Showing papers on "Directional solidification published in 1983"
TL;DR: In this article, the authors derived an asymptotic nonlinear equation which directly describes the dynamics of the onset and stabilization of cellular structure: ƒ τ + τ +▿ 4 + ǫ 4 +ǫ α = 0.
95 citations
Patent•
25 Feb 1983
TL;DR: In this paper, a columnar growth from a starter to a single crystal superalloy article is reduced from 9 degrees to 5 degrees by controlling the heat transfer in the starter section.
Abstract: Directional solidification of a single crystal superalloy article may be accomplished using a mold (20) with a starter section (36, 38), and a selector section (28) to convert columnar growth from the starter into single crystal growth. In such a process, the deviation of [001 crystallographic orientation with respect to the longitudinal axis of the article being formed is reduced from 9 degrees to 5 degrees by controlling the heat transfer in the starter section. A stepped starter section, wherein the lower subsection (38) has a volume of 52-98% of thetotal starter volume, and wherein the upper subsection (36) is relatively small in lateral dimension, has been found most useful. When the solidification interface moves into the smaller width upper subsection, it becomes more nearly planar, and results in improved columnar growth in the starter, and in reduction in the crystallographic deviation of the article.
30 citations
TL;DR: In this article, the magnetostrictions of rare earth-Fe 2 compounds have been measured under compressive stresses up to 24 MPa and the largest values of d∈/d H were found in Tb 0.27 Dy 0.73 Fe 1.95 prepared by directional solidification.
28 citations
27 citations
NEC1
TL;DR: In this article, a SiC coated carbon mold together with Si3N4 powder mold releasing agent was used for directional solidification of silicon, which achieved an AM1 maximum conversion of 10.8%.
22 citations
TL;DR: In this paper, the effect of forced convection on composite growth has been studied and simplified conditions of convection were established experimentally in order to investigate various influences of laminar flow parallel to the solidification front on the growth morphology of Pb-Sn and Cd-Zn eutectics.
22 citations
TL;DR: Etude du comportement de l'hydrogene pendant la solidification de Al pur pour des lingots solidifies a differentes vitesses de croissance as discussed by the authors.
Abstract: Etude du comportement de l'hydrogene pendant la solidification de Al pur pour des lingots solidifies a differentes vitesses de croissance
22 citations
Patent•
14 Jan 1983
TL;DR: In this article, a method of epitaxially casting single crystal metal articles in molds is described, which comprises causing the solidification interface velocity vector to rotate through at least 90 degrees, preferably 180-540 degrees, about the axis of overall directional solidification growth, and a small passageway configured to prevent line of sight communication between the portion where the seed is contained and the article portion of the mold.
Abstract: Disclosed is a method of epitaxially casting single crystal metal articles (32) in molds (34), which comprises causing the solidification interface velocity vector to rotate through at least 90 degrees, preferably 180-540 degrees, about the axis of overall directional solidification growth (54,56). In addition, a mold section (46) has a small passageway configured to prevent line of sight communication between the portion where the seed is contained and the article portion of the mold. Preferably, the passageway is shaped like a helix of 0.8-1.5 turns. A second seed (40) can be formed in the mold of an article made from a first seed (36), and used to make a second casting. The invention reduces the normal increase in crystallographic variability which would otherwise be associated with such practice.
21 citations
TL;DR: In this paper, a directional solidification technique was developed and applied to the problem of fractional crystallization of an iron meteorite parent body, where the secondary phases observed in iron meteorites were formed during primary solidification of austenite (taenite).
Abstract: A directional solidification technique was developed and applied to the problem of fractional crystallization of an iron meteorite parent body. Samples of Fe-Ni alloys close to meteorite compositions and containing S, P, and C were made. The solidified structures contain secondary phases such as sulphides within the proeutectic single crystal austenite (taenite). As a result of these experiments, we propose that the secondary phases observed in iron meteorites were formed during primary solidification of austenite (taenite). The measured composition profiles of Ni, P and C in the alloys were used to explain the elemental distribution within a chemical group of iron meteorites. An analytical procedure was applied to determine the equilibrium distribution coefficients as a function of fraction solidified for Ni and P from the composition profiles. The distribution coefficients of Ni and P agree with previous values. These distribution coefficients are of particular interest in the determination of the elemental distributions in iron meteorites.
14 citations
TL;DR: In this paper, the wave number changes in a discontinuous way through strongly nonlinear events which either create or destroy one cell at a time, leading toward a unique final wave number.
Abstract: The equations of motion for a slightly deformed planar solidification front advancing with a steady velocity and stabilized by a thermal gradient are integrated numerically. The regime where the interface develops a cellular pattern is analyzed. We study the case where the system is subjected to Gaussian white noise. The wave number is found to change in a discontinuous way, through strongly nonlinear events which either create or destroy one cell at a time. Ultimately, the process appears to lead toward a unique final wave number. The structure of the equations is examined with respect to the wave-number dependence and the selection phenomenon observed in the computer simulations is understood phenomenologically on the basis of a phase-space type of argument.
