Intermetallic Compound

Anisotropies of electrical resistivity, upper critical field, London penetration depth and critical currents have been measured in single crystals of the optimally doped iron pnictide superconductor Ba(Fe1−xCox)2As2, x=0.074 and Tc ∼23 K. The normal state resistivity anisotropy was obtained by employing both the Montgomery technique and direct measurements on samples cut along principal crystallographic directions. The ratio γρ = ρc/ρa is about 4±1 just above Tc and becomes half of that at room temperature. The anisotropy of the upper critical field, γH = H c2,ab /Hc2,c, as determined from specific heat measurements close to Tc, is in the range of 2.1 to 2.6, depending on the criterion used. A comparable low anisotropy of the London penetration depth, γ λ = λc/λ ab , was recorded from TDR measurements and found to persist deep into the superconducting state. An anisotropy of comparable magnitude was also found in the critical currents, γj = j c,ab /jc,c, as determined from both direct transport measurements (∼1.5) and from the analysis of the magnetization data (∼3). Overall, our results show that iron pnictide superconductors manifest anisotropies consistent with essentially three-dimensional intermetallic compound and bear little resemblance to cuprates.

69,71 Ga NMR spectroscopy and magnetic susceptibility experiments. The electron transport is predominantly mediated by the Ga-Ga p x-and p y-like electrons in the (001) plane. The specific heat capacity of BaGa 2 was determined and indicated the absence of phase transitions between 1.8 and 320 K.

Finite element simulations of the high-temperature behavior of single-phase ␥, dual-phase ␣ 2 ϩ ␥, and fully lamellar (FL) ␣ 2 ϩ ␥ TiAl intermetallic alloy microstructures have been performed. Nonlinear viscous primary creep deformation is modeled in each phase based on published creep data. Models were also developed that incorporate grain boundary and lath boundary sliding in addition to the dislocation creep flow within each phase. Overall strain rates are compared to gain an understanding of the relative influence each of these localized deformation mechanisms has on the creep strength of the microstructures considered. Facet stress enhancement factors were also determined for the transverse grain facets in each model to examine the relative susceptibility to creep damage. The results indicate that a mechanism for unrestricted sliding of ␥ lath boundaries theorized by Hazzledine and co-workers leads to unrealistically high strain rates. However, the results also suggest that the greater creep strength observed experimentally for the lamellar microstructure is primarily due to inhibited former grain boundary sliding (GBS) in this microstructure compared to relatively unimpeded GBS in the equiaxed microstructures. The serrated nature of the former grain boundaries generally observed for lamellar TiAl alloys is consistent with this finding.

The analytic construction of a many-body potential inspired from the Sutton-Chen parametrization is presented for copper and silver. A new approach is used to model the cross interaction for the Cu-Ag alloys. The parameters are fitted to first principles calculations based on the full potential linear plane wave method. The structural properties of the order and disorder Cu-Ag alloys in the B 2 and fcc structures are presented for different concentration.

Copper wire is getting well accepted as a reliable design alternative to the gold wire in the wire bonding process. In the present study, the shear strength results of the copper ball bond show better performance than the gold bond. Additionally, microhardness results also confirm that Cu ball bonds reveal a higher hardness of 111 VHN than that of initial Cu ball (84 VHN). The increased shear strength and hardness can be rationalized based on the strain hardening process due to application of the ultrasonic energy. Microstructural study of the deformed ball confirms the presence of subdivided grains (or cells) of a few microns in size. In addition, slip bands inside the cells are also observed.

Thermosonic bonding process is a viable method to make reliable interconnections between die bond pads and leads using thin gold and copper wires. This paper investigates interface morphology and metallurgical behavior of the bond formed between wire and bond pad metallization for different design and process conditions such as varying wire size and thermal aging periods. Under thermal aging, the fine pitch gold wire ball bonds (0.6 mil and 0.8 mil diameter wires) shows formation of voids apart from intermetallic compound growth. While, with 1-mil and 2-mil diameter gold wire bonds the void growth is less significant and reveal fine voids. Studies also showed void formation is absent in the case of thicker 3 mil wire bonds. Similar tests on copper ball bonds shows good diffusional bonding without any intermetallic phase formation (or with considerable slow growth) as well as any voids on the microscopic scale and thus exhibits to be a better design alternative for elevated temperature conditions.

