Theory of the magnetic reactions occurring in abrasive machining with a ferromagnetic powder

Conclusions An examination is made of the existing methods of calculation for the analysis of the magnetic interactions in magnetoabrasive polishing. An error in the approach to the problem is pointed out which has resulted in calculated values of forces being much smaller than experimental. The superposition method is employed for calculating the magnetization intensity of a magnetoabrasive powder particle and cylindrical ferromagnetic work placed in a magnetic powder medium. Formulas are derived for calculating the forces acting on a spherical powder particle during the MAP of a cylindrical part made of a ferromagnetic material.Translated from Poroshkovaya Metallurgiya, No. 11(263), pp. 62–67, November, 1984.     

Effect of Properties of Titanium Aluminide Powders and Detonation Spraying Conditions on Phase and Structure Formation in Coatings

We have studied phase formation in detonation coatings sprayed from Ti - 50 at.% Al powders. The powders of the alloy were obtained by various methods: crushing an ingot and mechanical alloying of Ti and Al. Using polyphase nanostructural materials activated by mechanical alloying makes the process of phase formation in the gas-thermal sprayed coatings based on them more general-purpose and controlled due to the more active and more subtle reaction of the material with the gaseous atmosphere. We have shown that from mechanically alloyed Ti - 50 at.% Al powder, using the detonation-gas spraying method we can consolidate a coating based on Al₂TiO₅ by oxidizing action of the working gas on the powder and also a coating based on titanium aluminides with TiN inclusions by nitriding action. The phase composition of the cast microstructural γ-TiAl powder is inherited by the coating.     

Effect of Rhenium on Formation of the Structure of Eutectic Alloys Based on β-NiAl + γ-Re

We have studied phase equilibria and plotted the partial phase equilibria diagram for Ni Al Re in the region of compositions ranging from 0.2 to 14 at.% rhenium. We have established the dependence of the structure and the phase composition of the alloys in the Ni Al Re system on the rhenium concentration. We have determined the optimal ratio of the components at which the alloys have the maximum melting point. We have shown that the structure of the alloys is a composite consisting of a NiAl-based matrix and -Re fibers.     

Effect of Scandium and Chromium on the Structure and Heat Resistance of Alloys Based on γ-TiAl

It is established that microalloying of γ-titanium aluminides with scandium provides an increase in heat resistance, structure refinement and modification, and formation of a dispersion-strengthened structure with a coherent bond between the strengthening and matrix phases. Proceeding from this an improvement might be expected in strength characteristics over a wide temperature range. The effect in scandium consists in changing the ratio of Al:Ti thermodynamic activities in the direction of forming aluminum oxide at the alloy surface during oxidation as a result of the deoxidizing effect of scandium and the formation of fine oxide inclusions. As a result of this aluminum does not form oxides within the alloy. The distribution of elements within the microstructure of γ-Ti ― Al with 5%Cr after oxidation at 900°C for 300 h is studied. It is established that the surface scale layer that forms sometimes contains Cr in addition to Al and O. A diffusion mechanism is suggested for realizing the Cr-effect according to which chromium and aluminum ions participate in place of titanium ions in forming Al₂O₃ ― Cr₂O₃ scale at the metal ― air atmosphere interface.     

Formation and high-temperature oxidation of thermal-barrier coatings with Ti-Al-Cr binding layer

The behavior of TiAlCr detonation coatings with an outside thermal barrier layer in high-temperature oxidation in air is examined. It is established that the efficiency of thermal-barrier coatings with a zirconia external layer on substrates of Ti-rich alloys and γ-TiAl depends on the oxidation of the binding TiAlCr layer and the diffusion at the coating-substrate interface. It is shown that the presence of a ceramic layer has no fundamental effect on the oxidation of γ-TiAl-based coatings. The behavior of TiAlCr coatings in high-temperature oxidation depends on the substrate structure, which determines the nature of diffusion at the coating-substrate interface. If the substrate is made of titanium-rich alloys, there is active diffusion of Al and Cr from and of Ti into the coating. Since the Al/Ti activity ratio changes, a mixed layer of TiO₂ and Al₂O₃ forms on the surface. In case of the γ-TiAl substrate, a layer on the TiAlCr surface consists of Al₂O₃ alone.     

Energy-Efficient Computing for Extreme-Scale Science

A many-core processor design for high-performance systems draws from embedded computing's low-power architectures and design processes, providing a radical alternative to cluster solutions.     

Structure and Properties of Detonation Coatings Based on γ-TiAl

Investigations of a coating ― substrate composite before and after oxidation in air at 900°C revealed that the main structural features were: formation of an Al₂O₃ scale on the surface of the TiAlCrSc(γ) coating (as a result of oxidation) and of inner layer at its interface with a 90% titanium substrate (as a result of diffusion in the composite). The observed phenomenon was caused by a Kirkendall effect resulting in the formation of titanium-enriched phases, apparently Ti₃Al and α-Ti, which have a broad homogeneity range. The formation of a diffusion zone in the system with displacement of the Kirkendall plane in the direction of the substrate has a positive effect on the adherence of the coating. Furthermore, the filling of vacancies and pores in the coating with additional material supplied by the diffusion of titanium should have a favorable effect on the strength and durability of the coating, particularly its fatigue resistance.