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Showing papers on "Alloy published in 1995"


Journal ArticleDOI
TL;DR: In this paper, the performance of the oxygen reduction reaction (ORR) on five binary Pi alloys (PtCr/C, PtMn/C and PtFe/C) supported on high surface area carbon in a proton exchange membrane fuel cell was investigated.
Abstract: The electrocatalysis of the oxygen reduction reaction (ORR) on five binary Pi alloys (PtCr/C, PtMn/C, PtFe/C, PtCo/C, and PtNi/C) supported on high surface area carbon in a proton exchange membrane fuel cell was investigated. All the alloy electrocatalysts exhibited a high degree of crystallinity with the primary phase of the type Pt3M (LI2 structure with fcc type lattice) and a secondary phase (only minor contribution from this phase) being of the type PtM (LIo structure with tetragonal lattice) as evidenced from x-ray powder diffraction (XRD) analysis. The electrode kinetic studies on the Pt alloys at 95~ and 5 atm pressure showed a two- to threefold increase in the exchange current densities and the current density at 900 mV as well as a decrease in the overvoltage at i0 mA em -2 relative to Pt/C eleetrocatalyst. The PtCr/C alloy exhibited the best performance. In situ EXAFS and XANES analysis at potentials in the double-layer region [0.54 V vs. reversible hydrogen electrode (RHE)] revealed (i) all the alloys possess higher Pt d-band vacancies per atom (with the exception of PtMn/C alloy) relative to Pt/C electrocatalyst and (it) contractions in the Pt-Pt bond distances which confirmed the results from ex situ XRD analysis. A potential excursion to 0.84 V vs. RHE showed that, in contrast to the Pt alloys, the Pt/C electrocatalyst exhibits a significant increase in the Pt d-band vacancies per atom. This increase, in Pt/C has been rationalized as being due to adsorption of OH species from the electrolyte following a Temkin isotherm behavior, which does not occur on the Pt alloys. Correlation of the electronic (Pt d-band vacancies) and geometric (Pt-Pt bond distance) with the electrochemical performance characteristics exhibits a volcano type behavior with the PtCr/C alloy being at the top of the curve. The enhanced electrocatalysis by the alloys therefore can be rationalized on the basis of the interplay between the electronic and geometric factors on one hand and their effect on the chemisorption behavior of OH species from the electrolyte. The role of Pt/C and Pt alloys on the mechanism of the oxygen reduction reaction (ORR) has been investigated previously, 1-4 however the mechanism still remains elusive. One of the first investigations I of the ORR on Pt alloy electrocatalysts was in phosphoric acid; the effect of changes in the Pt-Pt interatomic distances, caused by alloying, was examined. The strength of the [M-HO2]aas bond, the intermediate formed in the rate-determining step of the molecular dioxygen reduction, was shown to depend on the Pt-Pt bond distance in the alloys. A plot of the electrocatalytic activity vs. adsorbate bond strength exhibited a volcano type behavior. 5 It was shown that the lattice contractions due to alloying resulted in a more favorable Pt-Pt distance (while maintaining the favorable Pt electronic properties) for dissociative adsorption of 02. This view was disputed by Glass et al. ~ in their investigation on bulk alloys of PtCr (the binary alloy at the top of the volcano plot) of different compositions. The latter investigation showed no activity enhancement for the ORR in phosphoric acid. This study therefore suggested the possibility of differences in electrochemical properties of bulk vs. supported alloy electrocatalysts (small particles of 35-85 A). A recent study on supported PtCo electrocatalysts ~ revealed the possibility that particle termination, primarily at the vicinal planes in the supported alloy electrocatalyst, is the reason for the enhanced ORR electrocatalysis (i.e., vicinal planes are more active than ). Paffett et al., 3 attributed higher activities for the ORR on bulk PtCr alloys in phosphoric acid to surface roughening, and hence increased Pt surface area, caused by the dissolution of the more oxidizable alloying component Cr. In contrast to these findings on bulk alloys, the supported alloy electrocatalysts have been reported to retain their nonnoble alloying element in the electrode during long periods (6000-9000 h) of operation in phosphoric acid fuel cells (PAFCs) 6 and proton exchange membrane fuel ceils (PEMFCs). 7 Based on these previous investigations and in the context of the ORR mechanisms, the principle explanations for the

