Recent development of coloring alloys

In this study, we systematically reviewed the strategy of the tailoring intrinsic color characteristics of chromatic and achromatic metallic materials. Its scientific contribution involves defining and expanding the range of coloration of metallic materials, including single-phase solid-solution alloys and multiphase alloys that includes specific phases with chromatic colors. In chromatic single-phase alloys, the modulation of optical properties depends on the transition energy of the solid solution phase. The additional alloying elements significantly influence the optical properties, i.e., the reflectivity in the visible spectrum, by varying the transition energy of the solid solution phase. Another coloring alloy design strategy varies and realizes the intrinsic color based on the multiphase system. In particular, the microstructural design based on the multiphase forming alloy system, including the chromatic coloring phase, effectively improves the chromaticity of the alloys by blending effect from the constitutive phases. A methodological framework is subsequently suggested to realize chromatic characteristics based on the juxtaposition method. The novel alloy design method using the juxtaposition method can be considered an important strategy for developing novel coloring alloys with high chromatic color durability from achromatic metallic materials.