Investigation on the Relationship Between Transition Energy and the Color Change of Cu–M Alloys

A series of Cu–M color alloys were investigated with two additional elements, Zn and Ga, that have adequate solubility tocopper, which means that a wide region of solid-solution phase exists in the Cu-rich area in terms of color variation. Tomeasure the color change of the alloys, the reflectivity difference analysis, the color difference and the transition energywere utilized. As the amount of minor alloying elements increased, the proportional relationship was found between thetransition energy and the color difference compared to copper, for example, the color difference mounted with the increaseof transition energy. A significant color difference was found when gallium was employed as the minor element. In otherwords, the influence of gallium on the color change was more evident than with Zn. It appears to be about 4.5 of the colordifference when 3 at% of gallium was added.