Melting Point Of Metal Research Articles

Interfacial energies between uraniumdioxide and liquid metals

Abstract Interfaciai energies between solid uranium dioxide and liquid metals have been investigated for a number of systems. It was found, that at the metal melting point (1) the interfacial energies become approximately identical for all metals (γUO 2 -liquid metals ≈ 1.676 ± 0.142 J/m 2 ) with respect to an engineering approach, and (2) the respective contact angles (φ s > 90°) point out no wettability. Linear temperature functions of interfacial energies in UO 2 -liquid metal systems have been derived. By appropriate extrapolation procedures it is possible to estimate temperature coefficients of interfacial energies for not yet measured solid UO 2 -liquid metal systems.

Catalysis by Molten Metals and Molten Alloys

Abstract It appears pertinent for the opening of this review to cite the work of Ipatiew [1]. In 1901 he reported that certain metals catalyzed the decomposition of alcohols even above the melting points of the catalyst metals, However, he gave no special attention to the catalytic activity of the molten metal (liquid metal), and thus 20 years or more elapsed without any significant advances in the research on the catalysis of the liquid metal.

Joining of Self‐Bonded Silicon Carbide by Germanium Metal

Two self‐bonded SiC bodies containing free Si were joined with liquid Ge at 1180°C in vacuum. Bond strength was measured by four‐point bending test in vacuum at high temperature. The join had a significant strength even above the melting point of Ge metal. Electron probe microanalysis of joint showed a liquid formation temperature of thinner interlayer was ∼1200°C.

Correlation of the annealing temperature for radiation damage fields to the melting point of metals in DPAD experiments

Correlation of the annealing temperature for radiation damage fields to the melting point of metals in DPAD experiments

The high temperature phase diagrams for zirconium-molybdenum and hafnium-molybdenum

The high temperature regions of the Zr−Mo and Hf−Mo binary phase diagrams have been constructured from temperature-composition data obtained by gravimetric and pyrometric methods. The liquidus curves were obtained directly from the measurements of saturation solubilities of molybdenum (single crystal) in liquid Zr and Hf. The solubility results are supported by electron microprobe analyses which identify the formation of thin (∼10 μm) layers of nearly stoichiometric compounds ZrMo2 and HfMo2 on the surface of the single crystal molybdenum below the respective peritectic temperatures 1918±5 and 2206±5°C. These thin layers and the negligible diffusion zones of Zr and Hf in single crystal molybdenum do not significantly affect the measured solubilities. The diffusion coefficient of Hf in Mo-single crystal at 2080°C is ∼5×10−12 m2 s−1. The melting, solidus, liquidus, eutectic and peritectic temperatures were directly measured by pyrometrically observing the partial or complete destruction of “black-body” conditions inside an effusion cell with the appearance of a liquid phase that forms a highly reflecting mirror. The melting points of Zr and Hf metals, 1860±3 and 2228±3°C, respectively, are in good agreement with previously assessed values. The respective eutectic temperatures peratures and compositions 1551±2°C, 29.0±0.5 at. pct Mo and 1896±3°C, 40.5 at. pct Mo, are considerably more precise and only in fair agreement with previously measured or estimated values. The liquidus composition at the peritectic temperature for the Zr−Mo binary is precisely fixed at 54.0±1.0 at. pct Mo and that for the Hf−Mo binary is 61 ±3 at. pct Mo. The thermodynamic activities of molybdenum in the liquid Zr−Mo alloy indicate positive deviations from Raoult's Law.

Activation energy for electrotransport in thin aluminum films by resistance measurements

The activation energy for electrotransport in thin aluminum films was measured by a resistometric technique involving several individual resistance measurements along the stripe. An equation was derived which relates the rate of resistance change to the ion velocity. A thin film thermocouple which is free of any loss of heat was used to monitor the temperature of the stripe. This thermocouple was calibrated by the melting points of pure metals placed on the film. The activation energy for electrotransport in thin aluminum films was found to be temperature dependent and to vary between 0.45 and 0.72 eV in a temperature range between 220 and 360°C. The average ion velocity in the grain boundaries due to electrotransport was found to be around 10 −7 cm sec in agreement with the literature.

