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Showing papers by "Mines ParisTech published in 1977"


Journal ArticleDOI
L. Remy1, André Pineau1
TL;DR: In this article, the tensile properties of various alloys of the FeMn-Cr-C system were studied and the effect of temperature on both twinning and f.c.p.

323 citations


Journal ArticleDOI
TL;DR: In this article, the cyclic stress-strain response and the low cycle fatigue life of conventionally heat treated Inconel 718 were studied using optical and electron microscopy.
Abstract: The cyclic stress-strain response and the low cycle fatigue life of conventionally heat treated Inconel 718 were studied. Fully reversed strain-controlled tests were performed at room temperature and at 823 K. Optical and electron microscopy were used to study the development of deformation and cracking during cycling. A power-law relationship between life-time and plastic strain amplitude was obtained. A substantial decrease in fatigue life occurred as the temperature was increased from 298 to 823 K and as the cycling frequency was lowered from 3 cyclesJmin to 0.3 cyclesJmin at 823 K. At 298 K, for all the strain amplitudes investigated, an initial rapid hardening was followed by softening, while at 823 K only softening occurred. Electron microscopy showed that the precipitates were sheared in the course of cyclic straining and that plastic deformation proceeded by the propagation of planar bands. These bands were identified as twins. Twinning was found to be more abundant at elevated temperatures than at room temperature, especially at lower frequencies. Cracking was generally initiated along the interfaces between these twin bands and the matrix but, at elevated temperatures and low strain rates, intercrystalline cracking took place, as well. The influence of particles shearing and twinning on the cyclic stress-strain response of the material are discussed. The importance of planar deformation and twinning on intergranular cracking is emphasized.

270 citations



Journal ArticleDOI
TL;DR: In this article, the conditions of (Δ∈p/2, T) necessary to induce the γ → α′ phase transformation under low cycle fatigue conditions have been studied in an Fe 18Cr6.5Ni0.19C stainless steel, where the formation of α′ martensite was detected magnetically during testing and by using X-ray measurements at failure.

143 citations


Journal ArticleDOI
L. Remy1
TL;DR: The intrinsic stacking fault energy of a f.c. Alloy was measured for various temperatures in the temperature range 100 −390 K using observations of dislocation nodes by transmission electron microscopy and shear modulus determinations as discussed by the authors.

110 citations


Journal ArticleDOI
L. Remy1
TL;DR: In this article, the interaction of slip dislocations with an annealing twin was analyzed by transmission electron microscopy in a polycrystalline f.c. cobalt base alloy.

103 citations


Journal ArticleDOI
TL;DR: The influence of substituted elements on the DO3 type structure was investigated by electron microscopy and Mossbauer spectroscopy as discussed by the authors, and the hyperfine field-isomer shift correlation was discussed.
Abstract: The influence of substituted elements, such as Ti, Mn, Ni, Cu, Ge, on the DO3 type structure is investigated by electron microscopy and Mossbauer spectroscopy. The results lead to the assumption that titanium and presumably manganese substitute into the β-sublattice while nickel substitutes, in an ordered manner, into the α-sublattice. Copper and germanium substitute into the γ-sublattice. The last element improves the state of order of the Fe3Al structure. A strong repulsive interaction between aluminium and germanium is shown to exist. The hyperfine field-isomer shift correlation is discussed. L'influence des elements en substitution, tels que Ti, Mn, Ni, Cu, Ge, sur ľordre DO3 de Fe3Al a ete etudiee par microscopie electronique et spectrometrie Mossbauer. Nos resultats nous conduisent a supposer que le titane et vraisemblablement le manganese se substituent sur le sous-reseau β tandis que le nickel se place, de maniere ordonnee sur le sous-reseau α. Le cuivre et le germanium se substituent sur le sous-reseau γ. Le germanium ameliore l'etat ďordre de l'alliage et une forte interaction repulsive entre aluminium et germanium est mise en evidence. La correlation entre champ hyperfin et deplacement isomerique est discutee.

