Optimum Alloy Composition Research Articles

Trends and issues in Pb-free soldering for electronic packaging

A variety of Pb-free solder alloys have been proposed for use as interconnects for electronic packaging including Sn−Ag, Sn−Cu, Sn−Ag−Cu, Sn−Ag−Bi, and Sn−Sb, among others. This paper presents a review of the behavior of promising Pb-free solder alloys as related to their microstructure. Recommendations of optimal alloy composition as a function of performance requirements are given. For surface mount applications, eutectic Sn−Ag−Cu is recommended as the optimal alloy. For flip chip interconnects, the eutectic Sn-Cu alloy has the best performance. The materials and process trends of Pb-free packaging are summarized with optimal conditions identified.

Ｎｉ‐Ｍ３Ｂ２（Ｍ＝Ｎｉ，Ｍｏ，Ｃｒ，Ｗ）合金の耐摩耗性および曲げ強度

The effects of addition of Cu, Cr and W on the wear resistance and bending strength of the Ni-M3B2 (M=Ni, Cr, Mo, W) two phase alloy were investigated. The wear resistance and bending strength of the alloy were improved by the addition of Cu, Cr and W. The optimum alloy composition was found to be Ni-3.6mass%B-29.3mass%Mo-15mass%Cr-2mass%Cu-18.7mass%W. The wear resistance of the alloy with the optimum composition was superior to the conventional Ni-based wear resistant alloy with the composition of Ni 3mass%B-13.5mass%Cr-4.8mass%Fe-0.8mass%aC. Also, the bending strength of the present alloy showed 1.81 GPa. Furthermore, the corrosion resistance of the present alloy in 6% HNO3 aqueous solution and 10% HCI aqueous solution, was 70 times and 7 times higher respectively, than that of the conventional Ni-based wear resistant alloy. Therefore, the present alloy is expected to be a new corrosion and wear resistant alloy.

Thermodynamic Analysis and Experimental Study of Composite Structure Formation in Eutectic Alloys α -Al + Mg2Si

The Al ― Mg ― Si phase diagram was studied and the formation conditions for a regular two-phase eutectic structure (α-Al + Mg2Si) were established. Concentration limits were found for optimum alloy compositions with maximum melting point (∼595°C) and a narrow (or zero) melting (crystallization) range (less than 5°C). The structures of these alloys are formed by Mg2Si monocrystal fibers and lamellae with a high degree of ordering, located in the aluminum matrix.

Studies on multi-component rare earth-based hydrogen storage alloys with small amounts of boron

Several multi-component Mm-based alloys were prepared by the arc melting method and the electrochemical properties such as capacity, cycling stability and rate capability were examined in 6 N KOH at 30°C. Small amounts of boron in MH alloys noticeably improved the cycling stability of the alloy electrodes regardless of a modest decrease in capacity due to the contraction in unit cell volume. The optimum alloy composition from our experimental results would be of MmNi3.65Co0.62Mn0.36Al0.27B0.1. The initial capacity of this alloy was about 286 mAhg−1 at the 0.2 C rate. The capacity decay after 500 cycles at the 1.0 C rate was 25.7%. After annealing treatments, the alloy showed better cycling stability with a capacity decay of 16.6% after 500 cycles. In addition, the mechanism of hydriding–dehydriding on MH electrodes, and the relationship between the rate capability and the charge-transfer resistance as well as the polarization resistance of alloy electrodes were also discussed.

The effect of carbon, chromium and silicon content on wear resistance of ferritic FeCrC cast alloys

A semi-empirical model describing wear resistance of FeCrC white cast irons as a function of chemical composition and wear conditions has been used to analyse the effects of alloy composition. A wear criterion has been developed and then used to define an optimum alloy composition for a given set of wear conditions. The analysis is showed clearly that differing wear conditions require considerably different alloy compositions. For a set of wear conditions analysed in this work, the optimum C content appears to depend on the Si level. In particular, the following three compositions are recommended: (1) & 2% C and 0.16% Si; (2) & 1% C and 0.37% Si; and (3) & 0.5% C and 0.5% Si. The Cr content is not critical to wear resistance and should be selected using other criteria such as high temperature corrosion resistance.

