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Showing papers on "Grain growth published in 1972"


Journal ArticleDOI
R. L. Miller1
TL;DR: In this article, a variety of alloy steels with grain sizes in the range 0.3 to 1.1 μ were obtained in manganese and nickel steels by annealing 1 to 400 hr at temperatures between 450° and 650°C (840° to 1200°F).
Abstract: Ultrafine-grained microstructures can be developed in a variety of alloy steels by coldworking followed by annealing in theα +γ region. Because the annealing temperatures are relatively low and the recrystallized structure is two-phase, grain growth is restricted. Specimens with grain sizes in the range 0.3 to 1.1 μ.m (ASTM 20 to 16) were obtained in manganese and nickel steels by annealing 1 to 400 hr at temperatures between 450° and 650°C (840° to 1200°F). The expected improvement in yield strength through grain refinement was observed in almost all alloys. Other tensile properties depend on factors such as grain size, austenite stability, and specimen geometry, that determine which of three types of plastic behavior will occur. Transformation of austenite during straining improves the mechanical properties of ultrafine-grained specimens.

311 citations


Journal ArticleDOI
TL;DR: The effect of grain growth on stresses in films is discussed in this paper, where grain growth generally leads to stress relaxation when the film is under a compressive stress and further grain growth can occur if plastic flow relieves some of the strain energy.
Abstract: The effect of grain growth on stresses in films is discussed. Grain growth generally leads to stress relaxation when the film is under a compressive stress. When the initial grain size is below a critical value, grain growth can occur by normal boundary migration and generates a tensile stress in the plane of the film. Grain growth proceeds until a particular grain size is reached, at which the sum of the strain energy and surface energy is minimized. Further grain growth can occur if plastic flow relieves some of the strain energy. When the initial grain size is above the critical size, there is no minimum in the energy vs grain size relationship, and grain growth to infinite size can occur by normal boundary migration. In the presence of impurities, apparently anomalous intrinsic stresses in films may be produced.

273 citations


Journal ArticleDOI
TL;DR: Extensive grain growth was observed by scanning electron microscopy in very porous Al2O3 compacts, even at densities <40% of theoretical after ∼7% shrinkage at 1700°C, the grain size increased from ∼03 to 051 μm in a compact having a relative green density of 031 as mentioned in this paper.
Abstract: Extensive grain growth was observed by scanning electron microscopy in very porous Al2O3 compacts, even at densities <40% of theoretical After ∼7% shrinkage at 1700°C, the grain size increased from ∼03 to 051 μm in a compact having a relative green density of 031 During grain growth in highly porous compacts, the grains appear initially to be chainlike, then to be oblong, and finally to be equiaxed The proposed mechanism of initial grain growth involves the filling of necks between adjacent grains followed by the movement of the grain boundary through the smaller grain Although grain growth in very porous compacts is quite different from coalescence and ordinary grain growth, the kinetics are similar

207 citations


Journal ArticleDOI
01 Sep 1972
TL;DR: The changes in matrix structure that occur during tempering of an Fe-0.2C martensite at 400° to 700°C have been investigated in this article, showing that the fine martensitic lath structure coarsens while retaining the elongated packet-lath morphology.
Abstract: The changes in matrix structure that occur during tempering of an Fe-0.2C martensite at 400° to 700°C have been investigated. Light and electron metallographic observations show that when tempered, the fine martensitic lath structure coarsens while retaining the elongated packet-lath morphology. The as-quenched hardness 504 Khn and total grain boundary area per unit volume 50,800 cm−1 decrease abruptly at the higher tempering temperatures and in seconds reach relatively stable values that decrease slowly with time. The decrease in low angle boundaries accounts for most of the initial grain boundary area change, while the large angle boundary component of total boundary area decreases gradually with tempering time. Recovery processes are responsible for the initial changes in matrix structure, and carbide boundary pinning suppresses recrystallization until grain growth dominates in the later stages of tempering.

143 citations


Journal ArticleDOI
TL;DR: The transverse rupture strength of hot-pressed and annealed composites of magnesium oxide and dispersed metallic phases (nickel, iron, cobalt) increases with increasing volume fraction of metal and the annealing temperature as discussed by the authors.
Abstract: The transverse rupture strength of hot-pressed and annealed composites of magnesium oxide and dispersed metallic phases (nickel, iron, cobalt) increases with increasing volume fraction of metal and annealing temperature. The strengthening effect of the metal is attributed to an inhibition of grain growth while flaw healing occurs during the annealing of the composites.

