Search results for "intermetallic"

Differences and Similarities between the Isotypic AntimonidesMFe1−xSb, ScCo1−xSb, andMNiSb (M=Zr, Hf)

1999

The new antimonides MFe{sub 1{minus}x}Sb can be synthesized by arc-melting of M, Fe, and MSb{sub 2} (M = Zr, Hf). All title compounds crystallize in the TiNiSi structure type (space group Pnma, Z = 4). The lattice parameters of the new phases of MFe{sub 1{minus}x}Sb, as obtained from the bulk samples of the nominal compositions MFeSb, are a = 681.4(1) pm, b = 417.87(7) pm, c = 740.3(1) pm for ZrFe{sub 1{minus}x}Sb and a = 674.0(1) pm, b = 412.0(2) pm, c = 729.7(2) pm for HfFe{sub 1{minus}x}Sb. Under the reaction conditions used, the occupancy factors of the iron position content of ZrFe{sub 1{minus}x}Sb does not exceed 68(1)% (i.e., x = 0.32(1)). Extended Hueckel calculations, performed on …

Magnetic Domain Structure and Intrinsic Magnetic Material Parameters of Ternary Intermetallic RMn2Ge2 Compounds (R ? La, Ce, Pr and Nd)

2000

Applying a powder pattern method the magnetic domain structures of polycrystalline intermetallic RMn2Ge2 (where R ≡ La, Ce, Pr, Nd) compounds were studied. The domain structures observed are typical for uniaxial materials. The domain wall energy density γ was determined from analysis of domain structure patterns, using different models of the domain structure. The obtained values are used to determine the intrinsic magnetic material parameters: domain wall width δB, critical diameters of single domain particles Dc and exchange constants A.

High Temperature Oxidation of TiAl and TiAl8Nb Alloys in Air

2011

Isothermal oxidation of two g-TiAl-based intermetallic alloys: Ti48Al and Ti46Al8Nb alloys was studied in synthetic air at 1073-1223 K for up to 240 hrs. Mass change per unit area for the oxidized samples followed approximately the parabolic rate law. The kp values for the studied temperature interval were in the range from 7.2×10-13 to 1.8×10-11 g2cm-4s-1. The activation energy for oxidation of Ti48Al alloy in air at 1073-1223 K was Ea = 165±12 kJ/mol. Niobium addition to Ti48Al alloy in the amount of 8% increased its oxidation resistance. Structure and chemical composition of the oxidation products, and morphology of the oxidized samples were investigated using XRD, SEM-EDS, and TEM. The …

Electrochemical behavior of nanocrystalline iron aluminide obtained by mechanically activated field activated pressure assisted synthesis

2004

Abstract The corrosion behavior of nanocrystalline iron aluminide obtained by mechanically activated field—activated pressure—assisted synthesis was investigated in sulphuric acid media using potentiodynamic curves. The effect of microstructure on the electrochemical corrosion resistance was investigated by examining samples which were heat treated to effect a change in crystallite size and microdistorsion.

Evolution of microstructures and mechanical properties during dissimilar electron beam welding of titanium alloy to stainless steel via copper interl…

2013

Abstract The influence of operational parameters on the local phase composition and mechanical stability of the electron beam welds between titanium alloy and AISI 316L austenitic stainless steel with a copper foil as an intermediate layer has been studied. It was shown that two types of weld morphologies could be obtained depending on beam offset from the center line. Beam shift toward the titanium alloy side results in formation of a large amount of the brittle TiFe2 phase, which is located at the steel/melted zone interface and leads to reducing the mechanical resistance of the weld. Beam shift toward the steel side inhibits the melting of titanium alloy and, so, the formation of brittle…

Elaboration of Nickel Aluminide Diffusion Coatings: Application to Oxidation Resistance

2008

Aluminide diffusion coatings are widely used in aeronautic domain. Nickel based superalloys present good mechanical properties and creep resistance at high temperature but their corrosion resistance is somewhat poor. In order to enhance their lifetime at high temperature, aluminide coatings can be applied on alloy surface. Aluminium present on material surface can form, at high temperature, alumina scale which is a protective oxide scale. In the present study, nickel aluminide coatings were carried out by aluminisation in a single step pack cementation process on nickel based superalloys 600 and AM1. Ni-Al intermetallic was obtained in each case. Oxidation tests were carried out at 900°C in…

The formation of intermetallics in dissimilar Ti6Al4V/copper/AISI 316 L electron beam and Nd:YAG laser joints

2011

Abstract The welds of titanium alloys with steels suffer from the brittleness of resulting intermetallic compounds. In present study, we report the feasibility of Ti6Al4V to stainless steel AISI 316L welding through pure copper interlayer carried out by electron beam and pulsed Nd:YAG laser. The nature and the localization of intermetallic phases in these welds have been studied by SEM, EDS, XRD and microhardness measurements. The simplified scenario of weld formation has been proposed in order to understand the mechanism of weld formation and to explain the way local phase content determines the mechanical properties. It can be concluded that the insertion of 500 μm pure copper interlayer …

In-situ time resolved X-ray diffraction study of the formation of the nanocrystalline NbAl3 phase by mechanically activated self-propagating high-tem…

1999

The mechanically activated self-propagating high-temperature synthesis (MASHS) technique was used to produce a NbAl3 intermetallic compound. This process results from the combination of two steps: a mechanical activation of the Nb 3Al powder mixture which is followed by a self-propagating high-temperature synthesis (SHS) reaction, induced by the exothermal character of the reaction Nb3Al. An original experiment was designed to study in-situ the formation of the NbAl3 phase in the combustion front: time-resolved X-ray diffraction coupled with an infrared imaging technique and a thermocouple measurement were performed to monitor the structural and thermal evolution during the SHS reaction. Ow…

Effect of Microstructure on the High Temperature Oxidation and Pesting Behaviour of MoSi<sub>2</sub>

2004

One-Step Synthesis and Consolidation of Nanophase Iron Aluminide

2001

The simultaneous synthesis and densification of nanophase iron aluminide is investigated. Elemental nanophase reactants produced by mechanical activation were reacted by field activation with the simultaneous application of uniaxial pressure. The process was demonstrated in this work by the synthesis of dense nanometric FeAl. Iron and aluminum powders were co-milled in a specially designed planetary mill to obtain nanometric reactants and to avoid formation of any product phases. These powders were then subjected to high AC currents (1250–1500 A) and pressures in the range of 70–106 MPa. Under these conditions, a reaction was initiated and completed within a short period of time (2.5–3.5 mi…