Showing papers on "Alloy published in 1969"

Magnesium-base alloy for use in bone surgery

Abstract: A magnesium-base alloy for use in bone surgery which contains the following components, wt.%: Rare earth element 0.4-4.0 Cadmium 0.05-1.2 An element from the group consisting of calcium and aluminum 0.05-1.0 Manganese 0.05.05 Silver 0-0.8 Zirconium 0-0.8 Silicon 0-0.3 Magnesium remainder

Solid-Solution Strengthening in Single Crystals of Iron Alloys

Abstract: To elucidate the mechanism of the substitutional solid-solution strengthening of iron, evaluation of the modulus parameter and the direct observation of dislocation configuration were made for six alloy systems; Fe–Be, Fe–Al, Fe–Si, Fe–V, Fe–Ge and Fe–Mo. The rate of the solid-solution strengthening at 300°K was best described as a function of the combined mismatch parameters by the equation d (τ/µ)/ d c =0.04( e µ '+1.5 e a ) 2 , where e a and e µ ' are the size and the modulus mismatch parameter, respectively. The dislocations observed at the lower yield point were almost of screw type in all the alloys but their densities were extensively different from alloy to alloy. It was concluded that the elastic interaction of screw dislocations with the solute atoms was the dominant cause of the solid-solution strengthening of iron at 300°K. The wide variety of dislocation density was well-explained by a proposed model that it is determined by the condition for the applied stress to be minimum in a constant str...

Applicability of Vegard's Law to the PbxSn1−xTe Alloy System

Abstract: The relationship between lattice constant a0, alloy fraction x, and stoichiometry has been studied for the PbxSn1−xTe alloy system. Using the hole concentration p as a measure of the deviation from stoichiometry, it is shown that a0 for SnTe varies with p according to a0(SnTe)=−1.7×10−23 p+6.327, where a0 is measured in A, and p in cm−3. For small deviations from stoichiometry it is shown that the alloys obey Vegard's law. Evidence is presented that Vegard's law holds in general providing fixed deviations from stoichiometry are considered. The functional relationship between a0, x, and p may be expressed as a0(alloy)=0.133x+a0(SnTe), where a0(SnTe) is given by the expression presented above. On the basis of this equation it is shown that previously reported deviations from Vegard's law arise in a natural way from the varying deviations from stoichiometry which characterize these alloys.

Electroluminescence of Diffused GaAs1 − xPx Diodes with Low Donor Concentrations

Abstract: The optical and electrical properties of electroluminescent diodes formed by Zn diffusion into vapor epitaxially grown substrates with donor concentrations in the range 1016–1017 cm−3 have been studied. This doping range, which is somewhat lower than has been previously investigated in the GaAs1−xPx alloy system, has been found to be the optimum range for the fabrication of high efficiency diodes. The spectral emission is appreciably different than has been previously observed. Throughout the alloy composition range at 300° and 77°K a high energy peak occurs within ∼20 meV of the conduction bandedge, and at 77°K a second peak ∼30 meV lower in energy is present. Donor‐acceptor‐pair recombination peaks similar to those observed in GaP, located ∼0.1 and ∼0.37 eV below the bandedge, are found to occur and remain the same distance below the bandedge throughout the indirect region of alloy composition. At 300°K direct recombination from the higher lying k = 0 minimum is observed to persist into the indirect gap...

The thermal conductivity of sintered semiconductor alloys

Abstract: The thermal conductivity of sintered semiconductor alloys is calculated using the Klemens-Callaway model assuming that the boundary scattering can be adequately described by a mean free path. It is shown that the relative increase in thermal resistance increases with the amount of alloy disorder scattering and should be substantial in sintered germanium silicon alloys with particle sizes of the order of one micron.

Protective diffusion layer on nickel and/or cobalt-based alloys

Abstract: Nickel and/or cobalt-based alloys are given a protective coating by diffusing into the surface of the alloy metallic aluminum and one or more metals of the platinum groups.

The structure of directionally frozen Al–CuAl2 eutectic alloy

Abstract: The structure of Al–CuAl2 eutectic alloy has been examined by transmission electron microscopy. The orientations of phases and of preferred lamellar interfaces have been determined and it is shown how small deviations from these preferred orientations are accommodated by tilt and/or twist boundaries. The dislocation structures of sub-boundaries and of the semicoherent phase boundaries are illustrated. The hardness of the eutectic material is more sensitive to the rate of cooling in the solid state than it is to the lamellar spacing and the dislocation distribution in quenched and slowly cooled alloy is compared.

