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Showing papers on "Microstructure published in 1984"


Journal ArticleDOI
01 Dec 1984-Wear
TL;DR: In this paper, a sequence of events involved in sliding wear is outlined, where the plastic deformation changes the near-surface microstructure in ways which make the material unstable to local shear.

365 citations


Patent
19 Oct 1984
TL;DR: The hardness and microstructure of aluminous abrasives produced from alumina gels are enhanced by introduction of seed material as by wet vibratory milling of the material with alumina media, or by the direct addition of very fine alpha alumina particles in the amount of 1% or less.
Abstract: The hardness and microstructure of aluminous abrasives produced from alumina gels are enhanced by introduction of seed material as by wet vibratory milling of the material with alumina media, or by the direct addition of very fine alpha alumina particles in the amount of 1% or less.

352 citations


Journal ArticleDOI
TL;DR: In this article, a consistent model of the microstructure of the membranes and an explanation of its uniformity are presented, and the minimum modal pore size which has been obtained is 2.5 nm.
Abstract: Alumina films less than 20μm thick are prepared by a process in which a boehmite sol is successively gelled, dried and calcined. The resulting structure has the unique property that only ultra-fine pores with a narrow pore size distribution are present within large crack-free layers. The microstructure can be influenced by the sintering temperature and the acid concentration of the precursor sol. The minimum modal pore size which has been obtained is 2.5 nm. A consistent model of the microstructure of the membranes and an explanation of its uniformity are presented.

299 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure, texture, and whisker orientations in 6061 Al-20 wt pct SiC whisker composites have been examined using transmission electron microscopy and X-ray diffraction.
Abstract: The microstructure, texture, and whisker orientations in 6061 Al-20 wt pct SiC whisker composites have been examined using transmission electron microscopy and X-ray diffraction. Tension creep tests of the composite material have also been conducted in the temperature range 505 to 644 K (450 to 700 F). The steady state creep rate of the composite depends strongly on the temperature and applied stress. The stress exponent for the steady state creep rate of the composite is approximately 20.5 and remains essentially constant within the range of test temperatures. The activation energy is calculated to be 390 kJ/mol, nearly three times as high as the activation energy for self-diffusion of aluminum. No threshold stress was observed. Fracture surface examination using scanning electron microscopy shows that the composite fails by coalescence of voids in the aluminum matrix which originate at the aluminum-SiC interface. It is demonstrated that SiC paniculate composites are less creep resistant than SiC whisker composites.

270 citations



BookDOI
01 Jan 1984

213 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the dependence of the microstructure on γ pl and its possible consequences and found that the decrease of critical stress required for the development of PSBs with increasing γpl is related to the corresponding variations in the matrix structure.

190 citations


Journal ArticleDOI
TL;DR: The model of fragmentation due to the formation and subsequent melting of high energy grain boundaries is discussed and is shown to be compatible with a wide range of microstructural observations.

190 citations


Journal ArticleDOI
TL;DR: In this paper, a series of Ag-Cu alloys between 1 wt pct Cu and the eutectic composition (28.1 wtpct Cu) at speeds between 1.5 and 400 cm per second were used for beam solidification.
Abstract: Electron beam solidification passes have been performed on a series of Ag-Cu alloys between 1 wt pct Cu and the eutectic composition (28.1 wt pct Cu) at speeds between 1.5 and 400 cm per second. At low growth rates conventional dendritic or eutectic structures are obtained. The maximum growth rate of eutectic structure is 2.5 cm per second. At high growth rates microsegregation-free single phase structures are obtained for all compositions. The velocity required to produce this structure increases with composition for dilute alloys and agrees with the theory of absolute stability of a planar liquid-solid interface with equilibrium partitioning. For alloys between 15 and 28 wt pct Cu, the velocity required to produce the microsegregation-free extended solid solution decreases with composition and is related to nonequilibrium trapping of solute at the liquid solid interface. At intermediate growth rates for alloys with 9 wt pct Cu or greater, a structure consisting of alternating bands of cellular and cell-free material is obtained. The bands form approximately parallel to the local interface.

