Showing papers on "Microstructure published in 1968"
TL;DR: In this paper, the morphology and growth of extended chain crystals of polyethylene are discussed on the basis of optical and electron microscopy, and spherulite centers have been identified down to the primary lamella.
Abstract: : The morphology and growth of extended chain crystals of polyethylene is discussed on the basis of optical and electron microscopy. The spherulitic habit is shown to be caused by nucleation of new lamellae on the (001) surface of lamellae, branching of lamellae on their growth face, and thickening of lamellae. Spherulite centers have been identified down to the primary lamella. Analysis of intersections of lamellae during crystallization allowed the identification of intermediate stages of crystal growth. Fracture surfaces parallel to the growth face and the (001) face are discussed. 'Ripple decoration' by surface recrystallization is developed as a tool for fracture surface study. Kink bands are described as growth defects. Bending of lamellae is shown to go by slip parallel to the polymer chains. Ripple and drawn out fiber annealing is analyzed. All observations on extended chain crystals are used to propose a mechanism of extended chain crystal growth of polyethylene under elevated pressure. (Author)
118 citations
TL;DR: The radial distribution function for an electrodeposited amorphous nickel-phosphorus (149 wt% P) alloy has been determined in this article, and the atomic distribution was found to be similar to that in a liquid metal.
Abstract: The radial distribution function for an electrodeposited amorphous nickel‐phosphorus (149 wt% P) alloy has been determined The atomic distribution was found to be similar to that in a liquid metal, and more disordered than that observed in an amorphous nickel‐phosphorus alloy produced by chemical deposition Two transformations (both exothermic) were observed in this alloy; the first of which occurred at 280°±2°C with an energy of 185 cal/g (960 cal/g atom) and the second at 410°±5°C with an energy of 60 cal/g (310 cal/g atom) As deposited, the alloy exhibits only a very weak small‐angle x‐ray scattering, apparently not due to the presence of the phosphorus
68 citations
TL;DR: The microstructure of diamonds formed from the graphite in cast iron by an explosive shock process was investigated by means of transmission electron microscopy electron, diffraction, and selected beam microscopy.
Abstract: The microstructure of diamonds formed from the graphite in cast iron by an explosive shock process was investigated by means of transmission electron microscopy electron, diffraction, and selected beam microscopy. Morphologically, the material consists of a mixture of two different forms: compact aggregates of of usually acicular crystallites with a strong preferred orientation, and single crystals. The latter partly consist of hexagonal diamond, the recently discovered modification of carbon, and contain many stacking faults. Hexagonal diamond is also randomly distributed in the polycrystalline fraction.
65 citations
TL;DR: In this paper, the microstructure of Sic from methyltrichlorosilane in a fluidized bed was studied over a range of deposition temperatures, carrier gas flow rates, and reactant fluxes.
Abstract: Vapor deposition of Sic from methyltrichlorosilane in a fluidized bed and the microstructure of the deposit were studied over a range of deposition temperatures, carrier gas flow rates, and reactant fluxes. The rate-determining factor for the deposition of Sic was the rate of supply of reactant. The microstructure of vapor-deposited Sic was primarily dependent on the deposition temperature; however, carrier gas flow rate and reactant flux had a secondary influence on microstructure. At low temperatures and high carrier gas flow rates, laminar deposits containing excess silicon were produced. At higher temperatures and lower carrier gas flow rates deposits were characterized by faulted columnar grains. The grain diameter increased from about LP at 1400°C to about 15 μ at 1800°C. The grain size also increased, but less markedly, with increasing reactant flux. The deposits characterized by columnar grains were predominantly β-Sic with traces of a-SiC and excess carbon.
65 citations
Journal Article•
64 citations
TL;DR: The sulfide cracking behavior of a number of carbon and low alloy steels is described in this paper, where it is shown that the susceptibility of a steels to sulfide crackability depends primarily on the microstructure of the steels.
