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Showing papers in "Powder Metallurgy in 1984"


Journal ArticleDOI
TL;DR: In this article, the authors made a study of the effect of experimental variables such as punch spacing, punch contact area, and diamond indentation load on the crack growth and found that the cracks grew to a stable depth, the value of which could be determined by suitable choice of indentation parameters.
Abstract: Bridge indentation involves the initiation of a precrack at thq centre of the top surface of the sample by meajns of diamond indentation (i.e. a Palmqvist crack). Growth of this crack is then induced by pressing either side of it with rectangular punches having their edges parallel with the crack direction. With I increasing load, the crack grows outwards and downwards, and eventually forms a straight-through crack. The present authors have made a study of the effect of experimental variables such as punch spacing, punch contact area, and diamond indentation load on the crack growth. Specimens of a WC–6Co alloy cracked in this way were subsequently used for K 1C measurement. An important result was that the cracks grew to a stable depth, the value of which could be determined by suitable choice of indentation parameters. Numerical analysis using a boundary element method (BEM) was used to explore the stress situation in bridge indentation and provided a qualitative prediction of the experimental r...

86 citations


Journal ArticleDOI
TL;DR: The elimination of isolated large pores during liquid phase sintering has been studied in a 96Mo-4Ni alloy (wt-%). The large pores have been produced at the site of spherical Ni particles upon the i... as discussed by the authors.
Abstract: The elimination of isolated large pores during liquid phase sintering has been studied in a 96Mo–4Ni alloy (wt-%). The large pores have been produced at the site of spherical Ni particles upon thei...

48 citations


Journal ArticleDOI
TL;DR: Le modele des spheres creuses de Torre est employe pour etudier l'influence d'un ecrouissage sur le compactage des metaux poreux and des poudres metalliques.
Abstract: Le modele des spheres creuses de Torre est employe pour etudier l'influence d'un ecrouissage sur le compactage des metaux poreux et des poudres metalliques. L'ecrouissage est decrit par la loi de Voce-Palm. Pour certaines valeurs de l'une des constantes de cette loi (la deformation caracteristique), le probleme du compactage spherique admet une solution de forme fermee. Pour l'une de ces valeurs, l'equation pression-densite relative en resultant est celle proposee par Konopicky et par Shapiro et Kolthoff. Ainsi le modele de sphere creuse avec la loi d'ecrouissage de Voce-Palm fournit une base theorique a cette equation empirique largement utilisee

41 citations


Journal ArticleDOI
TL;DR: Inconel alloy MA 6000 as discussed by the authors is an advanced turbine blade material strengthened by solid solution additions, γ′, and yttrium oxide compounds, which is used to achieve a highly directional coarse grain structure which further enhances creep resistance.
Abstract: Developments in the production of prealloyed oxide dispersion strengthened superalloy powders have resulted in the commercial scaling-up of the mechanical alloying process. This method incorporates a uniform dispersion of yttrium oxide particles of 20–40 nm dia. into superalloy base compositions and effectively extends the maximum temperature capabilities of such alloys by several hundred degrees kelvin. Powder metallurgical consolidation techniques and controlled thermo-mechanical working processes are required to achieve optimum properties in a range of commercial alloys and product forms. One of the alloys, Inconel alloy MA 6000, is an advanced turbine blade material strengthened by solid solution additions, γ′, and yttrium oxide compounds. A zone annealing technique is used to achieve a highly directional coarse grain structure which further enhances creep resistance. In addition to components in the hot section of gas turbines, Inconel alloy MA 754 and Incoloy alloy MA 956 now are found in a ...