In IC packages, thermosonic wire bonding is the preferred method for making electrical connections between the die pad and lead frame. These interconnect are made using fine metal wires. On thermal aging (under 175 8C for 5 h) gold aluminide easily forms in gold ball bonds while formation of intermetallic compound is absent in case of copper ball bonds. An analysis of the atomic property of the elements bonded explains that atomic radii and electronegativity factors favor gold aluminide formation.

Thermosonic bonding process is a viable method to make reliable interconnections between die bond pads and leads using thin gold and copper wires. This paper investigates interface morphology and metallurgical behavior of the bond formed between wire and bond pad metallization for different design and process conditions such as varying wire size and thermal aging periods. Under thermal aging, the fine pitch gold wire ball bonds (0.6-and 0.8-mil-diameter wires) show formation of Kirkendall voids apart from intermetallic compound growth. With 1-and 2-mil-diameter gold wire bonds, the void growth is less significant and reveals fine voids. Studies also showed that void formation is absent in the case of thicker 3-mil wire bonds. Similar tests on copper ball bonds show good diffusional bonding without any intermetallic phase formation (or with considerable slow growth) as well as no voids on the microscopic scale and thus promises to be a better design alternative for elevated temperature conditions.

A methodology was developed to establish baseline metrics for assessing the isothermal aging of 63Sn‐37Pb (or 60Sn‐40Pb) solder joints in circuit board assemblies. Those metrics were the intermetallic compound layer thickness at the Sn‐Pb solder/Cu interface and the Pb‐rich phase particle size distribution in the solder. The baseline, or as‐fabricated, values for these metrics were 0.71±0.27 μm and 3.2±6.5×10−6 mm2, respectively. The rate kinetics were determined for growth of the intermetallic compound layer and coarsening of the Pb‐rich phase particles by isothermal aging experiments. The/were: (1) intermetallic compound layer thickness (μm)=0.714+ 3.265×103 t0.58 exp(−52200/RT); and (2) Pb‐rich phase particle size (mm2)=3.2×10−6+1.47× 10−3 t0.32 exp(−31000/RT).

Solid-state interface reactions were investigated when Cu-Fe alloy leads were attached to an electroplated Au layer using 50In-50Pb (wt.%) solder. Two Au layers of different plating process quality were studied. The annealing temperatures were 70, 100, 135, and 170 • C and the times were 1-2000 h. The dominant reaction layer was a composite of (Au, Cu)In 2 IMC and Pb-rich phases. A Au 9 In 4 layer remained <2 m in most specimens. Linear rate kinetics (0.8 < n < 1.2) were observed, indicating an interface-controlled mechanism. The mean apparent activation energy, H, was 56 < H < 73 kJ/mol. The Au 9 In 4 , layer growth kinetics parameters were 0.5 < n < 0.9 and 45 < H < 80 kJ/mol, respectively, suggesting a contribution by grain boundary diffusion. Annealing at 100 • C caused significant degradation to the interconnections through extensive void growth, more so for the poor plating process. Void development began with small Kirkendall voids at the In-Pb/Au interface caused by differing diffusion rates of Au and In through the IMC layer. That initial process was sensitive to the Au layer quality. Void enlargement was caused by a dissociation of the (Au, Cu)In 2 IMC and Pb-rich phases in the absence of Au flux; this process was insensitive to Au layer quality.

UPtAl crystallizes in the ZrNiAl-type hexagonal structure and orders ferromagnetically with uranium magnetic moments parallel to the c axis below 43 K. We present the results of a polarized neutron experiment on a UPtAl single crystal and electronic structure calculations. The experimental data were analyzed by the maximum entropy method and within the atomic model. The main magnetic contribution originates from the uranium atoms. The ratio Ϫ L / S between the orbital and spin uranium moment is reduced in comparison to the free ion value, indicating a delocalization of the uranium 5 f states. It remains unchanged between 1 and 9.6 T. Induced magnetic moments are observed on both platinum sites ͑within the U-Pt and Al-Pt layers͒. An additional magnetization density is observed around the aluminum positions. The first-principles electronic structure calculations were performed in the framework of the density functional theory and confirmed the ferromagnetic state. The calculated and experimental magnetic moments are compared and the results discussed in the context of the previous studies on isostructural UTX compounds.

