Heterogeneously stacked multi layered metallic structures with adiabatic shear localization under uniaxial dynamic compression

Abstract

The present disclosure is directed to significantly improving the adiabatic shear banding susceptibility of pure refractory metals as well as overcoming the physical dimension limitations when making kinetic energy penetrators. These improvements may be achieved by arranging interlayers between plasticly deformed refractory metal material layers. Disclosed herein are methods of making material for kinetic energy penetrator applications, the methods comprising: severely plasticly deforming a refractory metal material until the grain size of the refractory metal material is within one of ultrafine grain and nanocrystalline regimes; arranging an interlayer material adjacent the refractory metal material; and diffusion bonding the interlayer material to the refractory metal material.

Claims

1. A method of making material for kinetic energy penetrator applications, the method comprising: severely plasticly deforming a refractory metal material until the grain size of the refractory metal material is within one of ultrafine grain and nanocrystalline regimes, thereby forming refractory metal material layers; arranging an interlayer material between the refractory metal material layers; and diffusion bonding the interlayer material to the refractory metal material layers.

2. The method of claim 1, wherein the grain size is greater than about 100 nm.

3. The method of claim 1, wherein the grain size is less than about 100 nm.

4. The method of claim 1, wherein severely plasticly deforming the refractory metal material is achieved through cold rolling.

5. The method of claim 1, wherein the refractory metal material includes at least one of titanium, vanadium, chromium, zirconium, niobium, molybdenum, ruthenium, rhodium, hafnium, tantalum, tungsten, rhenium, osmium, and iridium.

6. The method of claim 1, wherein the interlayer material includes iron.

7. The method of claim 1, wherein arranging the interlayer material between the refractory metal material layers is achieved through stacking the interlayer material atop one of the refractory metal material layers.

8. The method of claim 1, wherein diffusion bonding the interlayer material to the refractory metal material layers is achieved using a hot press.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like device components/method steps, as appropriate, and in which:

(2) FIG. 1 shows a schematic of a heterogeneous multilayer structure with alternating layers of a refractory metal material and an interlayer material, in accordance with certain embodiments of the disclosed technology;

(3) FIG. 2 shows an image of a diffusion bonded heterogeneous multilayer structure with alternating layers of tungsten and iron, in accordance with certain embodiments of the disclosed technology;

(4) FIG. 3 shows a schematic of adiabatic shear banding propagating through the heterogeneous multilayer structure of FIG. 1, in accordance with certain embodiments of the disclosed technology;

(5) FIG. 4 shows an image of adiabatic shear banding observed in the multilayer structure of FIG. 2 upon impact loading, in accordance with certain embodiments of the disclosed technology;

(6) FIG. 5 shows a side-view image of a heterogeneous multilayer structure prepared by diffusion bonding, in accordance with certain embodiments of the disclosed technology;

(7) FIG. 6 shows a top-view image of the heterogeneous multilayer structure of FIG. 5 prepared by diffusion bonding and indicating the rolling direction of the plasticly-deformed refractory metal material layer, in accordance with certain embodiments of the disclosed technology;

(8) FIG. 7 shows a back-facing view of a penetration tunnel in a halved target material created by a heterogenous multilayer stacked kinetic energy penetrator, in accordance with certain embodiments of the disclosed technology;

(9) FIG. 8 shows a cross-sectional side view of the heterogenous multilayer stacked kinetic energy penetrator of FIG. 7 embedded into halved target material, in accordance with certain embodiments of the disclosed technology;

(10) FIG. 9 shows an assembled optical micrograph mapping of the projectile residues of the kinetic energy penetrator of FIGS. 7-8 within the target material, in accordance with certain embodiments of the disclosed technology.