38 citations


Journal ArticleDOI
TL;DR: The authors decrit les progres realises a ce jour pour reduire le probleme de la precipitation aux joints entre particules originelles qui se produit lors du traitement des superalliages en metallurgie des poudres.
Abstract: On decrit les progres realises a ce jour pour reduire le probleme de la precipitation aux joints entre particules originelles qui se produit lors du traitement des superalliages en metallurgie des poudres. Des donnees sont presentees illustrant l'influence des parametres du compactage isostatique a chaud et du traitement thermique sur le degre de decoration des joints entre les particules originelles dans le superalliage PM APK1 (Nimonic Alloy AP-1). Les facteurs influant sur les proprietes de traction et de fluage a chaud de cet alliage sont discutes en detail

32 citations


Journal ArticleDOI
TL;DR: In this paper, three types of commercially used iron powder of different specific surfaces and compressibilities were cold compacted with 10wt-%Cu over a range of pressures before sintering at a temperature of 1140°C.
Abstract: Three types of commercially used iron powder of different specific surfaces and compressibilities were cold compacted with 10wt-%Cu over a range of pressures before sintering at a temperature of 1140°C. A study of dimensional changes during sintering showed that swelling was inversely related to the specific surface of the powder, but directly proportional to the compacting pressure. Metallo- graphie, dilatometric, and microprobe studies showed that the observed swelling in the compacts was almost totally due to grain boundary penetration by liquid Cu, while diffusion of Cu into grains made only a small contribution. However, analyses of the relevant experimental parameters have shown that the particle internal micropores are energetically more favourable for attracting and accommodating the liquid Cu than the grain boundaries, and therefore, when present, they inhibit volumetric growth. In support of the above, it has been shown that the vol.%, change for various powders compacted over the range ...

30 citations


Journal ArticleDOI
TL;DR: In this article, the powder rolling process has been analyzed using the mechanics of powder compaction with a view to the prediction of the thickness and density of the strip, and a method of analysis taking account of these variables is described.
Abstract: The powder rolling process has been analysed using the mechanics of powder compaction with a view to the prediction of the thickness and density of the strip. Factors such as roll speed, initial roll gap, feed rate or flowrate of the powder, and friction condition are discussed and a method of analysis taking account of these variables is described. Combined with the experimentally derived rigidity of the rolling mill, it is possible to determine the thickness and density of the strip produced using an electrolytic copper powder; calculated results agree well with experimental results. It is possible to apply the present method to other powders, provided the powder characteristics are known. PM/0268

26 citations


Journal ArticleDOI
TL;DR: In this paper, the dependence of green strength on green density and on compacting pressure was investigated for the bidirectional die pressed and isostatically pressed Cu powder compacts, and the green strength seemed to be directly proportional to the contact area between powder particles.
Abstract: The dependence of green strength on green density and on compacting pressure was investigated for the bidirectional die pressed and isostatically pressed Cu powder compacts. The breaking strength of the pressed Cu compact was found to increase with green density and also with compacting pressure. The green strength seemed to be directly proportional to the contact area between powder particles. A theoretical equation for the relationship between green density and contact area was derived from a geometrical consideration, and agreed well with experimental findings. PM/0272

19 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of Ni/Co ratio on microstructure, density, hardness, and transverse rupture strength of WC powders of 5·7 μm with Co and Ni powders was investigated.
Abstract: The effect of the Ni/Co ratio in WC–10(Co–Ni) and WC–15(Co–Ni) alloys on microstructure, density, hardness, and transverse rupture strength is investigated. The specimens have been prepared by mixing WC powders of 5·7 μm with Co and Ni powders. The compacts have been sintered in vacuum to full density. The density after sintering decreases slightly with increasing Ni content, and the effect is attributed to the increase of C content with Ni, which contains less oxygen than Co in powder form. The hardness decreases with Ni content and appears to depend mainly on the hardness of the matrix alloy phase. The transverse rupture strength does not show any variation with Ni content and appears to depend on the grain size, which also remains unchanged. The results show that Co in WC–Co hardmetal can be replaced by Ni without greatly affecting the transverse rupture strength if the microstructure remains constant. PM/0289

19 citations


Journal ArticleDOI
TL;DR: In this article, the development of microstructure during processing of WC, (W, Ti)C, and TiC carbides alloyed with 0-15 wt-% Co has been examined.
Abstract: The development of microstructure during processing of WC, (W, Ti)C, and TiC carbides alloyed with 0–15 wt-% Co has been examined. Changes that occur in carbide and carbide-cobalt powder characteri...

