Electron Beam Floating Zone Melting Research Articles

Математическое моделирование тепловых и гидродинамических процессов при электронно-лучевой бестигельной зонной плавке монокристалла кремния в условиях микрогравитации

Математическое моделирование тепловых и гидродинамических процессов при электронно-лучевой бестигельной зонной плавке монокристалла кремния в условиях микрогравитации

Solid-Solution Strengthening by Oxygen in Nb-Ta and Nb-Mo Single Crystals

We have investigated the high-temperature solid-solution strengthening by oxygen in Nb, Nb–Ta and Nb–Mo single crystals by compression tests with constant strain rate. Nb, Nb–20Ta, Nb–40Ta, Nb–20Mo, and Nb–40Mo single crystals with various O content were grown by use of the electron-beam floating zone melting method. It is found that Nb and Nb–Ta single crystals are strengthened by oxygen at temperatures below 1100 K, while Nb–20Mo single crystals are strengthened even at 1473 K. The critical resolved shear stress (c.r.s.s.) of Nb–Ta single crystals at 298 K increases linearly with increasing O content, irrespective of Ta content. Furthermore, the increment of c.r.s.s. of Nb–Ta single crystals is larger than that of Nb. The c.r.s.s. of Nb-Mo single crystals is higher than that of Nb for all temperatures tested, and the c.r.s.s. of Nb–20Mo single crystals also increases with increasing O content. These results indicate that the interstitial–substitutional (i–s) interaction between O and Ta or Mo affects the mechanical properties in the Nb-based alloys at high temperature.

Electron-beam growing and purification of W crystals

High-purity W single crystals have been grown by the electron-beam floating zone melting technique. The structural quality of these crystals was subsequently improved by the application of a strain-annealing technique. X-ray diffraction methods revealed a near-perfect crystallographic structure. Well-ordered clean W surfaces free from all contaminants were obtained by a two-step heating procedure. Low-energy ion scattering and Auger electron spectroscopy confirmed that the cleaning procedures removed all impurities and that the crystal faces expose only W in the outermost atomic layers. Thin layers of Re were deposited on a W(1 1 0) single crystal by magnetron sputtering and investigated by ion scattering and Auger electron spectroscopy.

Growth, characterisation and surface cleaning procedures for high-purity tungsten single crystals

High-purity tungsten (W) single crystals have been prepared by the electron-beam floating zone melting technique. The structural quality of these crystals was subsequently improved by the application of a strain-annealing technique. X-ray diffraction methods revealed the near-perfect crystallographic structure, and confirmed the absence of first- and second-order subgrains. The observation of the anomalous transmission of X-rays through the thick crystals, also referred to as the Borrmann effect, further substantiated the structural perfection of the crystals. Well-ordered clean W surfaces free from all contaminants, were obtained by a two-step heating procedure. First, the crystals were heated to 1500 K in an oxygen atmosphere for the removal of the carbon impurities. Subsequent flashing to high temperatures (approximately 2500 K) removed the excess oxygen remaining on the surface from the carbon-removal procedure. Low-energy ion scattering and Auger electron spectroscopy confirmed that the cleaning procedures removed all impurities and that the crystal faces expose only tungsten in the outermost atomic layers. Low-energy electron diffraction patterns showed unreconstructed (1×1) surfaces for the main crystallographic orientations.

Growth and characterization of monocrystalline tungsten substrates

High-purity tungsten single crystals of different crystallographic orientations were prepared by electron beam floating zone melting as well as by a strain-annealing technique. The substructure of these substrates was examined by SEM, optical microscopy and X-ray diffraction methods. Samples were prepared with different crystallographic planes and with substructures free from small-angle boundaries. The samples had excellent structure parameters, as deduced from the full-width at half-maximum of the rocking curves which was less than 0.1° for the substrates prepared by strain annealing. The substrates were subsequently cleaned in UHV using a newly designed compact electron beam gun for heating to 2500°C. The surface cleaning procedures were studied using AES, LEIS and LEED. Clean and well-ordered surfaces were obtained.

The perfection of tungsten single crystals grown from the melt and solid state

High-temperature gradients at the solid–liquid interface during the growth of W single crystals from the melt by electron beam floating-zone melting do not allow one to grow high-purity W single crystals free from small-angle boundaries with misorientation angles less than 3–5 min of arc and subgrain dislocation densities of less than 2×10 6 cm -2. W single crystals with a more perfect crystallographic structure can be obtained by strain annealing. In such single crystals there are no subboundaries and the dislocation density is about 8×10 4 cm -2.

