Abstract
Adiabatic shear bands in uranium alloy projectiles/penetrators, during penetration, allow them to “self-sharpen,” a process that is absent in most tungsten alloy projectiles/penetrators. U-0.75 wt % Ti alloy samples have been accelerated to impact steel targets, and the distribution of adiabatic shear bands in residual samples has been studied in detail to understand the effect of self-sharpening on penetration. In our study, self-sharpening was evidenced by the distribution of the shear bands in the recovered sample. The shear bands formed during impact were observed to change direction when they crossed grain boundaries, which indicated that the grain boundaries had an influence on the adiabatic shear bands of U-0.75 wt % Ti. Micro-hardness test results showed that the Vickers micro-hardness in the adiabatic shear zone was 18% lower than that in the matrix. In the split-Hopkinson pressure bar (SHPB) experiment, a strain rate of around 2891 s−1 was the threshold strain rate that triggered the formation of adiabatic shear bands in the U-0.75 wt % Ti alloy.
Highlights
Depleted uranium (DU) alloys have enormous advantages in military applications both in vehicular protective armor and in armor-piercing rounds, as uranium is a moderately strong and ductile metal that can be cast, formed, and welded by a variety of standard methods
Pure uranium is found in three crystal phases: a low-temperature orthorhombic α-phase, a high-temperature tetragonal β-phase, and a body-centered cubic (BCC) γ-phase that exists at higher temperatures [16,17,18]
While the uranium carbides that may form during solidification are dispersed throughout the ingot or casting, titanium carbides float to the surface of the melt and can be removed
Summary
Depleted uranium (DU) alloys have enormous advantages in military applications both in vehicular protective armor and in armor-piercing rounds, as uranium is a moderately strong and ductile metal that can be cast, formed, and welded by a variety of standard methods. This process is so rapid that the produced heat is concentrated, so it is considered adiabatic For uranium alloys such as U–Ti, the uranium shear band initiates at the mantle near the transition that begins in the mushroomed region and the relatively undeformed rod, at which point a cusp forms, which is the so-called self-sharpening effect. Metals 2018, 8, 145 with the phenomena of the self-sharpening mechanism, and only one shear band occurred in the tungsten heavy alloy (WHA) ejecta in contrast, which was followed by more uniform deformations. They observed that, compared with the WHA rods, the DU rods penetrated deeper, and the tunnels had smaller diameters and rougher surfaces relative to the essentially smooth tunnels that arose from the WHA penetrators. We used the SHPB experiment to explore the shear strain required for the formation of the strain rate
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