9 citations


Journal ArticleDOI
TL;DR: Une serie dalliages Astroloy modifies par de petites additions de Hf and diverses teneurs en carbone ont ete prepared par les techniques de la metallurgie des poudres sur la base d'une poudre produite par le procede de l'electrode tournante as discussed by the authors.
Abstract: Une serie d'alliages Astroloy modifies par de petites additions de Hf et diverses teneurs en carbone ont ete prepares par les techniques de la metallurgie des poudres sur la base d'une poudre produite par le procede de l'electrode tournante L'analyse de la surface des poudres a l'aide de la spectroscopie electronique pour l'analyse chimique et de la microscopie Auger a balayage a revele que la surface possedait une mince couche d'oxyde dans laquelle avaient segrege Al, Ti et Hf La precipitation aux joints des particules dans le materiau compacte etait plus sensible a la teneur en oxygene de l'alliage qu'a sa teneur en carbone Une explication proposee de ce phenomene est que l'oxyde de surface attire les elements carburigenes vers le joint lors du compactage isostatique a chaud Des additions de Hf jusqu'a 0,46% ne diminuent pas notablement la precipitation aux joints des particules originelles (PPB) La resistance a la traction a la temperature ambiante des alliages n'etait pas affectee par une contamination moderee des joints PPB mais leur ductilite etait reduite

Journal ArticleDOI
TL;DR: The considerable upsurge of interest in the development of PM aluminium alloys in the past 10 years is examined against the background of commercial aluminium powder production in this article, which has created a need for radical departures from the more orthodox powder pressing and sintering techniques.
Abstract: The considerable upsurge of interest in the development of PM aluminium alloys in the past 10 years is examined against the background of commercial aluminium powder production. Although it is likely that PM will remain a relatively small but highly specialized proportion of the total consumption of aluminium powder, which has numerous large scale uses, it is expected that it will grow in its share of the total of PM metals. The pressure for these developments has come largely from the potential consuming industries. It has created a need for radical departures from the more orthodox powder pressing and sintering techniques. It has produced more highly developed powder making processes and a much wider range of subsequent fabricating techniques. Rapid solidification technology, metal matrix composites, and mechanical alloying, for example, combined with powder extrusion, rolling, and forging, are presenting opportunities for creating new alloys and forms of material with tailormade properties mor...

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the densite a la pression zero du compact vert a diverses pressions a ete calculee en mettant sous forme numerique the courbe charge-deplacement and the pression d'ejection a eite determinee a partir de la charge maximale de glissement donnee par la Courbe charge d"ejection-mouvement du compact.
Abstract: Plusieurs fractions granulometriques, allant de −100/+140 a −400 mesh, de poudres de cuivre electrolytique ou reduit ont ete compactees a 1650 MPa. La densite a la pression zero du compact vert a diverses pressions a ete calculee en mettant sous forme numerique la courbe charge-deplacement et la pression d'ejection a ete determinee a partir de la charge maximale de glissement donnee par la courbe charge d'ejection-mouvement du compact. L'analyse des donnees a l'aide de l'equation de compactage de Heckel montre que trois mecanismes differents de consolidation sont en jeu dans differents domaines de pression

Journal ArticleDOI
TL;DR: In this article, the influence of compaction has been determined in the range 600-1000 MPa with a sintering range of 1450-1550 K and times of 2-24 h.
Abstract: The present paper concerns the production of dc magnetic materials by a PM route. The influence of compaction has been determined in the range 600–1000 MPa with a sintering range of 1450–1550 K and times of 2–24 h. The properties measured include magnetic permeability and coercive force. It is shown that, within the ranges studied, permeability and coercive force relate to density and structure, but resistivity induction and power loss are less affected. PM/0205

Journal ArticleDOI
TL;DR: In this article, the effects of argon contamination in PM MERL 76 hot isostatically pressed at 103·4 MPa (15 ksi) and 193·1 MPa(28 ksi).
Abstract: The effects were studied of argon contamination in PM MERL 76 hot isostatically pressed at 103·4 MPa (15 ksi) and 193·1 MPa (28 ksi). Microstructures were characterized and mechanical properties at 704°C (1300°F) were determined for material containing 59 ppm argon (by weight) in the powder container. Baseline hipped PM MERL 76 was also evaluated. The argon contamination resulted in a significant level of porosity in the final material. Contaminated PM MERL 76 hipped at 103·4 MPa (15 ksi) was 97·6% dense, and that hipped at 193·1 MPa (28 ksi) was 98·7% dense, in both cases after heat treatment. Porosity due to argon adversely affected the notch stress rupture life and tensile properties of the alloy. The creep crack growth resistance was only slightly degraded by argon contamination and the resultant distributed pores. PM/0290

