Dislocation dynamis studies of dislocation interaction in 位错动力学的研究中的位错的相互作用

1、dislocation dynamics studies of dislocation interaction in multilayers urop 03 stage ii presentationbyrajlakshmi purkayastha (04011013)under the guidance ofprof. prita pantmetallurgical engineering and materials science departmentiit bombayoutlineintroduction and backgroundimage forcesinterface stre

2、ngthstrengthening mechanisms in multilayersconclusionsintroduction : multilayersa series of thin films of different materials deposited on top of each otherextraordinary strength, hardness, friction and wear, higher temperature operation, corrosion resistance, fracture toughness, low electrical resi

3、stivity, heat-resistancee.g. nicraly bondcoat used as a thermal coating for turbine bladeshigher strength-to-weight ratios co-ni multilayers(http:/cms.tnw.utwente.nl/magnetic_multilayers/magn_mult.htm)introduction : experimental vs simulationexperimental results a. misra, m. verdier, y.c. lu, h. kun

4、g, t.e. mitchell, m. nastasi, j.d. e embury. scripta materialia, 39(4/5):555-560, 1998.simulation results f. akasheh ,h. m. zbib, j. p. hirth, r. g. hoagland, and a. misra. journal of applied physics, 101:08414, 2007.introduction : problem formulationcopper nickel two layers each 400 nm thickeach ha

5、ving different moduli (cu =41.35 gpa , ni = 80.15 gpa)sharp interface with misfit dislocations factors to be considered while determining strengthening mechanismimage forcesinterface strengthdislocation interactions outlineintroduction and backgroundimage forcesinterface strengthstrengthening mechan

6、isms in multilayersconclusionsimage forces : theory (a) a screw dislocation placed at distance -x from the interface, along the z axis. (b) dislocation and its image which produce the stress for x0.origins :motion of a dislocation towards a free surfaceviolate laws of conservationconcept of an image

7、 dislocation, from electrostaticson left side :on right side : image forces : koehler barrierscrew dislocationedge dislocationnet stresswhere, 1image forces : simulation resultsscrew dislocationmixed dislocationimage forces : simulation resultsscrew dislocationmixed dislocationoutlineintroduction an

8、d backgroundimage forcesinterface strengthstrengthening mechanisms in multilayersconclusionsinterface strength : misfitsmisfit dislocations at the interface of two crystal lattices with a 0.05 mismatch www.tf.uni-kiel.de/matwis/amat/semien/kap5/illustr/mistdislocations.gif spacing of dislocation arr

9、ay is interface strength : resultsloop percolating throughinterface strength : resultsinterface strength vs misfit dislocation spacing cu-ni interface cu-cr interfaceinterface strength : comparisonarray of misfit dislocationsstrength arrived at = 975 mpaliterature : 1100 mpa from atomistics simulati

10、onscomparison with literature hoagland rg, mitchell te, hirth jp, kung h. philos mag a 2002;82(4):643.outlineintroduction and backgroundimage forcesinterface strengthstrengthening mechanisms in multilayersconclusionsstrengthening mechanisms self stress due to curvature of the loop image forces repul

11、sion due to the array of misfit dislocations at the interface interactions between different dislocations in the same layerstrengthening mechanismsall factors combinedstrengthening mechanisms: dislocation interactionsordered systemsemi-random systemstrengthening mechanisms: dislocation interactions2

12、0 loops completely random (a) initial configuration (b) some loops start shrinking(c) some loops have already begun to merge with each other (d) activity starts to take place at the interface (e) loops merge at the interface (f) more loops collidestrengthening mechanisms: dislocation interactionsa c

13、lose up the interface interactions (a) the blue loop in the copper layer is very close to the red loop in the nickel layer. (b) the loop is so close that the motion of the red loop is hindered. however the blue loop in the nickel layer advances.(c) the two blue loops merge (d) as the merged loop starts moving away , the red loop can now advance.strengthening mechanisms: image forcescomparison to see the effect of image