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Showing papers on "Alloy published in 1999"


Journal ArticleDOI
TL;DR: In this article, a co-reduction of chlorauric acid HAuCl4 and silver nitrate AgNO3 with sodium citrate is used to form homogeneous gold−silver alloy nanoparticles.
Abstract: Gold−silver alloy nanoparticles with varying mole fractions are prepared in aqueous solution by the co-reduction of chlorauric acid HAuCl4 and silver nitrate AgNO3 with sodium citrate. As the optical absorption spectra of their solutions show only one plasmon absorption it is concluded that mixing of gold and silver leads to a homogeneous formation of alloy nanoparticles. The maximum of the plasmon band blue-shifts linearly with increasing silver content. This fact cannot be explained by a simple linear combination of the dielectric constants of gold and silver within the Mie theory. On the other hand, the extinction coefficient is found to decrease exponentially rather than linearly with increasing gold mole fraction xAu. Furthermore, the size distribution of the alloy nanoparticles is examined using transmission electron microscopy (TEM). High-resolution TEM (HRTEM) also confirms the formation of homogeneous gold−silver alloy nanocrystals.

1,327 citations


Journal ArticleDOI
TL;DR: In this article, both voltametric (potentio-dynamic) and chrono-amperometric (constant voltage, either applied directly or progressively increased during the first steps of the treatment) experiments are conducted.

733 citations


Journal ArticleDOI
TL;DR: Experimental results indicated that crystal structure and morphology of the cast alloys were sensitive to their molybdenum contents, and the alpha" phase Ti-7.5Mo alloy had the lowest hardness.

585 citations


Journal ArticleDOI
TL;DR: In this article, the authors used transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS) to characterize the surface electronic state of the as-prepared samples and found that boron donated electron to nickel in Ni-B alloy, resulting in electron-enrichment of elemental Ni.

321 citations


Journal ArticleDOI
TL;DR: In this article, the feasibility of friction stir welding (FSW) of steel has been investigated and it has been shown that the mechanical properties of FSW of 12% chromium alloy and low carbon steel joints compare favorably with the properties of the parent metal.
Abstract: The feasibility of friction stir welding (FSW) of steel is demonstrated. Tensile and bend testing have confirmed that the mechanical properties of friction stir welded 12% chromium alloy and low carbon steel joints compare favourably with the properties of the parent metal. Some initial feasibility studies of FSW of both 12% chromium alloy and low carbon steel are described. Although more development work is needed, particularly to improve tool materials, the prognosis for continued developments in FSW of steel is shown to be good.

320 citations


Journal ArticleDOI
TL;DR: In this paper, hardness measurements, differential scanning calorimetry and transmission electron microscopy have been used to study the precipitation hardening behavior in aluminum alloy 6022, and the results showed that the hardness of 6022 can be improved with a change in composition, processing and aging practices.

295 citations


Journal ArticleDOI
TL;DR: In this article, the role of the metastable intermediate precipitate phase(s) in the nucleation of successive intermediate or equilibrium precipitate phases remains to be established, and the authors report experimental observations of the precipitation sequence in a WE54 alloy during isothermal ageing at 250 C.

200 citations


Journal ArticleDOI
TL;DR: Amorphous and nanocrystalline Mg-based alloys were produced by rapid quenching (melt-spinning) and their hydrogenation properties were studied as discussed by the authors.

170 citations


Journal ArticleDOI
TL;DR: The probability and appropriate processing parameters for diffusion bonding of a titanium alloy to a stainless steel web with an Ni interlayer have been investigated in this paper, and the microstructure of the diffusion bonding joint has been observed by microscopy, SEM, and EPMA, and the main factors affecting diffusion bonding have been analyzed.

