Study on the anodic oxidation performance of a rolled AA5252 aluminum alloy sheet with different thicknesses

Microstructures of AA5252 aluminum alloy sheets from surface to the center were observed by use of scanning electron microscope with electron backscatter detector assembly, and treated by anodic oxidation. Results showed that changes of the grain structures and textures of the AA5252 alloy sheets occur from the surface to the center layers. The anodic oxidation surface quality of the AA5252 aluminum alloy is closely related to the area ratio and distribution uniformity of Cube texture.

Studies of Zinc and Zinc Oxide Nanofilms of Different Thickness Prepared by Magnetron Sputtering and Thermal Oxidation-=SUP=-*-=/SUP=-

Polycrystalline zinc films with the thickness of about 20, 40, 60, and 80 nm and mainly granular morphology comprising nearly spherical particles involving hexagonal crystals are obtained by magnetron sputtering on cover glass supports. Subsequently, the prepared layers were subjected to thermal oxidation in the air to obtain transparent zinc oxide layers. The synthesized films are studied by SEM and UV-vis spectroscopy. Based on the obtained spectra, optical properties of the layers are studied as a function of their thickness. The optical band gap Eg for the films with the thickness from 40 to 80 nm is estimated on the level about 3.28 eV similar to the reference value 3.3 eV for bulk zinc oxide, while for the thickness of 20 nm Eg slightly drops to about 3.24 eV. Keywords: zinc; zinc oxide; nanolayers; magnetron; oxidation; surface morphology; transparency; optical bandgap.

Experimental Study on Friction Characteristics of Micro-Arc Oxidation Modified Layer on Titanium Alloy Surface

In order to study the effect of microarc oxidation modification treatment on the friction properties of titanium alloy surface, the surface treatment layer of Ti-6Al-4V ELI specimen modified by Microarc oxidation surface was sampled, the surface layer hardness, roughness and treatment layer thickness were tested, the microscopic morphology was analyzed, The friction tests of TC4 substrate and micro-arc oxidation treatment surface disc with 25% glass fiber, 15% fiberglass +5% graphite and 60% tin bronze reinforced PTFE pin were carried out, and the results showed that the thickness increased slightly and the surface layer hardness increased by about 75% after the micro-arc oxidation surface modification treatment. Compared with the substrate, the surface roughness is obviously improved, and the friction coefficient of the surface treatment specimen is similar to that of the TC4 titanium alloy substrate, but the wear amount is higher than that of the TC4 titanium alloy substrate.

Effect of Nb Content on Cyclic Oxidation Behavior of As-Cast Ti-1100 Alloys

The cyclic oxidation behaviors of the as-cast Ti-1100-xNb (x = 0.5, 1.0, 1.5, 2.0) alloys exposed at 650 °C for up to 100 h were systematically investigated. The aim of this work is to explore the in-depth oxidation mechanism by using the oxidation kinetics and the structure of the oxide products. The oxidation kinetics were determined by thermogravimetrically, and the microstructure and composition of the oxidation scale were studied by using XRD and SEM. The results demonstrate that Nb can significantly improve the oxidation resistance. However, the average weight gains of the alloys decrease firstly and then increase with the increase of Nb content. The oxidation kinetics obeys a parabolic model. The Ti-1100-1.0Nb alloy has the lowest kp value, which is 5.7 × 10−13 g2cm−4s−1. The surface oxidation products are mainly composed of massive or acicular rutile-TiO2, TixO (x = 3, 6), NbO2 and Al2O3. Besides, Al2(MoO4)3 oxide is also presented on the oxidation surface of the Ti-1100-1.5Nb alloys. Ti-1100-1.0Nb alloy shows the best oxidation resistance property revealed by combining weight gains and EDS-SEM element content profiles analysis. The interaction of Nb, O, Ti, and other elements retarded the diffusion of O atoms into the alloys, which improves the oxidation resistance.