Method for forming a metal matrix composite structure

A method for friction stir forming a metal matrix composite (MMC) structure, the method including the steps of:

• a) providing a substrate comprising a metallic material and securing a preformed MMC layer comprising an MMC material in a position overlying at least a portion of the substrate;
• and
• b) friction stirring the preformed MMC layer with a friction stirring tool which includes a rotating probe, including locating the probe at a stirring depth at which the probe extends through the preformed MMC layer into a portion of the substrate and passing the rotating probe through the preformed MMC layer at the stirring depth to friction stir the preformed MMC layer and integrate the preformed MMC layer with the substrate;
• wherein the rotating probe is passed through the preformed MMC layer along an overlapping stir path and wherein the stir path is configured to relocate defects to an edge of the MMC structure to facilitate subsequent removal.