Observations of partial dislocations and basal twin boundaries in shock-wave-deformed sapphire

Chen, S.-J.; Howitt, D. G.

doi:10.1080/01418619808241935

Cited by 9 publications

(7 citation statements)

References 14 publications

(5 reference statements)

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“…Inelastic behaviours include basal, prism and pyramidal slip and basal and rhombohedral twinning. Estimates of room temperature resistances to slip or twin initiation follow from nonlinear thermoelastic analysis and results of prior shock physics experiments (Barker & Hollenbach 1970;Graham & Brooks 1971;Chen & Howitt 1998;Hare et al 2002;Reinhart et al 2006). These estimates are combined with other existing data to provide yield criteria over a range of temperatures.…”

Section: Discussionmentioning

confidence: 99%

“…This agrees with experimental observations of 1=3! 1 100O partial dislocations in shockloaded crystals of the same orientation (Chen & Howitt 1998). Stresses that would cause twinning or shear fracture are depicted in figure 4b for a 608-oriented crystal.…”

Section: Application: Sapphire Single Crystalsmentioning

confidence: 99%

“…Driving forces for slip, twinning and fracture can be computed and compared with (4.1)-(4.3) and observations from shock physics experiments (Barker & Hollenbach 1970;Graham & Brooks 1971;Chen & Howitt 1998;Reinhart et al 2006) to provide more suitable estimates for yield and failure criteria. This analysis also provides insight into which inelastic deformation mechanisms are most likely responsible for macroscopic yielding in shock physics experiments.…”

Section: Application: Sapphire Single Crystalsmentioning

confidence: 99%

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A continuum description of nonlinear elasticity, slip and twinning, with application to sapphire

Clayton

2008

Proc. R. Soc. A.

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A model is developed for elasticity, plasticity and twinning in anisotropic single crystals subjected to large deformations. Dislocation glide and deformation twinning are dissipative, while energy storage mechanisms associated with dislocation lines and twin boundaries are described via scalar internal state variables. Concepts from continuum crystal plasticity are invoked, with shearing rates on discrete glide and twinning systems modelled explicitly. The model describes aspects of thermomechanical behaviour of single crystals of alumina over a range of loading conditions. Resolved shear stresses necessary for glide or twin nucleation at low to moderate temperatures are estimated from nonlinear elastic calculations, theoretical considerations of Peierls barriers and stacking fault energies and observations from shock physics experiments. These estimates are combined with the existing data from high-temperature experiments to provide initial yield conditions spanning a wide range of temperatures. The model reflects hardening of glide and twin systems from dislocations accumulated during basal slip. Residual elastic volume changes, predicted from nonlinear elastic considerations and approximated dislocation line energies, are positive and proportional to the dislocation line density. While the model suggests that generation of very large dislocation densities could influence the pressure-volume response, volume increases from defects are predicted to be small in crystals deformed via basal glide on a single system.

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Section: Discussionmentioning

confidence: 99%

Section: Application: Sapphire Single Crystalsmentioning

confidence: 99%

Section: Application: Sapphire Single Crystalsmentioning

confidence: 99%

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A continuum description of nonlinear elasticity, slip and twinning, with application to sapphire

Clayton

2008

Proc. R. Soc. A.

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“…Basal twins and partial dislocations in basal planes are two of the most commonly observed microstructures in shock-wave-deformed sapphire. Chen and Howitt [21] have found that the partial dislocations are the twinning dislocation for basal twins. A large volume of information about deformation mechanisms, including basal and pyramidal slips and basal and rhombohedral twins, in sapphire under hypervelocity impact has been obtained by means of molecular dynamic simulations [22].…”

Section: Introductionmentioning

confidence: 99%

“…Graham and Brooks then measured the Hugoniots of c-cut, a-cut (11)(12)(13)(14)(15)(16)(17)(18)(19)(20), and n-cut (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23) sapphire crystals [4]. The normals to the flat surfaces of a-cut and of n-cut crystals are parallel to the a axis and n axis, respectively.…”

Section: Introductionmentioning

confidence: 99%

Response of seven crystallographic orientations of sapphire crystals to shock stresses of 16–86 GPa

Kanel

Nellis

Савиных

et al. 2009

Journal of Applied Physics

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Shock-wave profiles of sapphire (single-crystal Al 2 O 3 ) with seven crystallographic orientations (c, d, r, n, s, g, and m-cut) were measured with time-resolved VISAR interferometry at shock stresses in the range 16 to 86 GPa. Shock propagation was in the direction normal to the surface of each cut. The angle between the c-axis of the hexagonal representation of the sapphire crystal structure and the direction of shock propagation varied from 0 for c-cut up to 90 degrees for m-cut in the basal plane. Based on published shock-induced transparencies for 3 directions of shock propagation, shock-induced optical transparency correlates with the smoothness of the mechanical shock-wave profile. The ultimate goal was to find the direction of shock propagation for which shock-compressed sapphire is most transparent as a window material. In the experiments particle velocity histories were recorded at the interface between a sapphire crystal and a LiF window. In most cases measured wave profiles are noisy as a result of heterogeneity of deformation. Measured values of Hugoniot Elastic Limits (HELs) depend on direction of shock compression and peak shock stress. The largest HEL values (24 GPa) were recorded for shock loading along the c-axis and perpendicular to c along the m-direction. Shock compression along the m-and s-directions is accompanied by the smallest heterogeneity of deformation and the smallest rise time of the plastic shock wave. m-and s-cut sapphire most closely approach ideal elastic-plastic flow, which suggests that m-and s-cut sapphire are probably the sapphire orientations that remains the most transparent to the highest shock pressures. Under purely elastic deformation sapphire demonstrates very high spall strength, which depends on both load duration and peak stress. Plastic deformation of sapphire causes loss of its tensile strength.2

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Reactions of Ceramics: Oxides, Nitride, Carbide, Sulfides, etc.

Sekine

2024

Shock Wave and High Pressure Phenomena

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Observations of partial dislocations and basal twin boundaries in shock-wave-deformed sapphire

Cited by 9 publications

References 14 publications

A continuum description of nonlinear elasticity, slip and twinning, with application to sapphire

A continuum description of nonlinear elasticity, slip and twinning, with application to sapphire

Response of seven crystallographic orientations of sapphire crystals to shock stresses of 16–86 GPa

Reactions of Ceramics: Oxides, Nitride, Carbide, Sulfides, etc.

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