To realize a carbon-neutral society, metallic materials must have higher strength and ductility. This research improves the mechanical functionality of metallic materials by controlling high-density lattice defects using high-pressure torsion (HPT), a type of severe plastic deformation, and heavy cold rolling (CR), which is widely used in industry as microstructure control methods other than conventional alloy composition and heat treatment. It can also control microstructures through processing and heat treatment with HPT and CR. We are working to improve the mechanical functionality of metallic materials by controlling the microstructure through heat treatment.

Metallic materials are known for their properties being degraded by various factors. These include stress corrosion cracking, creep fracture, and low-temperature embrittlement. The higher the strength of a metallic material, the more likely brittle fracture is to occur due to hydrogen accumulation at stress concentrations. Furthermore, with the development of new processing methods, such as giant strain processing in recent years, there have been many reports of unique strengthening and deformation mechanisms that have never been reported before, and evaluation of hydrogen embrittlement resistance properties is required. This study focuses on alloy compositions, fabrication processes such as high-pressure torsion (HPT) and intense cold rolling, and heat treatment processes such as solution annealing and aging to evaluate microstructural conditions and hydrogen diffusion/trap sites within the material for superior resistance to hydrogen embrittlement. We are researching microstructure control methods to suppress hydrogen embrittlement of high-strength metallic materials.