Interaction élastique dislocation – joints interphases dans des matériaux de structure cubique à faces centrees
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The majority of materials mechanical properties are due to the crystalline defects interactions, in particular the interaction between dislocations and interfaces. The interaction energy between a dislocation and an interphase boundary is calculated on the basis of the anisotropic linear elasticity. Dislocations in elastic interaction with the interphase boundary are submited to a force called the image force, Fi ,which is derived from the elastic interaction energy. The image force by its sign and intensity can predict the dislocation behavior. The elastic interaction energies are calculated for biphase bicrystals CFC materials, Pb, Al, Au, Ag, Cu and Ni, between matrix dislocations having Burgers vector b = a/2, and interphase boundaries (R, ), with R =  and is in the range [0 °, 90 °] varying by steps of 10 °. Dislocations are located in the crystal 1 at a distance d from the boundary plane, they are parallel to the boundary plane. The main results are: - For each bicrystals family, the intensity of the image force Fi increases with shear moduli difference . It may be null for some dislocations, in bicrystals having elastic and crystallographic parameters very close. - The dislocation motion under image force effect depends on the value of if: > 1, all dislocations in the softest crystal are repelled far from the interface. <-1, all dislocations in the harder cristal, are attracted to the interface. -1 <1, the located dislocation in the crystal 1 can be attracted, repulsed or don’t suffers no image force. The number and the character of dislocations with, Fi = 0, is related to the two crystals nature and disorientation. - The image force Fi is constant for a screw dislocation parallel to the rotation axis . - The isoenergy cards have different symmetries according to the bicristal disorientation. - For each bicrystal family, image force distance effectiveness is related to absolute value of shear moduli difference. - The position of the dislocation and the image forces sense Fi-Sh1 et Fi-Sh2 favoured recombination of partial dislocations or dissociation of the perfect screw dislocation.
- Doctorat (Physique)