Effect of Samarium on the Properties of Mg–Y–Gd–Zr Alloys

The microstructure, the aging kinetics, and the strength properties of Mg–Y–Gd–Zr cast alloys, in particular, a samarium-alloyed IMV7-1 alloy, at room and high (250, 300°C) temperatures after homogenization without and with subsequent aging are studied. Alloying with samarium accelerates the decomposition of the supersaturated magnesium solid solution and enhances the properties of the Mg–Y–Gd–Zr alloys.     

Effect of gadolinium on the properties of Pr–Dy–Fe–Co–B materials

Sintered (Pr_1–x–y Dy _x Gd _y )_13–14(Fe_1–z Co _z )_balB_6–7 materials (x = 0.18–0.58, y = 0.05–0.33, z = 0.2–0.36) have been studied. The magnetic moments of gadolinium ions and those of the sublattice formed by Fe and Co ions are shown to be ordered antiferromagnetically. It is noted that an increase in the content of gadolinium, which substitutes for dysprosium, leads to an increase in residual induction B _r , a decrease in coercive force H _cJ , and an increase in the absolute value of the temperature coefficient of induction. The opposite effect takes place in the case of substitution of gadolinium for praseodymium in materials with a fixed dysprosium content.     

Experiments on the aging of Sn–Ag–Cu solder alloys

Abstract

The microstructural stability of the Sn–3·8%Ag–0·7%Cu solder alloy was investigated by studying microstructural changes caused by heating small samples for various times, up to 1000 h, at 150°C. The first change, evident at high magnification after heating for 1 h, occurred from the as cast lamellar plus fibrous form of the Ag₃Sn and Cu₆Sn₅ interdendritic eutectic phases to a particulate form. With further heating, coarsening of the two compound phases occurred, gradually rendering the Sn dendrite pattern less distinct. Due to the very rapid diffusion of Cu in solid Sn, the Cu₆Sn₅ phase coarsened most rapidly, growing from its originally finely divided (200 nm) size in the ternary eutectic to form many particles up to 3 m m or more in size in a time of 100 h. At that time, nearly 50% of the total Cu was contained in these particles. The Ag₃Sn phase coarsened more slowly. Approximate measurements of average particle size as a function of time suggested that coarsening occurs by Ostwald ripening, controlled by diffusion in the Sn phase.     

Influence of titanium microalloying on the properties of low-alloy Cr–Mo–V steel

The influence of titanium, which readily forms nitrides, on the structure and the long- and short-term mechanical properties of Cr–Mo–V steel is investigated. Increase in the Ti content to 0.075% increases the thermal stability of the steel. With increase in Ti content to 0.13%, the thermal stability of the steel declines sharply, on account of structural changes.     

Effect of modification on the solidification of Al–Si aluminum alloys

The solidification of the AK12 alloy processed by a standard flux and a combined modifying flux, which significantly increases the mechanical properties of the alloy at a significant increase in the modifying effect time, is studied. The experimental results are simulated using the ProCAST software package.     

Influence of the Structure of Fe–Si–Mg–Rare Earth Modifiers on the Production of Compacted Graphite Iron for Camshafts

The structure of a modifier in two forms (ingot and chip) for the production of compacted graphite iron (also known as vermicular graphite iron) is investigated by means of an electron microscope and also by X-ray microspectral analysis. The possibility of qualitative identification of the phase composition and surface macroanalysis of the modifier particles is considered.     

Effect of Vacuum Hot Pressing Temperature on the Mechanical and Tribological Properties of the Fe–Cu–Ni–Sn–VN Composites

Powder Metallurgy and Metal Ceramics - The mechanical (hardness and elastic modulus) and tribological (friction force and wear rate) properties of the Fe–Cu–Ni–Sn–VN...     

Effect of cobalt on the oxidation resistance of Pr(Nd)–Dy–Fe–Co–B materials

The effect of cobalt on the oxidation resistance of (Nd_0.85Dy_0.15)_16.4(Fe_0.89Co_0.11)_74.4Ti_1.3B_7.9 and (Pr_0.56Dy_0.39Sm_0.05)_14.5(Fe_0.75Co_0.25)_78.8B_6.7 alloys has been studied. The storage of magnet blanks made from these alloy in air for 200 h does not affect the magnetic properties of the sintered magnets owing to the presence of the phases (Pr, Dy)(Fe, Co)₂, (Pr, Dy)(Fe, Co)₂B₂, (Pr, Dy)(Fe, Co)₄B, (Pr, Dy)(Fe, Co)₃B₂, and (Pr, Dy)(Fe, Co)₃, which are resistant to oxidation and ensure liquid-phase sintering of magnets. After 200-h exposure to air, oxidation of the blanks takes place, the rate of which decreases by more than two times at the expense of an increase in the cobalt content in the alloy.     