112 citations


Journal ArticleDOI
01 Jan 1972
TL;DR: In this article, it was shown that void formation, void growth, and tensile ductility in an α-β titanium alloy, Ti-5.5V-0.9Fe- 0.5Cu, heat treated to a constant yield strength, is intergranular in nature and occurs when a critical crack length-stress relationship is satisfied.
Abstract: An investigation has shown that it is possible to relate void formation, void growth, and tensile ductility to microstructural features in an α-β titanium alloy, Ti-5.25A1-5.5V-0.9Fe-0.5Cu, heat treated to a constant yield strength. Equations relating tensile void growth rates to microstructure for both equiaxed,E, and Widmanstatten plus grain boundaryα, W + ITG. B.,in aged β morphologies have been derived. A mechanism for void formation at α-β interfaces is presented which accounts for the observed fact that voids do not form at Widmanstatten α platelets. Tensile fracture is shown to be intergranular in nature and occurs when a critical crack length-stress relationship is satisfied. The amount of ductility achievable in a specimen depends upon the rate of void growth. If the rate is large, the void reaches a critical size for fracture at a lower applied stress and strain and hence the ductility is less.

106 citations


Journal ArticleDOI
TL;DR: In this article, the effect of oxygen activity on the sintering of high-purity Cr2O3 is shown, and the theoretical density is approached at the equilibrium O2 partial pressure needed to maintain the Cr2 O3 phase (Po2=2×10−12 atm).
Abstract: The effect of oxygen activity on the sintering of high-purity Cr2O3 is shown. Theoretical density was approached at the equilibrium O2 partial pressure needed to maintain the Cr2O3 phase (Po2=2×10−12 atm). The presence of N2 in the atmosphere during sintering did not prevent final sintering. The addition of 0.1 wt% MgO at this equilibrium pressure effectively controlled the grain growth and further increased the sintered density to very near the theoretical value. The solute segregation of MgO at the grain boundaries, followed by nucleation of spherulites of magnesium chromite spinel on the boundaries, accounted for the grain-growth control. It is speculated that these isolated spherulites locked the grain boundaries together, changing the fracture mode of the sintered oxide from inter-to intragranular and also that larger MgO additions produced a more continuous spinel formation at the boundaries, resulting in decreased sintered density. Weight loss, which was also monitored as a function of O2 activity, correlated with the changing predominant volatile species in the Cr-O system.

94 citations


Journal ArticleDOI
TL;DR: In this paper, the grain size of WC-20%Co alloy with addition carbides such as TiC, VC, Cr3C2, ZrC, NbC, Mo2C, HfC and TaC was investigated.
Abstract: The grain size of WC-20%Co alloy affected by the addition carbides such as TiC, VC, Cr3C2, ZrC, NbC, Mo2C, HfC and TaC was in detail investigated. Specimens were sintered mainly at 1400°C for 1 hr. The mean grain size of starting WC powder was about 0.6μ.Results obtained were as follows: (1) When the liquid phase was saturated by the addition carbides at sintering temperatures, the restriction effect of VC on the grain growth of WC was the largest, followed by Mo2C, Cr3C2, NbC, TaC, TiC, ZrC(≅HfC). In this case, there existed a strong correlation. between the restriction effect of addition carbides and the solubility limit in the liquid phase (or the formation free energy). (2) On the other hand, when the liquid phase contained a certain amount of dissolved metals of addition carbides, i.e., about 1.5at% for the starting Co, the effectiveness was in the following order; VC>NbC>TaC>TiC>Mo2C>Cr3C2>ZrC≅HfC. (3) Considering the restriction effect and the shape of carbides precipitated, VC addition was considered to be the most suitable for the grain growth inhibitation of WC, followed by Cr3C2, NbC and TaC.

93 citations


Journal ArticleDOI
TL;DR: In this paper, it is shown that grain boundary sliding contributes additional axial strain to polycrystalline aggregates due to Lifshitz boundary sliding, where egb(L) is the grain strain due to the sliding, ed is the strain a poly crystaline aggregate would experience if only stress-directed diffusion were to occur without the necessary grain boundary separation would occur.
Abstract: Grain boundary sliding is necessary during diffusion creep to maintain continuity across the grain boundaries. In this paper it is shown, by use of a two-dimensional hexagonal array, that grain boundary sliding will contribute additional axial strain to the specimen as predicted by R. N. Stevens (1971). It is shown, however, that there is a difference between the macroscopic effect of this type of sliding and that of ‘ordinary’ grain boundary sliding, in that the former, named Lifshitz grain boundary sliding, does not increase the number of grains along the length of the specimen, whereas, the latter, named Rachinger grain boundary sliding, does. Considering only diffusion creep, it is concluded that where egb(L) is the strain due to Lifshitz grain boundary sliding, ed is the strain a polycrystalline aggregate would experience if only stress-directed diffusion were to occur without the necessary grain boundary sliding in which case grain boundary separation would occur, egb is the grain strain et...