A correction to optimum alloy composition for design of high-temperature high-strength Al [sbnd]Ti [sbnd]V [sbnd]Zr alloys through thermodynamic calculations

It is very likely that high-strength Al-base alloys up to 698K can be developed in view of the behavior of nickel base superalloys which resist degradation of mechanical properties to 75 pct of their absolute melting temperature. For high temperature Al alloys, the dispersed hardening phase must not undergo phase transformation to an undesirable phase during long time exposure at the temperature of interest. According to a review paper by Adam, several Al-base systems containing transition metal elements for potential elevated temperature use were suggested based on low values of diffusivities and solubilities. At the temperatures of interest, around 698K, vanadium and titanium are mutually substitutable in the form of Al{sub 3}(Ti,V). Much of titanium and vanadium can be substituted for zirconium in the DO{sub 23}-type Al{sub 3}Zr compound, creating Al{sub 3}(Ti,Zr) and Al{sub 3}(V,Zr), respectively. It was of interest to design the Al-Ti-V-Zr system and optimize the compositions of added transition elements to minimize the lattice mismatch, and thus an interfacial energy, and maximize the strengthening effects at high temperatures. The authors were able to do experiments on phase stabilities of Al{sub 3}Ti-Al{sub 3}V-Al{sub 3}Zr system and revise the thermodynamic parameters of this system. Therefore, this study reports onmore » the new optimum alloy composition which is supposed to maximize the coarsening resistance of the strengthening Al{sub 3}(Ti,V,Zr) phase at high temperatures of service in this system.« less

The oxidation behavior of Fe-20Cr alloy foils in a synthetic exhaust-gas atmosphere

Oxidation tests of rare-earth-modified and Ti-modified Fe−20Cr alloy foils, which are under consideration for catalytic converter supports, were performed in a synthetic exhaust-gas atmosphere (N2+H2O+CO2) between 900°C and 650°C. Between 900°C and 750°C, the rare earths had no effect on oxide growth rates while Ti increased growth rates. Oxide growth rates for the rareearth alloys at 800°C and 750°C are much lower than those found in the literature for oxidation of Fe−Cr alloys or pure Cr in O2-rich atmospheres. The slow growth rates for the rare-earth alloys agree with literature data for oxidation of stainless steels containing >20% Cr in wet atmospheres and are caused by growth of an oxide scale only one grain thick. At temperatures ≤700°C, Fe−20Cr alloys grow massive Fe oxides; however, this can be suppressed by adding rare earths or Ti. To ensure good oxide adherence, free sulfur must be eliminated in the alloy by tying it up with a reactive-element addition. Both Ti and the rare earths can be used to tie up S, but the rare earths are more effective. For converter applications, the optimum alloy composition may contain rare earths for good oxide adherence and a small amount of Ti to suppress growth of Fe-rich oxides.

Oxidation and hydrogen uptake of Zr based Nb alloys at 400°C under 10 MPa H 2O steam atmosphere

Oxidation and hydrogen uptake of Zr based Nb alloys were studied as functions of Nb content and heat treatment in 400°C H 2O steam, and the results of the oxidation were compared to those obtained in 400°C D 2O steam. From the higher weight gain of the alloys in H 2O steam than that in D 2O steam, it is suggested that the oxidation rate of the alloys is controlled by cathodic reduction of the hydrogen ion. The changes of the weight gain and of percentage hydrogen uptake of the quenched and aged alloys with Nb content and heat treatment were discussed with respect to the aliovalent effects of Nb in matrix phase. The optimum alloy composition of the ZrNb binary system is proposed as the aged binary alloy less than 5 wt% Nb from the view points of weight gain, hydrogen uptake and microstructure.

In vitro biocompatibility, mechanical properties, and corrosion resistance of Ti-Zr-Nb-Ta-Pd and Ti-Sn-Nb-Ta-Pd alloys.

There is much discussion about the toxic effect of vanadium and aluminum contained in Ti-6Al-4V alloy for prosthetic implants. The goal of the present investigation was to develop new titanium alloys with sufficient mechanical properties using more biocompatible alloying elements: zirconium, tin, niobium, tantalum, and palladium. The relative growth rates of L929 and MC3T3-E1 cells were significantly higher when cultured with the extraction of Ti-10Zr-8Nb-2Ta-0.2Pd or Ti-15Zr-4Nb-2Ta-0.2Pd alloys than when cultured with the extraction of Ti-6Al-4AV ELI alloy. The tensile strength, elongation, and reduction of area for Ti-15Sn-4Nb-2Ta-0.2Pd alloy were 989 MPa, 14.4%, and 49.3%, respectively, surpassing Ti-6Al-4V ELI alloy. (ASTM F138-84); those for Ti-15Zr-4Nb-2Ta-0.2Pd alloy were 725 MPa, 23.6% and 54.9%, respectively. More than 15% addition of tin as well as zirconium deteriorated the tensile properties. Titanium release into a 5% hydrochloric acid solution from the new titanium alloys was 20-50 micrograms/cm2 per day, though that from Ti-6Al-4V ELI alloy was 1300 micrograms/cm2 per day. The optimum alloy compositions are Ti-15Zr-4Nb-2Ta-0.2Pd and Ti-15Sn-4Nb-2Ta-0.2Pd, judging from cytocompatibility, corrosion resistance, and mechanical properties. The former is characterized by its higher level cytocompatibility and corrosion resistance, while the latter is characterized by mechanical properties.