(11) FIG. 10 shows an enlarged section of the optical micrograph of FIG. 9 illustrating the adiabatic shear banding behavior of the kinetic energy penetrator of FIGS. 7-8 having a heterogenous multilayered structure, in accordance with certain embodiments of the disclosed technology;

(12) FIG. 11 shows another enlarged section of the optical micrograph of FIG. 9 illustrating the adiabatic shear banding behavior of the kinetic energy penetrator of FIGS. 7-8 having a heterogenous multilayered structure, in accordance with certain embodiments of the disclosed technology;

(13) FIG. 12 shows yet another enlarged section of the optical micrograph of FIG. 9 illustrating the adiabatic shear banding behavior of the kinetic energy penetrator of FIGS. 7-8 having a heterogenous multilayered structure, in accordance with certain embodiments of the disclosed technology; and

(14) FIG. 13 shows a final enlarged section of the optical micrograph of FIG. 9 illustrating the adiabatic shear banding behavior of the kinetic energy penetrator of FIGS. 7-8 having a heterogenous multilayered structure, in accordance with certain embodiments of the disclosed technology.

DETAILED DESCRIPTION OF THE DISCLOSURE

(15) The present disclosure is directed to significantly improving the adiabatic shear banding susceptibility of pure body-centered-cubic (BCC) lattice structure metals as well as overcoming the physical dimension limitations. These improvements may be achieved by arranging interlayers between plasticly-deformed BCC or refractory metal material layers.

(16) An underlying principle of kinetic energy penetrators is using kinetic energya function of the mass and velocityto force a way through armor. Therefore, to be a good candidate for kinetic energy penetrator applications, a material should exhibit high mass density. For example, tungsten and tantalum are potential kinetic energy penetrator materials due to their high mass density of about 17-19 g/cm.sup.3. In general, all of the elements in the class of the refractory metals exhibit a sufficient mass density for use as a kinetic energy penetrator material.

(17) Another key attribute of kinetic energy penetrators is self-sharpening. The self-sharpening characteristic is key for all kinetic energy penetrators to maintain the sharpness of the piercing head of the penetrator during penetration into the target, such that the maximum amount of kinetic energy is primarily used to damage the target. By reducing the penetrator head size through discarding material along plastic localizations, the penetrators may displace a smaller diameter penetration tunnel in the armor, thereby penetrating more efficiently and delivering superior ballistic performance. The rapid development of the flow and shear failure behaviors lead to a quick discarding of the penetrator material, which would otherwise build up at the head of the projectile. This head-sharpening material shedenabled by flow softening and adiabatic shear banding helps deliver a superior ballistic performance by effectively conserving the kinetic penetration energy.

(18) This self-sharpening effect is rooted in a material's propensity to adiabatic shear localization or banding when under uniaxial dynamic (high strain rate) compression or loading. Overall, adiabatic shear banding is a failure pattern of materials at high strain rates. This adiabatic shear localization occurs when thermal softening overcomes both strain hardening and strain rate hardening effects.

(19) Pure refractory metalsi.e., titanium, vanadium, chromium, zirconium, niobium, molybdenum, ruthenium, rhodium, hafnium, tantalum, tungsten, rhenium, osmium, and iridiummay exhibit adiabatic shear banding or adiabatic shear localization. More specifically, BCC metals and alloys with severe plastic deformation tend to develop adiabatic shear banding under dynamic compression or high strain rate loading. Iron, since it has BCC structure at ambient temperature, also shows adiabatic shear localization under similar loading conditions. In particular, these refractory metal materials exhibit adiabatic shear banding under uniaxial dynamic (high strain rate) loading, where an applied severe plastic deformation process has refined their grain size into either the ultrafine grain (with grain size larger than 100 nm, but less than 1000 nm) or nanocrystalline (with grain size less than 100 nm) regime. However, prior to the present disclosure, these metals (e.g., tungsten), even after undergoing severe plastic deformation methods, have not yet been able to be incorporated as a primary material in kinetic energy penetrators due to strict dimensional limitations.

(20) Refractory metals are widely defined as titanium, vanadium, chromium, zirconium, niobium, molybdenum, ruthenium, rhodium, hafnium, tantalum, tungsten, rhenium, osmium, and iridium. This specific class of metals features high melting points (above 2,123 K) as well as strong heat- and wear-resistance. The high melting point property of the refractory metals class ties to a characteristically superior creep deformation resistance. The mass densities of refractory metals range from about 4.5 g/cm.sup.3 to about 23 g/cm.sup.3 (even greater than uranium's).

