New model for strengthening by dislocation nucleation in nanoscale in situ composite microwires

In situ fibre-reinforced composites are prepared by very heavy straining that elongates the minor phase into very fine ribbons, producing materials of extremely high strength. Strengthening is usually explained by the many geometrically necessary dislocations or by pile-ups produced at the many interfaces. It is shown here by transmission electron microscopy that nanoscale ribbons become dislocation-free and the matrix too fine to accommodate dislocation substructures. A modified strengthening model is proposed based on ribbons having the ideal strength in the substructure-free matrix.