Useful functions of hydrogen in materials are studied. (a) Simultaneous improvements of electrical conductivity and mechanical strength for Cu–3mass%Ti hydrogenated alloy were achieved. The hydrogenation reaction proceeds within the range of spinodal decomposition temperature, and then the tensile strength of the alloy was increased. (b) Hydrogen-treatment for a β-rich α + β type Ti–4.5Al–3V–2Mo–2Fe alloy yields the fine grain with the size of about 0.3 μm. This alloy exhibited the high superplastic elongation of 10,600% at 923 K. (c) Pressure induced magnetic phase transition of hydrogenated La(Fe x Si 1− x ) 13 compounds was applied to magnetostrictive stress-sensor. (d) Ordering and Catalytic activity of CuPd nanoalloys are promoted by hydrogen treatment.