165 citations


Journal ArticleDOI
TL;DR: In this article, the friction wear properties of designed alloys and typical conventional biomedical titanium alloys were evaluated using a pin-on-disk type friction wear testing system and measuring the weight loss and width of groove of the specimen.
Abstract: Metallic materials such as stainless steel, Co–Cr alloy, pure titanium and titanium alloys have been used for surgical implant materials. The α+β type titanium alloy such as Ti-6Al-4V ELI has been most widely used as an implant material for artificial hip joint and dental implant because of its high strength and excellent corrosion resistance. Toxicity of alloying elements in conventional biomedical titanium alloys like Al and V, and the high modulus of elasticity of these alloy as compared to that of bone have been, however, pointed out [1] , [2] . New β type titanium alloys composed of non-toxic elements like Nb, Ta, Zr, Mo and Sn with lower moduli of elasticity, greater strength and greater corrosion resistance were, therefore, designed in this study. The friction wear properties of titanium alloys are, however, low as compared to those of other conventional metallic implant materials such as stainless steels and Co–Cr alloy. Tensile tests and friction wear tests in Ringer’s solution were conducted in order to investigate the mechanical properties of designed alloys. The friction wear characteristics of designed alloys and typical conventional biomedical titanium alloys were evaluated using a pin-on-disk type friction wear testing system and measuring the weight loss and width of groove of the specimen.

163 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure and tensile behavior of two Al-7 pct Si-Mg casting alloys, with magnesium contents of 0.4 and 0.7pct, have been studied.
Abstract: The microstructure and tensile behavior of two Al-7 pct Si-Mg casting alloys, with magnesium contents of 0.4 and 0.7 pct, have been studied. Different microstructures were produced by varying the solidification rate and by modification with strontium. An extraction technique was used to determine the maximum size of the eutectic silicon flakes and particles. The eutectic Si particles in the unmodified alloys and, to a lesser extent, in the Sr-modified alloys are larger in the alloys with higher Mg content. Large Fe-rich π-phase (Al9FeMg3Si5) particles are formed in the 0.7 pct Mg alloys together with some smaller β-phase (Al5FeSi) plates; in contrast, only β-phase plates are observed in the 0.4 pct Mg alloys. The yield stress increases with the Mg content, although, at 0.7 pct Mg, it is less than expected, possibly because some of the Mg is lost to π-phase intermetallics. The tensile ductility is less in the higher Mg alloys, especially in the Sr-modified alloys, compared with the lower Mg alloys. The loss of ductility of the unmodified alloy seems to be caused by the larger Si particles, while the presence of large π-phase intermetallic particles accounts for the loss in ductility of the Sr-modified alloy.

Journal ArticleDOI
TL;DR: In this paper, the semiconducting properties of passive films formed on nickel-base alloys type Alloy 600 in borate buffer solution were studied by capacitance measurements and photoelectrochemistry.

Patent
24 May 1999
TL;DR: In this paper, magnetically permeable, high magnetic saturation, primarily iron NiFe alloys are formed on thin seed layers by sputtering and electroplating, and the magnetically superlative NiFe alloy has increased concentration of a body centered cubic crystalline phase and/or a decreased concentration of face centered cubic crystaline phase compared with conventional Ni0.45Fe0.55.
Abstract: Magnetically permeable, high magnetic saturation, primarily iron NiFe alloys are formed on thin seed layers by sputtering and electroplating. Pole layers a few microns in thickness can be formed of magnetically superlative, primarily iron NiFe alloys in this manner for transducers that may be used in information storage systems. The seed layers may include Ni0.55Fe0.45 or Cr, and the magnetically superlative NiFe alloy may be Ni0.45Fe0.55. The magnetically superlative NiFe alloy has increased concentration of a body centered cubic crystalline phase and/or a decreased concentration of a face centered cubic crystalline phase compared with conventional Ni0.45Fe0.55. A laminated pole structure has a dielectric interlayer along with seed layers and magnetically superlative, primarily iron NiFe layers.

