Metallurgical Alchemy by Ultra-Severe Plastic Deformation via High-Pressure Torsion Process

Ultra-severe plastic deformation (ultra-SPD) is defined as the SPD processes in which the shear strains over 1,000 are introduced to a work piece.Despite significant activities on various SPD processes, limited studies have been conducted on the behavior of materials at shear strains over 1,000.The main reason for such limited studies is a consensus that the microstructural, mechanical and functional features usually saturate to the steady states at shear strains below 100.However, recent studies using the high-pressure torsion (HPT) method confirmed that significant changes occur at shear strains in the range of 1,000100,000.Here, some of the main findings reported recently by the application of ultra-SPD are reviewed: appearance of new levels of steady-state microhardness, atomic-scale elemental mixing in the miscible and immiscible systems, formation of new nanostructured phases / intermetallics, achievement of ultrahigh strength / high plasticity / room-temperature superplasticity, and development of advanced superconductors and hydrogen storage materials.[