Metal Matrix Composites from Severe Plastic Deformation by the Example of High-Pressure Torsion as a Promising Tool to Manufacture Smart Materials

High-pressure torsion (HPT), a method of severe plastic deformation, allows to alloy even immiscible phases to supersaturated nanocrystalline (nc) solid solutions and to produce bulk material of metal matrix composites (MMCs) with a nc matrix with out additional thermal load. With the aim of producing MMCs with functionalized ceramic particles (so-called intelligent or smart materials) a large variety of ceramic dispersoids was shown to be susceptible for the incorporation into a metallic matrix by HPT, independent of the mechanical contrast of the individual phases with a well engineered process route. The dispersoids are partially broken to a stabilized geometry and are finely dispersed. However, the microstructure evolution in the vicinity of these inclusions is strongly affected by the mechanical contrast between dispersoids and matrix material. For the material performance, especially in case of fatigue, a strong cohesion between matrix and particles is essential to avoid crack initiation. This interfacial cohesion was characterized by micro-beam bending fracture tests. The thermal stability of the microstructure was investigated by in situ heating in the SEM and examined regarding Zener pinning. The ceramic particles significantly influence the thermal stability compared to particle-free reference material.