Journal ArticleDOI
TL;DR: In this article, the mechanism for the formation of powders of pure nickel and cobalt, and of nickel-cobalt and nickel-copper alloys is discussed.
Abstract: Reduction of aqueous NiSO 4 , CoSO 4 and CuSO 4 with hydrazine has been investigated systematically to obtain ultrafine powders of pure nickel and cobalt, and of nickel–cobalt and nickel–copper alloys. The results show that the pH value and the temperature are the key factors to influence the reactions. When pH ≥ 10.0 and the temperature is higher than 85°C, pure nickel particles are obtained. Pure cobalt, and nickel–cobalt and nickel–copper alloy powders can be formed only when pH ≥ 13 and the temperature is above 120°C. The mechanism for the formation of powders of nickel and cobalt, and of nickel–cobalt and nickel–copper alloys is discussed. The XRD patterns reveal that the as-synthesized pure cobalt is the hexagonal phase (h.c.p.), the pure nickel is the cubic phase (f.c.c.) and the Co 1–x Ni x and Cu 1–x Ni x alloys are the f.c.c. phase only when the ratio of Ni to Co is above 1∶1 and Ni∶Cu is below 1∶9, respectively.

Journal ArticleDOI
TL;DR: In this paper, bimetallic Pt-Mo catalysts supported on a high surface-area carbon black were studied and the Pt:Mo atomic ratios in the catalysts were 3:1 and 4:1.
Abstract: Electro‐oxidation kinetics of and mixture were studied on bimetallic Pt‐Mo catalysts supported on a high‐surface‐area carbon black. The Pt:Mo atomic ratios in the catalysts were 3:1 and 4:1. Characterization of these catalysts by X‐ray diffraction indicated the existence of a face‐centered cubic metallic phase with an average particle size of ca. 4 nm. Because the lattice constants for the Pt‐Mo solid solutions are so close to those of pure Pt, the composition of the nanocrystalline phase could not be determined. The kinetic results with the supported catalysts were compared quantitatively with results from bulk alloy electrodes having well‐characterized surface compositions varying from 15 to 33 atom % Mo. The kinetic properties of the supported catalysts were comparable to those of bulk alloys having somewhat higher Mo concentrations than the atomic ratios in the catalysts. This suggests that either the surface segregation phenomena in the alloy nanocrystals are different from those in the bulk or that the alloying by Pt is incomplete, and the alloy nanocrystals are rich in Mo relative to the atomic ratios in the catalysts. We prefer the latter interpretation. These Pt‐Mo alloy catalysts are predicted to have significantly better "CO tolerance" in polymer electrolyte membrane fuel cells than Pt‐Ru alloy catalyts, consistent with previous predictions based on studies of bulk alloy electrodes. © 1999 The Electrochemical Society. All rights reserved.

Journal ArticleDOI
TL;DR: In this article, the stacking fault energies of face-centered-cubic (f.c.) iron-based alloys have been investigated and the segregation of alloying elements to stacking faults and the interaction of substitutional and interstitial alloying element in solid solution and their effect on stacking fault energy have been taken into account.

Journal ArticleDOI
TL;DR: The corrosion performances in simulated human body fluids of commercial equiatomic Ni-Ti orthodontic wires having various shape and size and produced by different manufacturers were evaluated; for comparison purposes wires made of stainless steel and of cobalt-based alloy were also examined.

Journal ArticleDOI
TL;DR: In this article, the Pd/Ni composite membranes were fabricated on a SUS disk and tested with hydrogen and nitrogen at temperatures ranging from 623 to 823 K and pressures from 10.3 to 51.7 K. The composite membranes prepared in this technique yielded excellent separation performance for hydrogen: hydrogen permeance of 5.79×10−2.2

Journal ArticleDOI
TL;DR: In this paper, three aluminum-silicon alloys containing 7, 10 and 19 wt −% silicon were synthesized using a novel technique commonly known as disintegrated melt deposition technique, and the results following processing revealed that a yield of at least 80% can be achieved after defacing the shrinkage cavity from the as-processed ingots.