187 citations


Journal ArticleDOI
TL;DR: The characteristic fatigue behavior of carburized and quenched steel with internal oxides and non-martensitic microstructure near the surface was presented through rotating bending fatigue test as discussed by the authors.
Abstract: The characteristic fatigue behavior of carburized and quenched steel with internal oxides and non-martensitic microstructure near the surface was presented through rotating bending fatigue test. The S-N diagram revealed two knees and the specimens continued to fail over 107 stress cycles. The fatigue limit could not be obtained even at 108 stress cycles. The test results were compared to those for the specimens without surface structure anomalies to show the effect of structure anomalies on the fatigue behavior of carburized steel.

166 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the influence of a preferred crystallographic orientation on mechanical properties of textured Ti-6Al-4V material and found that high cycle fatigue and fatigue crack growth were performed in vacuum, laboratory air, and a 3.5 pct NaCl solution.
Abstract: Tensile properties, high cycle fatigue strength, and fatigue crack propagation behavior were evaluated on highly textured Ti-6Al-4V material to investigate the influence of a preferred crystallographic orientation on mechanical properties. Thermomechanical treatments were used to develop three different textures: a basal, basal/transverse, and transverse type, all of which exhibited the same homogeneously equiaxed microstructure. The Young’s modulus was found to vary between 107 and 126 GNm-2, and yield strength changed from 1055 to 1170 MNm-2. Ductility was only slightly affected by texture. High cycle fatigue and fatigue crack growth measurements were performed in vacuum, laboratory air, and a 3.5 pct NaCl solution. It is shown that laboratory air can be regarded as a quite corrosive environment. In vacuum the highest fatigue strength values were measured whenever loads were perpendicular to basal planes. However, these conditions had the highest susceptibilities to air and 3.5 pct NaCl solution environments. Nearly no influence of texture on fatigue crack propagation was found in vacuum, but in a corrosive environment crack growth parallel to (0002)-planes was much faster than perpendicular to these planes. To explain the corrosive effect on the fatigue properties of the textured material hydrogen is thought to play a key role.

Journal ArticleDOI
TL;DR: It was found that subjecting a polished Ti-6Al-4V specimen to the heat treatment required for sintering resulted in delineation of prior beta grain boundaries and it is suggested that this contributes to the inferior fatigue strength of porous coated Ti- 6Al- 4V.
Abstract: The fatigue behaviour of Ti-6Al-4V (extra low interstital) alloy coated with Ti-6Al-4V powder was investigated using rotating bending fatigue testing. It was found that the high cycle fatigue strength of porous coated specimens exhibited a substantial decrease compared to uncoated specimens of the same microstructure. Chemical analysis of the sintered surface revealed significant increases of interstitials compared to the bulk analysis, but it is concluded that this would not adversely affect the fatigue strength. Scanning electron microscopy revealed crack initiation close to particle/substrate contact interfaces and it is concluded that stress intensification due to these interface regions are major sources of weakness with respect to fatigue strength. Finally it was found that subjecting a polished Ti-6Al-4V specimen to the heat treatment required for sintering resulted in delineation of prior beta grain boundaries and it is suggested that this also contributes to the inferior fatigue strength of porous coated Ti-6Al-4V.

Journal ArticleDOI
TL;DR: In this article, a combined torsion and compression mode of deformation was used to deform copper and silver to equivalent tensile true strains of ≃ 8, and the microstructures have been determined by transmission electron microscopy.
Abstract: A combined torsion and compression mode of deformation has been used to deform copper and silver to equivalent tensile true strains of ≃ 8. The microstructures have been determined by transmission electron microscopy. It has been found that at true strains within the range 4–8 there is no change in microstructure or Vickers hardness with strain. The type of microstructure is that of fine grains, similar to those formed by recrystallization. The yield stress of the fine grained structures in .copper corresponds to that predicted from the Hall- Petch relationship.

Journal ArticleDOI
TL;DR: In this paper, the structure of porous silicon is described by using both electron microscopy observations and gas adsorption experiments and a quite narrow pore size distribution is found, with pore diameters ranging between 50 and 100 A.

