TWINNING THRESHOLD MODELING. QUASI-ICE VS. SHOCK. OBJECTIVES: Understanding deformation mechanisms of  Cu under various high-pressure and high-strain rate loading conditions. Microstructural characterization.
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QUASI-ICE VS. SHOCK
Shock: Instantaneous loading.
Quasi-ICE: Controlled “ramped” loading.
Slices cut from
Where and are work hardening saturation stress and yield stress, respectively.
is the value of taken at zero temperature, , θ are the strain and work
hardening rate, respectively, and p is a dimensionless material parameter.
Dislocation cell size vs. distance from sample free surface:
Cell size vs. pressure: quasi-ICE,
laser shock and flyer-plate
Strong Shock Regime
Thermal Activation Regime
Strain-rate regimes in shock and Quasi ICE-Gas-Gun
Dislocation sell size vs. distance from sample free surface:
Temperature rise in shock and ICE (gas-gun)
Hardness, Temp. vs. Peak Pressure: Gas-gun quasi-ice
Source: M.Pullington et al., Discovery.
TRANSMISSION ELECTRON MICROSCOPY (TEM) OF KEY FEARURES AT:
Twinning at 52GPa
Dislocated laths at 34GPa
Stacking faults at 26GPa
Flow stress vs. peak pressure: gas-gun modeling
Flow stress vs. peak pressure: laser modeling
CONCLUSIONS AND FUTURE WORK
Dislocation cells at 18GPa
Dislocation cells and stacking
faults at 24GPa
Twins/laths at 59GPa
Stacking faults at 30GPa
Micro-twins at 57GPa
(Experimental data unavailable)
Staking faults at 40GPa
Dislocation cells at 20GPa
Micro-twins at 55GPa
This work was performed under the auspices of
the U.S. Department of Energy by University of
California, Lawrence Livermore National