(21) The adiabatic shear banding phenomenon has been studied in terms of high strain rate deformation (such as high-velocity punching and forming, high-speed machining, cryogenic deformation, ballistic testing, etc.) through experiments and mathematical methods to examine the shear localization and its temperature dependence. The results for stainless steels showed that temperatures as high as the melting temperature were reached throughout the shear band shortly after the peak load was attained. By contrast, in a tantalum shear band, the observed temperature rise (from room temperature to about 898 K) was less than the steels' calculated results. Validation of such temperature increases is very difficult to measure experimentally. This adiabatic shear banding may also be evaluated in metallic glass and composite materials using instrumented indentation tests and ballistic tests, respectively.

(22) In 1943, Zener and Hollomon first recognized the relationship between plastic deformation and loading strain rate in steels. Since then, much research has been conducted to develop criteria to explain this plastic instability. Recht developed a hypothesis that high strain rate plastic behavior was influenced by temperature gradientsa function of thermophysical properties, strain rate, and shear strength. In 1981, Bai derived a criterion for thermo-plastic shear instability, in which titanium initialized instability at low strains, and this instability developed fully at high strain rates. However, for mild steel, this phenomenon was reversed. Then, Bai calculated the width of a shear band to be approximately 10-100 m.

(23) In contrast to the above, a twinning induced plasticity steel with a composition of Fe-15Mn-2.5Si-2Al-0.6C and a face-centered-cubic (FCC) lattice structure has been found to exhibit strong strain and strain rate hardening upon the mechanical loading, resulting in outstanding adiabatic shear banding resistance. The strain and strain rate hardening mechanisms have been experimentally investigated as a function of strain rate under uniaxial tension and compression. The steel sample is characterized by a constant strain hardening rate as well as by high strength and high ductility under tension. This extraordinarily strong strain rate hardening behavior in the context of deformation kinetics is described as high strain rate sensitivity and low activation volume compared with coarse-grained FCC counterparts. It has been discovered that a marginal size effect exists in this twinning induced plasticity steel. This size effect is believed to be due to an extremely small activation volume. According to the Zener-Hollomon equation, increasing the strain rate has an equivalent effect to that of a decrease in deformation temperature which favors the formation of twins with small thickness and spacing.

(24) FIG. 1 shows a schematic of a heterogeneous multilayer structure and/or composition 100 with alternating layers of a refractory metal material 102 and an interlayer material 104.

(25) The refractory metal material layer 102 may include titanium, vanadium, chromium, zirconium, niobium, molybdenum, ruthenium, rhodium, hafnium, tantalum, tungsten, rhenium, osmium, and/or iridium. The interlayer material layer 104 may include iron, nickel, carbon, aluminum, silicon, and/or manganese.

(26) The refractory metal material layers 102 may be diffusion bonded to the interlayer material layers 104, such as through a diffusion welding process using a hot press, for example. To diffusion weld material layers 102 and 104 together, pressure may be added inside a heated furnace full of argon gas.

(27) The grain size, crystallite size, or grain diameter of a material is inversely proportional to the material's yield strength. The ultrafine grain regime of materials is defined by having an average grain size between about 100 nm and about 1000 nm. The next level beyond ultrafine, having higher yield strength and smaller average grain size, is the nanocrystalline regime of materials, in which the average grain size is less than about 100 nm. The upper limit on material yield strength based on refined grain microstructure occurs around an average grain size of about 10 nm, since below this diameter, grains are susceptible to grain boundary sliding.

(28) Severe plastic deformation is the application of high strains to a material that increases the material's defect density such that its grain size is refined to be within the ultrafine grain or nanocrystalline regime. In preparing the heterogeneous multilayer structure 100, the refractory metal material layer 102 may undergo severe plastic deformation through various cold-working processes, such as two-step or multi-step cross rolling, for example. Any alternative methods may be used to generate dislocations within the refractory metal material 102, such as other cold-working techniques, accumulative roll bonding, milling, and/or surface treatments.

(29) The thickness of the refractory metal material layer 102 may be from about 100 m to about 800 m. For example, the refractory metal material layer 102 may be about 465 m thick.

(30) The thickness of the interlayer material layer 104 may be from about 10 m to about 50 m. For example, the interlayer material layer 104 may be about 25 m thick.