Aluminum ion implantation of vanadium, niobium, and tantalum improved the metals' oxidation resistances at 500 ~ and 735 ~ Implanted vanadium oxidized only to one-third the extent of unimplanted vanadium when exposed at 500 ~ to air. The oxidative weight gains of implanted niobium and tantalum proved negligible when measured at 500 ~ and for times sufficient to fully convert the untreated metals to their pentoxides. At 735 ~ implantation of vanadium only slightly retarded its oxidation, while oxidative weight gains of niobium and tantalum were reduced by factors of 3 or more. Implanted niobium exhibited weight gain in direct proportion to oxidation time squared at 735 ~ Microstructural examination of the metals implanted with selected fluences of the 180 kV aluminum ions showed the following. The solubility limit of aluminum is extended by implantation, the body centered cubic (bcc) phases being retained to-60 at. pct A1 in all three metals. The highest fluence investigated, 2.4 • 1022 ions/m s, produced an-400-nm layer of VA13 beneath the surface of vanadium, and-300-nm layers of an amorphous phase containing-70 at. pct A1 beneath the niobium and tantalum surfaces. All three metals, implanted to this fluence and annealed at 600 ~ contained tri-aluminides, intermetallic compounds known for their oxidation resistances. Specimens implanted to this fluence were thus selected for the oxidation measurements.

Iron nano particles have been embedded in an aluminium matrix through high energy ball milling. The Mossbauer spectrum of the as-milled sample at room temperature shows the presence of a magnetic hyperfine sextet, a paramagnetic singlet and a quadrupole doublet with relative areas of nearly 78, 16 and 6%, respectively. The value of the hyperfine field for the sextet corresponds to that of α-Fe. The quadrupole component, which is indicative of formation of an Al-rich solid solution, is broad with a width of 0.73 mm/s indicating a distribution in the quadrupole fields. The value of the average splitting is 0.5mm/s and isomer shift (IS) equal to 0.49mm/s with respect to metallic iron. M-H measurements show that the unmilled system is non-magnetic while the milled system of 30 min is ferromagnetic and exhibits very soft magnetic properties. Unreacted Fe clusters embedded at the nano-crystalline Al grain boundaries seem to be responsible for the observed net magnetic moment.

Two isostructural series of polycrystalline compounds: Er 2−x Y x Fe 14 B and Er 2−x Ce x Fe 14 B have been studied by 57 Fe Mössbauer spectroscopy in the temperature range 80−370 K. The spin reorientation phenomenon (a transition from basal plane to axial easy magnetisation direction) has been studied extensively by a narrow step temperature scanning in the vicinity of the transition. Using the procedure of subtracting the Mössbauer spectra taken for the same compound at different temperatures, it was possible to follow the influence of transition on the shape of spectra. From this procedure it was concluded that in the region of transition each subspectrum splits into two Zeeman sextets, which are characterised by different hyperfine magnetic fields and quadrupole splittings. The consistent way of describing the Mössbauer spectra was proposed. The spin reorientation temperatures have been established for all compositions and compared with the values obtained from theoretical calculations of spin orientation angle based on phenomenological model. The spin arrangement diagrams have been constructed.

The Er 2−x Gd x Fe 14 B (x = 0.5, 1.0, 1.5) and Er 2−x Th x Fe 14 B (x = 0.0, 0.5, 1.0, 1.5, 2.0) polycrystalline compounds have been investigated with 57 Fe Mössbauer spectroscopy and differential scanning calorimetry (DSC). A comparison of results related to spin reorientation phenomena obtained for Gd-and Th-substituted compounds is presented in this paper. Spin reorientation phenomena (changes from planar to axial spin arrangements) have been studied extensively by a narrow step temperature scanning in the neighbourhood of the spin reorientation temperature, T SR. From the analysis of Mössbauer spectra, it was deduced that in the region of transition each subspectrum was split into two Zeeman sextets, which were characterised by different hyperfine magnetic fields and quadrupole splittings. A consistent way of fitting the spectra in the wide range of temperatures was proposed. The composition and temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. DSC studies proved that the spin reorientations were accompanied by thermal effects for all compositions of the Gd-and for x = 0.5 of the Th-series. Transformation enthalpy and T SR were determined from these studies and the two-stage character of transition was confirmed. Magnetic spin arrangement diagrams for R = Th and Gd series were constructed and compared using combined data obtained with both methods.

