High-strength materials:: in-situ investigations of dislocation behaviour in Cu-Nb multifilamentary nanostructured composites

The fundamental mechanisms of the deformation of heavily deformed multiphase materials are not clearly understood despite the vast literature and the amount of data on this subject. This paper presents a new plastic flow mechanism observed by in-situ transmission electron microscopy deformation on Cu-Nb continuous multifilamentary nanostructured composites. The observed mechanism is interpreted in terms of dislocation loops nucleating in closely spaced parallel planes in the Cu channels. This behaviour explains many previous observations made on such composites such as the semicoherency of the interface and the 4degrees disorientation between the two phases. The modelling of the loop mechanism predicts the strength of the Cu-Nb nanocomposites. The very good agreement between the model and the experimental data suggests that the assumptions based on the in-situ observations are valid. The basic aspects of codeformation of fcc-bcc nanostructured systems are reviewed in this new context.