1,063 citations


Journal ArticleDOI
Akihisa Inoue1
TL;DR: A review of the recent research results on new amorphous alloys can be found in this paper, where the main topics consist of the following five parts ; (1) the finding of new AMO alloys with extremely large glass-forming ability in a number of alloy systems, (2) the mechanism for the achievement of the large AMO ability, (3) the clarification of fundamental properties of the new amOAlloys, (4) the successful examples of producing bulk amOOD alloys by four different techniques of water quenching, metallic mold casting
Abstract: This paper aims to review our recent research results on new amorphous alloys. The main topics consist of the following five parts ; (1) the finding of new amorphous alloys with extremely large glass-forming ability in a number of alloy systems, (2) the mechanism for the achievement of the large glass-forming ability, (3) the clarification of fundamental properties of the new amorphous alloys, (4) the successful examples of producing bulk amorphous alloys by four different techniques of water quenching, metallic mold casting, arc melting and unidirectional zone melting, and (5) the high tensile strength of the bulk amorphous alloys. These new results enable the elimination of the limitation of sample shape which has prevented the development of amorphous alloys as engineering materials and are expected to give rise to the revisit age to amorphous alloys.

878 citations


Journal ArticleDOI
TL;DR: In this article, an overview of the metallurgical reactions during the vacuum sintering process of powder mixtures for the manufacture of cermets is presented, together with differential thermal analysis.
Abstract: An overview of the metallurgical reactions during the vacuum sintering process of powder mixtures for the manufacture of cermets is presented. The relatively complex phase reactions in the multi-component system Ti/Mo/W/Ta/Nb/C,N-Co/Ni are discussed. The liquid binder phase reacts with titanium carbonitride by preferentially dissolving titanium carbide leaving titanium nitride undissolved. The compositions and the amounts of the gas species set free during the sintering process were monitored and led —together with differential thermal analysis — to a better understanding of the mechanisms that govern the sintering behaviour. The properties and the microstructure of cermets depend on the nature and the alloy status of the prematerials. The composition of the prematerials with respect to the carbon-nitrogen ratio, the stoichiometry of the hard phase and the amount and composition of the binder phase have a decisive influence on the properties and the cutting performances of the final products. Optimization of the properties with respect to the desired performance is possible. Examples of the cermet cutting performance in various applications are discussed.

520 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the evaporation of FeCl2(g) and its outward diffusion through the scale is the rate controlling step of the active oxidation of a low alloy steel at 500°C and high alloy steels at 600 and 700°C.

431 citations


Journal ArticleDOI
TL;DR: In this article, the potential impact of grain boundary design and control on the bulk sensitization and intergranular corrosion resistance of a commercial corrosion resistant nickel-based austenitic alloy: Alloy 600 (UNS N06600) was assessed.
Abstract: The objective of this study was to assess, for the first time, the potential impact of ``Grain Boundary Design and Control`` on the bulk sensitization and intergranular corrosion resistance of a commercial corrosion resistant nickel-based austenitic alloy: Alloy 600 (UNS N06600). Increasing the special grain boundary ({Sigma} {le} 29) frequency in thermomechanically processed Alloy 600 from 37% to 71% has been shown to result in commensurate decreases in bulk intergranular corrosion susceptibility in both the solution annealed and sensitized condition; these findings being attributed to both the intrinsic corrosion resistance, and resistance to solute segregation and precipitation exhibited by structurally-ordered low {Sigma} grain boundaries. These results provide considerable promise for the practical application of grain boundary design and control considerations in the general field of corrosion prevention and control.

