Nanosecond white-light Laue diffraction measurements of dislocation microstructure in shock-compressed single-crystal copper

Abstract

Under uniaxial high-stress shock compression it is believed that crystalline materials undergo complex, rapid, micro-structural changes to relieve the large applied shear stresses. Diagnosing the underlying mechanisms involved remains a significant challenge in the field of shock physics, and is critical for furthering our understanding of the fundamental lattice-level physics, and for the validation of multi-scale models of shock compression. Here we employ white-light X-ray Laue diffraction on a nanosecond timescale to make the first in situ observations of the stress relaxation mechanism in a laser-shocked crystal. The measurements were made on single-crystal copper, shocked along the [001] axis to peak stresses of order 50 GPa. The results demonstrate the presence of stress-dependent lattice rotations along specific crystallographic directions. The orientation of the rotations suggests that there is double slip on conjugate systems. In this model, the rotation magnitudes are consistent with defect densities of order 10 12 cm À 2 .

Single Hit Energy-resolved Laue Diffraction

“…The resulting Laue spots are a) Now at: Institute for Shock Physics, Washington State University, Pullman, Washington, 99164-2816, USA b) Now at: York Plasma Institute, University of York, Heslington, YO10 5DD, UK recorded on image plate based detectors, with their positions related to the orientation of the diffracting lattice planes 17 . This ability to record plane orientation allows access to information on symmetry of the unit cell, and in the context of laser compression, has been used successfully to infer strength 18 and defect mediated lattice rotation 19 . However, as only plane orientation and not spacing can be determined from this technique, a full determination of volumetric compression, a key quantity for the interpretation of data, is lacking.…”

Femtosecond X-Ray Diffraction Studies of the Reversal of the Microstructural Effects of Plastic Deformation during Shock Release of Tantalum

“…Here we use XRD to directly monitor lattice orientations during shock release. The technique of in situ XRD to study shock-compressed materi-als has been developed over several years utilizing a number of different shock drivers and x-ray sources, including diodes [24][25][26][27], laser-produced-plasmas [28][29][30][31][32][33] and 3 rd generation synchrotrons [34][35][36][37]. More recently, with the advent of 4 th generation light sources such as the Linac Coherent Light Source (LCLS) single-shot 100-fs diffraction patterns can be obtained from laser-shocked crystals, providing lattice-level information on a timescale shorter than even the fastest phonon period [38][39][40][41][42][43].…”

“…As has been shown in [43] under [110] compression in these samples, the shock-induced shear stress is relieved by either slip on {112} 111 system or {112} twinning. Since the material is laterally confined, in order to preserve the geometry of uniaxial compression, both slip and twinning induce crystal lattice rotations [31,43,50] about [110] which can be directly related to the amount of shear stress relieved.…”

Collective nature of plasticity in mediating phase transformation under shock compression

“…It is well known that if a material undergoes shock compression beyond the Hugoniot elastic limit, it exhibits rapid plastic flow which is expected to occur via the generation and propagation of defects (twin, dislocations, etc.) [1,[6][7][8][9][10], and possible phase transformations [11][12][13][14]. In the presence of large peak stresses, strain rates, and significant inelastic strain due to shock, these plastic deformation modes can differ from those observed under longer time scales or more quasistatic conditions [1,6], and may interact with the phase transformations [15,16].…”