Journal ArticleDOI
TL;DR: Conclusions are drawn as to how the two types of microstructure influence general film properties and, in particular, how they influence possible laser damage mechanisms.
Abstract: The microstructure of thin films applied by conventional physical vapor deposition for use as optical coatings is columnar for most of the materials commonly used. This has been established for about a decade through numerous experimental observations employing microfractographical replication for use with high resolution transmission electron microscopes. Scanning electron microscopes are more useful investigating coating defects, the most remarkable of these defects being known as nodules. From fundamental considerations of nucleation and growth of thin films, the origin of both columns and nodules and the dependence of their appearance on the deposition conditions are discussed in some detail. A simple 2-D simulation model assuming limited surface mobility of adatoms or admolecules shows striking similarities to peculiar properties of both columnar and nodular growth seen in actual investigations. Conclusions are drawn as to how the two types of microstructure influence general film properties and, in particular, how they influence possible laser damage mechanisms.

Book
31 Jul 1984
TL;DR: In this article, the authors present a survey of colloidal processing of advanced ceramics, novel power-forming and powder-processing methods, the derivation of ceramic by polymer processing, chemical vapor deposition techniques, ion beam deposition methods, hot isostatic pressing and dynamic compaction, shock conditioning, and very high pressure processing methods.
Abstract: The present conference covers colloidal processing of advanced ceramics, novel power-forming and powder-processing methods, the derivation of ceramics by polymer processing, chemical vapor deposition techniques, ion beam deposition methods, the laser and ion beam modification of surfaces, hot isostatic pressing and dynamic compaction, shock conditioning and subsequent densification of ceramics, and very high pressure processing methods. Specific attention is given to the preparation of shaped glasses by the sol-gel method, the synthesis of powders and thin films by laser-induced gas phase reactions, the plasma sintering of ceramics, laser chemical vapor deposition, the microstructure and mechanical properties of ion-implanted ceramics, a computer simulation of dynamic compaction, shock-induced modification of inorganic powders, and diamond anvil technology.

Journal ArticleDOI
TL;DR: In this article, individual powder particles of a droplet-processed and rapidly solidified 303 stainless steel are characterized in terms of microstructure and composition variations within the solidification structure using scanning transmission electron microscopy (STEM).
Abstract: Individual powder particles of a droplet-processed and rapidly solidified 303 stainless steel are characterized in terms of microstructure and composition variations within the solidification structure using scanning transmission electron microscopy (STEM). Fcc is found to be the crystallization phase in powder particles larger than about 70 micron diameter, and bcc is the crystallization phase in the smaller powder particles. An important difference in partitioning behavior between these two crystal structures of this alloy is found in that solute elements are more completely trapped in the bcc structures. Massive solidification of bcc structures is found to produce supersaturated solid solutions which are retained to ambient temperatures in the smallest powder particles. Calculated liquid-to-crystal nucleation temperatures for fcc and bcc show a tendency for bcc nucleation at the large liquid supercoolings which are likely to occur in smaller droplets. The importance of small droplet sizes in rapid solidification processes is stressed.

Journal ArticleDOI
TL;DR: In this paper, the authors used micro-structural properties of Fecralloy steel to characterize the appearance of the protective scales formed on steel exposed to an oxidizing environment at temperatures of 1000, 1100 or 1200°C with the aid of microstructural techniques.

Journal ArticleDOI
T. Sato1, M. Shimada1
TL;DR: In this paper, changes in the phase composition and microstructure of yttria-partially-stabilized zirconia by low-temperature annealing were investigated at 100° to 500°C using bodies sintered from coprecipitated fine ZrO2-Y2O3 powders at varied temperatures.
Abstract: Changes in the phase composition and microstructure of yttria-partially-stabilized zirconia by low-temperature annealing were investigated at 100° to 500°C using bodies sintered from coprecipitated fine ZrO2-Y2O3 powders at varied temperatures. Tetragonal zirconia on the surfaces of bodies sintered at <1500°C transformed to the monoclinic phase at 100° to 400°C. Transformation behavior was strongly affected by grain size.

