Martensitic transformation of γ-Fe particles during compression of Cu-Fe single crystals in connection with prior coherency loss

Deformation induced martensitic transformation in gamma -Fe particles embedded in copper single crystals was studied in compression at 77K. The three kinds of particles were identified after straining: transformed alpha -Fe particles and coherent and semi-coherent gamma -Fe particles. It is suggested, based on the structural observations of these particles, that coherency loss in gamma -Fe particles can take place prior to the MT. The critical diameters for coherency loss coincide with those calculated from the formula for coherency loss induced by plastic deformation given by Brown. The dependence of MT on gamma -Fe particle size may, therefore, be explained on the relation to particle coherency loss relative on the particle size. The influence of interface dislocations in semi-coherent gamma -Fe on MT should be further examined together with a model of MT assisted by the shear stress of moving dislocation.