The equilibrium shapes of small liquid droplets in solid–liquid phase mixtures: metallic h.c.p. and metalloid systems

Abstract: Solid–liquid interfacial free energy is shown to be highly anisotropic in alloys of some h. c. p. metals and of two metalloids. This anisotropy is evaluated from a study of the equilibrium shapes of small droplets of alloy liquid entrained within solid grains. Factors affecting the attainment of equilibrium in such droplets are considered, and γ -plots are obtained for solid–liquid interfaces in the h. c. p. metals zinc and cadmium. In the magnesium alloys studied, spherical droplet shapes were observed, indicative of essentially isotropic interfacial energies. Droplet shapes were also analysed in some alloys of bismuth and of antimony. The results are related to current ideas of solid–liquid interfacial structure.

The determination of the diffusion constants of oxygen in nickel and α-iron by an internal oxidation method

Abstract: The diffusion constants of oxygen in nickel and α-iron are calculated from experimentally determined internal oxidation rates in dilute silicon-bearing alloys. A single crystal alloy of composition 0.058 wt % silicon in nickel and polycrystalline alloys of composition 0.48 wt % silicon in nickel and 0.072 wt % silicon in iron were oxidised and allowance is made for the absorption of oxygen in the reaction with silicon. For nickel the values of activation energy Q=73.9 kcal/g atom in the range 800 to 1200° C and Q=74.4 kcal/g atom in the range 900 to 1300° C are in good agreement with a previous result. The activation energy required for oxygen diffusion in α-iron was found to be 39.9 kcal/g atom in the range 700 to 850° C.

The Design of Iron-Chromium-Nickel Alloys for Use at High Temperatures

Abstract: The design of iron-chromium-nickel alloys for use at high temperatures ought to be based on a knowledge of the alloy compositions that will give rise to a chromic oxide scale. For this reason, the nickel-chromium and iron-chromium-nickel alloy systems have been investigated at 1000°C under oxidizing conditions, and the isothermal sections of the nickel-chromium-oxygen and the iron-chromium-nickel-oxygen equilibrium diagrams have been determined. On the basis of these determinations, several ternary compositions are recommended as being the most suitable to form the basis of high-temperature alloys for use in oxidizing environments.

Thermal Stability of Hastelloy Alloy C-276

Abstract: Hastelloy Alloy C has long been of major importance to the chemical process industry, but in many applications, vessels fabricated from Alloy C had to be solution heat treated to remove harmful weld heat affected zone precipitates which reduced corrosion resistance. Modification of the chemical composition produced Hastelloy Alloy C-276, which is more resistant to the precipitation of grain boundary particles than Alloy C. In order to fully utilize the improved alloy, and to understand its responses to fabrication techniques, it is helpful to understand the time-temperature-transformation characteristics. Grain boundary precipitates can form in Alloy C-276 when it is exposed to temperatures from 1200 to 2000 F (649 to 1093 C). The precipitation characteristics of Alloy C-276 compared to those of Alloy C can be shown through the use of a time-temperature-transformation curve (T-T-T). The precipitates have been identified as either “P” or Ni7Mo6-type phases. No M6C precipitate was found in Alloy C-...

Grain‐Boundary Fine Structure in an Iron Alloy

Abstract: Regular substructures were observed in grain boundaries of an annealed Fe‐0.75% Mn alloy by transmission electron microscopy. A detailed analysis was made on one of the grain boundaries. The result indicates that the analyzed grain boundary may be considered as a coincidence site grain boundary.

Thermal expansivities, thermal conductivities, and densities of vanadium, titanium, chromium and some vanadium-base alloys: A comparison with austenitic stainless steel

Abstract: Computer-fitted polynomial expressions are presented that define the linear thermal-expansion behavior of vanadium, titanium, chromium, certain VTi and VTiCr alloys, and AISI Types 304 and 316 stainless steels between 0 ° and 1000 °C. The mean expansion coefficients for the vanadium-base alloys differ only slightly from those for unalloyed vanadium (plus or minus 6%), and are 65% to 80% lower than the mean expansion coefficients for the austenitic stainless steels. Densities of the vanadium-base alloys and the austenitic stainless steels were determined at 25 °C by liquid displacement. The VTi alloys show a non-linear decrease in density with increasing titanium for titanium contents greater than 30 wt.%. The VTiCr alloys also exhibit a non-linear change in density for compositions containing greater than 15 wt.% titanium, and greater than 5 wt.% chromium. A comparison of the mechanical and thermal properties of two vanadium-base alloys and two austenitic stainless steels was made to determine their relative usefulness as reactor fuel jackets for service between 500 ° and 700 °C. This comparison shows that vanadium alloy fuel jackets would be subjected to only one-third the thermal stresses generated in austenitic stainless steel jackets during reactor excursions between 500 ° and 700 °C under conditions where the fuel is not in intimate contact with the jacket. This difference in thermal stresses in the two jacket materials is the result of the 37% higher tensile strength, 40% higher thermal conductivity, and 70% lower thermal expansivity exhibited by the vanadium alloys as compared with austenitic stainless steel.