389 citations


Journal ArticleDOI
TL;DR: In this article, a copper mold casting method was used to construct a bulk glassy alloys with diameters of 0.5 and 1.0 mm, and the results showed that the maximum thickness for glass formation is about 10 times larger than the largest thickness for Fe-based alloys reported up to date.
Abstract: Bulk glassy Fe 73 Al 5 Ga 2 P 11 C 5 B 4 alloys in cylindrical form with diameters of 0.5 and 1.0 mm were found to form by a copper mold casting method. The further increase in diameter causes the formation of coexistent glassy, Fe 3 (B, C), Fe 2 B and Fe 3 P phases for the 1.5 mm ? sample and coexistent Fe 3 (B, C), Fe 2 B and Fe 3 P phases for the 2.0 mm ? sample. It is to be noticed that the maximum thickness for glass formation is about 10 times larger than the largest thickness for Fe-based glassy alloys reported up to date. The glass transition temperature (T g ), crystallization temperature (T x ) and heat of crystallization of the 1.0 mm ? glassy alloy are 732 K, 785 K and 3.76 kJ/mol, respectively. No appreciable difference in the thermal stability and magnetic properties is seen between the bulk glassy alloys and the melt-spun ribbon. The 1.0 mm ? glassy alloy has ferromagnetism with a Curie temperature of 606 K and exhibits 1.26 T for saturation magnetization (B s ), 82 A/m for coercivity (H c ) and 0.38 for the ratio of residual magnetization to B s at room temperature. The large ΔT x ( = T x - T g ) and large glass-forming ability can be obtained for the Fe-based alloy containing simultaneously the five solute elements. The effectiveness of the multiplication is presumably due to the combination of the following three effects ; (1) the suppression of crystalline nuclei due to the increase in dense random packing density for the glassy structure containing P, C and B with significantly different atomic sizes, (2) the difficulty of atomic rearrangements for the precipitation of the Fe-metalloid compounds caused by the generation of Al-metalloid pairs with strongly attractive bonding nature, and (3) the decrease in the preferential precipitation tendency of Fe-B and Fe-C compounds by the dissolution of Ga which is immiscible to B and C and soluble to Fe.

380 citations


Journal ArticleDOI
TL;DR: In situ current density mapping, scanning electron microscopy, and energy dispersive spectroscopy were used to study the effects of cerium as a corrosion inhibitor for an aluminum copper alloy (Al 2024-T4) in chloride containing solutions.
Abstract: In situ current density mapping, scanning electron microscopy, and energy dispersive spectroscopy were used to study the effects of cerium as a corrosion inhibitor for an aluminum copper alloy (Al 2024-T4) in chloride containing solutions. It was found that cerium inhibits corrosion of this alloy by reducing the rate of the cathodic reaction. This was due to the formation of cerium-rich films over copper containing intermetallics which act as local cathodic sites. Results from tests carried out on an aluminum/copper galvanic couple, which was used to simulate the electrochemical behavior of the copper containing intermetallics, showed that corrosion inhibition was associated with the formation of a Ce-rich film over the copper in agreement with that observed for the alloy.

284 citations


Journal ArticleDOI
TL;DR: In this article, a liquid mixing and casting process that can be used to produce SiC particulate-reinforced magnesium metal matrix composites via conventional foundry processes is presented.
Abstract: Magnesium metal matrix composites (MMCs) have been receiving attention in recent years as an attractive choice for aerospace and automotive applications because of their low density and superior specific properties. This article presents a liquid mixing and casting process that can be used to produce SiC particulate-reinforced magnesium metal matrix composites via conventional foundry processes. Microstructural features, such as SiC particle distribution, grain refinement, and particle/matrix interfacial reactions of the cast magnesium matrix composites, are investigated, and the effects of solidification-process parameters and matrix alloys (pure Mg and Mg-9 pct Al-1 pct Zn alloy AZ91) on the microstructure are established. The results of this work suggest that in the solidification processing of MMCs, it is important to optimize the process parameters both to avoid excessive interfacial reactions and simultaneously achieve wetting, so that a good particle distribution and interfacial bonding are obtained. The tensile properties, strain hardening, and fracture behavior of the AZ91/SiC composites are also studied and the results are compared with those of the unreinforced AZ91 alloy. The strengthening mechanisms for AZ91/SiC composite, based on the proposed SiC particle/matrix interaction during deformation, are used to explain the increased yield strength and elastic modulus of the composite over the magnesium matrix alloy. The low ductility found in the composites is due to the early appearance of localized damages, such as particle cracking, matrix cracking, and occasionally interface debonding, in the fracture process of the composite.