Journal ArticleDOI
TL;DR: The effect of cooling rate on the microstructure, mechanical behavior, corrosion resistance, and subsequent age hardenability of U-6 wt pct Nb is described and discussed in this paper.
Abstract: The effect of cooling rate on the microstructure, mechanical behavior, corrosion resistance, and subsequent age hardenability of U-6 wt pct Nb is described and discussed. Cooling rates in excess of 20 Ks-1 cause the parent γ-phase to transform martensitically to a niobium supersaturated variant of the α-phase. This martensitic phase exhibits low hardness and strength, high ductility, good corrosion resistance, and substantial age hardenability. As cooling rate decreases from 10 Ks-1 to 0.2 Ks-1, fine scale microstructural changes (consistent with spinodal decomposition) occur to an increasing extent. These changes produce large increases in hardness and strength and large decreases in ductility, slight decreases in corrosion resistance, and slight changes in age hardenability. At cooling rates less than 0.2 Ks-1 the parent phase undergoes cellular decomposition to a coarse two-phase lamellar microstructure. This lamellar microstructure exhibits intermediate strength and ductility, substantially reduced corrosion resistance, and no age hardenability. An analysis of the cooling rates at the centers of water quenched plates indicates that fully martensitic microstructures can be obtained in plates as thick as 50 mm.

Journal ArticleDOI
TL;DR: In this paper, the influence of thermal deformation of hardened cement paste on its microstructure was investigated using complex thermal analysis (DTA, DTD, TD) and both optic and electron microscopes.
Abstract: The paper presents the results of an experimental investigation of the influence of thermal deformations of phases present in hardened cement paste on its microstructure. For the observation of the thermal deformation course in the range of temperature20–800°C, a method of complex thermal analysis (DTA, DTD, TD) was employed. The microstructure of heated cement pastes was observed by both optic and electron microscopes.

Journal ArticleDOI
TL;DR: The results of this study revealed endurance limits for Ti- 6Al -4V alloy tested with a rotating beam system and the low-endurance limit of the porous-coated material is due to both the transition from the as-received equiaxed microst structure to a lamellar microstructure upon sintering and to the notch effect created by the porous coating.
Abstract: A porous metal coating applied to a solid substrate implant has been shown, in vivo, to offer advantages over current polymethylmethacrylate cement fixation in orthopedic devices. These advantages may be lost, however, in devices requiring a sintering heat treatment to apply the coating since these treatments may have a detrimental effect on the substrate material mechanical properties. In addition, more biocompatible interface coating materials have come of interest with recent literature reports of metal ion release. These coatings may be of particular use in porous-coated systems since the surface area of implant in contact with the surrounding tissues is greatly increased. This study investigated the effects that both a porous Ti- 6Al -4V alloy coating and a ULTI carbon coating have on the fatigue properties of a Ti- 6Al -4V alloy substrate system. The fatigue properties of uncoated as-received, uncoated sinter heat treated and notched Ti- 6Al -4V material were also investigated. The results of this study revealed endurance limits for Ti- 6Al -4V alloy tested with a rotating beam system of 617 MN/m2 (uncoated as-received), 624 MN/m2 ( ULTI carbon-coated), 377 MN/m2 ( sinter heat treated), 220 MN/m2 (notched) and 138 MN/m2 (porous-coated). No effects on fatigue properties were observed when testing the material in saline compared with air. The slight increase in fatigue strength for the carbon-coated material is thought to be due to the increase in surface hardness resulting from the formation of titanium carbides on the surface. The low-endurance limit of the porous-coated material is due to both the transition from the as-received equiaxed microstructure to a lamellar microstructure upon sintering and to the notch effect created by the porous coating.

Journal ArticleDOI
TL;DR: The microstructure of powder metallurgical high speed steel (ASP 60) has been investigated by combined analytical electron microscopy and atom-probe field-ion microscopy as mentioned in this paper.