68 citations


Proceedings ArticleDOI
01 Jan 1977
TL;DR: The aim is to extend these results, for the three following reasons : first, though every program can be transformed to match Vuillemin's conditions, the transformations may affect the costs of computations : a more direct proof can be investigated.
Abstract: Procedure call mechanisms have mainly been studied in the framework of recursive programs without assignments, for the simplicity of their operational and denotational semantics (See Scott [16], Nivat [14], Vuillemin [17]). According to operational semantics, procedure calls act as textual rewritings ; "computation rules" select at each computation step the occurrences of unknown functions to be rewritten. A computation rule is called correct if the value it computes is the one given by the denotational semantics. Correctness and efficiency of computation rules have been studied in Vuillemin [17,18], Montangero-Pacini-Turini [13], Downey-Sethi [7]. The main results are well-known: innermost evaluation (call by value) is not correct, parallel outermost or full substitution are correct. Vuillemin [17,18] gives a sufficient condition for a rule to be correct, (safety), later extended by Downey-Sethi [7] into a necessary and sufficient one (security). Vuillemin also studies particular implementation of call-by-name, the delay rule ; he shows its optimality with respect to a reasonable implementation cost, provided interpretations satisfy a sequentiality condition. This result is in fact twofold : sequentiality allows elimination of useless steps, and optimality follows by using sharing mechanisms in term implementation. The basis of all these studies is the following theorem (Vuillemin [17,18]) : provided some restrictive conditions on programs are satisfied, the set of terms derivable from a given term is a lattice under the derivation ordering. Our aim is to extend these results, for the three following reasons : first, though every program can be transformed to match Vuillemin's conditions, the transformations may affect the costs of computations : a more direct proof can be investigated. Second, a direct generalization to the e-calculus is not straightforward, since e-terms definitely do not form lattices. Third, the symbolic (or Herbrand) interpretation [5] is not sequential in the sense of Vuillemin, and no optimality result is known for it. Our point of view will be purely syntactic : we reconstruct the lattice property in derivations. We study minimal computations (i.e. finite or infinite derivations)in the symbolic interpretation, and transform them into optimal ones. Eventually, we characterize interpretations to which similar results apply. Extension towards the e-calculus is done in [10]. The lattice property of terms breaks down in general : two very different derivations may lead to the same term by syntactical accidents, which collapse two a priori different terms. In section I, we take care of this fact by introducing an equivalence and a preorder on derivations. We give three characterizations of these relations. For the main one, we extend the classical notion of residuals [4] by defining residuals of derivations by derivations. We show that derivation classes form a lattice. In section II, we study the "simple derivations" defined by Vuillemin with use of labels (named here complete derivations). We give two characterizations of them in the usual formalism. Section III, is devoted to minimality and optimality results. Ordering infinite derivations as well as finite one, we construct least computations of every syntactic approximation of the infinite tree determined by the program. The associated complete derivation are optimal with respect to Vuillemin's cost. Extension to interpretations is then straightforward, as soon as they satisfy a syntactic condition. All classes of sequential interpretations considered in [2,6,11,17] do satisfy this condition. The "computation rule" we use for constructing the optimal computations is very inefficient in general, but reduces to the usual delay rules in sequential interpretations.

47 citations


Journal ArticleDOI
TL;DR: In this paper, a Hankel transformation is used to solve the problem of stress and displacement expression for any point of the medium, and a curve of numerical results is presented for the results.

47 citations


Journal ArticleDOI
TL;DR: In this article, the hcp ϵ phase which is obtained by splat quenching of Fe-C and FeC-Si alloys has been studied by electron diffraction and Mossbauer spectroscopy.

38 citations


Journal ArticleDOI
L. Remy1

Journal ArticleDOI
TL;DR: In this paper, a low-alloy steel containing 0.12% Sb and 2% Mn was heat treated to induce reversible temper embrittlement, and the grain boundaries thus exposed were analysed successively by XPS and AES.

Journal ArticleDOI
Luc Rémy1
TL;DR: In this paper, the amount of phase transformation vs applied strain was determined by density measurements at various temperatures, assuming that e-platelets form from stacking faults, the volume fraction can be expressed as an implicit function of strain.
Abstract: The kinetics of the strain-induced γ (fcc)→e (hcp) transformationi.e. the amount of phase transformationvs applied strain were determined by density measurements at various temperatures. The transformation curve has a sigmoidal shape and approaches saturation below 100 pct transformation. Assuming that e-platelets form from stacking faults, the volume fraction can be expressed as an implicit function of strain. The saturation value is constant and can be evaluated from quantitative metallography. The approach to saturation is determined by only one temperature-dependent parameter related to the stacking fault energy. Good agreement with experimental results was obtained. The model was also applied to transformation kinetics after a prestrain inducing both slip and twinning. The prestrain stabilizes austenite with respect to the strain-induced transformation through a block-refining of austenite by the substructure. In addition the nucleation is enhanced through the introduction of stacking faults. This effect vanishes at high applied strains but causes the shape of the transformation curve to become parabolic. It is concluded that decreasing the size of the e platelets provides a simple means for reducing the temperature dependence of the transformation kinetics.

