Ultrafine‐Grained Laminated Metal Composites: A New Material Class for Tailoring Cyclically Stressed Components

Abstract

The service life of technical components is often limited by the fatigue strength of the deployed materials. The accumulative roll bonding (ARB) process, which has the ability to produce ultrafine‐grained (UFG) laminated metal composites with tailored properties, offers a unique method to significantly enhance the fatigue life of materials that are cyclically loaded in three‐point bending. Detailed microstructural investigations reveal the material‐ and load‐specific deformation and damage mechanisms. Composites that have a sufficiently high difference in strength between the different constituent layers exhibit a significantly impeded crack growth and therefore an extended fatigue life at high stress amplitudes compared with those laminates with a rather similar strength of the different constituents. In the former composites, the fatigue crack is deflected at the material interface as it propagates from the softer to the harder layer. At low stress amplitudes, a prolonged fatigue life of the composites is mainly because of a significantly increased resistance to crack initiation. On the one side, this is as a result of the introduction of an UFG microstructure. On the other side, a load transfer toward stiffer layers in the interior of the composites also accounts for the enhanced fatigue life, if elastically dissimilar materials are combined in the right manner.