An Al-20 vol% Sn metal-metal composite was deformation processed by extrusion, swaging, and wire drawing to a total true strain of 7.4, resulting in a microstructure with Sn filaments in an Al matrix. Both the size and spacing of the Sn filaments decreased as deformation processing progressed. The strength of these composites increased exponentially with the reduction in spacing of the Sn filaments. Immediately after deformation, the Sn second phase showed a convoluted, ribbon-shaped filamentary morphology, but the Sn filaments spheroidized during prolonged storage at room temperature. A thermodynamic assessment is presented for this spheroidization phenomenon.