Effect of the sintering temperature and time on the structure and phase composition of temperature stable hard magnetic materials of the REM–Fe–Co–B system

The structure, the phase composition, and the distribution of alloying elements in the structure of temperature stable hard magnetic materials of the REM–Fe–Co–B system (REM = rare-earth metals), which are prepared under different manufacturing conditions, namely, at different sintering temperatures and times, have been studied. The phase composition, the local chemical composition of phases, the volume fraction of pores, and the manufacturing conditions that allow one to prepare the structure ensuring high magnetic properties have been determined.     

Effect of Zr Content on the Microstructure and Corrosion Resistance of Al–Cu–Mn Alloy

Russian Journal of Non-Ferrous Metals - In order to improve the overall properties of cast Al–Cu–Mn alloy, the effect of Zr content on the microstructure and corrosion resistance of...     

Effect of Speed on the Tribological Behavior of Fe–Cu–C Based Self Lubricating Composite

In this work, the effect of different speeds on the tribological properties of sintered iron–copper–graphite (Fe–Cu–C) based self lubricating composites have been studied. Fe–Cu–C based self-lubricating composites were prepared by powder metallurgical compaction and sintering method. CaF₂, a solid lubricant in weight percentages of 0, 3, 6, 9 and 12 was added to the base matrix consisting of Fe-2Cu-0.8C. The fabricated samples were tested for friction and wear at a constant load of 10 N and three different speeds of 0.5, 5 and 10 m/s. The surface properties of unworn and worn surfaces were analyzed using optical and scanning electron microscope. The friction and wear test of the composites exhibited decrease in coefficient of friction and increase in wear loss with the increase in speed. The results also revealed different trends in the friction behavior of the developed composites at low (0.5 m/s) and high speeds(5 and 10 m/s). However, at all test speeds, COF of samples with 3, 6 and 9 wt.% was less than the base matrix, and wear loss of 3 wt.% CaF₂ sample was the lowest at all speeds. Ploughing, adhesive and delamination wear were the dominant wear mechanism as revealed by SEM. Based upon the findings, the developed material could be used for low and high speed antifriction applications.     

Effect of Barothermal Treatment on the Structure and the Mechanical Properties of a High-Strength Eutectic Al–Zn–Mg–Cu–Ni Aluminum Alloy

The effect of barothermal treatment by hot isostatic pressing (HIP) on the structure and the properties of castings of a promising high-strength cast aluminum alloy, namely, nikalin ATs6N4 based on the Al?Zn–Mg–Cu–Ni system, has been studied using two barothermal treatment regimes different in isothermal holding temperature. It is shown that the casting porosity substantially decreases after barothermal treatment; eutectic phase Al3Ni particles are additionally refined during exposure to the barothermal treatment temperature: the higher the HIP temperature, the more substantial the refinement. The improvement of the casting structure after HIP increases their mechanical properties. It is found, in particular, that the plasticity of the alloy in the state of the maximum hardening increases by a factor of more than 8 as compared to the initial state (from 0.82 to 6.9%).     

Development of the Aluminum Powder Composite Based on the Al–Si–Ni System and Technology of Billet Fabrication of This Composite