Directional solidification of monocrystal superalloy by electron beam floating zone-melting

With the development of the aircraft engine, the monocrystal superalloy with homogeneous microstructure, low segregation and high purity is desired. This can be achieved by increasing the cooling rate under high vacuum condition to obtain the dendritic microstructure with superfine primary arm spacing. Using the electron beam floating zone-melting (EBFZ) technique, the single crystals of DD3 superalloy, having alternately planar, cellular and dendritic S/L interface, have been prepared by the seed crystal method in this paper. The misorientation between the single crystal's [100] crystallographic direction and the crystal growth direction is less than 10°. The interface morphology evolution is investigated. It can be seen that, when the zone melting rate is 100 μm/s, the primary dendrite arm spacing is five times smaller than that of the original seed. Meanwhile, the γ′ phase and the γ/γ′ eutectic are all fined and the microsegregation of the alloy elements decreased. The technical experiments show that, with carefully regulating the heating power and the zone melting rate, the melting zone can be kept stable. When the zone melting rate is small, the heating power can be increased in order to increase the temperature gradient. Whereas, when the zone melting rate is large, the heating power must be decreased in order to keep the growth processing steady.

Study of Pd single crystals grown by crucibleless zone melting

The electron-beam floating zone melting technique has been used to grow oriented single crystals of high-purity Pd. Ultra-high vacuum cleaning procedures of Pd(1 1 0) were developed. Low-energy ion scattering spectrometry showed a crystallographically well-defined monocrystalline structure free of contaminants after cleaning procedures. Growth and segregation of Pt on the Pd(1 1 0) surface as a function of the temperature was studied.

Electron-beam floating zone growing of high-purity cobalt crystals

A detailed study of the preparation of high-purity cobalt crystals is presented. The procedure consisted of the hydrogen reduction of high-purity cobalt chloride, the annealing of the resulting cobalt powder under chlorine flow, and the growth of cobalt crystals by electron-beam floating zone melting. The residual resistivity ratio of cobalt crystals was a maximum of 240. The different chemical and metallurgical procedures for the preparation of high-purity cobalt crystals have been compared and discussed.

Preferential sputtering and oxidation of NbTa single crystals studied by low-energy ion scattering

To study preferential sputtering and oxidation, three monocrystalline Nb x Ta 1 − x(110) alloys ( x = 0.25, 0.5, 0.75) as well as pure single crystals of Nb and Ta have been prepared by electron beam floating zone melting (EBFZM) and investigated by low-energy ion scattering (LEIS). After sputter cleaning, LEIS showed the enrichment of tantalum at the surface of all alloys. After exposure to oxygen, linear relationships between the oxygen and both the niobium and tantalum signals demonstrate that matrix effects do not influence the LEIS signals for these systems. The oxygen coverages of the different alloys have been determined by calibration against the Ni(100)- O c(2 × 2) surface.

Study of the microstructure of a Ni(100) single crystal grown by electron beam floating zone melting

The electron beam floating zone melting technique was used to grow oriented single crystals of high-purity nickel. Procedures for the preparation of monocrystalline seeds as well as for the growth of Ni single crystals were developed. Studies of the chemical composition of (100)-oriented single crystals were made. Electrochemical and metallographical methods coupled with microstructural observations by scanning electron microscopy showed the high structural uniformity of the grown single crystals.

Preparation of FeSi single crystals and bicrystals for diffusion experiments by the electron-beam floating zone technique

An electron-beam floating zone melting technique has been used to grow oriented single crystals and bicrystals of FeSi alloys with 6, 10, 12 and 14 at% Si. Procedures for the preparation of monocrystalline and bicrystalline seeds as well as for the growing of single crystals and bicrystals of these alloys are described. Studies of chemical composition of the bicrystalline specimens with aid of electron probe microanalysis revealed a homogeneous distribution of the main components. The behaviour of FeSi bicrystals in contact with a Zn-rich melt has been investigated. The wetting of grain boundaries by the melt and different types of Zn diffusion along the grain boundaries in several concentration intervals with a sharp transition from high to low diffusivity have been observed.

Growing Single Crystals of High-Purity Refractory Metals by Electron-Beam Zone Melting

Crucible-less methods are very important and useful for melting, study and preparation of high-purity refractory metals and alloys because of the high melting points and chemical reactivity of these materials in the liquid state. The modified electron-beam floating zone melting (EBFZM) technique has been used for purification of refractory metals from both gaseous and metallic impurities and for growing single crystals. The growing processes of bicrystals of refractory metals from the melt, with desired grain boundary type and other bicrystalline parameters, have also been studied. Application of the EBFZM technique to the growth of W and Mo single crystal tubes is discussed, and the possibilities of using the EBFZM technique for preparation of highly pure refractory metals and alloys for advanced technologies are shown.