Correlation of superconducting and metallurgical properties of a Ti-20 at.% Nb alloy

Abstract: The effects of heat treatment and cold work on the superconducting properties of Ti-20 at. % Nb have been studied by measurement of magnetization, M(H), critical current density, J c(H) and transition temperature, T c. The metallurgy has been determined by electron and optical microscopy and x-ray diffraction. Quenching the recrystallized alloy from the single phase β region above 500°C produces a martensitic α″ phase characterized by H c2 = 50 koe, T c = 6·5°K and a high J c arising from pinning of flux lines by the α″ structure. After very short ageing times at 330°C the α″ reverts to the β phase and H c2 and T c fall to 15 koe and 4·5 °K respectively and J c drops by several orders of magnitude. On further ageing ω-Ti precipitates and H c2 and T c increase because of Nb enrichment of the matrix. Pinning by the ω precipitate causes J c to increase. A pronounced peak effect in the J c(H) and M(H) curves has been studied in detail. There is strong evidence for a barrier to flux line entr...

Anodic Polarization of Titanium and Titanium Alloys in Hydrochloric Acid

Abstract: : Commercially pure titanium and the alloys studied exhibited active to passive transitions in HCl. Increasing the acid concentration increased the critical current for passivity and shifted the critical potential for passivity in the noble direction. Increasing the temperature served only to increase the critical current for passivity. Activation energies for the anodic polarization process were the right order of magnitude for a reaction controlled by reactivity at the metal surface. For the alpha-beta alloy 6Al-6V-2Sn the critical current for passivity increased as the ratio of amounts of beta-to-alpha phase decreased with increasing strength level. The addition of Fe(3+) and Cu(2+) (0.03 M) to the HCl facilitated passivation of the metal and its alloys. The maximum dissolution current densities for the metal and alloys in HCl were double those in H2SO4. Pitting of several of the alloys occurred in HCl but not in H2SO4. (Author)

Composite coating for the superalloys

Abstract: Improved operating lifetimes are provided for the superalloys through use of a composite coating comprising a chromium or chromium-rich interlayer adjacent the superalloy substrate surface and an oxidation-resistant outer layer comprising an alloy of iron, cobalt and/or nickel alloyed with selected amounts of chromium, aluminum and yttrium.

Method of forming metal alloys

Abstract: A method of forming superplastic metal alloys by heating the alloy to a temperature at which it is superplastic and then forming the alloy, in which the formed alloy is heated to a temperature above the superplastic temperature range in order to render it resistant to deformation before it is removed from the forming tool.

Carbide grain growth during the liquid-phase sintering of the alloys NbCFe, NbCNi, and NbCCo

Abstract: An investigation has been made of the microstructural changes which occur during the liquid-phase sintering of the alloys NbC-22 wt.% Fe andNbC-22 wt.% Ni. It was found that the growth of the carbide grains, dispersed in either of the liquid metals, is consistent with the theoretical equation, derived by Wagner, for a solution/ precipitation growth process controlled by the diffusion of the solid constituent through the liquid. The same growth behaviour has been observed earlier in a similar alloy of NbC in cobalt. The effect of temperature on grain growth was measured and “activation energies” of the growth rates were determined.

The inhibition of deformation twinning by precipitates in a magnesium-zinc alloy

Abstract: Deformation twinning can be inhibited in a Mg-5·1 wt. % Zn alloy by the presence of effective precipitates. This is true even in single crystals favourably oriented for twinning. This resistance to twinning precludes those premature fractures which frequently nucleate at twins. At 4·2°k twinning is highly favoured but effective precipitation postpones it until twice the glide strain observed in quenched crystals with no precipitates. Twin related fracture at 4·2°k is resisted in the fully hardened condition until three times the glide strain for fracture in the quenched condition. In polycrystals, grain size and texture as well as precipitation have profound effects on the deformation mechanism as a function of temperature. The flow stress in the quenched ease can decrease with decreasing temperature when grain size is large and the texture is appropriate for twinning. This behaviour is similar to that of quenched single crystals when twinning predominates. Conversely, the flow stress increases w...

Refractory hard metal composite cathode aluminum reduction cell

Abstract: The present invention is directed to cathodes of fused refractory hard metal alloy composited with certain bonding agents and their use, replacing the conventional carbon lining of an aluminum reduction cell.