Abstract: The sulfide cracking behavior of a number of carbon and low alloy steels is described Susceptibility to sulfide cracking is shown to depend primarily on microstructure Steels with uniform, spheroidized carbides in a ferrite matrix have the greatest cracking resistance at any given strength level The presence of untempered martensite in the microstructure drastically reduces cracking resistance Lamellar carbides resulting from either normalizing and tempering or isothermal transformation give rise to cracking resistance intermediate between steels fully quenched and tempered and steels containing untempered martensite
56 citations
TL;DR: In this article, the authors describe the routes to the equiaxed fine structure needed for superplastic behaviour in two-phase Zn-Al alloys and indicate that the development of a spinodal structure is not an essential step towards achieving a superplastically structure in this alloy.
Abstract: Studies are described which involve the routes to the equiaxed fine structure needed for superplastic behaviour in two-phase Zn–Al alloys. These indicate that the development of a spinodal structure is not an essential step towards achieving a superplastic structure in this alloy. Some microstructural aspects and mechanical behaviour characteristics of superplastic Zn–Al alloys are presented which suggest that the major mechanism of deformation in these alloys is crystallographic slip accompanied by grain boundary migration or recrystallization.
45 citations
TL;DR: In this article, the authors proposed that the equiaxed structure is produced by spinodal decomposition of an eutectoid Zn-Al alloy and showed tensile elongations of > 1000% at a deformation temperature of 250°C.
Abstract: The mode of decomposition of a eutectoid Zn–Al alloy has been related to the superplastic properties of the alloy. Decomposition during slow quenches or at high transformation temperatures produces a typical lamellar eutectoid structure with conventional mechanical properties. Decomposition at room temperature after a rapid quench produces a fine (∼ 1 μ) mixture of equiaxed zinc-rich and aluminium-rich grains and the alloy then shows tensile elongations of > 1000% at a deformation temperature of 250°C. It is proposed that the equiaxed structure is produced by spinodal decomposition.
43 citations
TL;DR: In this article, a study by electron microscopy, electron diffraction and optical microscopy is reported concerning the initial stages of the reaction of tantalum with oxygen, which appears in the shape of plates in a layer near the surface highly enriched in oxygen.
34 citations
TL;DR: In this article, the effects of thickness and testing direction upon the plane strain and plane stress fracture toughness of 7075-T6 and -T651 aluminum alloy were examined, both by static center-notched tests and precracked Charpy impact tests.
TL;DR: In this paper, the authors examined the stippled area surrounding the mirror-smooth area at the origin of fracture using an optical microscope and progressive etching, and showed that the area can be regarded as a collection of large numbers of individual local elements of but two basic types.
Abstract: The mist zone, the arc of stippled surface surrounding the mirror-smooth area at the origin of fracture, was examined in detail using an optical microscope and progressive etching. The results show that the stippled area can be regarded as a collection of large numbers of individual local elements of but two basic types, and that microscopic cracks exist below the fracture surface which are related to the structure on the exposed surface.
TL;DR: The internal friction and electrical resistivity of amorphously decomposed binary sodium silicate glasses containing from 4.0 to 18.4 mole % Na2O have been measured as discussed by the authors.
Abstract: The internal friction and DC electrical resistivity of amorphously decomposed binary sodium silicate glasses containing from 4.0 to 18.4 mole % Na2O have been measured. The observed phase separation has little effect upon the internal friction of these glasses. The magnitude and temperature behaviour of the DC electrical resistivity is affected by the degree and type of amorphous decomposition.
TL;DR: Four types of alloys were investigated from the viewpoint of effect of composition and casting technic on the microstructure and mechanical properties.
Abstract: Four types of alloys were investigated from the viewpoint of effect of composition and casting technic on the microstructure and mechanical properties. The microstructures are shown and correlated with the mechanical properties.
