involving high strain rates over 105 s−1 [2,3]
The mechanical response of liner materials under both high strain rate and adiabatic deformation conditions is similar to the dynamic tensile extrusion (DTE) test proposed by Gray III et al [4]
Summary
In defense and civilian applications, extreme operating conditions such as supersonic impact, penetration, and explosion accompany the dynamic mechanical behavior of materials These can cause severe plastic deformation involving considerable increases in temperature due to the adiabatic heating conditions at high strain rates [1]. As explosive energy is transmitted to a conical metal sheet called a liner, it deforms forward along the axis, becoming a high-velocity jet of metallic particles which accompany very large plastic deformation involving high strain rates over 105 s−1 [2,3]. The length of this jet is an important parameter in penetration capacity. The DTE ductility can be defined as the sum of the axial length of each fragment with respect to the initial projectile diameter as follows:
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