Superconducting coils impregnated with Wood's metal

This report describes the stability of superconducting coils wound with fine multi-filamentary wires and impregnated with Wood's metal.The training effect and current degradation observed before impregnation are remarkably improved after impregnation. The instability of superconductin coils seems to originate in “wire movement” in the winding. In comparison with organic impregnants, low melting point-metals such as Wood's metal are effective impregnants in suppressing “wire movement” in the winding and in elevating the stability of superconductin coils, because cracks and voids do not exist in the winding owing to good osmosis in the melting state and coils are well cooled owing to good thermal conductivity.

Effect of surface conditions on the normal spectral emittance of titanium and zirconium between 1000 and 1800 K

The normal spectral emittance of Ti and Zr was obtained in the temperature range 1100 to 1800 K and wavelength 0.645 μ for electrochemically polished, mechanically polished and 60 grit ground surfaces at a pressure below 10-8 mm Hg. The emittance at the melting point of both metals was obtained by extrapolation of an empirical equation fitted to the experimental data obtained for the electrochemically polished surface and was found to be in good agreement with reported values. The considerable grain growth on the surface affected the emittance. The emittance was found to increase with temperature up to 1300 K and then decreased with further increase in temperature.

Vacuum Brazing

Brazing is a process of joining metals in which molten filler metal is drawn by capillary attraction into the space between closely adjacent surfaces of the parts to be joined. In general, the melting point of the filler metal is above 500°C.

Determination of work functions near melting points of refractory metals by using a direct-current arc

A direct-current arc in argon at atmospheric pressure was used to determine effective work functions of refractory metals, including tantalum, tungsten, molybdenum, and niobium. The procedure is experimentally advantageous because surface cleanliness of the specimen is not critical, high vacuum is not required, and the anode-cathode spacing is not critical. The experimental procedure involves striking an arc to a metal wire cathode to form a melted ball having an emitting area defined by its diameter. The literature melting point of the metal is taken as the emitting temperature. By using these parameters and the known arc current, effective work functions were calculated from the Richardson-Dushman equation. The calculated work functions agree with recommended handbook values to within about 0.1 V and have typical repeatabilities of 0.02 V. By varying the arc current, Richardson plots can be made over a temperature range from a few hundred degrees below the melting point to about 50° over the melting point of the test metal. A Richardson plot over this temperature range is presented for tantalum.

The significant liquid structure theory applied to the critical properties of the alkali metals

The significant liquid structure theory has been used to estimate the critical properties of the alkali metals. The argon partition function is used at the critical point and the equilibrium between the monomer and the dimer of the alkali metals is considered in this work. It is found that the compressibility coefficient P cV c (RT c) of the alkali metals at the critical point varies about the value 0·40. Our calculations indicate that there are about 70% of gas-like degrees of freedom at the critical point compared with less than 2·5% at the melting point of the alkali metals. The calculated results are compared with various estimated values and with the available experimental data.

Effect of pressure on the melting temperature of metals

In this paper an equation is derived to relate the melting points of metals to the application of pressure on the basis of the theory that an entrapped gaseous fraction comes into being when a metal changes from the solid to the liquid state. A correlation is made between the parameters of this new equation and those of equations derived by F. E. Simon and G. C. Kennedy. The validity of the equation is tested by comparing its prediction with the experimental data obtained for Li, Na, K, Rb, Fe, and Ni, and the expected limitations of the equation are discussed.

NMR Study of Self-Diffusion and the Electronic Structure of Metallic Copper in the Solid and Liquid States

