The absence of thermal expansion mismatch strengthening in nanostructured metal–matrix composites

A bulk particulate reinforced nanostructured metal–matrix composite (MMC) was synthesized via cryomilling and consolidation. The effect of thermal expansion mismatch strain on strengthening was investigated in detail. The results indicate that, unlike in conventional coarse-grained MMCs, thermal expansion mismatch strengthening does not occur. Transmission electron microscopy demonstrates that formation of geometrically necessary dislocations is constrained to a nanostructured interfacial layer with grains ∼30–50 nm in size, thus limiting strain hardening in the bulk region of the matrix.