270 citations


Journal ArticleDOI
TL;DR: In this article, the microstructure of both 5000 and 6000 series alloy sheet can be controlled to provide the properties required for particular automotive applications, and the annealed strength and formability is strongly dependent upon grain size, Mg content, and, to a lesser extent, on crystallographic texture.

266 citations


Journal ArticleDOI
TL;DR: In this article, the effect of eutectic morphology on the room temperature fracture toughness of different NiAl-based alloys was evaluated, and the results showed that directionally solidified alloys exhibited superior toughness compared to binary NiAl or conventionally cast alloys, but the principal mechanism responsible for the improved toughness was dependent on the second phase morphology.

244 citations


Journal ArticleDOI
TL;DR: In this article, a difference in the Kerr rotation spectrum is observed between ordered, but not disordered, [001] and [111] films, respectively, for all deposition temperatures at high temperatures (≥400 and ≥520°C for FePt and CoPt, respectively).
Abstract: Equiatomic CoPt and FePt alloy films were deposited by cosputtering at substrate temperatures between 25 and 640 °C. Those deposited at high temperatures (≥400 and ≥520 °C for FePt and CoPt, respectively) contained ordered intermetallic compounds with the L10 crystal structure while those deposited at lower temperatures were chemically disordered. Deposition on single crystal [001] MgO and [0001] Al2O3 resulted in [001] and [111] oriented films, respectively, for all deposition temperatures. Ordered alloys have out‐of‐plane magnetic easy axes and modified magneto‐optic Kerr rotation spectra relative to the disordered case. A difference in the Kerr rotation spectrum is observed between ordered, but not disordered, [001] and [111] films.

Patent
24 Aug 1995
TL;DR: In this article, a process for electrolessly depositing cobalt-tin alloys with adjustable tin contents from 1 to over 25 atomic percent tin is described, which is useful in the electronics and computer industries for device, chip interconnection and packaging applications.
Abstract: A process for electrolessly depositing cobalt-tin alloys with adjustable tin contents from 1 to over 25 atomic percent tin is disclosed. The deposited alloy is useful in the electronics and computer industries for device, chip interconnection and packaging applications. When used for chip interconnection applications, for example, the invention replaces the currently used complicated ball-limiting-metallurgy. The invention may also be used to inhibit hillock formation and electromigration in copper wire structures found in computers and micron dimension electronic devices.

Journal ArticleDOI
TL;DR: In this paper, the electrochemical behavior of Cu, Cu-Al and Al-Al-Ag alloys in aqueous solutions of NaCl (0.5 M, pH = 3.00) was studied by means of voltammetric methods and electrochemical impedance spectroscopy.

Journal ArticleDOI
TL;DR: In this article, the effects of increased diffusivity at base material grain boundaries, of grain boundary motion, and grain boundary grooving, on isothermal solidification during TLP bonding are described.
Abstract: Modelling of transient liquid phase (TLP) bonding is reviewed. The outputs produced during analytical and numerical modelling are discussed in detail and compared with actual experimental results produced when joining simple binary alloy systems. The effects of increased diffusivity at base material grain boundaries, of grain boundary motion, and of grain boundary grooving, on isothermal solidification during TLP bonding are described. There is a critical need for detailed research in which modelling output is closely related to direct microstructural observations during bonding of complex alloy systems.