83 citations


Journal ArticleDOI
Abstract: Effects of additives Li2CO3, Ag2O, NiO, Cr2O3, Fe2O3, Gd2O3, Bi2O3, TiO2, MnO2, Nb3O5 and WO3 on piezoelectric and related properties of PbTiO3 ceramics are studied. Additives partly dissolve in lattice and the rest segregate at grain boundary. These additives act as grain growth inhibitors and binders. Additions of Li2CO3, NiO, Fe2O3 and MnO2 are most effective for densification. The additives Gd2O3, Bi2O3, Nb2O5 and WO3 give high resistivity probably by compensating Pb vacancies. Many piezoelectric and related properties depend on species and content of additives. Grain size is a main factor influencing these properties. The specimens with Cr2O3 and MnO2 characterized by coarse grain have small e*, small dissipation factor, short poling time, large coupling factors, high mechanical Q and small elastic compliance. These features may be explained by diminishing of stress between grains, decrease of interfacial polarization and large binding force at grain boundary.

74 citations


Journal ArticleDOI
A. Gangulee1, François M. d'Heurle1
TL;DR: Second phase Al 2 Cu particles were found to have a considerable effect in retarding secondary growth as discussed by the authors, presumably by rearrangement of misfit dislocations, only when Cu was introduced as a layer sandwiched between two equal Al layers.

Journal ArticleDOI
TL;DR: In this article, the effect of annealing on various properties of PtSi has been studied over the temperature range 800-900°C, for 200 and 900-A-thick PtSi films on singlecrystal silicon substrates.
Abstract: The thermal stability of PtSi is an important parameter in large‐scale integration processing schemes which involve postmetallization high‐temperature operations. For this reason, the effect of annealing on various properties of PtSi has been studied over the temperature range 800–900°C, for 200‐ and 900‐A‐thick PtSi films on single‐crystal silicon substrates. The as‐prepared films, produced by backsputter cleaning of Si surface followed by sputtering of Pt, in situ sintering at 700°C for 10 min, and etching to dissolve any unreacted Pt, were found to be single‐phase PtSi. The 200‐A‐thick PtSi films on (111) Si possess a strong degree of preferred orientation with grains which are triply positioned with (100) PtSi ∥ (111) Si and [010] PtSi ∥ 〈110〉 Si; the orientation remains unchanged upon further annealing. On going to higher thickness (900 A), the preferred orientation of PtSi changes to (010) type and then to a partial (111) type on annealing at 900°C. Rapid grain growth is observed on annealing in the range 800–900°C; the grain size increases from 0.01–0.25 μ in the as‐deposited film to several μ at 850°C. The grain growth is followed at 900°C by agglomeration, i.e., a changeover from continuous film to island‐type microstructure. The final stage of agglomeration, which has been observed in 200‐A PtSi at 900°C, is associated with a drastic increase in resistivity. The resistivity of as‐prepared PtSi films is estimated to be 15 (±5) μΩ cm. Partial agglomeration of 900‐A PtSi occurs at 900°C; it produces only a 10% increase in resistivity. It is concluded that for PtSi films 200–900 A thick, 800°C is a safe upper‐limit (and 850°C, absolute‐limit) temperature below which there is no agglomeration, no change in crystallographic orientation, and grain growth is not excessive.

Journal ArticleDOI
TL;DR: In this paper, the microstructural changes that occur during the liquid-phase sintering of VC-Co alloys were studied and it was found that considerable growth of the carbide grains takes place and that this growth can be described by the equation:
Abstract: A study was made of the microstructural changes that occur during the liquid-phase sintering of VC-Co alloys. It was found that considerable growth of the carbide grains takes place and that this growth can be described by the equation: $$\bar d^3 - \bar d_o^3 = Kt$$