Journal ArticleDOI
TL;DR: In this article, the influence of matrix microstructures on age-hardening behavior in copper containing steels, the precipitation and the phase transformation of copper particles during isothermal aging were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and AP-FIM.
Abstract: In order to make clear the influence of matrix microstructures on age-hardening behavior in copper containing steels, the precipitation and the phase transformation of copper particles during isothermal aging were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and atom-probe field ion microscopy (AP-FIM). In ferrite, it was found from the DSC analysis and the TEM observations that copper clusters, bcc and 9R structures exist prior to the formation of the stable fcc copper phase, and that the main structure of the particles in a maximum hardness specimen is a bcc structure. The bcc→9R transformation was found to occur during the particle coarsening by the qualitative analysis of the DSC curves and the kinetics was discussed by the free energy calculation in Fe-matrix/Cu-precipitate system. In martensite, most of the copper precipitated on laths and on dislocations during isothermal aging. This resulted in the decrease of the amount of bcc particles and the considerable decrease of maximum age-hardness of the specimen. On the other hand, the age-hardening behavior of 80%-deformed ferrite was almost the same as that of ferrite, although the dislocation density of the deformed ferrite was larger than that of ferrite. In this paper, the factors controlling the precipitation and the phase transformation of copper particles in association with the hardening behavior are discussed with focus on the effect of defects (dislocation, vacancy) in steels. Moreover, the effect of manganese addition on the precipitation of copper particles is discussed.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the influence of Mo on the film capacitance can be related to a decrease of the number of donors in the iron oxide layers of the film, and the presence of Mo also affects the defect structure of the inner chromium oxide region.

Patent
02 Feb 1999
TL;DR: A corrosion resistant, high-strength, low-modulus, titanium based alloy having about 5-11 weight percent Mo and about 6-15 weight percent Hf was described in this article.
Abstract: This invention describes a corrosion-resistant, high-strength, low-modulus, titanium based alloy having about 5-11 weight percent Mo and about 6-15 weight percent Hf. This alloy is suitable for use in the fabrication of articles for medical and non-medical applications having low modulus, improved corrosion resistance and surface hardening. To increase strength, Cr, Si and Fe can be added in small amounts as well as increasing levels of interstitial oxygen, nitrogen or carbon. To maintain low elastic modulus, Mo can be partially substituted by Nb.

Journal ArticleDOI
TL;DR: In this article, it was shown that with continued anodizing, the essentially alumina film detaches from the alloy surface, which is followed by growth of new film on the exposed substrate.

Journal ArticleDOI
TL;DR: In this article, electron beam welding was performed on three different aluminium alloys, namely alloys 2024, 5005, and 6061, to establish the local microstructure-property relationships that would satisfy the service requirements for an electron beam welded aluminium alloy component with weld zone strength undermatching.
Abstract: Electron beam (EB) welding was performed on three different aluminium alloys, namely alloys 2024, 5005, and 6061 (plate thickness 5 mm except alloy 5005 which was 3 mm in thickness), to establish the local microstructure–property relationships that would satisfy the service requirements for an electron beam welded aluminium alloy component with weld zone strength undermatching. Microstructural characterisation of the weld metals was carried out by optical and scanning electron microscopy. A very low level of porosity was observed in all EB welds owing to surface cleaning before welding and the vacuum environment of the EB welding process. Extensive microhardness measurements were also conducted in the weld regions of the joints. Global tensile properties and fracture toughness properties (in terms of crack tip opening displacement, CTOD) of the EB joints were determined at room temperature. The effects of strength mismatch and local microstructure on fracture toughness of the EB joints are discuss...

Journal ArticleDOI
TL;DR: In this article, the effect of magnesium addition as well as other melt treatment parameters such as Sr modification and grain refinement on the heat treatment behavior of the A319.2 alloy was investigated.
Abstract: The present study was performed on primary A319.2 alloy to investigate the effect of magnesium addition as well as other melt treatment parameters such as Sr modification and grain refinement on the heat treatment behaviour of the alloy. The results show that increasing the Mg content in A319.2 up to 0.45% considerably enchances the alloy response to heat treatment in the T5 and T6 tempers, more particularly, the T6 temper. Modification of the high-Mg version of 319 alloy with Sr in amounts of ∼350 ppm results in a marked amount of porosity formation which counteracts the beneficial effect of the modification, leading to a noticeable decline in the alloy strength. Grain refining the Sr-modified (A319.2 + 0.45% Mg) alloy produces sounder castings and, hence, an identical ageing response to that offered by unmodified high-Mg alloys. The properties, however, are more consistent. Addition of Mg (∼0.45%) leads to the precipitation of coarse particles of Al5Mg8Si6Cu2. Modification with Sr tends to cause severe segregation of both Cu-containing intermetallics, i.e., Al2Cu and Al5Mg8Si6Cu2 in areas away from the growing Al-Si eutectic regions. Thus, their dissolution rates are fairly sluggish upon solutionizing at 505 °C. Increasing the solutionizing temperature would lead to incipient melting of the phases and, hence, a catastrophic failure. Fracture of intermetallic phases in the interdendritic regions is mostly brittle, with the formation of microcracks at the Si, Cu, Fe-base intermetallics and aluminium interfaces. Fracture of the α-aluminium is always ductile. Hardening during ageing occurs by cooperative precipitation of Al2Cu and Mg2Si phase particles.

