陽極酸化処理層の有無が異なるAl試験片を用いたアルマイトの引張特性評価

抄録

Conventionally, anodizing treatments have been performed on aluminum alloy combustion chamber of internal-combustion engine to suppress occurrence of heat cracks. Recently, it has been found that the alumite layer formed by the treatments is effective in improving the thermal efficiency of internal-combustion engines. Therefore, some anodizing methods have been proposed to form thick alumite layers on aluminum alloy parts in internal combustion engines, and the parts made by the methods have already been put into practical use. To evaluate the strength reliability of those anodized parts, it is essential to understand the tensile characteristics of the alumite. In this study, we proposed a method based on the rule of mixtures (ROM) to evaluate the tensile properties of the alumite. Then, tensile tests were conducted using anodizing treated aluminum specimens and non-treated aluminum specimens. Before the tests, the thickness of the alumite layer in the anodizing treated aluminum specimen was measured by using X-ray CT, and it was used to estimate the area ratio of the layer in the cross-section of the specimen. By using the stress-strain relations obtained from the tensile tests with the estimated area ratios, the tensile stress-strain relations of the alumite layers were estimated and they were used to discuss the tensile characteristics of the alumite layers. In addition, the fracture surface was observed using a microscopy, to check a fracture morphology of the alumite. These results showed that the alumite had larger Young's modulus than Al, and was fractured for brittleness.