Journal ArticleDOI
TL;DR: In this article, diffusion between vanadium and Cu-20 at.% Ga alloy and that between V3Ga and V3Si alloy were studied and a large superconducting critical current density, Jc, was obtained in the V3 Ga formed at temperatures below 700° C while a much smaller Jc was obtained by the V 3Si formed at 800° C. Changes in Jc due to the heat-treatment can be interpreted by the grain growth of the compounds.
Abstract: In the present work, diffusion between vanadium and Cu-20 at.% Ga alloy and that between vanadium and Cu-20 at.% Si alloy were studied. An intermetallic compound, V3Ga, is formed easily by the selective diffusion of gallium from the Cu-Ga alloy to the vanadium. V5Si3 and V3Si are formed also by the selective diffusion of silicon from the Cu-Si alloy to the vanadium. Copper scarcely dissolves either in V3Ga, V5Si3 or V3Si. Copper is not effective for enhancing the formation of V3Si unlike the case of V3Ga. A large super-conducting critical current density, Jc, is obtained in the V3Ga formed at temperatures below 700° C while a much smaller Jc is obtained in the V3Si formed at 800° C. Changes in Jc due to the heat-treatment can be interpreted by the grain growth of the compounds.

Journal ArticleDOI
01 Sep 1972
TL;DR: In this paper, electron microscopy, quantitative optical microscopy and texture studies were made on swaged and recrystallized titanium wire of three impurity contents: zone refined, a special lot of intermediate purity, and commercial A-70.
Abstract: Transmission electron microscopy, quantitative optical microscopy, and texture studies were made on swaged and recrystallized titanium wire of three impurity contents: zone refined, a special lot of intermediate purity, and commercial A-70. The electron microscopy studies revealed that a) during recrystallization a number of processes overlap, and b) during grain growth there occurs a decrease in the dislocation density within the grains along with the increase in the average grain size. The quantitative microscopy studies indicated that the linear intercept grain size distribution is approximately log normal and that for a given mean grain size the distribution is relatively independent of the combination of annealing time and temperature used to obtain it. Moreover, there exists a range of grain sizes in space, the numbers of grains in each class interval changing with increase in grain size. The so-called grain shape factor decreases with increase in mean grain size (annealing time) at a constant temperature and with decrease in temperature for a constant grain size. The texture of the as-swaged wire and the changes in the texture during grain growth are in qualitative accord with those previously reported for deformed and recrystallized titanium. Impurity content influences the degree of these various structural characteristics but not their substance.

Journal ArticleDOI
16 Oct 1972-Nature
TL;DR: In this paper, a two-step quenching procedure from high austenizing temperatures (for example, 1,200°C→870° C→quench) was shown to eliminate any danger of quench cracking, whilst causing only a small reduction in fracture toughness.
Abstract: ZACKAY et al.1 have discussed the increase in fracture toughness of untempered ultra-high strength steels resulting from the use of high austenizing temperatures for solution treatment. Their results indicate that the toughness is increased suddenly and dramatically, by a factor of more than two, when the steels are austenized at temperatures greater than 1,100° C (Fig. 1). The effect is promoted by fast quenching rates. They show further that a two-step quenching procedure from high austenizing temperatures (for example, 1,200° C→870° C→quench) can eliminate any danger of quench cracking, whilst causing only a small (7%) reduction in fracture toughness. This improvement in toughness, obtained by using high austenizing temperatures, was attributed to the retardation of grain boundary nucleation of a second phase when high energy grain boundaries, associated with small grains, are eliminated by grain growth.

Journal ArticleDOI
TL;DR: In this article, the restriction effects of the additional VC on the grain growth of WC in WC-Co alloy were investigated in relation to the grain size of starting WC powder, and Co and carbon contents of the alloy.
Abstract: The restriction effects of the additional VC on the grain growth of WC in WC-Co alloy were in detail investigated in relation to the grain size of starting WC powder, and Co and carbon contents of the alloy. The WC powder was prepared by heating the mixture of W powder (-0.5μ) and carbon black powder at 1000-1300°C for 1.5 hr in hydrogen atmosphere. The grain size of this WC powder was reduced to various sizes by ball-milling. WC-(0-2)%VC-(5-20)%Co alloys with various grain sizes and 'carbon contents were vacuum-sintered mainly at 1400°C for various times.The results obtained were as follows: (1) The restriction effect was found to be controlled almost by the ratio of VC/Co, and not by the ratio of VC/WC. Even under the same ratio of VC/Co, the effect was affected by the carbon content of the alloy. (2) When the mean grain size of starting WC powder exceeded a certain critical value, the addition of VC more than a definit value resulted in the normal grain growth of WC in VC contained alloys. However, in the case of the mean grain size smaller than the critical value, it resulted in the abnormal grain growth of WC (with fine grain size of WC in the matrix). For instance, in the usual WC powder having grain size larger than -0.3μ, addition of VC more than -5% in the binder checked the abnormal grain growth (mean grain size of WC in the matrix decreased with increasing amount of VC). However, in the fine grained WC powder having mean grain size smaller than -0.2μ, such a restriction method of adding VC was by this time invalid because of the occurrence of the abnormal grain growth, leading to the impossibility of obtaining micro-grained alloys. The above critical grain sizes (0.2-0.3μ) and the critical amount of VC were naturally considered to vary according to size distributions of the starting WC powder, sintering temperatures, Co contents, etc. (3) The three phase region and the compositions of the binder phase in WC-VC-Co alloys were also examined.