Journal ArticleDOI
Akihisa Inoue1
TL;DR: In this article, the authors investigated the stability of supercooled liquid for a number of alloys in Mg-, lanthanide-, Zr-, Ti-, Fe-, Co- and Pd-Cu-based systems.
Abstract: Conventional bulk metallic materials have ordinarily been produced by the melting and solidification processes. The metallic liquid is unstable at temperatures below melting temperature and solidifies immediately into crystalline phases. Consequently, all bulk engineering alloys had been composed of a crystalline structure. Recently, the common concept has been exploded by the findings of the stabilization phenomenon of supercooled liquid for a number of alloys in Mg-, lanthanide-, Zr-, Ti-, Fe-, Co- and Pd–Cu-based systems. The alloys with the stabilized supercooled liquid state have three features in their alloy components, i.e. multi-component systems, significant atomic size ratios above 12%, and negative heats of mixing. The stabilization mechanism has also been investigated from experimental data of structure analyses and fundamental physical properties. The stabilization has enabled the production of bulk amorphous alloys in the thickness range of 1–100 mm by using various casting processes. The bulk amorphous Zr-based alloys exhibit high mechanical strength, high fracture toughness and good corrosion resistance. The stabilization also leads to the appearance of a wide supercooled liquid region before crystallization and enables the achievement of high-strain superplasticity through Newtonian flow in the supercooled liquid region. The Newtonian flow in the strain rate range just below the transition from Newtonian to non-Newtonian flow was also found to cause the suppression of crystallization of the supercooled liquid. In addition to the finding of the stabilization phenomenon, the clarification of the stabilization criteria of the supercooled liquid will lead to the future definite development of bulk amorphous alloys as basic science and engineering materials.

Journal ArticleDOI
TL;DR: In this article, Bismuth additions of 1% to 10% were made to the 96.5Sn-3.33Ag-4.83Bi/Cu couples resulted in the growth of an intermetallic compound layer at the solder/substrate interface comprised of Cu3Sn and the Cu6Sn5 sublayers.
Abstract: Bismuth additions of 1% to 10% were made to the 96.5Sn-3.5Ag (wt.%) alloy in an effort to develop a Sn-Ag-Bi ternary composition. A DSC evaluation of the melting properties of the 91.84Sn-3.33Ag-4.83Bi composition suggested the appearance of metastable, short-range order in the atomic structure as a result of low temperature, thermal aging. More extensive solid-state aging studies on 91.84Sn-3.33Ag-4.83Bi/Cu couples resulted in the growth of an intermetallic compound layer at the solder/substrate interface comprised of Cu3Sn and the Cu6Sn5 sub-layers. The growth kinetics of the total layer thickness (x) as a function of solid-state aging time (t) and temperature (T) were represented by the following expression: $$x - x_o = A t^n \exp ( - Q/RT)$$ where x0=0.57 × 10−6 m; A=6.22 × 10−3 m/sn; n=0.46±0.15; and Q=49±8 kJ/mol. TEM analysis of the 91.84Sn-3.33Ag-4.83Bi composition indicated that solid-solution and precipitation strengthening mechanisms were a likely consequence of the Bi additions. Contact angle measurements, Cu/solder/Cu solder joint shear strength tests, and microhardness evaluations were also performed on the Sn-Ag-Bi alloys; those results are reported in Part II.