Results of an investigation into the development of the composition and fabrication technology of compact billets of the aluminum powder composite material based on the Al–Si–Ni system for space-rocket hardware are presented. The composite production was performed as follows: initially the powder of the matrix alloy is prepared by gas sputtering, and then a mixture of the matrix alloy powder and alloying dispersed additives is subjected to mechanical alloying in high-energy apparatuses. The method of degassing the mechanically alloyed composition in a thin layer (in order to exclude material ejection from a container when degassing a larger volume of powder) and process regimes of composition compaction are developed using the unique equipment available at OAO Kompozit (Korolev, Moscow oblast)—a vacuum press. Using this technology, cylindrical briquettes up to 100 mm in diameter and up to 120 mm in height are fabricated. Newly developed and patented Kompal-301 composite material has substantial advantages over SAS-1-50 power alloy applied for similar purposes. Its thermal linear expansion coefficient is lower by a factor of 1.5, while the precision limit of elasticity is higher by a factor of 2–3 upon similar strength characteristics. The final structure of a compact briquette is a matrix in which dispersed particles of excess silicon are distributed rather uniformly against the background of the aluminum solid solution. Coarser isolated silicon particles are met in separate regions of the structure. Unfortunately, they are the cause of low plasticity of briquettes, which prevents the formation of semifinished products by plastic deformation; however, such low plasticity does not immediately negatively affect the fabrication of the briquettes themselves.     

The effect of FeS film on the surface of iron powder particles on mechanical properties and fracture of Fe–Cu–C alloys

This article provides a new kind of P/M processing by designing thin-layered FeS film coated on the surface of iron powder particles for preparing high density Fe–Cu–C materials. Experimental results showed that FeS lubricating coating on the surface of iron powder particles was significant as a means of reducing friction in the pressing process of Fe–Cu–C alloys. After being pressed, the green density increased from 7.18 to 7.42?g?cm^?3. The sintered density increased from 7.10 to 7.37?g?cm^?3. In the sintering process, the FeS was liquid, and useful in purifying particle surface and strengthening grain boundaries to improve the mechanical properties. The hardness and tensile strength of the Fe–2.0Cu–0.9C–0.5FeS₂ material were 80.5 HRB and 590?MPa. Analysis of fracture showed the main fracture was transgranular fracture. And FeS spherical particles gathered in the pores of the Fe–Cu–C alloys.     

A longitudinal study of the role of negative affectivity on the work stressor–strain process.

A significant proportion of previous research in the occupational stress area has tended to treat the personality variable negative affectivity (NA) as a nuisance variable. This perspective has led researchers to routinely control for the effects of NA. However, P. E. Spector, D. Zapf, P. Y. Chen, and M. Frese (2000) have proposed a number of different mechanisms by which NA could have substantive effects. The current research used a longitudinal framework to test several competing mechanisms proposed by Spector et al. (specifically, the perception, hyperresponsivity, and causality mechanisms) on the relationship between work stressors and psychological well-being. Customs workers and dentists constituted the longitudinal sample (N = 345). Results provided strong support for the perception mechanism, indicating that the effects of NA on psychological health were partially mediated by work stressors. The authors discuss the theoretical and practical relevance of the perception mechanism to occupational health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of the temperature–rate parameters of directional solidification on the structure formation in high-temperature materials

The effect of the temperature gradient and the crystal growth rate on the structure formation in nickel and niobium superalloys is studied under the conditions of the flat, cellular, dendritic, or dendritic–cellular configuration of a solidification front during directional solidification.     

Cerium Effect on the Phase Composition and Crystallization Behavior of Aluminum Casting Alloys Based on the Al–Mg–Si System

Russian Journal of Non-Ferrous Metals - Using a Thermo-Calc software package (TCAl4.0 database), unexplored data concerning the phase composition and crystallization behavior of...     

Effect of the Al–Zr–Y master alloy composition on the modifying effect in the Al–4% Cu alloy

The results of modifying the Al–4% Cu alloy with test Al–1.04% Zr–0.70% Y and Al–1.23% Zr–0.39% Y master alloys are reported; the Zr-to-Y atomic-percentage ratio in the alloys is 1.41 and 3.08, respectively. The effect of small amounts of Zr and Y (from 0.1 to 0.3%) added in the form of test ternary master alloys of different compositions and binary Al–Zr and Al–Y master alloys on the grain refinement in the Al–4% Cu alloy has been studied. The structure of the initial alloy is characterized by pronounced directional solidification of the α phase. As the Zr + Y content increases, the columnar-crystal zone decreases and the equiaxed-crystal zone increases; at a (Zr + Y) content of 0.326%, only equiaxed crystals ~200 μm in size are present in an ingot. When Zr and Y are added with binary master alloys, the macrostructure of the modified Al–4% Cu alloys indicates that columnar crystals grow until their contact at the center of the ingot, and their growth is independent of the amount of added Zr and Y.