Composite structures and methods of their manufacture are provided. In one embodiment, the composite structure includes a substrate which includes a relatively soft material, and nanoparticles which include a relatively hard material and which are embedded (i) within at least a surface region of the substrate, or (ii) uniformly within and throughout the substrate, in an amount effective to improve the wear resistance of the substrate. Methods for forming these composite structures include a hot-rolling process, a roll-bonding process, or a combination thereof.