Journal ArticleDOI
TL;DR: In this article, the effects of environment and grain size on the steady-state creep and creep rupture properties of Ni-6 pct W solid solution are examined by testing in vacuum and commercial purity argon at 5000 psi and 900°C.
Abstract: The effects of environment and grain size on the steady-state creep and creep rupture properties of a Ni-6 pct W solid solution are examined by testing in vacuum and commercial purity argon at 5000 psi and 900°C. The steady-state creep rate is found to decrease with increasing grain size at small grain sizes, both in vacuum and argon, owing to the effects of grain boundary sliding. At large grain sizes the creep rate is independent of grain size in vacuum and increases with grain size in argon. It is suggested that the increase in creep rate with increasing grain size is associated with fact that large-grained samples tested in argon do not reach steady-state before rupture occurs.

Patent
31 Jan 1972
TL;DR: In this article, the authors propose a method for producing a HOT WORKED HIGH TEMPERATURE HEAT RESISTANT DISPERSION-STRENGTHENED ALLOY, which is the zone of an ELEVATED GERMINATIVE GRAIN GROWTH TEMperATURE.
Abstract: A MTHOD IS PROVIDED FOR PRODUCING A HOT WORKED HIGH TEMPERATURE HEAT RESISTANT DISPERSION-STRENGTHENED SUPERALLOY, CHARACTERIZED BY A METALLOGRAPHIC STRUCTURE CONSISTING ESSENTIALLY OF LARGE COARSE GRAINS HAVING A PREFERRED ORIENTATION RELATIVE TO THE AXIS OF WORKING, THE METHOD COMPRISING SUBJECTING A DISPERSION-STRENGTHENED ALLOY, E.G., SUPERALLOY, THE ZONE ANNEALING AT AN ELEVATED GERMINATIVE GRAIN GROWTH TEMPERATURE TO FORM COARSE GRAINS DISPOSED IN THE WORKING DIRECTION OF THE ALLOY AND TO ACHIEVE IMPROVED PROPERTIES.

Journal ArticleDOI
I. Amato1
TL;DR: In this article, an explanation of the nickel and iron activating effect is given both through oriented vacancy flow generated by the Frankel-Kirkendall effect, originated by the widely different iron and nickel-tungsten diffusion coefficients, and through annihilation of the tungsten dislocations by dissolution in the activating agent.


Journal ArticleDOI
TL;DR: In this article, a correlation between surface structures of the chromium films and the environment in which they were grown could be made, and it was found in wet or dry environments that the stable Cr2O3 formed at all times and temperatures during the oxidizing process, and two forms of the nitride were observed.
Abstract: Reflection electron diffraction, electron microscopy, and ellipsometric techniques have been used to study the effect of various oxide and nitride treatments on the surface of chromium films. Thin films of chromium prepared by evaporation and deposited on glass substrates in 10−6-Torr vacuum were oxidized or nitrided for varying times at 50°C intervals in a 400°–600°C temperature range. In this study a correlation between surface structures of the films and the environment in which they were grown could be made. It was found in wet or dry environments that (1) the stable Cr2O3 formed at all times and temperatures during the oxidizing process, (2) two forms of the nitride were observed—the fcc CrN and the hexagonal βCr2N both always in combination with Cr2O3, (3) CrN was detected at a temperature of 450°C, (4) at temperatures above 450°C βCr2N was found and the CrN phase disappeared, (5) an increase in time at all temperatures resulted in grain growth of all compounds. Data obtained for varying conditions ...

Journal ArticleDOI
TL;DR: This paper showed that the density of solute adsorbed at grain boundaries is a function of the distance through which the boundary has migrated, and given sufficient boundary motion, a solute concentration approximating that of a monolayer will be developed regardless of specimen purity.