Journal ArticleDOI
TL;DR: It was concluded that new alloys for biomedical materials should be designed as titanium-zirconium base alloys.
Abstract: Mechanical properties of titanium-zirconium binary alloys were investigated in order to reveal their possible use for new biomedical materials and to collect useful data for alloy design through a hardness test, a tensile test, and optical microscopy. The hardness of the alloy containing 50% zirconium was approximately 2.5 times as large as the hardness of pure titanium and pure zirconium. Tensile tests showed a similar tendency. No changes between hardness of as cast specimens and as homogenized specimens were observed, nor were changes in microstructures noted. Comparisons between the Ti-6Al-4V alloy and the Ti-Zr-6Al-4V alloy indicated that a titanium-zirconium alloy could provide a base material for a new biomedical alloy. From these results, it was concluded that new alloys for biomedical materials should be designed as titanium-zirconium base alloys. © 1995 John Wiley & Sons, Inc.

Journal ArticleDOI
TL;DR: In this article, the authors reported the production of full strength compacts of metallic glass by warm extrusion of powders at the supercooled liquid state just above the glass transition temperature.
Abstract: We report the production of full strength compacts of metallic glass by warm extrusion of powders at the supercooled liquid state just above the glass transition temperature. The alloy used was Zr65Al10Ni10Cu15 (at. %) which has the lowest viscosity among Zr‐based metallic glasses with large supercooled liquid region. The tensile strength and Young’s modulus of the glassy powder compacts were 1520 MPa and 80 GPa, respectively, which are similar to that obtained in the as‐cast bulk alloy and melt‐spun ribbon. This opens up possibilities of producing high strength amorphous alloys with complex shapes.

Journal ArticleDOI
TL;DR: In this paper, the synthesis and gas permeation properties of ceramic supported ultrathin palladium-silver alloy membranes were studied. But the authors focused on the synthesis of the Pd-Alumina support.

Journal ArticleDOI
TL;DR: In this article, the compositional effect for the large glass-forming ability has also been discussed by taking the present data into consideration, and the cast amorphous Zr 60 Al 10 Co 3 Ni 9 Cu 18 alloy subjected to tensile testing exhibits distinct serrated flow before final fracture.
Abstract: Bulky amorphous alloys were found to form in Zr-Al-M (M=Co, Ni, Cu) systems by arc melting on a copper hearth. The largest thickness for glass formation is 6. 1 mm for Zr 60 Al 10 Co 3 Ni 9 Cu 18 , 6.8 mm for Zr 60 Al 15 Co 5 Ni 15 Cu 5 and 6.2 mm for Zr 55 Al 20 Co 17.5 Ni 2.5 Cu 5 . The optimum composition for glass-forming ability shifts from the Cu-rich side to the Co-rich side through the Ni-rich side with increasing Al content from 10 to 20%. The use of a metallic mold casting process enabled the formation of amorphous cylinders with the largest diameter of 7 mm for the three alloys. The compositional effect for the large glass-forming ability has also been discussed by taking the present data into consideration. The cast amorphous Zr 60 Al 10 Co 3 Ni 9 Cu 18 alloy subjected to tensile testing exhibits distinct serrated flow before final fracture. The generation of the serrated flow is noticed because the alloy has a ductile nature which enables the momentary stop of the shear sliding. The Young's modulus, tensile fracture strength and fracture elongation are 97 GPa, 1510 MPa and 2.0%, respectively. The fracture occurs along the maximum shear plane and the fracture surface consists of a well-developed vein pattern. The size of their veins is about 10 times as large as that for the melt-spun ribbon and hence the shear deformation region occurs in a much wider region for the cast alloy, indicating the necessity of a larger amount of energy up to final fracture. The finding of the amorphous alloys with the large glass-forming ability and the extremely ductile nature is important for the subsequent development of metallic glassy materials.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the grain size, macrotexture and microtexture of Ni and Ni-Fe alloy is strongly dependent on the amount of iron co-deposited with nickel.