Journal ArticleDOI
Guy Cohen1
TL;DR: The main contribution of this paper is the derivation of a new coordination algorithm from this principle, in a quite simple manner, also using the idea of interaction operators, which is explained in the general framework of optimization problems.

Journal ArticleDOI
TL;DR: In this paper, a plate-like precipitate having the βm-alumina structure was identified within intergranular spinel inclusions in MgO-doped sintered aluminum oxide ceramics.
Abstract: Potassium-containing plate-like precipitates having the βm-alumina structure were identified within intergranular spinel inclusions in MgO-doped sintered aluminum oxide ceramics. Transmission electron microscopy revealed the corresponding epitaxial relation: (0001) βm{111} spinel and 1120 βm110 spinel. Chemical analyses and quantitative metallography suggested that in α-Al2O3 the 1800°C solubility limits of magnesium and potassium do not exceed 300 to 400 ppm and 5 to 10 ppm by weight, respectively.

Journal ArticleDOI
TL;DR: In this article, the applied stresses between the rollers during calendering (pressure curve-maximum pressure and shear stress-roll separating force and the applied opposing torque) as well as the temperature evolution of the polymer in the contact were computed.
Abstract: Using a power-law viscosity, then connecting power-law fluid and thermo-dependence of the viscosity, we compute the applied stresses between the rollers during calendering (pressure curve-maximum pressure and shear stress-roll separating force and the applied opposing torque) as well as the temperature evolution of the polymer in the contact. We checked this model by measuring r (ratio of spread height to nip width), the power consumed by the roll of the calender, the roll separating force, and the torque on a simulation apparatus.

Journal ArticleDOI
TL;DR: In this paper, a thermodynamic model using Bromley's correlation of activity coefficients in concentrated electrolytic solution, predicts the influence of the concentration of major ions in the aqueous phase on distribution curves of copper(II) between an organic solution of complexing extractant (LIX 64N) and an organic phase at low loading of the organic phase.

Journal ArticleDOI
TL;DR: In this article, the conditions for the appearance of air bubbles and mattness were studied for the particular case of calendering crystal-clear, rigid, toughened PVC.
Abstract: Major types of defects appearing in calendered films and sheets are described. The conditions for the appearance of air bubbles and mattness were studied for the particular case of calendering crystal-clear, rigid, toughened PVC. A correlation was found between the presence of air bubbles in the film and a distribution of air inclusions in the bank. The existence of air inclusions is also related to a critical pressure, which has been calculated with the aid of a theoretical model (pseudoplastic fluid). The variation of mattness with various parameters of the calendering process, such as speed, friction, temperature, and lubrication, was measured on a laboratory calender. The influence of the calender size (laboratory and industrial) on the occurrence of mattness was also investigated. The calculated critical parameters to be considered, in order to define the onset of mattness, appear to be a shear stress or a maximum pressure. A comparison of model calculations and experimental observations all...


Journal ArticleDOI
TL;DR: In this article, the influence of ionic strength and chloride concentration in aqueous phase on distribution coefficients and measured pH is given and interpreted for cupric ion extraction by LIX 64N solution in xylene.

Journal ArticleDOI
J.J. Favier1, G. Lesoult1
TL;DR: In this paper, the selection mechanisms of the eutectic grains have been studied during controlled solidification of Pb-Sn alloys with a view to grow monograins.