31 Dec 1972
TL;DR: In this article, large tubular crystals of alpha-SiC, which can become strength limiting, tend to grow during the hot-pressing of boron containing betaSiC powder.
Abstract: : Large tubular crystals of alpha-SiC, which can become strength limiting, tend to grow during the hot-pressing boron containing beta-SiC powder. The exagerrated grain growth was controlled by several methods: Stabilization of beta-SiC by nitrogen; nucleation of alpha-SiC by seeding; and, decreasing the hot-pressing temperature by using SiC powders with increased sinterability. Nitrogen doping was achieved by the addition of either Si3N4 or BN and yields electrically conductive materials which are amenable to electro discharge machining. The hot-pressing of large billets of nitrogen-doped materials revealed that specimen thickness and the applied pressure are critical parameters which affect the final density. Pressure-less sintering was achieved in submicron beta-SiC powders by the addition of boron and carbon. Results of microstructural examination, room temperature and high temperature bend strength, creep and impact tests are presented. (Modified author abstract)

Journal ArticleDOI
01 May 1972
TL;DR: In this article, the transformation of coarse grain in TD-nickel 1 in. bar under certain conditions of deformation and annealing was examined, showing that the transformation exhibits Avrami-type kinetics, with an activation energy of 250 kcal per mole.
Abstract: Characteristics of the coarse grain transformation occurring in TD-nickel 1 in. bar under certain conditions of deformation and annealing were examined. The transformation exhibits Avrami-type kinetics, with an activation energy of 250 kcal per mole. Characteristics of untransformed regions are like those of the as-received state. The transformed grain size increases with increasing deformation and decreasing annealing temperature. Transformed grains have a {7, 5, 15} 〈•5, •1•4, 7〉 annealing texture. The coarse grain transformation is significantly different from primary recrystallization in pure nickel. Its characteristics cannot be rationalized in terms of primary recrystallization concepts, but may be explained in terms of an abnormal grain growth description. This provides support for the suggestion, deduced from the previous electron microscopy investigation, that the coarse grain transformation in TD-nickel is abnormal grain growth rather than primary recrystallization. The analysis suggests an explanation for the effect of “thermomechanical history” on the deformation and annealing behavior of TD-nickel.

Journal ArticleDOI
01 Jan 1972
TL;DR: In this article, the growth rates of dispersed thoria particles in nickel have been measured as a function of time at 1350°C in gases of two separate oxygen partialpressures.
Abstract: The growth rates of dispersed thoria particles in nickel have been measured as a function of time at 1350°C in gases of two separate oxygen partialpressures. Samples were prepared for electron microscopic study after these treatments for particle size distribution measurements. The diffusion coefficient and solubility of thorium in nickel placed in contact with thoria were also determined under the same conditions. The results of the measurements then provide the necessary information for the elucidation of the kinetics of Ostwald ripening in the ThO2-Ni system. A linear relationship was found between the cube of the mean radius of the dispersed particles and the time at temperature. Substitution of the experimental results into the Lifshitz-Wagner equation for particle growth under diffusion control yielded values of the ThO2-Ni solid-solid interfacial energy, which are in good agreement with what is expected by comparison with the corresponding solid oxide-liquid metal interface. Further studies were made of the coarsening of thoria in 20 pct Cr-Ni alloys. It was found that the enhanced rate of particle growth could be accounted for by the increased value of the diffusion coefficient of thorium in the alloy over the value in pure nickel.

Journal ArticleDOI
TL;DR: In this paper, it was shown that when the sintering temperature is increased from 930 to 1130°C, the film density increases and a surface roughness is created.
Abstract: Thin polycrystalline NiFe2O4 films in the thickness range 0.1–0.7 μm were prepared by subsequent oxidation of a metallic film deposited under vacuum. The experimental requirements to obtain a stoichiometric single‐phase ferrite film are described in detail. The influence of preparation parameters on crystallographic and magnetic properties is extensively studied. It is shown that when the sintering temperature is increased from 930 to 1130°C, the film density increases and the grain growth occurs. During the grain growth a |111| fiber texture is formed and a surface roughness is created. The formation of the |111| fiber texture which is more pronounced for higher sintering temperatures is explained in terms of surface energy. It is shown that the magnetic properties measured by ferromagnetic resonance are determined by the density and microstructure of the thin film, but the surface roughness has no marked effect on the position and linewidth of the main resonance mode. The thermally induced strains are m...

Journal ArticleDOI
TL;DR: In this paper, the final stage sintering of uranium dioxide has been investigated in the temperature range 1623 −1973 K where the residual porosity is situated mainly on grain boundaries.