Journal ArticleDOI
01 Oct 1995-Langmuir
TL;DR: In this paper, the optical spectra and HRTEM were used to obtain phase-separated composites of silver and copper, whose observed spectra are very similar to the theoretical spectra of silver/copper alloy particles.
Abstract: Ultrafine metal particles (copper, silver, and gold) have been prepared by UV irradiation of their salts dissolved in ethanol. The photoreduction of their metal salts is greatly accelerated by using benzoin as a photoinitiator. Highly dispersed copper and silver particles are obtained through the photoreduction. In the case of gold, the average diameter of the gold particles increases from 7 to 17 nm with increasing benzoin concentration. This method has been applied to obtain silver/copper and silver/gold composite particles. The optical spectra and HRTEM show that the silver/copper composite particles are phase-separated composites of silver and copper, whose observed spectra are very similar to the theoretical spectra of silver/copper alloy particles. In the silver/gold system, the observed spectra are in good agreement with the theoretical spectra of the alloy particles since that the surface plasmon band remains as a single peak and shifts continuously by varying the silver/gold composition. This strongly suggests the formation of silver/gold alloy particles.

Journal ArticleDOI
TL;DR: In this article, the authors performed hot torsion tests on Al-Zn-Mg-Cu alloys (7012 and 7075), which had been direct chill cast, homogenized and precipitation treated to give fine, well-dispersed precipitates.
Abstract: Hot torsion tests, in the range 250–450 °C and 0.05–5.0 s−1, were performed on AlZnMgCu alloys (7012 and 7075), which had been direct chill cast, homogenized and precipitation treated to give fine, well-dispersed precipitates. Additional tests were conducted on material that had been extruded, solution treated or precipitation treated at deformation temperature. The peak flow stress was related to the strain rate by the hyperbolic sine equation; the activation energy for precipitated alloys was close to that of the bulk self-diffusion of pure aluminium. For solution-treated metal, the peak stress was very high at low temperatures due to dynamic precipitation; as a consequence, the activation energy was about 50% higher than that of precipitated alloys. The ductility was almost independent of temperature in the investigated range, but decreased with rising strain rate. The ductility of the extruded alloys was almost double that of the as-cast material, with the exception of the solution-treated material where, at low temperature, the ductility of the extruded alloy was lower. The original grains were elongated with precipitates on the boundaries. The dynamically recovered subgrains exhibited sub-boundaries with a high density of fine precipitates and an interior network of dislocations also tied to precipitates.

Journal ArticleDOI
TL;DR: In this article, the authors show that the ductility of the Al7Si-0.4Mg casting alloy depends on the dendrite cell size and the size and shape of the silicon particles.
Abstract: By changing the solidification rate, chemical modification and length of solution treatment we show that the ductility of the Al7Si0.4Mg casting alloy depends on the dendrite cell size and the size and shape of the silicon particles. For the strontium-modified alloy the ductility has a minimum at intermediate cell sizes, the fracture mode being transgranular for the larger cell sizes and intergranular for the finer cell sizes. For the unmodified alloy, the ductility also has a minimum at intermediate cell sizes and the fracture mode is, again, transgranular at large cell sizes and intergranular at fine cell sizes. The ductility of the large cell size unmodified materials is low, being dominated by the large elongated silicon particles. If the unmodified alloy is solution treated for shorter times it is more brittle because the silicon particles are more elongated.

Journal ArticleDOI
TL;DR: In this article, two commercial oxide dispersion strengthened alumina-forming FeCrAl alloys, Inco alloy MA956 and Kanthal alloy APM, were studied in order to look at the effect of reactive elements on their oxidation behavior.
Abstract: Two commercial oxide dispersion strengthened alumina-forming FeCrAl alloys, Inco alloy MA956 and Kanthal alloy APM, were studied in order to look at the effect of reactive elements on their oxidation behaviour. MA956 has a distribution of Y2O3−Al2O3 particles, while APM has a ZrO2—AI2O3 distribution. Isothermal oxidation at 1000°C and 1200°C showed a reduced oxidation rate for both alloys compared to that of an undoped FeCrAl alloy. In short-term cyclic tests at 1200°C, both alloys exhibited excellent scale adhesion. Using scanning transmission electron microscopy with X-ray energy dispersive spectroscopy, both Y and Zr, respectively, were found to segregate to the oxide grain boundaries and the metal-scale interface after oxidation at 1000°C and 1200°C. These experimental observations are discussed with regard to a new theory to explain the reactive element effect.

