Real time synchrotron x-ray diffraction measurements to determine material strength of shocked single crystals following compression and release

Abstract

We present a method to use real time, synchrotron x-ray diffraction measurements to determine the strength of shocked single crystals following compression and release during uniaxial strain loading. Aluminum and copper single crystals shocked along [111] were examined to peak stresses ranging from 2 to 6 GPa. Synchrotron x rays were used to probe the longitudinal lattice strains near the rear free surface (16 and 5 μm depths for Al and Cu, respectively) of the metal crystals following shock compression and release. The 111 diffraction peaks showed broadening indicating a heterogeneous microstructure in the released state. The diffraction peaks also shifted to lower Bragg angles relative to the ambient Bragg angle; the magnitude of the shift increased with increasing impact stress. The Bragg angle shifts and appropriate averaging procedures were used to determine the macroscopic or continuum strength following compression and release. For both crystals, the strengths upon release increased with increasing impact stress and provide a quantitative measure of the strain hardening that occurs in Al(111) and Cu(111) during the shock and release process. Our results for Al(111) are in reasonable agreement with a previous determination based solely on continuum measurements. Two points are noteworthy about the developments presented here: Synchrotron x rays are needed because they provide the resolution required for analyzing the data in the released state; the method presented here can be extended to the shocked state but will require additional measurements.

Shock compression modeling of metallic single crystals: comparison of finite difference, steady wave, and analytical solutions

“…Here, following the latter approach, H has been calibrated such that cumulative plastic deformation predicted by the analysis for 5 and 25 GPa shocks is in relatively close agreement (within ≈20% error) with that predicted by SW and FD models, as is evident from Tables 6 and 7. Results for all end state variables and shock velocity are nearly equal for FD and (48) [18,19,[35][36][37][38][39] indicative of viscoplastic relaxation rates (e.g., strength, precursor decay, wave profiles in single crystals and polycrystals) in previous publications [6,10], these numerical results are deemed physically accurate. Results for volumetric compression ratio, adiabatic temperature rise, particle velocity, and shock velocity obtained from the analytical solution are also very close to corresponding numerical results, and effective plastic strain is reasonably close as noted already, although it is reiterated that the hardening parameter H entering the analytical method is obtained by fitting plastic deformation to the FD results.…”

“…Concluding discussion follows in "Conclusion". The material of study is pure aluminum [Al, face centered cubic (FCC) structure], which is advantageous because of the extensive data available for its thermoelastic and shock response [17][18][19], and because it typically does not undergo twinning which would require more elaborate constitutive theory [20] than that employed herein.…”

Shock-compressed graphite to diamond transformation on nanosecond time scales

“…Regarding microscopic mechanisms, wave profile measurements and analyses reported here will need to be augmented with real-time x-ray diffraction measurements 44,45 and related analyses in shock compression experiments. Such developments are now underway.…”

Nanosecond x-ray Laue diffraction apparatus suitable for laser shock compression experiments

“…One area where these methods, such as time-resolved nanosecond x-ray diffraction and extended x-ray absorption fine structure ͑EXAFS͒, have been successfully applied is the study of materials during the passage of a shock wave, [1][2][3][4][5][6][7][8][9][10][11][12] and much has been learnt about both rapid plastic deformation of materials, as well as the mechanisms underlying shock-induced polymorphic phase transitions.…”

“…14 The x-rays emitted by individual electron bunches within a synchrotron have also been shown to be sufficiently bright to enable single shot diffraction patterns from shocked crystals to be registered. As well as the use of a variation on the diverging beam geometry using monochromated x-rays ͑⌬ / Ϸ 10 −4 ͒, 11,15 it has also been demonstrated that a quasiwhite beam ͑⌬ / Ϸ 0.15͒ can be used at a high photon energy to produce Laue patterns of shocked single crystals. 16 Each source and geometry type has its merits: the potential advantages of the white-light Laue technique is that it is well suited to detecting changes in unit-cell shape, which provides information about the degree of strength of a material subject to uniaxial compression, and unit-cell symmetry, which gives important information about the crystalline phase.…”