Evaluation of Tensile and Thermal Properties of Alumite Using Al Alloy Specimen Having Anodized Layer

Abstract

Aluminum alloys used i internal combustion engines have been coated with an alumite layer. Conventionally, the alumite layer has been provided to suppress thermal cracking. Recently, it has been found that the alumite layer is effective in improving the thermal efficiency of internal combustion engines. To evaluate the strength reliability of those anodized parts, it is necessary to understand the tensile and thermal properties of anodized aluminum. In this study, we proposed a method based on the rule of mixtures to evaluate the tensile deformation behavior and the linear coefficient of expansion of the alumite. Al alloy specimens with and without anodized treatment were used to conduct tensile tests at R.T., 473 K, 573 K, 623 K, and linear expansion coefficient measurement tests. By using the stress-strain relations obtained from the tensile tests, the tensile stress-strain relations of the alumite layers were estimated and they were used to discuss the tensile characteristics of the alumite layers. As a result, the stress-strain relation and linear expansion coefficient of the alumite could be estimated. It was also found that the alumite has higher strength than Al alloys at RT., 473 K, 573 K, and 623 K.