14 citations
TL;DR: In this paper, the tensile and compressive strength of naphthalene, benzil, and their eutectic in the faceted-faceted benzil-naphalene system have been determined.
Abstract: The tensile and compressive strengths of directionally and randomly grown samples of naphthalene, benzil, and their eutectic in the faceted-faceted benzil-naphthalene system have been determined. The tensile strength of naphthalene and the eutectic increased significantly on directional solidification. Directional solidification substantially enhanced the compressive strength of the eutetic whes rea decrease in compressiv strength was observed in case of directionally grown naphthalene. In case of benzil, no appreciable change in strength was observed on directional solidification. A comparison between the tensile and compressive strength was made. The compressive strength was 2.5–3.8 times more than the tensile strength of naphthalene, grown randomly, benzil and their eutectic grown randomly and directionally.
TL;DR: In this paper, single crystals of Mo 3 Si and TaTi have been made in a travelling solvent growth mode using cold crucibles and skull crucibles, respectively, and attempts have also been made to grow Mo 3 Al using this method.
TL;DR: In this paper, the crystallization behavior of beryllium was investigated by examining single crystals grown by zone melting and other directional solidification techniques, and it was shown that the solidification of BER does not yield a preferred growth orientation of the crystals.
01 Jun 1983
TL;DR: By the use of a vertical Bridgman growth method, the Al-Si eutectic alloy containing 11.6 wt% Si was directionally solidified in a vertical magnetic field of 35,000 Oe and without the magnetic field as mentioned in this paper.
01 Apr 1983
TL;DR: An ADSS-P directional solidification furnace was reconfigured for operation on the KC-135 low-g aircraft as discussed by the authors, which offers many advantages over quench ingot methods for study of the effects of sedimentation and convection on alloy formation.
Abstract: An ADSS-P directional solidification furnace was reconfigured for operation on the KC-135 low-g aircraft. The system offers many advantages over quench ingot methods for study of the effects of sedimentation and convection on alloy formation. The directional sodification furnace system was first flown during the September 1982 series of flights. The microstructure of the hypereutectic cast iron sample solidified on one of these flights suggests a low-g effect on graphite morphology. Further experiments are needed to ascertain that this effect is due to low-gravity and to deduce which of the possible mechanisms is responsible for it.
01 May 1983
TL;DR: In this paper, the authors describe in situ refinements of commercially available MG silicon by the Heat Exchanger Method (HEM) and demonstrate the effect of vacuum, slagging, argon blowing through the melt and double solidification on refinement.
Abstract: This paper describes in situ refinements of as-received, commercially available MG silicon by the Heat Exchanger Method (HEM). Samples of MG silicon from six different sources were directionally solidified and nearly single crystal structure was achieved in 15 cm square ingots. The effect of vacuum, slagging, argon blowing through the melt and double solidification on refinement of impurities was studied. The simultaneous incorporation of vacuum, slagging, moist argon blowing through the melt and a directional solidification reduced the impurities to less than 1 ppm levels. These procedures were also effective in reducing the B and P contents.
Patent•
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29 Mar 1983
TL;DR: In this paper, a titled mold is installed with a water cooled chiller 9 in the bottom surface of the mold and a rotary magnetic field type electromagnetic agitator 3 on the circumference in the riser part of a casting.
Abstract: PURPOSE:To prevent defects such as shrinkage cavities, segregation and the like and to reduce the rate of feeding by cooling the bottom surface of a mold while rotating and electromagnetically agitating the molten metal in a riser part and making directional solidification possible CONSTITUTION:A titled mold which is installed with a water cooled chiller 9 in the bottom surface of the mold and a rotary magnetic field type electromagnetic agitator 3 on the circumference in the riser part of a casting A riser part 2'' is rotated and agitated by said device 3 At the same time, the molten metal 2' in the body part of the casting is agitated by the viscosity of the molten metal The solidification of the casting is initiated from the bottom surface by the chiller 9, whereby the solidification from the side surfaces is suppressed and the directional solidification is accomplished Thus defects such as shrinkage cavities, segregation and the like are prevented and the rate of feeding is reduced
TL;DR: In this article, γ-ray diffraction was used to study copper single crystals during growth by directional solidification of the melt in a graphite crucible, and the growth rate was determined.
Patent•
12 Aug 1983
TL;DR: In this paper, the melt-back of a seed crystal is controlled to provide high casting yield, measured as a fraction of the original length of the seed, more preferably between 33-67%.