Journal ArticleDOI
TL;DR: In this paper, the influence of the starting material and the deformation process on the properties of metal-glass composites is discussed, showing that hardness, strength, and wear resistance can be increased in excess of those predicted by the law of mixtures whereas the elastic modulus and physical properties essentially conform to this law.
Abstract: Composite materials can be produced by PM means. If both components can be deformed, an atomic bond is formed between the new surfaces generated. The structure, properties, and technological applications of metal-glass composites are illustrated by the Al-glass system. The influence of the starting material and the deformation process on the properties is discussed. For the same starting material and production methods, the hardness, strength, and wear resistance can be increased in excess of those predicted by the law of mixtures, whereas the elastic modulus and physical properties essentially conform to this law. Once formed, the composite materials can be further hot worked, and cold worked to a limited extent. They can also be soldered and glued. It is possible to surface treat them, e.g. anodize or enamel. PM/0248

Journal ArticleDOI
TL;DR: In this paper, the authors proposed that carbon transfer from graphite to iron takes place through interparticle contacts after the adsorbed gases, which form a hindrance at the contacts, have been removed.
Abstract: It has been shown previously that the existing theories on the mode of carbon transfer during sintering of iron-graphite are inadequate to explain the results obtained. From the literature, it is seen that large amounts of oxygen are adsorbed on graphite. Graphite was vacuum degassed at high temperature and sintering experiments using iron-degassed graphite were carried out at 1040°C in hydrogen and in vacuum. These results are also inexplicable by either of the existing theories. Thus it is proposed that carbon transfer from graphite to iron takes place through interparticle contacts after the adsorbed gases, which form a hindrance at the contacts, have been removed. The results of other authors have been explained in the light of this proposal. PM/0211

Journal ArticleDOI
TL;DR: In this article, the authors show that direct explosive powder compaction cannot be explained by only one parameter, i.e., the energy consumed by the powder and the prevailing parameter is R 2.
Abstract: Direct explosive compaction of powder is a process that is not widely exploited. It has been investigated by several workers. The mechanisms proposed were based on the fact that the energy developed by the explosive promotes compaction by (a) the kinetic energy acquired by the container or (b) the pressure transmitted by the container. The relevant parameters used for these explanations were either R 1, weight of explosive/weight of container, or R 2, weight of explosive/weight of powder to be compacted. Experiments using iron and copper powders and tubular containers of different internal diameter (i.d.) show that direct explosive powder compaction cannot be explained by only one parameter. When the container i.d. is small, the process is governed by the energy consumed by the container and the prevailing parameter is R 1. When the container i.d. is large enough, the process is governed by the energy consumed by the powder and the prevailing parameter is R 2. Between these, there is a zone in whi...

Journal ArticleDOI
W. Pompe, G. Leitner, K. Wetzig, G. Zies, W. Grabner 
TL;DR: In this paper, a fracture model for a single sintered neck was proposed and the fracture toughness showed a strong dependence on porosity and thermal treatment, and the behavior was discussed on the basis of the fracture model.
Abstract: Crack development has been investigated in sintered iron with porosities between 10 and 20%. The ductility of the samples was changed by O2 or N2 annealing and low temperature deformation. Depending on the work hardening ratio, various characteristic fracture modes have been observed by means of tensile experiments combined with analyses of acoustic emission within the scanning electron microscope (SEM). Corresponding to these fracture modes, the fracture toughness (J c values) showed a strong dependence on porosity and thermal treatment. The behaviour is discussed on the basis of a fracture model for a single sintered neck. PM/0204