TL;DR: In this article, the effect of deformation and heat-treatments on magnetisation of superconducting Mo/34 at.% Re alloy was investigated using optical and electron microscopy.
Abstract: The effect of deformation and heat-treatments on magnetisation of superconducting Mo/34 at.% Re alloy was investigated. The microstructure was studied using optical and electron microscopy. The values of the parameterκ of the GLAG theory were determined by using three different methods, and they are found to be in accordance with some of the predictions of the Maki theory. The results show that in deformed specimens the magnetic hysteresis is mainly due to the interaction of Abrikosov supercurrent vortices with dislocation tangles; both twin boundaries and grain boundaries are relatively ineffective in causing flux hindrance. The hysteresis observed after annealing has been explained in terms of the occurrence of dislocation rearrangement and the precipitation of the sigma phase. Flux-pinning by dislocation tangles has been treated as a special case of pinning by normal particles and a magnitude of the resulting pinning force is obtained. The experimental results are compared with the predictions of a theoretical model of flux-pinning.
TL;DR: In this article, a discrepancy has been observed between the experimental behavior of electrical resistivity and temperature coefficient of resistivity as a function of film thickness in thin singlecrystal silver films when compared with geometrical size effect theory.
Abstract: A discrepancy has been observed between the experimental behavior of electrical resistivity and temperature coefficient of resistivity as a function of film thickness in thin single‐crystal silver films when compared with geometrical size effect theory. The discrepancy has been attributed to the observed change in the microstructure of the films as shown by the transmission electron microscopy study and to the effect of lattice as well as electron energy quantization on electrical conduction. The study calls for an exact calculation of the role of quantization in structurally perfect thin films.
01 Jan 1968
TL;DR: In this article, the authors construct a class of models of continuous media which includes many known models, as well as new ones, and within the framework of which viscous, elastic and plastic effects and the motion of the imperfections combine.
Abstract: In the continuum theory of dislocations a continuous medium with continuously distributed microstructure imperfections—dislocations, is investigated. The previous papers essentially dealt with the statics of dislocations and the relation between the theory of plasticity and the continuum theory of dislocations has not been clearly shown. In the following we shall construct a class of models of continuous media which includes many known models, as well as new ones, and within the framework of which viscous, elastic and plastic effects and the motion of the imperfections—dislocations, combine.
Patent•
01 Aug 1968
TL;DR: In this article, the alloys are processed to have a fine grained MICROSTRUCTURE and IMPROVED PROPERTIES by heating to a TEMPERATURE SUFFICIENTLY High to DISSOLVE at least a SUBSTANTIAL PROPORTION of the more soluble PHASE FOLLOWED by a PRECIPITATION of the DISsOLVED PHASE at a lower temperature.
Abstract: DIRECTED ESPECIALLY TO READILY WORKABLE STAINLESS STEELS HAVING A DUPLEX, E.G., AUSTENITE-FERRITE, MICROSTRUCTURE CONTAINING ABOUT 18% TO ABOUT 35%, E.G., ABOUT 26% CHROMIUM, ABOUT 2% TO ABOUT 12%, E.G., ABOUT 6.5% NICKEL, UP TO ABOUT 1.5%, E.G., ABOUT 0.2%, TITANIUM, UP TO ABOUT 1% VANADIUM, NOT MORE THAN ABOUT 0.08%, E.G., UP TO ABOUT 0.05%, CARBON AND THE BALANCE SUBSTANTIALLY IRON. THE ALLOYS ARE PROCESSED TO HAVE A FINE GRAINED MICROSTRUCTURE AND IMPROVED PROPERTIES BY HEATING TO A TEMPERATURE SUFFICIENTLY HIGH TO DISSOLVE AT LEAST A SUBSTANTIAL PROPORTION OF THE MORE SOLUBLE PHASE FOLLOWED BY A PRECIPITATION OF THE DISSOLVED PHASE AT A LOWER TEMPERATURE ACCOMPANIED BY, OR SUBSEQUENT TO, A PLASTIC DEFORMATION. D R A W I N G
TL;DR: In this paper, the fine microstructure of boronated pyrolytic graphite was studied using optical and X-ray diffraction techniques and significant changes in the behaviour of all investigated parameters were observed in the 0.50 to 0.75 wt % borons.
