Studies of dynamic properties of shock compressed single crystals by in situ dynamic x-ray diffraction and sample recovery

Meyers, Marc A. ; Schneider, M. S. ; Jarmakani, H. ; Kad, B. ; Remington, B. A. ; Kalantar, D. H. ; McNaney, J. ; Cao, B. ; Belak, J. ; E Bringa, G. Collins ; Paisley, D. ; Holian, B. ; Lomdahl, P. ; Boehly, T. R ; Wark, J.

关键词: ENERGY LEVELS;    MECHANICAL PROPERTIES;    STACKING FAULTS;    TRANSMISSION ELECTRON MICROSCOPY;    X-RAY DIFFRACTION;    MONOCRYSTALS Shock Compression;    Laser Shock;    Copper;    Single Cry;   

DOI  :  10.2172/909884
RP-ID  :  DOE--FG03-03SF22694
PID  :  OSTI ID: 909884
Others  :  TRN: US0805842

美国|英语

来源: SciTech Connect

【 摘 要 】

Laser compression provides pressures ranging from a few to hundreds of GPa at pulse durations of the order of nanoseconds or fractions thereof. The short duration ensures a rapid decay of the pulse and quenching of shocked sample in times that are orders of magnitude lower than in conventional explosively driven plate impact experiments. Systematic experiments carried out in specimens well suited for transmission electron microscopy characterization are revealing that laser compression, by virtue of a much more rapid cooling, enables the retention of a deformation structure closer to the one existing during shock. The smaller pulse length decreases the propensity for localization. Copper and copper aluminum (2 and 6 wt% Al) with orientations [001] and [ ] were subjected to high intensity laser pulses with energy levels of 70 to 300 J delivered in a pulse duration of approximately 3 ns. Systematic differences of the defect substructure were observed as a function of pressure and stacking fault energy. The changes in the mechanical properties for each condition were compared using micro- and nano-hardness measurements and correlated well with observations of the defect substructure. Three regimes of plastic deformation were identified and their transitions modeled: dislocation cells, stacking faults, and twins. An existing constitutive description of the slip to twinning transition, based on the critical shear stress, was expanded to incorporate the effect of stacking-fault energy. A new physically-based criterion accounting for stacking fault energy was developed that describes the transition from perfect loop to partial loop homogeneous nucleation, and consequently from cells to stacking faults. These calculations predict transitions that are in qualitative agreement with the effect of SFE.