Optimum alloy compositions in reduced-activation martensitic 9Cr steels for fusion reactor

In order to obtain potential reduced-activation ferritic steels suitable for fusion reactor structures, the effect of alloying elements W and V on the microstructural evolution, toughness, high-temperature creep and irradiation hardening behavior was investigated for simple 9Cr-W and 9Cr-V steels. The creep strength of the 9Cr-W steels increased but their toughness decreased with increasing W concentration. The 9Cr-V steels exhibited poor creep rupture strength, far below that of a conventional 9Cr-1MoVNb steel and poor toughness after aging at 873 K. It was also found that the Δ-ferrite should be avoided, because it degraded both the roughness and high-temperature creep strength. Based on the results on the simple steels, optimized martensitic 9Cr steels were alloy-designed from a standpoint of enough thoughness and high-temperature creep strength. Two kinds of optimized 9Cr steels with low and high levels of W were obtained; 9Cr-1WVTa and 9Cr-3WVTa. These steels indeed exhibited excellent toughness and creep strength, respectively. The 9Cr-1WVTa steel exhibiting an excellent roughness was shown to be the most promising for relatively low-temperature application below 500°C, where irradiation embrittlement is significant. The 9Cr-3WVTa steel was the most promising for high temperature application above 500°C from the standpoint of enough high-temperature strength.

A model-based comparison of AlInAs/GaInAs and InP/GaInAs HBT's: a Monte Carlo study

The high-speed performances of AlInAs/GaInAs and InP/GaInAs heterojunction bipolar transistors (HBTs) are investigated using a one-dimensional self-consistent particle simulator. Optimum alloy compositions for a graded-gap base structure are obtained for both transistors through the tradeoff between the emitter-charging time and base transit time. The saturation velocity in the GaInAs n-type collector is found to be smaller than that in InP, which has been attributed to the diffusion of a large number of hot back-scattered Gamma -valley electrons in the GaInAs collector. The difference in the collector transit time in p-type collectors is trivial, since the maximum electron velocity was restricted to below 1.2*10/sup 8/ cm/s due to a strong nonparabolicity effect. The cutoff frequency for the former and the latter are estimated to be 2 and 1.5 times higher, respectively, than for AlGaAs/GaAs HBTs. These results are attributed to a larger bandgap difference between the emitter and base, to yield a high base built-in field, rather than a larger Gamma -L band separation energy in the collector to enhance the velocity overshoot effect.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

New method of making Nd-Fe-Co-B full dense magnet

A novel method for fabricating an isotropic fully dense Nd-Fe-Co-B magnet is described. This method consists of a plasma-activating process and a hot-pressing process. The magnetic powder is heated by resistance heating. Plasma activation produces an improvement in the H/sub cj/ of the compacted magnet. The pressure range is from greater than 200 kg/cm/sup 2/ to less than 500 kg/cm/sup 2/. Optimum alloy composition is Nd/sub 13.5/Co/sub 1.5/B/sub 6/Fe/sub 64.5/, specified by magnetic properties and formability in hot pressing. The magnetic properties of this magnet are 15 MG-Oe for BH/sub max/ and 17 kOe for H/sub cj/. The temperature coefficient of B/sub r/ is -0.07 to -0.08%/ degrees C, and that of H/sub cj/ is -0.39 to -0.42%/ degrees C. >

Compositional Effect on Soft Magnetic Properties of Co&amp;ndash;Fe&amp;ndash;Si&amp;ndash;B Amorphous Alloys with Zero Magnetostriction

This paper is intended to examine the compositional dependence of magnetic properties (coercivity, permeability and saturation magnetization) in rapidly solidified and annealed states for zero magnetostrictive Co-Fe-Si-B amorphous alloys and to find an optimum alloy composition at which high saturation magnetization and good soft magnetic properties are obtained simultaneously.

&amp;gamma;&amp;prime;-Ni&lt;SUB&gt;3&lt;/SUB&gt;(Al, Ti)L1&lt;SUB&gt;2&lt;/SUB&gt;型規則相中への不規則&amp;gamma;相の析出

Optimum alloy compositions and heat treatments to obtain fine dispersion of disordered γ particles in an L12 ordered γ′-Ni3(Al, Ti), and the morphology change of γ precipitates during aging have been investigated by means of transmission electron microscopy.A uniform solid solution of γ′-L12 ordered phase supersaturated with Ni can be obtained by solution annealing in a suitable temperature range. The γ′ phase hardens appreciably by the fine precipitation of disordered γ. The shape of γ precipitates formed during aging is initially spherical or round-cubic and grow into platelets as aging proceeds. High resolution electron microscopy revealed that the γ precipitates are perfectly coherent with the matrix γ′ as long as the γ-precipitates are plates. The loss of coherency initiates by the introduction of dislocations at the γ⁄γ′ interface followed by the step formation at the dislocations. The γ precipitates become grobular after the loss of coherency.The chemical compositions of the matrix and the precipitates have been determined by means of EDS microanalysis in an analytical electron microscope. The sense and magnitude of misfit between the γ′ matrix and γ precipitates are determined from the spacings of misfit dislocations and the chemical compositions of γ and γ′ phases.