Abstract: A study of the fine microstructure of boronated pyrolytic graphite was made utilising optical and X-ray diffraction techniques. The influence of boron content on the laminar structure, the lattice parameter, the lattice strain, the particle size, and the flexural strength of pyrolytic graphite was studied. Significant changes in the behaviour of all investigated parameters were observed in the 0.50 to 0.75 wt % boron range. A mechanism relating these changes to the appearance of a boron carbide deposit is hypothesised.
TL;DR: In this paper, a course particle microstructure was used to determine the nature of the field-ion image from these carbides and the study was then directed at samples which were heat treated to produce a micro-structure on a finer scale where the amount of information which could be obtained from the electron microscope was slight.
Abstract: This note reports some preliminary results of a combined field-ion microscope and electron microscope study of a pure iron alloy containing 2 wt. % vanadium and 0·2 wt. % carbon. After isothermal transformation particles of vanadium carbide are formed with a size and distribution which depends on the heat treatment conditions. A course particle microstructure was used to determine the nature of the field-ion image from these carbides and the study was then directed at samples which were heat treated to produce a microstructure on a finer scale where the amount of information which could be obtained from the electron microscope was slight. This note reports some preliminary results of a combined field-ion microscope and electron microscope study of a pure iron alloy containing 2 wt. % vanadium and 0·2 wt. % carbon. After isothermal transformation particles of vanadium carbide are formed with a size and distribution which depends on the heat treatment conditions. A course particle microstructure wa...
TL;DR: In this article, the effect of annealing on the microstructure of cylindrical electrodeposited 81-percent Ni, 19-percent Fe films was studied with the electron microscope.
Abstract: The effect of annealing on the microstructure of cylindrical electrodeposited 81-percent Ni, 19-percent Fe films was studied with the electron microscope. The films were deposited onto 5-mil Be-Cu wires having either Au or Cu intermediate layers. The annealing was performed on both free-standing films and on films still attached to the substrate. The initial change in the free-standing films was a rapid recrystallization. After the whole film had recrystallized, normal grain growth was observed. There is evidence that the driving force for the annealing is provided by stresses present in the films. Films annealed while attached to a Au-Be-Cu substrate did not exhibit recrystallization or grain growth, and the electron microscope studies showed that the Ni-Fe grains were pinned by Be-Au which diffuses into the grain boundaries but does not alloy with the Ni-Fe. The films which were annealed while attached to a Cu-Be-Cu substrate behaved essentially like free-standing films. Electron beam microanalysis and electron diffraction studies revealed that Be-Cu diffuses into the Ni-Fe grain boundaries and then alloys with the Ni-Fe. Recrystallization of the alloy can then take place freely.
TL;DR: In this paper, the habit and the monocrystalline structure of the compound were investigated by chemical, X-ray, and microstructure methods, and the following semiconductor parameters were determined (at room temperature): Eg ≈ 1,4 eV, n = 7.5× 1017 to 8 × 1017 cm−3, α = + 800 μV/deg, and σ = 10 Ω−1 cm−1.
Abstract: CuP2 monocrystals of about 1 cm2 area are grown by crystallization from the solution in tin. The habit and the monocrystalline structure of the compound is investigated by chemical, X-ray, and microstructure methods. Following semiconductor parameters are determined (at room temperature): Eg ≈ 1,4 eV, n = 7.5× 1017 to 8 × 1017 cm−3, α = + 800 μV/deg, and σ = 10 Ω−1 cm−1.
[Russian Text Ignored].
