Relationship between Specular Reflectance in Visible Light Range and Surface Roughness in AZ31 Magnesium Alloy Subjected to Acidic Aqueous Solution Treatment

Abstract

To develop an improved surface treatment for producing metallic luster on magnesium alloys by controlling surface roughness, we analyzed the angle of incidence c, the instrument acceptance angle Du and the root mean square slope m, for experimental results on specular glossiness Gs and root mean square roughness s. First, we derived a theoretical equation from the theory of electromagnetic waves and a model of surface roughness, assuming that the root mean square roughness is much smaller than the wavelength of the incident radiation. In this equation, the ratio R/R 0 of the specular reflectance of the specimens to the specular reflectance of a smooth surface indicates the sum of the specular reflection component and the scattering reflection component for the instrument acceptance angle. This reflectance is a function of the angle of incidence. In this study, angles of incidence of 20°, 60°and 85°were used. Next, the specular glossiness and the root mean square roughness were measured for the surface of AZ31 magnesium alloy specimens treated with acidic aqueous solution. The value of the root mean square slope was obtained from the theoretical equation and was compared with the experimental results. We found that the experimental results matched the results calculated for an angle of incidence of 20°. These results clarified that the reflectance R/R 0 is a function of s/l, the angle of incidence c, the instrument acceptance angle Du and the root mean square slope m. These results will be useful for developing better surface treatments for producing metallic luster on magnesium alloys. ( 1 )

Surface Treatment to Provide a Metallic Luster to AZ31 Magnesium Alloy

“…(1), 9) and found that the experiment results closely matched those obtained by the equation. Figure 3 shows the relation between R=R 0 and '=!…”

“…¼ 500 nm, of the optimum acid aqueous solution treatment was 0.029, and R=R 0 was 0.72. 9) This result shows the range where metallic luster is produced, and is shown in Fig. 3.…”

“…[2][3][4][5][6][7][8][9] We applied this treatment to a chassis, and formed a metallic luster on the entire chassis whole surface. To expand the design range of exterior parts, we maintained geometric patterns such as the hair line and blast finishing, etc.…”