In continuous search for advanced electrocatalytic materials for the hydrogen evolution reaction (HER), based on transition metal series, two types of intermetallic compounds, TiPt and MoPt 2 , were investigated as cathode materials. Additionally, ionic activator (i.a.), the mixture of Na-molybdate and tris(ethylenediamine)Co(III) chloride, was in situ added into electrolyte, 6 M aqueous potassium hydroxide solution. The objective was to qualitatively compare their electrocatalytic efficiency evaluated by quasi-potentiostatic and galvanostatic technique. Results are presented to show: the Tafel slope, the exchange current density, the overpotential needed for a fixed hydrogen production rate and the apparent energy of activation. Obtained kinetic parameters reveal advanced catalytic ability of the MoPt 2 over the TiPt cathode towards HER. Also, important step forward was achieved by using ionic activator. The presence of Mo and Co species attached to the cathode surface was confirmed by XRF analysis. Thus, enhanced catalytic activity was assigned to the formation of Mo-Co-based electrodeposit. Results suggest to significant catalytic performance of the MoPt 2 cathode specially if used with ionic activator in alkaline water electrolysis.

Using an aberration-corrected transmission electron microscope, we report on imaging individual atomic columns of Li in the intermetallic compound Al 3 Li. The effect of electron energy on the imaging characteristic of Li is investigated by performing measurements at 80 kV employing a monochromated electron beam with an energy spread ⌬E of 0.2 eV and at 300 kV with ⌬E of 0.8 eV. These settings enable similar information transfer at both microscope operation conditions and allow a direct comparison between the 80 and the 300 kV measurements. Our experimental data show that the phase of the reconstructed exit-plane wave is highly sensitive to light atoms and that the displacement damage of light elements of low threshold recoil energy can be larger at 80 kV than at 300 kV. This behavior can be understood in terms of the relativistic elastic-scattering cross section between electrons and atoms.

This is the new wire evaluation work for the reliability of the wire-bonding process. There is a trend for the plastic integrated-circuit package to function at higher junction temperature with thinner wire. New alloy Au wires have been developed to meet the reliability requirements. Two types of alloy Au wires, Au-Pd and Au-Cu, were evaluated in this study. These samples were aged between 155°C and 205°C under air from 0 h to 3,000 h. According to this study, the phase-formation sequence of Au 2 Al, Au 5 Al 2 , and Au 4 Al intermetallic is similar to the pure Au wire. There is a Pd-rich layer working as a diffusion barrier to slow down the growth rate of intermetallic phases in the Au-Pd wire. The Au-Cu wire also slowed down the growth rate with a different mechanism. Both wires have better reliability based on the microstructure examination. The reliability test results show longer working life at higher temperatures in comparison with the regular Au wire.

Nanocrystalline Ni 3 Fe powders were obtained via wet mechanical alloying using benzene as surfactant. The differential scanning calorimetry (DSC) measurements showed the presence of an exothermic peak which does not correspond to any phase transformation or phase formation as was proved by X-ray diffraction measurements. The exothermic peak was observed neither for the dry milled samples nor for the wet milled and subsequently annealed powders at 350 • C for 4 h. The infra-red (IR) spectra registered for the wet milled samples showed a series of vibration bands corresponding to C 6 H 6 and also to a series of fragments resulting from benzene decomposition. The results obtained by IR investigation were confirmed by thermogravimetry and mass spectrometry (TG + MS) investigations. The main fragments resulting from the benzene decomposition on the surface of the nanocrystalline Ni 3 Fe powders are: CO 2 , CO and C. The evolution of the particle size distribution versus the milling time has been determined for the wet mechanical milling process of nanocrystalline Ni 3 Fe powders. The DSC analysis reveals a displacement of the exothermic peak onset towards lower temperatures and an increase of the surface of this peak attributed to the changes in the particles specific surface and to the quantity of benzene added in the milling experiments.

The destabilization of magnesium hydride (MgH 2) by solid-state reaction with Si in a nanoscale under vacuum was studied. The nanostructured Si films were deposited on the nanocrystalline MgH 2 /Mg composite substrate by the pulsed laser deposition (PLD). The cross-sectional transmission electron microscopy (TEM) shows that the metastable Mg 5 Si 6 is the only intermetallic compound formed in the Si-Mg region during the deposition. The destabilization of MgH 2 by Si forming the Mg 2 Si intermetallic compound was not observed in a nanoscale at 150°C under vacuum.

