GPa Shock Pressure Research Articles

Pressure and temperature dependence of shear modulus and yield strength for aluminum, copper and tungsten under shock compression

Experimental data of shear modulus and yield strength of shocked aluminum, copper and tungsten were analyzed systematically. Comparison between these data and t he results calculated by using SCG(Steinberg-Cochran-Guinan) constitutive model (J.Appl.Phys.51(3):1498) shows that shear modulus and yield strength have simila r dependence on pressure and temperature under conditions for aluminum below 50 GPa, copper below 100 GPa and tungsten below 200 GPa shock pressures. So the as sumptions in the SCG model,Y′pY0=G′pG0,Y′TY0=G′TG0, are approximately correct in these pressure ranges, and the SCG model can be used to describe the shear modulus and yield strength of these metals at high shock pr essure and high temperature.

Equation of state and phase stability of mantle perovskite up to 140 GPa shock pressure and its geophysical implications

We performed shock wave experiments on a natural pyroxene with chemical composition close to (Mg0.92, Fe0.08)SiO3 and initial density of 3.06 g/cm3, between 48 and 140 GPa. The relationship of shock wave velocity us and particle velocity up can been described linearly by us = 3.76(±0.24) + 1.48(±0.07) up (km/s). The model Hugoniot for the assemblage of (Mg0.92, Fe0.08)O (Mw) + SiO2(St) is significantly different from the experimental data, excluding the possibility of chemical decomposition of perovskite to oxides during the shock compression. The Grüneisen parameter γ obtained by fitting the experimental data can be expressed by γ = γ0 (ρ0/ρ)q, where γ0 = 1.84(2) and q = 1.69(3). Using the third‐order Birch‐Murnaghan finite strain equation of state, the shock experimental data yield a zero‐pressure bulk modulus K0s = 260.1(9) GPa and its pressure derivative K′0s = 4.18(4), with ρ0 = 4.19 g/cm3. A comparison of the experimental Hugoniot densities of perovskite with the PREM density profile prefers a perovskite‐dominant lower mantle model.

Shock compression response of magnetic nanocomposite powders

The shock compression response of magnetic Pr 2Fe 14B/α-Fe nanocomposite powders, pressed at different packing densities, was studied in the range of 11–23 GPa shock pressure, using a single-stage gas gun. Bulk compacts (97.5–99% dense) recovered in the form of 12 mm diameter by 4 mm thick disks, were analyzed to determine the structural changes occurring within the particles and at particle boundaries. Scanning electron microscopy observations revealed presence of laminar morphology and strong inter-particle bonding. X-ray diffraction and transmission electron microscopy analysis revealed the retention of nanoscale structure and localized grain refinement. Shear bands were observed and thought to be responsible for the grain refinement. The compact of powders pressed at the intermediate packing density (∼76% dense) showed the best densification characteristics, correspondingly, the best magnetic properties with strongest exchange coupling between hard and soft phases.

Effect of phase change on shock wave attenuation in GeO2

Stress-wave profiles in vitreous GeO2 induced by planar and spherical projectile impact were measured using piezoresistance gauges in the 4 to 18 GPa shock pressure range. The planar experiments demonstrate the response of vitreous GeO2. This response can be divided into three regimes: (1) An elastic shock regime with ramp 4 GPa Hugoniot elastic limit (HEL) precursor. Shock propagation velocity decreases from an initial longitudinal elastic wave speed of 3.5 to 2.8 km/s at 4 GPa. (2) A transition wave regime where the ramp wave is superimposed on the precursor with an additional amplitude of 0 to 2 GPa followed by a sharp increase in shock pressure achieving peak loading pressures of 8 to 14 GPa. Above 4 GPa the ramp wave velocity decreases to a value below 2.5 km/s (the speed of the bulk wave, at the HEL). (3) A shock wave achieving the final shock state forms when peak pressure is >6 GPa specified by linear shock-particle velocity relation D=0.917+1.71 u (km/s) over the 6–40 GPa range for an initial density of 3.655 g/cm3. The Hugoniots of GeO2 and SiO2, both initially vitreous, are found to be virtually coincident if pressure in SiO2 is calculated by multiplying the GeO2 pressure by the ratio of the initial densities of vitreous GeO2 to fused SiO2. The volume axes are translated by aligning the specific volumes for onset and completion of the four- to six-fold coordination phase change. Although only limited spherical impactor spherically diverging shock experiments were conducted, our present results demonstrate (1) The supported elastic shock in fused SiO2 decays less rapidly than a linear elastic wave when elastic wave stress amplitude is higher than 4 GPa. A supported elastic precursor in vitreous GeO2 decays faster with radius than a linear elastic wave; (2) in GeO2 (vitreous) unsupported shock waves decay with peak pressure in a phase transition range (4–15 GPa) with propagation radius (r) as ∝r−3.35.