(31) FIG. 2 shows an image of a diffusion bonded heterogeneous multilayer structure 100 with alternating layers of a refractory metal material 102, including tungsten, and an interlayer material layer 104, including iron.

(32) Moreover, the inhomogeneous stacking of heterogeneous multilayer structure 100 may cause adiabatic shear banding to be propagated through the composition 100, resulting in the desired self-sharpening effect, as shown in FIG. 3.

(33) FIG. 3 shows a schematic of adiabatic shear banding propagating through the heterogeneous multilayer structure 100 of FIG. 1. When the heterogeneous multilayer structure 100 is subjected to high impact loads, an adiabatic shear band 106 may develop across the refractory metal material layers 102 and the interlayer material layers 104.

(34) FIG. 4 shows an image of adiabatic shear banding 106 observed in the multilayer structure 100 of FIG. 2 upon impact loading.

(35) In some embodiments, as shown in FIGS. 1-2, by stacking tungsten 102 and binding interlayers 104 in an alternating fashion, a hierarchical structure 100 may be achieved without dimensional limitations. FIG. 5 shows a side-view image of a heterogeneous multilayer structure 100 of alternating refractory metal material layers 102 and interlayer material layers 104, 11 mm12 mm, stacked 11.75 mm tall, prepared by diffusion bonding.

(36) FIG. 6 shows a top-view image of the heterogeneous multilayer structure 100 of FIG. 5, indicating the rolling direction of the cold-worked refractory metal material layers 102. Using this heterogeneous multilayer structure 100 of FIGS. 5-6, subscale heterogeneous projectiles were fabricated for ballistic testing.

(37) The performance of prototype or subscale kinetic energy penetrators may be evaluated using a ballistic testing method where projectiles are fired into a steel target (or other target material) at strain rate up to about 10.sup.6 s.sup.1 in an indoor small-scale test range facility. By measuring and examining the diameter of the penetration tunnel formed through the armor plate or target material, the ballistic performance may be compared and evaluated.

(38) When comparing the depth and morphology of a penetration tunnel created by depleted uranium alloy penetrators with those of conventional tungsten-based heavy alloy penetrators, experiments have shown that the penetration tunnels produced by the depleted uranium alloy penetrators were narrower and deeper than the ones created by conventional tungsten-based heavy alloy penetrators. Moreover, conventional tungsten-based heavy alloy penetration tunnels were often more deteriorated because of the increased diameter caused by excessive plastic deformations at the conventional tungsten-based heavy alloy penetrator's piercing head, which further demonstrated a poor ballistic performance as compared to a depleted uranium alloy penetrator.

(39) FIG. 7 shows a back-facing view of the result of the ballistic testing methoda heterogenous multilayer stacked kinetic energy penetrator 200 after having been thrust into a target material 208, thereby creating a penetration tunnel 210, which now halved reveals the compacted and embedded penetrator 200.

(40) FIG. 8 shows a cross-sectional side view of the heterogenous multilayer stacked kinetic energy penetrator 200 of FIG. 7 compressed into the end of the penetration tunnel 210, embedded in the halved target material 208.

(41) FIG. 9 shows an assembled optical micrograph mapping of the projectile residues of the kinetic energy penetrator 200 of FIGS. 7-8 implanted within the target material 208. Adiabatic shear bandings identified at the head of the projectile residuals suggest an early onset of shear localization behavior during the ballistic event. The adiabatic shear bandings were observed to propagate through the heterogeneous layers and the bonding interfaces remained intact upon high rate loading.

(42) FIGS. 10-13 show enlarged sections of the optical micrograph of FIG. 9 illustrating the adiabatic shear banding behavior of the heterogenous multilayer stacked kinetic energy penetrator 200 of FIGS. 7-8 produced while tunneling into the target material 208. Notably, there is a lack of bulging deformations along the piercing head of the kinetic energy penetrator 200. This indicates a much higher kinetic energy conservation efficiency than exhibited in conventional tungsten-based heavy alloy penetrators.

(43) Although the present disclosure is illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present disclosure, are contemplated thereby, and are intended to be covered by the following claims for all purposes.