The Knight shift $K$ and the nuclear relaxation times ${T}_{1}$ and ${T}_{2}$ of Cu in metallic copper have been measured in the temperature range from room temperature up to the metal melting point, and into the liquid state up to 1200\ifmmode^\circ\else\textdegree\fi{}C. A pulse technique was used. ${T}_{1}$ and ${T}_{2}$ were measured with an accuracy of \ifmmode\pm\else\textpm\fi{}3%, using a spin echo method. ${T}_{2}$ becomes equal to ${T}_{1}$ at high temperatures. From the data of ${T}_{2}$ versus temperature, the diffusion constants for the Cu self-diffusion were calculated using the Eisenstadt-Redfield approach. The values of these constants are ${E}_{D}=1.97\ifmmode\pm\else\textpm\fi{}0.04$ eV and ${D}_{0}=0.11\ifmmode\pm\else\textpm\fi{}0.05$ ${\mathrm{cm}}^{2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ for ${\mathrm{Cu}}^{63}$, and ${E}_{D}=2.00\ifmmode\pm\else\textpm\fi{}0.04$ eV and ${D}_{0}=0.15\ifmmode\pm\else\textpm\fi{}0.07$ ${\mathrm{cm}}^{2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ for ${\mathrm{Cu}}^{65}$. The electronic structure of Cu was deduced from the effect of lattice expansion on $K$ and ${T}_{1}$. Assuming a free-electron model, one expects both ${({T}_{1}T)}^{\ensuremath{-}1}$ and $K$ to be temperature-independent. However, an increase of \ensuremath{\sim}10% in ${({T}_{1}T)}^{\ensuremath{-}\frac{1}{2}}$ and $K$ was observed as the temperature was raised from 25\ifmmode^\circ\else\textdegree\fi{}C to the mp. Upon melting, there is a jump of 5.0\ifmmode\pm\else\textpm\fi{}0.5% in ${({T}_{1}T)}^{\ensuremath{-}\frac{1}{2}}$ and $K$. In the liquid phase, $K$ rises moderately, whereas ${({T}_{1}T)}^{\ensuremath{-}\frac{1}{2}}$ shows a steep rise of 5% per 100\ifmmode^\circ\else\textdegree\fi{}C. This behavior is identical for both isotopes. It is shown that the main mechanism for the nuclear relaxation is the interaction with the conduction electrons. As the ${({T}_{1}T)}^{\ensuremath{-}\frac{1}{2}}$ and the $K$ temperature dependence cannot be explained by the free-electron model, we relate the behavior to the well-known band structure, using recent measurements and calculations which give the dependence of the density of states on the lattice constants. The jump in ${({T}_{1}T)}^{\ensuremath{-}\frac{1}{2}}$ upon melting is explained in terms of the removal of the Fermi-surface distortion. No explanation is offered for the rise in ${({T}_{1}T)}^{\ensuremath{-}\frac{1}{2}}$ with temperature in the liquid state.

Solid-liquid phase equilibria in the sodium + potassium system

Thermal methods were used to determine with high precision, the solid-liquid phase equilibria diagram for the sodium + potassium system. The melting points of the pure metals and the solid solubility limits were better established by the use of ultra-pure elements and precision thermometry. Considerable effort was expended in a search for intermetallic compounds. No compounds other than Na2K were formed.

モリブデンの拡散接合

It is generally acknowledged that the ductile joint of molybdenum is difficult to make by fusion welding because of its embrittleness due to recrystallization and grain growth.The purpose of this investigation is to obtain a ductile joint of pure molybdenum without recrystallization and extreme deformation by diffusion or pressure bonding processes with or without insert metals. The following resuls were obtained.1. Although the joint of molybdenum without insert metals was accomplished at higher temperature than the recrystallization temperature with 5-10% deformation, the joint made at higher temperature than 1200Δ was brittle due to recrystallization. A transfacial grain growth across the initial bonding interface was observed to occur at 1250Δ for 5 min and such migration of grain boundary was easily obtained relatively at lower temperature compared with that for various metals.2. It was found that the joint of molybdenum without recrystallization and extreme deformation was accomplished using insert metals such as iron, nickel, copper and silver by electroplating. The remelting temperature of these joints became too higher than the melting points of the insert metals. Although nikel formed an intermetallic compound with molybdenum, nickle insert metal made a stronger joint at low temperature than the others. Copper was also found to be applicable as an insert metal, but it did not alloy with molybdenum.