Electron beam floating zone melting of refractory metals and alloys: G. Glebovsky, V.N. Semenov (Inst. of Solid State Physics, Moscow, Russia) Int. J. Refractory Metals & Hard Materials, vol 12, no 5, 1993–1994, 295–301

Electron beam floating zone melting of refractory metals and alloys: G. Glebovsky, V.N. Semenov (Inst. of Solid State Physics, Moscow, Russia) Int. J. Refractory Metals & Hard Materials, vol 12, no 5, 1993–1994, 295–301

電子ビーム浮遊帯溶融法によるジルコニウムの高純度化

Removal of metallic and non-metallic impurities from zirconium with nominal purity of 99.8% has been investigated by the electron beam floating zone melting (EBFZM) in a high vacuum.Metallic impurities such as iron and chromium, being more volatile than zirconium, volatilized preferentially and their contents were reducible to below a few mass ppm after three zone passes at the zoning speed of 2 mm/min. Although no decrease of hafnium, with a slightly lower vapor pressure than zirconium, by volatilization was observed, the redistribution of hafnium, caused by segregation effect, has been found. Deoxidation of zirconium by evaporation of zirconium suboxide like ZrO was scarcely noticed, but it was found that the oxygen content was reduced to below one-half of the initial content in near the final end of the zone melted portion, due to the segregation effect. Segregation of carbon towards the final end was also found, although decarburization by the CO gas evolution was not observed. The effective distribution coefficients for oxygen and carbon at the zoning speed of 2 mm/min were estimated to be 1.5∼2 and 0.7∼0.8, respectively.

Electron-beam floating zone melting of refractory metals and alloys: Art and Science

Crucibleless methods are extremely important for melting, studying and preparation of high purity refractory metals because of their high melting point and chemical reactivity in the liquid state. The electron-beam floating zone melting technique (EBFZM) was used both for purification of refractory metals and alloys from gaseous and metallic impurities and growing single crystals with predicted dislocation structure. Growing processes of bicrystals of refractory metals from the melt, with the grain boundary type and other bicrystalline parameters determined in advance, are also studied. Bicrystals grown by EBFZM give the unique opportunity to study different grain boundary phenomena. Application of EBFZM to grow single crystal tubes of tungsten and molybdenum are discussed. Their real dislocation structure is studied. There is a possibility that high purity refractory metals prepared by EBFZM may be used as semiproducts for advanced metallurgical technology.

電子ビーム浮遊帯域溶融法によるニオブの高純度化

電子ビーム浮遊帯域溶融法によるニオブの高純度化

Preparation of ultra pure tungsten.

The method of Electron Beam Floating Zone Melting (EBFZM) is well known as an effective treatment in refining of metals that has high melting point and reactive properties at high temperature.1, 2, 3 However, the sintered tungsten rod contains a great deal of gases.4 Thus, degassing is very important process for purification.In this present work, we refined tungsten rods by method of EBFZM, and estimated a purity of tungsten rods by measurement of Residual Resistivity Ratio (RRR)5, 6 and micro Vicker's hardness.7 As a result, it was confirmed as follows.1. Annealing was very effective treatment in degassing of tungsten rods.2. EB Gun's fast travel brought about a difference in refining conditions between rod's inside and one's surface, resulting in the formation of gaseous pools in rod's inside.

Production of ultrapure tungsten by solvent extraction with a D2EHPA/TOPO mixture and electron-beam zone refining

Laboratory and pilot-plant investigations have been carried out for the preparation of ultrapure tungsten. The starting material was commercially available ammonium paratungstate. Uranium- and thorium-free tungsten powder was prepared in the laboratory using solvent extraction with D2EHPA and TOPO. Optimum conditions of the purification were established. Based on the results of the laboratory work, a pilot plant of 2·4 tons per year capacity was constructed and operated to produce tungsten powder of 99·99% purity. From this powder, tungsten rods of 99·999% purity were prepared by electron-beam floating-zone melting.

Effects of oxygen and substitutional impurities on the mechanical properties of high purity iron

The present paper shows that oxygen is removed from commercial high purity iron by electron beam floating-zone melting under ultrahigh vacuum, and that hydrogen treatment of α-Fe is also effective in removing oxygen if the iron is pure enough with respect to substitutional impurities. The mechanical properties already reported by the research group of the present authors on high purity iron prepared by the same technique as for the present iron are the inherent properties of iron. These findings are in contradiction to the argument by Maruyama et al. that the high purity iron described above may contain a substantial amount of oxygen and the reported properties are not inherent in iron. Also discussed in the present paper are the effects of substitutional impurities and of grain structure on the athermal yield stress and the appearance of a hump in the yield stress vs. temperature curve.