TL;DR: In this article, the phase behavior over regions of the ternary system Na2O/B2O3/Nb2O5 has been explored, and it has been shown that the system contains a liquid immiscibility gap, and some attention is given in the discussions to the influence that can be assigned to cations in determining the extent of such gaps and general structural relationships in borate/oxide systems.
Abstract: Phase behaviour over regions of the ternary system Na2O/B2O3/Nb2O5 has been explored. Liquidus temperatures and the stability regions of primary phases have been determined over selected composition ranges by high temperature microscopy. Crystallisation processes in melts and corresponding glasses have been followed using both conventional methods of thermal analysis and newly developed micro techniques combined with hot stage microscopy. An electron microscope has been employed to follow changes in the microstructure of quenched glasses after controlled heat treatments. It has been shown that the system contains a liquid immiscibility gap, and some attention is given in the discussions to the influence that can be assigned to cations in determining the extent of such gaps and general structural relationships in borate/oxide systems.
TL;DR: In this article, molybdenum powder was heated in 1 atm argon containing oxygen and water at temperatures ranging from 1200 ° to 1400 °C for up to 24 h Dendritic and needle-like crystals were grown in the cooler parts of the furnace at temperatures varying from 700 ° to 900 °C X-ray and electron diffraction analyzed these crystals, colorless or green in appearance, to be MoO3 containing small amounts of MoO2.
Abstract: Molybdenum powder was heated in 1 atm argon containing oxygen and water at temperatures ranging from 1200 ° to 1400 °C for up to 24 h Dendritic and needle-like crystals were grown in the cooler parts of the furnace at temperatures ranging from 700 ° to 900 °C X-ray and electron diffraction analyzed these crystals, colorless or green in appearance, to be MoO3 containing small amounts of MoO2 Small particles of molybdenum oxide were studied for comparison by X-ray and electron diffraction techniques and identified to be a similar mixture of MoO3 and MoO2 Optical and electron microscopy showed spiral-type growth mechanism on the crystallites Similar growth steps were observed in small particles of MoO3-MoO2 High temperature X-ray diffraction under vacuum up to 1155 °C showed an increase of MoO2 with a concomitant decrease in MoO3 Above 1155 °C, complete vaporization of the oxide layer was observed Small particles, studied by high temperature X-ray diffraction in air, recrystallized into small dendritic and platelet-shaped crystals These MoO3 platelets contained precipitates and growth twins analyzed by electron diffraction to be Mo02
TL;DR: In situ electron microscopic observations have been made of the defect structures of the solids formed by condensing the rare gases neon, argon, krypton and xenon, and also nitrogen and oxygen, on to cooled substrates mounted in a liquid helium stage as discussed by the authors.
TL;DR: In this article, a technique was developed for examining the microstructure of neutron generator target films of erbium deuteride, less than 6 μm thick, using both optical and electron metallography.
TL;DR: In this paper, the microstructure and mechanical strength of shock-deformed 70/30 copper-zinc alloy have been investigated by electron microscopy and hardness testing, and three types of defect structures were produced in the alloy when subjected to shock compressive waves in a pressure range of 50-400 kb.
Abstract: The microstructure and mechanical strength of shock-deformed 70/30 copper-zinc alloy have been investigated by electron microscopy and hardness testing. Essentially three types of defect structures were produced in the alloy when subjected to shock compressive waves in a pressure range of 50-400 kb. These included dislocations, stacking faults and twin-type structures. The dislocation structures consist of bundles of parallel dislocations plus a limited number of stacking faults which have been activated on {111} planes. The absence of a dislocation cell structure appears to be a consequence of the low stacking fault energy of 70/30 copper-zinc alloy. At high pressures imperfect fault bands occur in the matrix which have a predominant twin orientation. The observed increase in residual hardness is attributable to the shock-induced dislocation and twin-fault densities. The magnitudes of such increases in strength were found to be consistent with recent theory of flow stress and work hardening.