Journal ArticleDOI
D. Weber1, M. Meurtin1, D. Paris1, A. Fourdeux1, P. Lesbats1 
TL;DR: In this article, the authors studied the effect of quenching temperature on the elimination of vacancies in polycrystalline 40 at % Al alloy by resistivity measurements, and showed that vacancy elimination increases with increasing A1 content and does not vary monotonically with increasing quench temperature.
Abstract: Vacancy elimination is studied in quenched FeAl alloys containing 33 to 51 at % Al. The process occurs in localized regions in the specimen and the rate depends strongly on the quenching temperature. Introduction and experimental methods. It has been shown that B, FeAl alloys may retain a high concentration of vacancies after quenching from high temperatures [ l , 21. Vacancy concentration increases with increasing A1 content for a given quenching temperature and does not vary monotonically with increasing quenching temperature. The annealing of a quenched sample at temperatures near 400 0C eliminates the quenched vacancies. The elimination of vacancies during annealing has been previously studied in polycrystalline 40 at % Al alloy by resistivity measurements [3]. In the present study, vacancy elimination is followed in single crystal samples with 42 at % to 51 at % A1 (total impurities < 5 x 10-3 %) by dilatometry, microhardness measurements, transmission electron microscopy, field ion microscopy and positron annihilation. The foils for electron microscopy were cut with an electrolytic saw and thinned down by a standard method. All the samples were heat treated in a vertical furnace and quenched in a quenching medium equivalent to oil. The characteristics of vacancy elimination. Vacancy el~m~nation was followed during annealing in a differential dilatometer. As the lattice parameter a is supposed to be constant [4] the concentration of remaining vacancies at an annealing time t is Four parameters influence the vacancy elimination in B, FeAl alloys : quenching temperature. annealing temperature, A1 content and quenching conditions. In these experiments, all the samples were heat treated and quenched in the same conditions so that the influence of this parameter can be ignored. The influence of the three other parameters is studied below. QUENCHING TEMPERATURE. The influence of quenching temperature was examined for 42 at % A1 samples quenched from various temperatures and annealed at 400 OC. As the initial vacancy concentration is different for the different quenching temperatures, comparison between the curves is facilitated by considering the time tl12 to eliminate half the initial vacancy concentration. It is clear that t,,, increases markedly with decreasing temperature below 1 050 OC and appears relatively insensitive to temperature above 1 050 OC. A model proposed by Damask, Danielson and Dienes [5] leads to the expression for the vacancy concentration as a fonction of annealing time C,(t) = Cv(0) (cosh ~ r t ) ~ / p . The theoretical curves giving log Cv(t)/Cv(0) versus time are linear after a certain time. This model seems only to be applicable to low quenching temperatures [3] as these curves are no longer linear for quenching temperatures above 1 000 OC (figure I). ANNEALING TEMPERATURE. For the same samples (42 at % Al) quenched from 9500C vacancy elimination was studied for different annealing temperatures from 300 OC to 400 OC. These relatively low annealing temperatures were chosen in order to obtain as low a concentration of residual vacancies as possible after annealing. The vacancy elimination curves (figure 2) show that tl12 increases very strongly with decreasing annealing temperature. No vacancy Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1977764 VACANCY ELIMINATIOIS IN FeAl ALLOYS WITH B, STRUCTURE FIG. 1 . -Vacancy elimination curves in 42 at O/, A1 alloy during annealing at 400 UC. FIG. 2. Vacancy elimination curves in 42 at O/, A1 alloy after quenching from 950 OC. elimination, was observed at 3000C. It must be noticed that the parameter p is the same for annealing at 350 OC and at 400 OC (p = 0.89). ALUMINIUM CONTENT. The influence of aluminium content has been examined on samples quenched from 1 000 O C and annealed at 425 O C . The curves (figure 3) show that for high A1 content the model is inapplicable. It therefore seems apply to low vacancy concentrations and low quenching temperatures. Electron microscopy observations. The structure of a 42 at % A1 alloy has been studied by transmission electron microscopy after quenching from 1 000 OC and at different stages during ageing at 400 OC. These stages are denoted 1, 2, 3, 4 in figure 4. The foil plane was (001). Very few straight dislocations have been observed in the as quenched alloy. After ageing 75 min. (stage 1 ) the structure of the alloy is inhomogeneous. In some FIG. 3. -Vacancy elimination curves in FeAl alloys for different A1 contents (T, = 950 OC, T, = 425 OC). FIG. 4. --Vacancy elimination curve in 42 at % Al alloy (T, = 1 000OC, T, = 400 OC) : Stage 1 : after 75 min. ; Stage 2 : after 3 h 30 ; Stage 3 : after 6 h ; Stage 4 : after 8 h. areas, localized regions containing high densities of dislocations can be seen. The rest of the specimen is free of dislocations (figure 5a, 6 , c). The volume of these areas increases progressively from stage 1 to stage 4, where the foil is full of tangled dislocations (figure 5d). In the initial stages, tangled dislocations are observed in the center of the areas (figure 56) and numerous dislocation loops along the edges (figure 6). These dislocation loops are not entirely