The solubility of tantalum in eight liquid rare-earth metals

The solubilities of tantalum in liquid gadolinium, terbium, dysprosium, holmium, erbium and thulium have been determined from the melting point of the rare-earth metal to ~ 1800°C, to ~ 1900°C for scandium, and to ~ 2000°C for lutetium. The change of the transition and melting points by tantalum has been measured, and the partial molal heats of solution of tantalum in the rare-earth metals calculated from these data. The liquid solubility of tantalum was found to depend upon the atomic size difference between the rare-earth solvent and the tantalum solute, i.e. the smaller the size difference the greater the solubility at a given common temperature ( e.g. 1700°C). These results also suggest that the atomic size factor curves presented by Strauss, White and Brown for liquid alloys should be modified.

Struktur und thermisches Verhalten von Wachstumszwillingen in dünnen kubisch flächenzentrierten Metallschichten

Single crystal films prepared by evaporation of silver, gold, copper, and nickel on heated cleaved rocksalt crystals and polycrystalline films of silver, gold, copper, platinum, aluminum, and nickel have been studied by transmission electron microscopy and electron diffraction. By means of electron microscope dark-field image and selected area diffraction technique the existence of small growth twins in the films is shown. Extra spots observed in the electron diffraction diagram can be explained partly as spots of the four twin orientations, partly as arising from double diffraction of the (100) matrix orientation and of a twin orientation. In the case of polycrystalline films the double diffraction mechanism results in additional diffraction rings seeming not to belong to the normal face-centred cubic lattice. The assumption of an hexagonal phase or of stacking faults or of periodic lattice defects cannot explain all the extra spots and additional rings. The changing diffraction contrast of thick and thin microtwins obviously depends on the different reflection conditions in the electron microscope. It is shown that it is very complicated to distinguish stacking faults from microtwins, but some criteria of distinction are given. By means of a heating stage the single crystals have been heated in the electron microscope up to more than 1000 °C. The thermal behaviour of the twins has been studied in detail. It can be observed that up to 95% of the twins become invisible by transformation from the twin orientation to the (100) matrix orientation. It is concluded from the experiments that the transformation nucleates at the top or bottom of the thin films. Nevertheless more than 1013 twins and stacking faults per cm3 remain unchanged inspite of heating to temperatures near the melting point of the bulk metal.

TD-NICKEL

Abstract TD-NICKEL is a dispersion hardened nickel alloy offering high-temperature stability and useful mechanical properties virtually to the melting point of the base metal. It is easy to fabricate. It is capable of operating for long periods of time at high temperatures without degradation of mechanical properties. This datasheet provides information on composition, physical properties, and tensile properties as well as fracture toughness and fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-103. Producer or source: E. I. DuPont de Nemours & Company Inc..

Dynamic Indentation of Copper and an Aluminium Alloy with a Conical Projectile at Elevated Temperatures

The dynamic indentation of copper (B.S. 1433) and an aluminium alloy (B.S. 1476 HE 10) has been investigated, using cylindro-conical projectiles fired from an air-actuated gun. The experiments were performed with impact velocities varying between 1000 and 2500 in/s and at elevated temperatures up to 600°C for the copper and 550°C for the aluminium alloy. The magnitude of the corresponding range of mean strain rate was then 103-104/s, depending upon the material; impact velocity and temperature (see Appendix I).For the range of impact velocities investigated no consequential transition temperature†was encountered. The dynamic temperature coefficient† thus remained constant throughout the test temperature range for each material. This dynamic temperature coefficient was found to be equal to the static temperature coefficient corresponding to the sub-transitional temperature range for the respective materials.The mean effective dynamic indentation pressure is shown to decrease with temperature but the ratio of this dynamic pressure to the static indentation pressure increases with temperature.Strain rate effects for both materials were negligible for sub-transitional temperatures but become important at super-transitional temperatures. It was observed that the parameters on which the strain rate effect depends are in some way related to the absolute melting point of a pure metal.

High Temperature Furnace for Melting Point Determination

This paper describes a device for determining by optical methods the melting points of metals, alloys, oxides, and other materials at temperatures up to at least 3000°C. The furnace is simple in design and requires only vacuum and electrical connections. There is no water cooling and the heating element is a disposable tungsten conical basket purchased from a commercial supplier.