Static recrystallization of shock-wave (explosively) deformed Fe–40 at% Al–Zr–B intermetallic

A B2 Fe–40 at% Al–Zr–B iron aluminide was subjected to shock-wave (explosive) loading at ∼6 GPa shock pressure. The applied shock pressure was sufficient to generate high dislocation density in the material which, in turn, gave rise to primary static recrystallization process upon subsequent isothermal annealing at 700, 750 and 800°C for various lengths of time. At various annealing temperatures recrystallization occurs rather inhomogeneously. Nucleation occurs mostly at the triple points and grain boundaries, showing tendency for clustering. Recrystallization kinetics follows a general behavior according to the Johnson, Mehl, Avrami and Kolmogorov theory (JMAK) with the Avrami exponent, n∼2.3–2.9. The estimated apparent activation energy for recrystallization, ∼259 kJ/mol, is very close to the activation energy for self-diffusion in pure iron and iron in FeAl. The results of microhardness studies of partially recrystallized specimens indicate that the average Vickers microhardness values for recrystallized and unrecrystallized areas differ significantly, the former having higher microhardness. This phenomenon is discussed in terms of higher density of retained sinks for quenched-in vacancies in the unrecrystallized areas and lower efficiency of vacancy hardening.

Time-resolved particle velocity measurements at impact velocities of 10 km/s

Hypervelocity launch capabilities (9 – 16 km/s) with macroscopic plates have become available in recent years. It is now feasible to conduct instrumented plane-wave tests using this capability. Successfully conducting such tests requires a planar launch and impact at hypervelocities, appropriate triggering for recording systems, and time-resolved measurements of motion or stress at a particular point or set of points within the target or projectile during impact. We have conducted the first time-resolved wave-profile experiments using velocity interferometric techniques at impact velocities of 10 km/s. These measurements show that aluminum continues to exhibit normal release behavior to 161 GPa shock pressure, with complete loss of strength of the shocked state. These experiments have allowed a determination of shock-wave window transparency in conditions produced by a hypervelocity impact. In particular, lithium fluoride appears to lose transparency at a shock stress of 200 GPa; this appears to be the upper limit for conventional wave profile measurements using velocity interferometric techniques.

Preshock-induced phase transition in spalled U–0.75 wt% Ti

Uranium–0.75 wt% Ti samples were spalled in the range of 5–24 GPa shock pressure. One sample was preshocked to a pressure of 24 GPa, `soft' recovered, and then reloaded and spalled at 10 GPa. The spall strength of U–3/4 wt% Ti was found to range from −4.1 to −2.9 GPa when the Romanchenko correction is used in the spall strength calculation. The spall morphology of the sample that was preshocked and then spalled showed a significant change in microstructure from a parent alpha' martensite to a 2-phase eutectoid. The thermodynamically calculated temperature rise resulting from the preshock at 15–24 GPa in these samples is ∼555°C. This temperature is not sufficient to induce such a phase change. However, the preshock conditions additionally increase the flow stress of the U–34 wt% Ti, and it is postulated that this additional hardening is sufficient to increase the temperature above 885°C due to the increased amount of plastic work required during spall, thereby triggering the phase change.

Mechanical Disordering of Cubic Intermetallics By Unconventional Methods of Cold-Work and Their Reordering Upon Annealing

ABSTRACTTwo unconventional methods of cold-work: (a) controlled mechanical (ball) milling (under shear conditions), and (b) shock-wave (explosive) loading at ˜5 GPa shock pressure were applied to two cubic intermetallics: (a) Mn-stabilized cubic (L12) titanium trialuminide (AI3Ti(Mn)) and (b) B2 iron aluminide (FeAl). The long-range order (LRO) parameter S of both intermetallics decreases and their lattice constants increase with increasing milling time providing strong evidence that the mechanical milling disorder is due to antisite-atom pairs. A nanocrystalline structure is being formed in both intermetallics upon milling. A shock-wave loading gives rise to only a partial disorder of both A13Ti(Mn) and FeAl but their lattice constants are not affected (no point defects formation). Annealing at 600°C results in the restoration of LRO and lattice constants as well as microstructural evolution in Fe-45A1.

