Metal–Matrix Composites from High‐Pressure Torsion with Functionalized Material Behavior

Abstract

In composites, outstanding properties of two materials can be combined. In particular, metal–matrix composites (MMCs) can combine the properties of a high-strength ductile metallic matrix with special properties of embedded ceramic particles. This hybrid can be used to create a functional material. However, during consolidation, the thermal load of most common MMCprocessing routes is an obstacle for such functionalization, because the unique properties of the ceramic phases most likely degrade. Mechanical alloying, in this case, by high-pressure torsion (HPT), can overcome this challenge. Herein, the attempt to obtain smart materials through HPT processing is aimed. For that purpose, Cu-MMCs are produced from mixed powders with ZrO2 and BaTiO3 (BTO) with the challenge to incorporate their functional phase. BTO can provide a sensing ability for internal stress and ZrO2 can provide a fatigue lifetime by a retarded crack growth. The amount of the stabilized phase is evaluated by X-ray diffraction. Cu–BTO–MMCs exhibit a local piezoelectric effect when strained, shown by in situ scanning Kelvin probe force microscopy. Cu–ZrO2–MMCs feature a retarded fatigue crack initiation and an earlier crack closure during fatigue crack growth due to the volume expansion once ZrO2 transforms.