01 Jan 1984
TL;DR: In this article, methods of alloy preparation (including ingot casting, rapid solidification, and mechanical alloying); processing and alloying effects on microstructure and properties; superplastic deformation; and physical metallurgy fundamentals.
Abstract: The topics covered in this volume include: methods of alloy preparation (including ingot casting, rapid solidification, and mechanical alloying); processing and alloying effects on microstructure and properties; superplastic deformation; and physical metallurgy fundamentals. Other topics discussed include: weldability; sodium and hydrogen effects on fracture; corrosion behavior (including general corrosion, stress corrosion, and high-temperature oxidation); and monotonic and cyclic properties at ambient and elevated temperatures. Attention is also given to the use of Al-Li alloys in aircraft structures.

Journal ArticleDOI
09 Nov 1984-Science
TL;DR: This article illustrates how ion and laser beam modification is being applied to advance both the technology and the exploratory science of materials.
Abstract: An important trend in materials science is the use of increasingly sophisticated methods to control composition and microstructure during processing. Near-surface modification by ion implantation and laser treatment is one of these new methods for tailoring material properties. Novel materials have been formed which are far from thermodynamic equilibrium and which exhibit unexpected and useful properties. The most extensively studied property changes include modified electrical properties of semiconductors and improved wear, hardness, and corrosion resistance of metals. The high degree of control available with energetic beams allows relations between microstructure and properties to be systematically investigated at the atomic level. This article illustrates how ion and laser beam modification is being applied to advance both the technology and the exploratory science of materials.

Journal ArticleDOI
TL;DR: The effect of base-alloy composition on the microstructure and mechanical and thermal stabilities of aluminum diffusion coatings has been studied for 316, 310, and I800H stainless steels, by optical, microprobe, transmission/scanning transmission electron microscopy, and microhardness testing as discussed by the authors.
Abstract: The effect of base‐alloy composition on the microstructure and mechanical and thermal stabilities of aluminum diffusion coatings has been studied for 316, 310, and I800H stainless steels, by optical, microprobe, transmission/scanning transmission electron microscopy, and microhardness testing. In all the diffusion aluminized alloys, two distinct coating layers form: an outer aluminide layer and an inner, interdiffusion layer. The substrate austenite stability is the single most important parameter affecting the thickness, phase distribution, and microchemistry of these two layers. TEM/STEM analyses showed that the interdiffusion layer is a ‘‘natural composite’’ made up of a uniform dispersion of the hard nickel aluminide phase (B2) in a soft ferrite matrix. Formation of this layer involves ‘‘ferritization’’ of the substrate, a process akin to pearlitic transformation in carbon steels. The interdiffusion layer demonstrated high hardness with good mechanical integrity and its thermal stability with the subs...

Journal ArticleDOI
TL;DR: In this paper, the formation of the different microstructures is discussed in terms of surface energy minimization and thermally activated processes as surface and grain boundary migration, and the analysis of the microstructure shows that the growth of the film is markedly influenced by the substrate material.

Journal ArticleDOI
TL;DR: In this paper, an analytical approach is presented for investigating surface processing treatments used to improve the friction and wear behavior of engineering alloys, with specific examples cited for ion implantation of steels.

Journal ArticleDOI
TL;DR: In this article, the role of the substrate temperature during deposition is discussed in the greatest detail, and it is shown that it is possible to classify the structure of the thick films into four characteristic zones which depend on the substrate's temperature.
Abstract: Metallic films are today used in various technological applications. The grain structures of these films influence many properties including the hardness, corrosion resistance, and the electrical conductivity reactivity of thin films in electrical devices. It is therefore important to understand how the films grow and the mechanisms by which grain structures are developed during deposition . In this paper the role of the substrate temperature (Ts) during deposition is the variable that is discussed in the greatest detail. Earlier work has shown that it is possible to classify the structure of the thick films into four characteristic zones which depend on the substrate temperature.

Journal ArticleDOI
TL;DR: In this paper, the influence of temperature, pressure, time and heating and cooling rates on densification of boron carbide powders and on the microstructure of the hot-pressed specimen was studied.