An AES study of the oxidation of a 97Pb3Sn alloy

A 97Pb-3Sn alloy was oxidized at oxygen pressures below 10 mPa and temperatures from 20°C to 200°C. The reaction was monitored by Auger electron spectroscopy (AES). The oxide film formed most likely is SnO and is less than 2 nm thick. Lead is oxidized only if there is no tin at the surface. If tin can diffuse to the alloy surface sufficiently fast, lead will not be oxidized. Oxidized lead is reduced by metallic tin.     

The effects of carbon content in steel on the diffusion rate of chromium

Conclusions Thermal diffusion chromizing in metallic chromium under vacuum promotes impregnation and produces a thicker layer than in chromizing by means of a powder mixture only in steel with a maximum content of 0.2% C at 1100°C and higher.     

Improving the heat transfer of nanofluids and nanolubricants with carbon nanotubes

Low thermal conductivity is a primary limitation in the development of energyefficient heat transfer fluids required in many industrial and commercial applications. To overcome this limitation, a new class of heat transfer fluids was developed by suspending nanoparticles and carbon nanotubes in these fluids. The resulting heat transfer nanofluids and nanolubricants possess significantly higher thermal conductivity compared to unfilled liquids. Three types of heat transfer nanofluids and nanolubricants, each containing controlled fractions of single-wall carbon nanotubes, multiwall carbon nanotubes, vapor grown carbon fibers, and amorphous carbon have been developed for multifunctional applications, based on their enhanced heat transfer and lubricity properties. For more information, contact F.D.S. Marquis, South Dakota School of Mines and Technology, Department of Materials and Metallurgical Engineering, Rapid City, SD 57701; (605) 394-1283; fax (605) 394-3369; e-mail fernand.marquis@sdsmt.edu.     

A novel system for atmospheric corrosion experiments

Atmospheric corrosion testing in the laboratory requires the capability of achieving stable and realistic exposure conditions, exposure of multiple samples, wide ranges of concentrations of corrosive gases, and exposure times varying from seconds to weeks. This paper describes a system that meets these requirements. It utilizes polymer permeation as a source of corrosive gases, a hook-and-loop fastening system for sample manipulation, a multiport chamber for sample exposure, and a dedicated desktop computer system for sample monitoring and data reduction. System characteristics include the generation of corrosive trace gases from a low level of 8 ± 1 ppb to a high level of 5 ± 0.1 ppm, exposure times of less than 1 min to 5 weeks, and simultaneous exposure of 60–90 samples.     

Oxidation of a dilute aluminum magnesium alloy

The morphology and composition of the oxide film formed under various oxidation conditions on a 1.2% aluminum-magnesium alloy have been studied using electron microscopy and diffraction. Below 350° C the oxide film formed is highly protective and amorphous, while above this temperature the oxide becomes nonprotective. Initially, at temperatures above 350°C, the oxide film consists of only alumina, then with increasing time it contains first MgO, then MgO together with MgAl₂O₄, and finally it is entirely converted to MgAl₂O₄.     

The effects of silicon on the properties of tantalum

The microalloying of tantalum with silicon has been effectively used on a commercial scale. However, data on effects of microalloying on processibility, microstructure and mechanical properties are not readily available. To develop some data, tantalum powder with various levels of silicon (0–50 ppm) was processed under identical conditions. Sheet samples were then annealed at different temperatures and evaluated via microstructural, chemical and mechanical tests. The recrystallization temperature was found to increase with silicon content, most probably as a result of the presence of an intermetallic (Ta₃Si) phase. The mechanical properties of unrecrystallized tantalum are, as expected, significantly different from those of recrystallized tantalum.     

Tendency of steels 10KhSND and 09G2S towards brittle failure

Conclusions The tendency towards brittle failure of low-alloy steels type 10KhSND and 09G2S at low temperatures depends on the supply condition. The highest resistance to brittle failure occurs for steel after temper hardening, i.e., quenching and high-temperature tempering. A changeover into a brittle condition for temper hardened steels of the test melts commences at –60°C, and for hot-rolled steels it commences at –40°C."Kompozit." Scientific-Production Organization. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 14–16, May, 1993.