Journal ArticleDOI
TL;DR: In this paper, the development of a conversion coating in a stannate bath on magnesium-based ZC71 alloy and on a metal matrix composite (MMC), comprising a ZC 71 alloy matrix and 12 vol% SiC particles, has been studied using weight gain behaviour, measurements of corrosion potential, X-ray diffraction and microscopic examination.

Patent
19 Jul 1995
TL;DR: A new class of light or reactive elements and monophase α-matrix magnesium-and aluminum-based alloys with superior engineering properties, for the latter being based on a homogeneous solute distribution or a corrosion-resistant and metallic shiny surface withstanding aqueous and saline environments and resulting from the control during synthesis of atomic structure over microstructure to net shape of the final product, said α −matrix being retained upon conversion into a cast or wrought form as mentioned in this paper.
Abstract: A new class of light or reactive elements and monophase α′-matrix magnesium- and aluminum-based alloys with superior engineering properties, for the latter being based on a homogeneous solute distribution or a corrosion-resistant and metallic shiny surface withstanding aqueous and saline environments and resulting from the control during synthesis of atomic structure over microstructure to net shape of the final product, said α′-matrix being retained upon conversion into a cast or wrought form. The manufacture of the materials relies on the control of deposition temperature and in-vacuum consolidation during vapor deposition, on maximized heat transfer or casting pressure during all-liquid processing and on controlled friction and shock power during solid state alloying using a mechanical milling technique. The alloy synthesis is followed by extrusion, rolling, forging, drawing and superplastic forming for which the conditions of mechanical working, thermal exposure and time to transfer corresponding metastable α′-matrix phases and microstructure into product form depend on thermal stability and transformation behavior at higher temperatures of said light alloy as well as on the defects inherent to a specific alloy synthesis employed. Alloying additions to the resulting α′-monophase matrix include 0.1 to 40 wt. % metalloids or light rare earth or early transition or simple or heavy rare earth metals or a combination thereof. The eventually more complex light alloys are designed to retain the low density and to improve damage tolerance of corresponding base metals and may include an artificial aging upon thermomechanical processing with or without solid solution heat and quench and annealing treatment for a controlled volume fraction and size of solid state precipitates to reinforce alloy film, layer or bulk and resulting surface qualities. Novel processes are employed to spur production and productivity for the new materials.

Journal ArticleDOI
Chenming Hu1, K. P. Rodbell1, Timothy D. Sullivan1, K. Y. Lee1, D. P. Bouldin1 
TL;DR: Physical phenomena underlying failure due to electromigration and stress-induced voiding in fine Al and Al-alloy thin-film conducting lines are examined in the context of accelerated testing methods and structures.
Abstract: Physical phenomena underlying failure due to electromigration and stress-induced voiding in fine Al and Al-alloy thin-film conducting lines are examined in the context of accelerated testing methods and structures. Aspects examined include effects due to line isolation (the absence of reservoirs at conductor ends), solute and precipitate phenomena, conductor critical (Blech) length, microstructure, film deposition conditions, and thermal processing subsequent to film deposition. Emphasis is on the isolated, submicron-wide, Al(Cu)-based thin-film interconnection lines of IBM VLSI logic and memory chips.