This in-depth overview examines a number of key considerations relating to environmental effects on today's advanced materials. While certainly not inclusive of all environmental issues, the article does investigate hightemperature corrosion and crack growth in ceramics and ceramic composites, hydrogen effects on ceramics, the corrosion of metal-matrix composites, hydrogen effects on fracture ofintermetallics, and corrosion and hydrogen effects in amorphous or glassy metals.

In the most majority of the cases, at the electronic components soldered with tin-based alloys was noted the germination and the growth of the whiskers, which have caused damages in all areas. Given the preliminary researches, to mitigate the occurrence of defects in electronic components has been proposed a new soldering alloy from Sn-Cu-Ag family and a new obtaining technology based on melt spinning method. The solder joints were obtained from the new elaborated alloy and a commercial alloy from Sn-Cu-Ag family, using the reflow and soldering iron methods. The solder joints were structural characterized by optical microscope, scanning electron microscope (SEM) and X-ray diffraction. At the solder joints with new alloys it has been observed a reduction of the grain size as well as the proportion of intermetallic compounds.

Lead is one of the metals which affect both human health and the environment. Generally the effects on human health are classified as: acute, chronic, on vision, cancer risk. Because these effects the Pb was removed and replaced with tin based alloys. Soldering with Sn-based alloys appeared increasingly growth whiskers which have caused damage in all areas by shorting printed circuits boards and electronic components. Given the preliminary research to reduce the appearance of growths whiskers of electronic components is proposed to obtain a nano-alloy soldering for families Sn-Ni-Cu and Sn-Cu-Ga and a technology for obtaining based on melt-spinning method in the form of ribbons. These ribbons are characterized by scanning electron microscopy, differential thermal analysis and X-ray diffraction.

We investigated Intermetallic compound formation mechanisms and their effect on the integrity of ball grid array Cu/Ni/Au/solder joints integrity were investigated. Substrates with three types of Au plating, and thus three different thicknesses [ Electrolytic (2.6 and 0.75pm). Immersion (0.25pm), and Selective (0.02pm) ] were used. After solder reflow, the solder joints were annealed for up to 1000 hrs at 150°C. Optical and electronic metallography together with Energy Dispersive Spectroscopy were used to locate and identify phases present in the joint for different annealing times. Brittle failure of solder joints was ascribed to the formation of a ternary intermetallic (Auo.5Ni0.5)Snd at the interface solderhbstrate. In the absence of post-reflow thermal aging, only NiaSnd was observed at the interface and it did not decrease the mechanical reliability of the joint. Tensile-shear stress tests were performed on unaged samples as well as samples aged for 1 hr, 4 hrs and 450 hrs.

INC. TEAM, DUKE UNIVERSITY TEAM, GOTEBORG UNIVERSITY TEAM-We investigate the viability of formation of very small diameter (< 0.5nm) freestanding SWNTs by CVD based on concept of carbon diffusion through the catalyst particle, originated from the vapor-liquid-solid growth mechanism. We found that the decrease of particle size required for nucleation of small diameter tubes results in a significant increase of catalytic decomposition temperature of hydrocarbon and, accordingly, the temperature required for nucleation and growth of nanotubes. However, high temperature increases the mobility of particles and endorses their agglomeration with formation of bigger particles, as well as leads to deactivation of catalyst by formation of intermetallic compounds with support material. The results of Raman spectroscopy, (n,m) assignments of the grown tubes and TEM studies for the smallest diameter tubes are presented. Performed ab-inito and molecular dynamics simulations qualitatively explain the experimental finding based on size dependent carbon solubility of catalyst, by analyzing supported nanocatalyst-carbon binary phase diagram.

The thermal stability of Ni overlayers electrochemically prepared on a polycrystalline vanadium (V) surface, was studied by means of X-ray and UV photoelectron spectroscopies (XPS, UPS). The results showed that upon cathodic polarization, a mixed Ni-Ni(OH) 2 adlayer is formed, while V surface becomes partially oxidized into vanadium oxide (V 2 O x). The applied potential during nickel electrodeposition is crucial for both Ni-Ni(OH) 2 composition and V 2 O x film thickness. Annealing the Ni-Ni(OH) 2 /V 2 O x interface under UHV conditions leads to the gradual reduction of the films and the formation of a new Ni-V intermetallic phase. A solid state reaction accompanies the decomposition of nickel and vanadium oxides resulting in oxygen migration from the Ni adlayer to the V support. The electronic structure of Ni-V intermetallic phase formed after oxide decomposition is compared to previously reported results for Ni alloys and intermetallic compounds.

