Mechanical properties of structural alloys at low temperatures

Conclusions All alloys tested have satisfactory plasticity at all testing temperatures and are recommended for structures operating at temperatures from 20 to –253^o, although alloy VT3-1 should be used at temperatures above –196^o.Institute of Mechanical Sciences, All-Union Scientific-Research Institute of Cryogenic Machines, Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 34–36, October, 1970.     

Phase transformations in titanium alloys at low temperatures

Metal Science and Heat Treatment -     

The oxidation resistance of copper-aluminum alloys at temperatures up to 1,000°C

In this study, the high-temperature oxidation resistance of copper and copper-aluminum alloys in air was investigated using thermo-gravimetric analysis. Upon heating in air, copper starts to noticeably oxidize at temperatures above 400°C. It was found that as the temperature increased, more aluminum was required in order to protect the copper. Alloying with 4 wt.% aluminum leads to a remarkable improvement in oxidation resistance. The atmosphere used to heat the samples to the required test temperatures had a noticeable impact on the subsequent oxidation rates. When heated in argon before being oxidized, copper alloys with 3 wt.% and 4 wt.% aluminum showed excellent oxidation resistance with rates 1,000 times less than that of pure copper at 1,000°C. However, when these alloys were heated in air, they were much less effective at providing oxidation resistance. For more information, contact Gabriel Plascencia, University of Toronto, Materials Science & Engineering Department, 184 College St., Toronto, ON, Canada, M5S 3E4; (416) 978-0912; fax (416) 978-4155; e-mail g.plascencia@utoronto.ca.     

On the oxidation mechanism of Ni–Pt alloys at high temperatures

The oxidation mechanism of Ni–Pt alloys has been studied as a function of alloy composition, oxygen pressure and temperature. It has been found that the oxidation rate of all the alloys follows the parabolic rate law, being thus diffusion controlled. In agreement with Wagner’s theory, the slowest step of the overall oxidation rate of alloys with higher nickel content (?40 at.%) is determined by the outward diffusion of nickel cations in the growing NiO scale. On the other hand, the oxidation rate of alloys with a lower nickel content (<40 at.%) is governed by the solid state diffusion in the metallic phase.     

Early oxidation behaviors of Mg–Y alloys at high temperatures

The early oxidation behaviors of Mg–Y alloys (Y = 0.82, 1.09, 4.31 and 25.00 wt.%) oxidized in pure O₂ have been investigated at high temperatures. The results showed that the oxidation behaviors of the Mg–Y alloys (Y = 4.31 and 25.00 wt.%) obeyed a parabolic law, while that of the Mg–Y (Y = 0.82 and 1.09 wt.%) exhibited both parabolic and linear kinetics depending on the oxidation temperature. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses indicated that an oxide film with a single structure composed of MgO and Y₂O₃ had formed. Moreover, the higher the oxidation temperature was, the thicker the oxide film was. Finally, the corresponding oxidation mechanism has been discussed, and the improved oxidation resistance of the Mg–Y alloys can be due to the formation of a continuous Mg-dissolving Y₂O₃ protective film.