Abstract: In the manufacture of a single crystal article, by the directional solidification of a metal in a ceramic mold the melt-back of a seed crystal is controlled to provide high casting yield. The melt-back, measured as a fraction of the original length of the seed, is preferably between 25-75%, more preferably between 33-67%. Diametrical clearance between the seed and mold is also closely controlled, between 0.06-0.25 mm, to eliminate extraneous grain nucleation.
Patent•
27 Jan 1983
TL;DR: In this article, a method of epitaxially casting single crystal metal articles in molds is described, which comprises causing the solidification interface velocity vector to rotate through at least 90 degrees, preferably 180-540 degrees, about the axis of overall directional solidification growth, and a small passageway configured to prevent line of sight communication between the portion where the seed is contained and the article portion of the mold.
Abstract: Disclosed is a method of epitaxially casting single crystal metal articles (32) in molds (34), which comprises causing the solidification interface velocity vector to rotate through at least 90 degrees, preferably 180-540 degrees, about the axis of overall directional solidification growth (54,56). In addition, a mold section (46) has a small passageway configured to prevent line of sight communication between the portion where the seed is contained and the article portion of the mold. Preferably, the passageway is shaped like a helix of 0.8-1.5 turns. A second seed (40) can be formed in the mold of an article made from a first seed (36), and used to make a second casting. The invention reduces the normal increase in crystallographic variability which would otherwise be associated with such practice.
01 Aug 1983
TL;DR: In this paper, two types of aligned structures are obtained during directional solidification of monotectic systems: rows of spheres when the temperature gradient (G) to growth rate (R) ratio is large and rods when the G R ratio is small.
Abstract: Abstract During directional solidification of monotectic systems, two types of aligned structures are obtained. The second constituent appears as rods when the temperature gradient (G) to growth rate (R) ratio is large. It appears as rows of spheres when the G R ratio is small. The occurrence of these structures can be explained in terms of interface breakdown and capillary instability mechanisms between two liquid phases.
Journal Article•
TL;DR: The history of the coulee a la cire perdue in Inde can be found in this paper, where Fabrication par solidification dirigee d'aubes de turbines for l'industrie aeronautique
Abstract: Historique de la coulee a la cire perdue en Inde. Fabrication par solidification dirigee d'aubes de turbines pour l'industrie aeronautique
TL;DR: In this article, it was shown that the nonlinear system can select the propagating mode in which the leading edge of the pattern is just marginally stable. But, it is not well understood how these patterns are selected and controlled or even whether there ever exist sharp selection mechanisms.
Abstract: Directional solidification of alloys produces a wide variety of cellular or lamellar structures which, depending upon growth conditions, may be reproducibly regular or may behave chaotically. It is not well understood how these patterns are selected and controlled or even whether there ever exist sharp selection mechanisms. A related phenomenon is the spatial propagation of a pattern into a system which has been caused to become unstable against pattern-forming deformations. This phenomenon has some features in common with the propagation of sidebranching modes in dendritic solidification. In a class of one-dimensional models, the nonlinear system can be shown to select the propagating mode in which the leading edge of the pattern is just marginally stable. This stability principle, when applicable, predicts both the speed of propagation and the geometrical characteristics of the pattern which forms behind the moving front. A boundary-layer model for fully two or three dimensional solidification problems appears to exhibit similar mathematical behavior.
TL;DR: Anomalous behaviour of components in the first-to-freeze solid of Pb1−xSnx Te grown by vertical Bridgman technique has been observed.
Journal Article•
TL;DR: In this article, the effect of the melt superheat on the solute distribution coefficient and the critical condition of the interface morphology on the directional solidification has been studied and it is found that the actual distribution coefficient of solute is a function of liquid state.
Abstract: The effect of the melt superheat on the solute distribution coefficient and the critical condition of the interface morphology on the directional solidification has been studied. It is found that the actual distribution coefficient of solute is a function of liquid state. An increase of superheat of the melt causes the increase of actual distribution coefficient for such elements of K_01, and the decrease of the critical conditions of G/R associated with the stability of the solid-liquid interface morphologies which seems to be available to improving the directional solidification.
01 Apr 1983
TL;DR: In this article, a study of superconducting properties of Cu-rich CU-Nb wires prepared by directionally solidified and cold-rolled technique was conducted and a total of 12 wire specimens were tested.
Abstract: In addition to its superconducting properties, a superconductor is usually characterized by poor thermal conductivity and relatively high electrical resistivity in the normal state. To remedy this situation a study of superconducting properties of Cu-rich CU-Nb wires prepared by directionally solidified and cold-rolled technique was conducted. Some of the specimens were prepared by melting, directional solidification and diffusing in Tin. A total of 12 wire specimens was tested. Each specimen was analyzed by plotting experimental data into the following curves: the graph of the residual resistivity as a function of the specimen current at 4.3 K; and the graph of the electrical resistivity as a function of the temperature at a constant current.