This paper reports on the design, manufacturing and RF characterization of a zero-level packaging for RF-MEMS devices implementing TSVs (Through-Silicon Via’s) and metal bonding. Coplanar interconnection feedthroughs have been modelled and designed for low loss and wideband RF applications. The coplanar slot width of both sides in the vertical interconnection via’s pads have been enlarged and reshaped to compensate for the excessive shunt capacitance. Compensated packaged CPW lines have been manufactured and measured in the 0-40GHz frequency band. A significant improvement in terms of RF loss and frequency bandwidth have been obtained thanks to the compensation procedure. A comparison between simulated and measured data up to 40 GHz are presented and discussed.

Partial replacement of neodymium by cerium-rich Brazilian misch metal, has been studied on Fe (Nd \V MM V) B alloys by X-ray di!raction, thermomagnetic analysis, microprobe analysis and optical microscopy. Misch metal refers to a mixture of light rare-earth metals containing 56% Ce, 18% La, 13% Nd, 05% Pr, 02% Fe and 10% others rare-earths (wt%). Intermetallic compounds of Fe (Nd \V MM V) B with x"0.5, 0.7 and 0.9 were investigated. As-cast, pre-milled alloys present a binary microstructure with the Fe Nd B compound as matrix phase and Fe MM. The amount of Fe MM increases and the Curie temperature of the 14 : 2 : 1 compound decreases with increasing x. When these samples are submitted to 30 min of very high energy ball milling, the signal of the 14 : 2 : 1 phase disappears and the formation of a microstructure is observed with a new ferromagnetic stable phase with ¹ around 5003C together with an increase of-Fe in comparison for pre-milled samples.

The YCo system is characterized by a band structure which results in a magnetic instability of the itinerant subsystem. In such a case, the Co magnetism presents metamagnetic transitions upon application of an external magnetic "eld in the megagauss range. In the present paper we investigate the e!ect of substituting Co by Al in YCo. Polycrystalline samples of Y(Co \V Al V) (x"0.00, 0.03, 0.05, 0.07 and 0.10), in the Co-rich site were investigated by means of magnetization M(H), AC susceptibility ! (T) and nuclear magnetic resonance (NMR). The spontaneous magnetization as a function of Al concentration presents an anomalous behavior, which is closely related to N(E $ ,x), passing through a maximum at x"0.05, followed by a sharp decrease up to x"0.10. We show that the system becomes a very weak itinerant ferromagnet (VWIF) at x"0.10. NMR results show change in the Co hyper"ne "eld value upon Al alloying, which is related to changes in the conduction electrons density. An increase in the number of lines, with respect to YCo , attributed to the Al nucleus, was also veri"ed.

We have performed a temperature-dependent study of the Er L 3 and Co K edge X-ray magnetic circular dichroism (XMCD) in a (Er, Y)Co 3 system. The Co K XMCD signal shows a clear change at 35 K, which has been associated to a Co metamagnetic transition, previously reported. However, around the compensation temperature T com , no discontinuity is observed, as should be expected if the magnetic moments were just reversed. The observed smooth passage through T com is interpreted as a transition from a collinear to a non-collinear Co ordering, where Co moments assume intermediate orientations. The analysis of the E2/E1 ratio has allowed us to gain some insight into the magnetic properties of the 5d band. Finally, from our XMCD measurements, it is possible to complete the magnetic phase diagram of (Er, Y)Co 3 , previously proposed.

UC-V is an important alloying element for Ti since it stabilizes the high-temperature bcc phase of Ti at lower temperatures, while minimizing the formation of intermetallic compounds [1]. Theoretical determination of the Ti-V phase diagram must take into account structures based on both bcc and hcp lattices over the full V concentration range. With the cluster expansion formalism for alloys [2], DFT calculations determine the energies of all structures necessary for constructing the cluster expansion for the energetics of the alloy. Preliminary results indicate the DFT-based cluster approach determines solubility limits and transformation temperatures that are in good agreement with the experimental phase diagram [3].

The isothermal oxidation behavior of a ternary Ti-25Al-18Ta intermetallic alloy has been investigated in pure oxygen over the temperature range of 850°C to 1100°C. The oxidation kinetics was found to follow a parabolic rate. Effective activation energy of 259 kJ/mol was deduced from the oxidation data. The oxidation products were a mixture of Ti0 2 , the main component, A1 2 0 3 (alumina), and small amounts of tantalum oxide. The addition of Ta to Ti 3 Al alloy decreased the oxidation rate of the alloy. However, the oxidation scale was not compact and exhibited significant spallation especially at high temperatures.