Journal ArticleDOI
TL;DR: In this article, the preparation of an Al-3·8Fe−3·6Ni−3 ·8Co engineering material from atomized powders is described. And the properties of the product are superior at room temperature to those of existing non-heat treatable Al alloys and the material maintains its considerable strength at elevated temperatures.
Abstract: The preparation of an Al–3·8Fe–3·6Ni–3·8Co engineering material from atomized powders is described. The production route involves cold compaction followed by extrusion at 400–600°C. It is shown that products having acceptable surface finishes may be produced and that the properties of the products are related to the extrusion parameters. The structure is considerably modified during the deformation processing and is much coarser than that existing in the individual powder particles. The properties of the product are superior at room temperature to those of existing non-heat treatable Al alloys and the material maintains its considerable strength at elevated temperatures. PM/0284

Journal ArticleDOI
TL;DR: In this paper, the authors considered the role of graphite in the process of carbon transfer and showed that neither of the existing theories is adequate to explain all the results obtained, and that further experiments are necessary to understand the mechanism of the carbon transfer.
Abstract: Two theories exist concerning the mode of carbon transfer from graphite to iron during the sintering of iron-graphite. One is that carbon is transferred directly through the contacts between the iron and graphite particles, while in the other, the transfer is considered to take place through the formation of a gas phase. Sintering experiments were carried out in hydrogen and vacuum, using compacts of different densities and permeabilities. The results reveal that neither of the existing theories is adequate to explain all the results obtained. The existing theories have not considered the role of graphite in the process of carbon transfer. Further experiments are necessary to understand the mechanism of carbon transfer. PM/0210

Journal ArticleDOI
TL;DR: In this article, the properties of some magnetodielectric materials, based on iron powder and epoxy resin, are discussed, with particular attention paid to the effect of the materials upon magnetic properties, hysteresis loss especially.
Abstract: The properties of some magnetodielectric materials, based on iron powder and epoxy resin, are discussed. Particular attention is paid to the effect of the materials upon magnetic properties, hysteresis loss especially. Based on experimental evidence, component phase structure models and formulae for calculating magnetic, electric, and thermal parameters are given. Applications are suggested, taking into account the functions to be performed by magnetic cores in the magnetic circuits of an electrical machine. PM/0260

Journal ArticleDOI
TL;DR: In this article, the extrusion of powder compacts prepared from rapidly solidified Al-10 Mg powder was investigated and it was shown that the mechanical properties of the extrudate are related to the temperature compensated strain rate obtaining during the process.
Abstract: This communication reports work completed on the extrusion of powder compacts prepared from rapidly solidified Al–10 Mg powder. It is shown that mechanical properties of the extrudate are related to the temperature compensated strain rate obtaining during the extrusion process. Pressure requirements are much lower than are necessary for the extrusion of cast products of Al–7Mg and Al–5Mg and the corresponding increase in heat generation considerably widens the extrusion limits. In the as-extruded condition, the properties are comparable with a peak aged conventional 7050 alloy but the Al–10Mg is extremely unstable and requires an aging treatment to correct this instability. It is concluded that improvement in this alloy system would be obtained either by decreasing the Mg content or by developing a lower %Mg ternary alloy. PM/0280

Journal ArticleDOI
TL;DR: In this article, the authors present the technologie de la fabrication des cales magnetiques a l'echelle du laboratoire, with l'aide de la technique du moulage en matrice adaptee.
Abstract: On presente la technologie de la fabrication des cales magnetiques a l'echelle du laboratoire a l'aide de la technique du moulage en matrice adaptee. On decrit aussi la fabrication de toles magnetiques pour la coupe de diverses cales. Les proprietes magnetiques et mecaniques ont ete determinees; la permeabilite magnetique varie de 5 a 15 et la resistance a la flexion de 60 a 140 MNm −2 . On presente quelques applications des cales magnetiques dans les machines electriques ainsi qu'une comparaison entre des cales magnetiques et non magnetiques

