Development of super-strong high entropy alloys by a novel hybrid processing route

Super strong structural materials have gained greater attention in recent years. Novel thermomechanical processing strategies have high prominence in the development of advanced materials with heterogeneous microstructures. High entropy alloys (HEAs) were one of the new classes of materials that have shown superior mechanical properties development. We highlight the opportunities of combining the novel processing strategies with HEAs for developing super strong materials. In the present study a novel lamellar AlCoCrFeNi_2.1 eutectic HEA (EHEA) consisting of L12 and B2 phase was severely deformed by the unique hybrid-rolling process strategy consisting of cryorolling followed by warm-rolling imparting equal true strain in both steps. An extremely heterogeneous microstructure featured by retained lamellar and transformed nanocrystalline regions was achieved by this novel processing approach. The novel dual structure-compositional heterogeneous microstructure originated from the stored energy of the cryo-rolling stage, which accelerated the microstructural and phase transformations during subsequent warm-rolling at 600 °C while minimizing the grain and phase growth. The unique dual heterogeneous microstructure resulted in super-strong material with an outstanding combination of strength (~2000 MPa) and ductility (~8%). We further compare the properties developed by using this processing strategy with existing technologies and give a comprehensive overview. (author)