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Possible Micromechanical Model For Microtwinning

Possible Micromechanical Model For Microtwinning. Possible Micromechanical Model For Microtwinning. Energy of the 2-layer pseudotwin (~600 mJ/m 2 ?). Energy of the 2-layer true twin (15 mJ/m 2 ?). Possible Micromechanical Model For Microtwinning.

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Possible Micromechanical Model For Microtwinning

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  1. Possible Micromechanical Model For Microtwinning

  2. Possible Micromechanical Model For Microtwinning Energy of the 2-layer pseudotwin (~600 mJ/m2 ?) Energy of the 2-layer true twin (15 mJ/m2 ?)

  3. Possible Micromechanical Model For Microtwinning Energy of the 2-layer pseudotwin (~600 mJ/mol?) Energy of the 2-layer true twin (15 mJ/mol?)

  4. Possible Micromechanical Model For Microtwinning A pair of identical Shockleys on adjacent slip planes At steady state doing a work balance for a forward progress of b, we get: d2 t =Applied Stress b = Burgers Vector g(t) = Fault Energy gpt =Pseudo Twin Energy gtt = True Twin Energy K = Parameter determining the reordering kinetics (K=Dord/x2, where x is a measure of the short range diffusion length) t = time l Secondaries sheared athermally creating faults that eventually reorder into true twins Tertiaties sheared athermally creating pseudotwins Unsheared g’

  5. Possible Micromechanical Model For Microtwinning • Velocity for diffusion-mediated glide: • Assumptions: • the energy penalty due to the twin decreases exponentially with time • the shear of secondary g’ is thermally assisted while the shear of tertiary g’ is athermal. • the effective stress driving the shear of the secondary g’ is given by: • Strain rate: Microstructure Parameters: Obtain from direct TEM measurements Key Model Parameters: Obtain from transient creep experiments or modeling

  6. Possible Micromechanical Model For Microtwinning Applied Stress = 420 MPa Temperature = 950K gpt = 300 mJ/m2 gtt = 20 mJ/m2 Dord/x2 = 0.18/s Friction Stress = 25 MPa Applied Stress = 420 MPa Temperature = 950K gpt = 300 mJ/m2 gtt = 20 mJ/m2 Dord/x2 = 0.18/s Friction Stress = 25 MPa Effective stress dependence on tertiary volume fraction (for a given applied stress) Velocity dependence on tertiary volume fraction (for a given applied stress)

  7. Possible Micromechanical Model For Microtwinning Temperature = 950K gpt = 300 mJ/m2 gtt = 20 mJ/m2 Dord/x2 = 0.18/s f2 = 0.3 Friction Stress = 25 MPa Dislocation velocity vs Effective Stress. Stress exponent of velocity for low stresses is very close to unity. When the stress is large enough to athermally shear the secondaries, then there is “power-law” breakdown.

  8. Possible Micromechanical Model For Microtwinning If tertiary volume fraction is assumed to drop exponentially with time, then the transient creep behavior can be predicted

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