Journal ArticleDOI
TL;DR: The authors decrit une etude experimentale de depot chimique en phase vapeur de chrome par cementation en caisse sur un acier fritte a bas carbone (<0.02% C).
Abstract: L'article decrit une etude experimentale de depot chimique en phase vapeur de chrome par cementation en caisse sur un acier fritte a bas carbone (<0.02% C). Le revetement par diffusion est influence par la duree (1-8 h), la temperature du traitement de chromisation et la densite initiale des ebauches (6.2-7.2 g cm− 3 ). Il comprend essentiellement une couche de solution solide Cr-Fe. Le type de reaction thermochimique intervenant dans le processus de depot chimique en phase vapeur depend de la teneur initiale en carbone de l'echantillon fritte (reactions de deplacement ou de reduction). L'impregnation du depot chimique en phase vapeur ameliore la densification de la surface et du cœur. Par suite, toutes les proprietes liees a la forme et a la taille des pores sont ameliorees

Journal ArticleDOI
TL;DR: The progress made with respect to equipment used in the hardmetal industry over approximately the last 50 years is reviewed in this paper, where the manufacturing areas considered range from chemical processing of the tungsten bearing ores to the final sintering of the hard metal compact.
Abstract: The progress made with respect to equipment used in the hardmetal industry over approximately the last 50 years is reviewed. The manufacturing areas considered range from chemical processing of the tungsten bearing ores to the final sintering of the hardmetal compact. PM/0223

Journal ArticleDOI
TL;DR: In this article, the microstructure of engineering material prepared from rapidly solidified atomized powder has been investigated, and the structure was found to be inhomogeneous, and six types of microstructures have been identified.
Abstract: The microstructure of engineering material prepared from rapidly solidified atomized powder has been investigated. The material was prepared by cold compaction, heating to deformation temperature, and extrusion into rod. The structure was found to be inhomogeneous, and six types of microstructures have been identified. It is concluded that most of these structures have their origin in the metal powders and therefore that attention should be given to the atomization process. Structure resulting from solid state transformations was also identified, indicating that the thermomechanical working process must also be important in the preparation of materials from the powder phase. PM/0321

Journal ArticleDOI
TL;DR: On decrit les developpements recents de la metallurgie des poudres interessant les moteurs d'avions a turbine a gaz as discussed by the authors.
Abstract: On decrit les developpements recents de la metallurgie des poudres interessant les moteurs d'avions a turbine a gaz. En particulier, les benefices potentiels et les problemes prevus lies a l'utilisation de poudres d'aluminium, de titane, d'aciers et d'alliages a base de nickel sont soulignes

Journal ArticleDOI
TL;DR: In this paper, the design and operation of equipment to generate rapidly solidified samples in batches as large as 5 kg, under closely controlled atmosphere conditions, is described, and two modes of operation are possible at present: gas atomization-substrate solidification (GASS) and crucible melt extraction (CME).
Abstract: The design and operation of equipment to generate rapidly solidified samples in batches as large as 5 kg, under closely controlled atmosphere conditions, is described. Two modes of operation are possible at present: gas atomization-substrate solidification (GASS) and crucible melt extraction (CME). Both produce particulate, the former with a flake type morphology, the latter as a discontinuous fibre. Several aluminium alloys have been processed via GASS and one of them (Al–9 wt-%Mn) has been compared to the same composition processed in air access equipment. Tin and a lead-antimony alloy have been used to demonstrate the operational characteristics of the crucible melt extraction mode. PM/0319

Journal ArticleDOI
TL;DR: A project manned by staff from a rolling mill manufacturer, Davy McKee (Sheffield) Ltd, and the Capenhurst Research Centre of the Electricity Council has produced equipment capable of demonstrating the production of strip metal from powder feedstock as mentioned in this paper.
Abstract: A project manned by staff from a rolling mill manufacturer, Davy McKee (Sheffield) Ltd, and the Capenhurst Research Centre of the Electricity Council has produced equipment capable of demonstrating the production of strip metal from powder feedstock Although this concept is not new and some production plants are in operation, new technology has been introduced in the form of glow discharge electron beam heating to heat the ‘green’ strip before hot rolling The features of the glow discharge heater which make it ideal for this particular application include high power density, rapid non-contact heating to temperatures up to 1600°C, and built-in protective atmosphere with low gas consumption The paper describes a prototype plant rated at 100 kW which handles strip widths of 50 to 100 mm and thicknesses of 0·8 to 1·5 mm at speeds of up to 20 m min−1 The complete installation has been used to produce samples of hot rolled strip in stainless steel for evaluation This process route offers savings in