Structure and hardness of explosively loaded FeAl intermetallic alloys

Abstract The effect of the explosive loading at the 4.5–11.0 GPa shock pressure range and a subsequent heat treatment on the structure and hardness of FeAl intermetallic alloys were studied. As-cast FeAl intermetallic alloys were shock-wave deformed using various cylindrical explosive assemblies and type of explosives. It was found that the microhardness of explosively loaded FeAl intermetallic alloys increases with increasing applied pressure and is considerably higher than that of their as-cast and homogenized or hot-worked counterparts. The TEM examinations revealed many straight line dislocations with sharp jogs indicative of cross-slipping in explosively-loaded iron-rich intermetallics. In the regions of the highest dislocation density a tendency to formation a dislocation cell substructure in Fe–39,43 and 46Al was observed. Anneals of intermetallics explosively-loaded above 5.9 GPa lead to their primary recrystallization. The cracks in all the FeAl-based intermetallic specimens that were either explosively loaded at 5.9 and 11.0 GPa of the applied explosive pressure or contained the highest Al content (near-stoichiometric) were revealed.

Spall experiments and microscopy of depleted U-0.75% Ti alloy. A Romanchenko correction to a spall strength calculation

The spall strength of depleted U-0.75% Ti was found to be between −4.1 to −2.9 GPa within the range of 5–22 GPa shock pressure. The Romanchenko approach used, introduces correction to the spall-strength calculation, significantly increasing the conventionally calculated spall strength of the depleted U-0.75% Ti. The fracture surfaces of spalled U-0.75% Ti are presented.

Shock wave model for sputtering biomolecules using massive cluster impacts

A shock wave model is proposed to explain certian features of recently reported spectra obtained by massive cluster impact (MCI) mass spectrometry. It is suggested that clusters that impact glycerol matrices with energies/nucleon in the range 0.01 eV/u < E/N < 1.0 eV/u provide an extremely soft method for sputtering intact biomolecules. Compared to the high energy/nucleon characteristic of atomic or molecular ion primary beams (typically < 50 eV/u), massive cluster primary beams possess much lower energies/nucleon, which are insufficient to cause appreciable ionization and radiation damage of matrix material. Moreover, fragmentation products of parent molecular ions are effectively lower. With these benefits, MCI spectra show lower chemical noise background and enhanced signal-to-noise ratios. Rankine-Hugoniot analysis of the shock conditions is used to arrive at an estimate of the heat retained in the collision-affected matrix volume after bombardment by a characteristic cluster. For a cluster collision resulting in a 26.8 GPa shock pressure, by analogy with water data, rapid heating of the shocked volume to 1000 °C or more is plausible. In a beam consisting of clusters distributed in size and charge, an estimate is made for the range of cluster sizes over which hyrodynamic shock wave theory applies.

New mineralogical and chemical data on the Machinga (L6) chondrite, Malawi

Abstract— The Machinga, southern Malawi, Africa, L6 chondrite (observed fall, 22 January 1981) contains accessory phases of metal, troilite, chromite, and native Cu (which is associated with limonite and found in zones of aqueous alteration). Rare accessory phases are apatite and pentlandite, which are uncommon in L6 chondrites. Major mineral constituents (olivine, orthopyroxene, and plagioclase) indicate shock effects at a level of about 15–20 GPa shock pressure. The meteorite is thus classified to be of L6d type. Melt pockets of widely variable composition are abundant.

Laboratory shock emplacement of noble gases, nitrogen, and carbon dioxide into basalt, and implications for trapped gases in shergottite EETA 79001