contained in the foil. The dislocation loops show a fringe contrast when imaged using a superlattice reflection under two beam conditions, and a residual fringe contrast when imaged using a fundamental reflection under two beam conditions (figure 7a, b). Such a contrast is typical of antiphase boundaries inclined to the plane of the foil. Inside some loops, dendritic dislocations can be seen. Similar dislocations have been observed in B brass [6]. Dendritic dislocations give rise to the disappearance of the fringe contrast. It can be shown that these loops lie on { 1 11 } planes. This is verified by observation of a (1 11) foil. Figure 8 shows a well developed loop with a dendritic dislocation inside. This peculiar configuration could be C7-334 D. WEBER er al. FIG. 7. -Micrographs of dislocation loops observed in stage 2 (figure 4). The loops were imaged under two beam conditions using a fundamental reflection in (a), and a superlattice reflection in (b) . The foil plane was (001). FIG. 5. Micrographs corresponding to the 4 stages of figure 4 : 1 in (a), 2 in (b), 3 in (c), 4 in (d). The foil plane was (001). FIG. 8. Micrograph of a well developed dislocation loop observed in stage 3 (figure 4). The loop was imaged in the same conditions as in figure 6. The foil plane was (1 11). FIG. 6. Micrograph of dislocation loops observed in stage 2 (figure 4). The loops were imaged using a fundamental reflection under two beam conditions. The foil plane was (001). explained as follows : a dislocation is first formed by FIG. 9. Vacancy elimination and microhardness decreasing in 49.5 at % A1 alloy (T, = 1 000 OC, T, = 425 OC). clustering of vacancies on a (111) plane, but the condensation of a single layer of vacancies generates an antiphase boundary ; the clustering of vacancies on dislocation (the dendritic dislocation) which sweeps the neighbouring plane leads to the creation of another out the antiphase boundary. VACANCY ELIMINATION IN FeAl ALLOYS WITH B, STRUCTURE C7-335 4 \\ # b d \\ FIG. 10. -Electron diffraction patterns of a Fe 49 at % Al . 6 . . . alloy (T, = 1 000 OC in (u), 800°C in (b) and 1 150 *C in (c), T, = 1 000 OC, T, = 438 OC 24 h in (d)). Diffuse intensities are DAWSON AND S A S S ( ~ ~ f . 7 ) B= [I731 observed between the lattice reflections. C7336 D. WEBER el crl . Complementary methods. A good correlation can be found between the vacancy concentration after quenching and the hardening observed on quenched FeAl alloys [I]. The results of the investigation on a sample quenched from 1 OOOOC and annealed at 425 OC are shown in figure 9. The decrease in hardness fits in quite well with the elimination of vacancies, except, perhaps, for the lower vacancy concentrations. The electron diffraction patterns of the quenched alloys exhibit diffuse intensities between the reciprocal lattice points (figure 10). The diffuse intensities are similar to these of the diffuse w phase observed in Zr 22 wgt % Nb alloy [7]. For this reason, these diffuse intensities are thought to be due to the presence of a diffuse o phase in the b.c.c. lattice. The shape of the diffuse scattering varies with the vacancy concentration. This diffuse o phase is thought to be responsible for the hardening mentionned above. Field ion microscopy was performed on samples both, immediatly after quenching and after full annealing at 425 OC. Only iron atoms can be imaged by this technique in the FeAl alloys. Thus the vacancy sites imaged on the Fe sublattice can be either quenched in vacancies, field-induced vacancies or A1 antistructure atoms [8]. It is assumed that the number of field induced vacancies is the same in quenched and annealed samples. Let d be the total number of vacancies eliminated during the annealing and m the difference of vacant sites on the iron sublattice between quenched and annealed samples. Then it can be shown that the difference Au of Fe antistructure atoms is Measurements were performed for three compositions (46,49.5 and 51 at % Al) with samples quenched from 1 000 OC; Au was found to be respectively 0, 2.5 o/m and 4.5 0/ , ; it is therefore concluded that for high A1 contents, vacancy elimination is concomitant with a small improvement in the degree of order. The problem of the reference state. Low vacancy concentration in simple metals can be studied by positron annihilation down to concentrations of The angular correlation of the annihilation radiation method has been used to study the residual defect concentration in the above FeAl alloys. It has been shown that slow cooling from high temperatures of these alloys is not a good method to eliminate vacancies ; in this case, the residual concentrations are similar to those obtained after quenching from 700 OC in the two al





Journal ArticleDOI
TL;DR: In this paper, a qualitative investigation of CaO single crystal and hot-pressed polycrystal behavior in high K2O melts is presented, under carefully controlled anhydrous conditions, no intermediate crystalline compound was detected at temperatures up to 800° C.
Abstract: A qualitative investigation of CaO single crystal and hot-pressed polycrystal behaviour in high K2O melts is presented. Under carefully controlled anhydrous conditions, no intermediate crystalline compound was detected at temperatures up to 800° C. Calcium oxide dissolves preferentially along grain boundaries and/or along 〈1 0 0〉 directions on {1 0 0} faces. The melt viscosity gradually increases with its CaO content. The single crystal corrosion rate, therefore, decreases with time and a protective glassy layer may eventually develop on its surface.