Microstructure and toughness of Cr-W and Cr-V ferritic steels

In order to obtain an optimum alloy composition of reduced-activation Cr-W-V ferritic steels, the microstructural evolution during thermal aging at 823–973 K and its effect on the toughness were investigated for simple Cr-W and Cr-V steels by means of transmission electron microscopy and Charpy impact testing. The microstructural evolution of the Cr-W steels was similar to that of the conventional Cr-Mo steels. Carbides precipitated in the martensite and the intermetallic compound Fe2W precipitated in the δ-ferrite of the Cr-W steels. On the other hand, only carbides precipitated in both the martensite and the δ-ferrite of the Cr-V steels. The effect of Cr, W and V on the thermal embrittlement is discussed by taking account of the precipitation behavior.

Os-coated cathode for very high emission-density applications

Emission densities of 35 to 100 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , demanded by free-electron lasers (FEL's), have set far more stringent requirements on thermionic cathodes than what is considered state of the art with current technology. The purpose of the work described here is to evaluate Os-coated cathodes for these ultra-high-current-density applications. Organometallic CVD techniques were used to coat "B" type tungsten dispenser cathodes. The coatings were found to show good adhesion and rapid activation. The activation process involves not only the standard formation of a BaO layer on the surface but also the formation of an optimum surface alloy composition of near 50-percent Os and 50-percent W. These cathodes showed excellent emission capabilities, and at 1085°C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</inf> , a zero-field emission density near 50 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was obtained. Subsequent life studies at 1085° C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</inf> indicated that at an emission level of 40-50 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> over 800 h of life is obtainable with this type of cathode. During life, the pulsed emission density and surface composition were monitored. Surface Ba/BaO coverage as well as surface Os content were observed to decrease with life, but an S impurity was found to increase with life. However, the surface alloy composition change was identified as being the major cause for the emission degradation.

Nickel Aluminides for Structural Use

Nickel aluminides with the following compositions (at.%) have been developed: Ni—18±2% Al—8±2% Cr—1.0±0.8% Zr (orHf)—0.15±0.1% B. These aluminides possess superb mechanical and metallurgical properties and have potential to be used as new structural materials at elevated temperatures. This paper discusses the behavior of nickel aluminides and updates progress in developing methods of fabrication. Additional studies are expected to lead to optimum alloy compositions to further improve the creep resistance of the aluminides, particularly in wrought conditions.

TNW

Abstract TNW is a high-speed steel. It has an optimum alloy composition that combines the good toughness characteristics of a high-molybdenum steel and the excellent abrasion resistance provided by a 2% vanadium content. TNW is a popular choice for twist drills, taps, reamers, router bits, end mills and other similar cutting tools. Also its good toughness makes it well suited to punches and other difficult cold-forming tools requiring the properties of a high-speed steel. This datasheet provides information on composition, physical properties, hardness, and elasticity. It also includes information on high temperature performance as well as forming, heat treating, and machining. Filing Code: TS-433. Producer or source: Latrobe Steel Company.

Electrodeposition of the ternary iron-cobalt-nickel alloy from the fluoborate bath part I. Deposition, anode corrosion, mechanism

Ternary iron-cobalt-nickel alloys of a wide range of composition have been deposited from boric acid-saturated fluoborate baths under a variety of conditions: pH 1 to 5, temperature 30° to 80°C, current density 0.5 to 36 A/dm 2, in quiescent as well as agitated solutions, and the optimum conditions for deposition established. The bath gave smooth adherent deposits with high (80–95%) cathode efficiency and was particularly suitable for high rates of deposition; under optimum conditions, the efficiency and alloy composition were insensitive to change in plating variables like current density, pH and temperature. The anode corroded uniformly and at 100% efficiency at sufficiently low current densities without any chloride addition. Anomalous codeposition was observed in the entire range investigated. The depolarization for iron discharge during alloy deposition was considerable. The hydroxyl ion gradient in the cathode layer seems to have a profound influence on alloy deposition.

Production of electrical contacts from a silver ? Zirconium pseudo-alloy

In an investigation of silver-zirconium pseudo-alloys, the optimum alloy composition was chosen and a study was made of the effects of various technological factors upon the properties of such an alloy. A process has been developed enabling silver-zirconium pseudo-alloy parts to be produced without high-temperature sintering.