Journal ArticleDOI
TL;DR: In this article, it is shown that the exclusive scale formation of the more stable, slow-growing oxide is more difficult on a two-phase alloy, requiring a higher concentration of the reactive alloy component than for a corresponding single-phase alloys.
Abstract: The high-temperature corrosion behavior of two-phase alloys presents a number of differences compared to that of single-phase alloys. These differences are mainly a consequence of the limitations that the presence of two phases impose on the diffusion of the alloy components. In this review, it is shown that the exclusive scale formation of the more stable, slow-growing oxide is more difficult on a two-phase alloy, requiring a higher concentration of the more reactive alloy component than for a corresponding single-phase alloy. The main types of corrosion behavior for binary two-phase alloys are also considered, showing that if diffusion in the alloy is slow the scale structure will closely reflect that of the starting material. When diffusion in the alloy is not negligible, the scale structure becomes similar to what forms on single-phase alloys. The oxidation of two-phase ternary alloys is shown to be even more complex than the two-phase binary alloys. The principal added complexity compared to the binary alloys is that diffusion in the ternary alloys may also occur in the presence of two metal phases, as a result of an extra degree of freedom in the ternary system. The oxidation behavior of two-phase ternary alloys is discussed in the context of a number of recent experimental results.

Journal ArticleDOI
TL;DR: In this paper, the influence of various solutes on the as cast grain sizes of binary aluminium alloys has been examined using the ALCAN grain refinement assessment technique using an Al-Ti-B grain refiner.
Abstract: The influence of various solutes on the as cast grain sizes of binary aluminium alloys has been examined using the ALCAN grain refinement assessment technique. Studies were performed with and without melt inoculation with an Al–Ti–B grain refiner. In both cases, grain size was found to depend significantly on the magnitude of the constitutional supercooling parameter P. In each case, grain sizefell rapidly to a plateau as P increased from zero to a value of ~15–20.MST/3109

Journal ArticleDOI
TL;DR: Cerium-rich conversion coatings have been deposited onto aluminium 2024-T351 alloy by immersion into a solution containing 10 g L -1 CeCl 3 and 1% H 2 O 2 in a process described as "cerating" as mentioned in this paper.
Abstract: Cerium-rich conversion coatings have been deposited onto aluminium 2024-T351 alloy by immersion into a solution containing 10 g L -1 CeCl 3 and 1% H 2 O 2 in a process described as 'cerating'. Prior to deposition the alloy had been prepared either by using a standard chemical pretreatment used for aerospace alloys before conversion coating or by polishing. X-ray photoelectron spectroscopy and scanning electron microscopy have been used to characterize these cerium-containing conversion coatings. It was found that, during deposition, hydrated cerium oxide initially covered the intermetallics present in the alloy surface and then covered the surface generally. Deposition continued over the intermetallics throughout the conversion coating process, resulting in thick, heavily-racked regions considerably greater than the average thickness of the film (>0.3 μm). Elsewhere the coating was generally up to 0.2 μm thick, and appeared to comprised of deposited particles around 100 nm in size.

Journal ArticleDOI
TL;DR: In this article, the effect of mechanical milling on the structural stability of rapidly solidified aluminum-based metallic glasses is investigated using transmission electron microscopy (TEM) and X-ray diffraction methods.
Abstract: Various experimental techniques have been used to investigate the effect of mechanical milling on the structural stability of rapidly solidified aluminum-based metallic glasses. Using transmission electron microscopy (TEM) and X-ray diffraction methods, the formation of nanocrystalline Al particles in some ball-milled Al-rich metallic glasses (such as Al90Fe5Gd5 and Al90Fe5Ce5) is clearly observed. For other compositions with lower Al concentration such as Al85Ni5Y10, no such phase transformation can be detected by TEM or X-ray. However, differential scanning calorimetry (DSC) measurements show that the crystallization peaks of the ball-milled Al85Ni5Y10 metallic glass shifted to higher temperatures, while the crystallization enthalpy associated with the first exothermic peak decreased to a lower value, revealing that certain structural changes have taken place as a result of mechanical deformation. The compositional dependence of the structural stability of Al-based metallic glasses against mechanical deformation suggests that the nanocrystal formation induced by a deformation process is different from that caused by a thermal process. The large plastic strain induced atomic displacements and the enhancement of atomic mobility during the deformation process, are the possible mechanisms of mechanical deformation-induced crystallization. Our results demonstrate a new way of obtaining nanophase glassy composite alloy powders which are suitable for engineering applications upon further consolidation processing.