Journal ArticleDOI
TL;DR: In this paper, a large supercooled liquid region exceeding 60 K before crystallization was found in a wide composition range of 15 to 20 at%Cu and 25 to 30 at%Ni for the Ti 94-x-y Cu x Ni y Si 4 B 2 amorphous alloys which satisfy the three criteria of multi-components, significant atomic size ratios and negative heats of mixing.
Abstract: A large supercooled liquid region exceeding 60 K before crystallization was found in a wide composition range of 15 to 20 at%Cu and 25 to 30 at%Ni for the Ti 94-x-y Cu x Ni y Si 4 B 2 amorphous alloys which satisfy the three criteria of multi-components, significant atomic size ratios and negative heats of mixing. The glass transition temperature (T g ) and the reduced glass transition temperature (T g /T m ) of the Ti 50 Cu 20 Ni 24 Si 4 B 2 alloy are 742 K and 0.63, respectively. The high thermal stability of the supercooled liquid as well as the high reduced glass transition temperature enabled us to produce bulk amorphous alloys with a diameter of 1 mm by copper mold casting. The crystallization of the Ti 50 Cu 20 Ni 24 Si 4 B 2 amorphous alloy takes place through a single exothermic reaction and the four phases of Cu 4 Ti 3 , CuTi, NiTi and TiB precipitate almost simultaneously. The crystallization mode requires the long-range atomic rearrangements of the constituent elements and the necessity seems to cause the increase in thermal stability of the supercooled liquid. The success of forming the bulk amorphous alloys in the Ti-Cu-Ni-Si-B system with lower densities is important for the future development of bulk amorphous materials with a higher specific strength.

Journal ArticleDOI
TL;DR: In this paper, a Zn-4%Al-3%Mg 3%Ga alloy has been used for die-attaching, which has a 309°C solidus and a 347°C liquidus.
Abstract: Zn-based alloys have been investigated to replace Pb-5%Sn solder for die-attaching use. We have found that a Zn-4%Al-3%Mg-3%Ga alloy has a 309°C solidus and a 347°C liquidus. A die-attaching test was done with preforms of this alloy, Ag-plated lead-frames, and Au-plated dummy dies. Good die-attaching with a small amount of voids can be achieved at 320°C or higher. In subsequent reliability tests, no failure was observed until 1000 cycles between −65°C and 150°C or until 1000 h at 85°C and 85% humidity. Although the poor workability and poor ability of stress relaxation at room temperature of this alloy may somewhat limit its application areas, this solder is the first Pb-free solder for die-attaching use to our knowledge.

Journal ArticleDOI
TL;DR: In this paper, the passivation behavior of the amorphous Zr55Al10Cu30Ni5 alloy in a 0.1 M Na2SO4 (pH=8) electrolyte is characterized in comparison to its crystalline alloy counterpart and to zirconium.
Abstract: Bulk amorphous ZrAlCuNi alloy samples can be prepared by slow cooling from the melt due to their low critical cooling rate for amorphization. The passivation behaviour of the amorphous Zr55Al10Cu30Ni5 alloy in a 0.1 M Na2SO4 (pH=8) electrolyte is characterized in comparison to its crystalline alloy counterpart and to zirconium. Potentiodynamic and potentiostatic polarization measurements reveal that the alloys form strong protective surface layers by anodization, which is, in general, quite similar to the behaviour of zirconium. The barrier effect of surface layers grown on the alloys is slightly lower than that of films on zirconium. From AES investigations, it is obvious that all alloying elements participate in the formation of anodic films, which also show a gradient of composition along the growth direction. In 0.001–0.1 M NaCl electrolytes, pitting occurs on bulk amorphous ZrAlCuNi samples due to the existence of micrometer-sized crystalline inclusions. The oxygen-induced formation of such crystalline phases during slow cooling is studied in detail by characterizing samples of different oxygen content with X-ray diffraction, optical and scanning electron microscopy and differential scanning calorimetry.