Titanium aluminides are well-accepted elevated temperature materials. In conventional applications, their poor oxidation resistance limits the maximum operating temperature. Advanced reactors operate in nonoxidizing environments. This could enlarge the applicability of these materials to higher temperatures. The behavior of a cast gamma-alpha-2 TiAl was investigated under thermal and irradiation conditions. Irradiation creep was studied in beam using helium implantation. Dog-bone samples of dimensions 10 9 2 9 0.2 mm 3 were investigated in a temperature range of 300°C to 500°C under irradiation, and significant creep strains were detected. At temperatures above 500°C, thermal creep becomes the predominant mechanism. Thermal creep was investigated at temperatures up to 900°C without irradiation with samples of the same geometry. The results are compared with other materials considered for advanced fission applications. These are a ferritic oxide-dispersion-strengthened material (PM2000) and the nickel-base superalloy IN617. A better thermal creep behavior than IN617 was found in the entire temperature range. Up to 900°C, the expected 10 4 hour stress rupture properties exceeded even those of the ODS alloy. The irradiation creep performance of the titanium aluminide was comparable with the ODS steels. For IN617, no irradiation creep experiments were performed due to the expected low irradiation resistance (swelling, helium embrittlement) of nickel-base alloys.

In this study, it is aimed to determine the effect of Si3N4 ratio on wear behavior of aluminum matrix composite material produced by powder metallurgy method. Mixed aluminum powders containing 5 %, 10% and 15% by weight α-Si3N4 were pressed in the die under 500 MPa pressure and 10 mm diameter and 15 mm length block samples were produced. Then pressed samples were sintered in an atmosphere controlled tube furnace for 2 hours at 650 ° C. After the characterization study such as density and hardness measurements, dry sliding wear test all of the composite materials were performed by using pin-on-disk method. The tests were carried out on the TIRIBOMETER T10 / 20 abrasion tester according to ASTM G99-05. Dry sliding wear tests of composite were carried out under the different load (5-10-15 N) and at 1.41 m/s sliding speed for 2000 m wear distance. Wear test results showed that composite materials containing silicon nitride at different ratio have better wear resistance according to matrix powder metal parts produced under the same conditions.

The electrodeposition of aluminum-chromium alloy has been studied in the AICI3-EM ICI (l-ethyl-3-m ethylim idazolium chloride) melt containing CrCl2. No clear wave for the deposition of pure chromium is observed by voltammetric methods. The deposits always contain both aluminum and chromium, while the chromium deposition is preferred at low overpotential. The chromium content in the deposit increases by the use of the rotating disk electrode.

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We have propagated transverse sound in a magnetic field in the basal plane of UPt3, with the polarization vector oriented both in the basal plane and perpendicular to it. We observe a strong anisotropy in the magnetic field dependence of the attenuation for the two polarizations. Using a simple phenomenological model, we can understand the low-temperature field dependence as a

Manganese-copper(Mn-Cu) alloy has high damping and strength, but there are few engineering applications in the railway vehicles at present. For the suspended bracket made of Mn-Cu damping alloy (M2052) under the railway carbody, the strength, the damping and the vibration reduction capability of the M2052 was testified in this paper. Constant amplitude fatigue tests under different loads were implemented for verifying its fatigue strength, and corresponding S-N curves are fitted to prove that its strength and the fatigue properties are sufficient. Based on the single bracket and reducing vibrational system with the 500 kg counterweight, the Frequency Response Analysis (FRA) rig tests subjected to the sinusoidal and white noise signals were carried out and the comparison with similar shape made of Q355 proves that the single damping bracket has a better damping performance. In the vibration reduction test with a 500 kg counterweight, the Acceleration Spectral Density (ASD) response results in the range of 10-50 Hz subjected to the sine sweep show that the damping alloy bracket is lower by about 32.2% than the Q355 steel bracket, and the deduction amplitude is evident at other frequencies. However, under the excitation of the white noise signals, the acceleration and dynamic stress response of the M2052 and the Q355 brackets are not significantly distinguish. It is assumed that the size of the bracket is too small to fully exert the damping property of the structures. Finally, two suggestions are proposed for the development and application of the innovative damping alloy in the railway vehicles.