Basalt samples have been analyzed mass spectrometrically for shock-implanted noble gases, N 2, and CO 2 after exposure to 20–60 GPa (200–600 kbar) shock in the presence of .0045–3.0 atm of ambient gas. Isotopically labelled gases were used in some samples to distinguish implanted atmospheric gases from contaminant or indigenous gases. Abundances of emplaced gases varied linearly with ambient gas pressure for constant shock pressure, and gas emplacement was most efficient in the range of 35–50 GPa shock pressure. Uncrushed samples shocked in this range gave emplacement efficiencies (number densities of gases in shocked samples/number densities in ambient gas) of 2.0–6.7% for heavy noble gases and nitrogen, while powdered samples with higher effective porosity yielded 40–50% efficiencies, indicating that ~50% of noble gases and nitrogen available in porespaces was emplaced. No elemental or isotopic fractionation was detected with Ar, Kr, Xe, or N 2. Helium and, in some samples, Ne were lost by diffusion subsequent to shock. Emplacement efficiencies for CO 2 averaged a factor of 1.8 ± 0.2 greater than those of N 2 and noble gases in 4 samples with 20–50 GPa shock, and yielded 3.2 times greater efficiency in a sample shocked to 60 GPa. Enhanced CO 2 emplacement is thought to be due to reaction with silicate materials. Data from shergottite EETA 79001 glass may be consistent with CO 2 efficiencies a factor of 2–3 greater than noble gas efficiencies. Trapped gases in EETA 79001 glass were probably emplaced by shock. However, apparent emplacement efficiencies are somewhat higher than even shocked powder samples. Possible explanations for the difference include atmospheric overpressure at the time of shock, trapping of gas already in vugs by intruding melt material, or collapse of gas-filled vugs to form gas-laden glass inclusions. Not enough is yet known about the behavior of vugs under shock to discount the latter possibility.

High pressure infrared spectra of diaplectic anorthite glass

Samples of synthetic diaplectic anorthite glass (38 GPa shock pressure), thermal glass and synthetic anorthite crystals were investigated using infrared spectral methods at one atmosphere and high pressures (near 4 GPa). Band positions and pressure derivatives for the Si-O asymmetric modes in the region 1,300–900 cm−1 indicate that the diaplectic glass has more structural similarities with the crystalline material than with thermal glass even though the overall infrared spectral characteristics suggest a glassy state.

Molecular dissociation and shock-induced cooling in fluid nitrogen at high densities and temperatures.

Radiative temperatures and electrical conductivities were measured for fluid nitrogen compressed dynamically to pressures of 18-90 GPa (180-900 kbar), temperatures of 4000-14 000 K, and densities of 2-3 g/${\mathrm{cm}}^{3}$. The data show a continuous phase transition above 30 GPa shock pressure and confirm that ${(\frac{\ensuremath{\partial}P}{\ensuremath{\partial}T})}_{v}&lt;0$, as indicated previously by Hugoniot equation-of-state experiments. The first observation of shock-induced cooling is also reported. The data are interpreted in terms of molecular dissociation and the concentration of dissociated molecules is calculated as a function of density and temperature.

Shock effects in melilite

Shock recovery experiments on melilite samples in the pressure range from 11 to 50.5 GPa have been performed in order to examine the effects of shock waves on this material. The shocked samples were subsequently studied in the transmission electron microscope. All samples displayed the shock-induced amorphous areas, known as diaplectic glass. The amount of diaplectic melilite glass increased from a few percent at 11 GPa to about 85 percent at 50.5 GPa shock pressure. The shock waves also caused deformational effects as planar faults parallel to (001) and dislocations with a density in the order of 1010 cm−2. Regarding the present discussion on the origin and nature of diaplectic glass, diaplectic melilite glass is assumed to be the reversion product of a high-density phase produced in the shock front.

Preparation and magnetic properties of cobalt disulfide

A B2 Fe–40 at% Al–Zr–B iron aluminide was subjected to shock-wave (explosive) loading at ∼6 GPa shock pressure. The applied shock pressure was sufficient to generate high dislocation density in the material which, in turn, gave rise to primary static recrystallization process upon subsequent isothermal annealing at 700, 750 and 800°C for various lengths of time. At various annealing temperatures recrystallization occurs rather inhomogeneously. Nucleation occurs mostly at the triple points and grain boundaries, showing tendency for clustering. Recrystallization kinetics follows a general behavior according to the Johnson, Mehl, Avrami and Kolmogorov theory (JMAK) with the Avrami exponent, n∼2.3–2.9. The estimated apparent activation energy for recrystallization, ∼259 kJ/mol, is very close to the activation energy for self-diffusion in pure iron and iron in FeAl. The results of microhardness studies of partially recrystallized specimens indicate that the average Vickers microhardness values for recrystallized and unrecrystallized areas differ significantly, the former having higher microhardness. This phenomenon is discussed in terms of higher density of retained sinks for quenched-in vacancies in the unrecrystallized areas and lower efficiency of vacancy hardening.