Search Documents

By S. K. Murphy, S. M. Spottiswoode, A. M. Milev, D. Geyser

A portable, stand-alone instrument especially designed for recording strong ground motion was used in this study to create a large database of peak particle velocities measured underground. A total number of 39 sites located in stopes mining Carbon Leader and Ventersdorp Contact Reefs were investigated. Peak particle velocities whith values up to 3 m/s were recorded at some sites. The data recorded on the skin of the excavations were compared to the data recorded by the mine seismic networks to determine the site response. The maximum site response was obtained for source radii of between 5 m and 30 m and events locating within 200 m of the site. The extreme values of peak particle velocities were obtained in cases were the face-area lay within the source radius. Un instrument portable unique spécifiquement conçu pour enregistrer les mouvements dynamiques des terrains, a été utilisé dans cette étude pour créer une base de données importante sur la vélocité maximum des particules, mesurée en souterrain. Un nombre total de 39 sites situés dans les excavations exploitant les récifs appelés ‘Carbon Leader et Ventersdorp Contact Reefs’, a été investigué. Une vélocité maximale avec des valeurs allant jusqu’ à 3 m/s a été enregistrée sur certains sites. Les données enregistrées sur le bord de l’excavation ont été comparées aux données enregistrées par les réseaux séismiques de la mine pour déterminer la réponse du site. La réponse maximum du site a été obtenue pour des sources de rayons entre 5 m et 30 m et des évènements situés dans les 200 m du site. Les valeurs extrêmes de vélocités maximales ont été obtenues pour les cas où la zone de face se trouve à l’intérieur du rayon de la source. Ein mobiles, alleinstehendes Instrument, speziell entworfen um starke Formationsbewegungen aufzuzeichnen, wurde in dieser Studie verwendet um eine große Datenbank von Partikelspitzengeschwindigkeiten, die Untertage gemessen wurden, aufzuzeichnen. Eine Gesamtanzahl von 39 Aufstellungsorten in den Schichtabbauorten vom Carbon Leader und Ventersdorp Contact Reef wurden untersucht. Partikelspitzengeschwindigkeiten mit Werten bis zu 3 m/s wurden an einigen Standorten aufgezeichnet Die an der Oberfläche des Grubenraumes aufgezeichneten Daten wurden mit jenen Daten verglichen, die vom seismischen Netzwerk der Grube notiert wurden, um die örtliche Reaktion des Standortes zu bestimmen. Die maximale Standortreaktion wurde für Ursprungsradien von zwischen 5 m und 30 m erhalten und Ereignissen die sich innerhalb von 200 m vom Standort befanden. Die extremen Werte der Partikelhöchstgeschwindigkeiten wurdenin jenen Fällen erreicht wo sich der Abbaubereich innerhalb des Ursprungsradiuses befand.

Jan 1, 2003

By R. Webster

"Daniel Krige’s influence on soil science, and on soil survey in particular, has been profound. From the 1920s onwards soil surveyors made their maps by classifying the soils and drawing boundaries between the classes they recognized. By the 1960s many influential pedologists were convinced that if one knew to which class of soil a site belonged then one would be able to predict the soil’s properties there. At the same time, engineers began to realize that prediction from such maps was essentially a statistical matter and to apply classical sampling theory. Such methods, though sound, proved inefficient because they failed to take account of the spatial dependence within the classes.Matters changed dramatically in the 1970s when soil scientists learned of the work of Daniel Krige and Georges Matheron’s theory of regionalized variables. Statistical pedologists (pedometricians) first linked R.A. Fisher’s analysis of variance to regionalized variables via spatial hierarchical designs to estimate spatial components of variance. They then applied the mainstream geostatistical methods of spatial analysis and kriging to map plant nutrients, trace elements, pollutants, salt, and agricultural pests in soil, which has led to advances in modern precision agriculture. They were among the first Earth scientists to use nonlinear statistical estimation for modelling variograms and to make the programmed algorithms publicly available. More recently, pedometricians have turned to likelihood methods, specifically residual maximum likelihood (REML), to combine fixed effects, such as trend and external variables, with spatially correlated variables in linear mixed models for spatial prediction. They have also explored non stationary variances with wavelets and by spectral tempering, although it is not clear how the results should be used for prediction. This paper illustrates the most significant advances, with results from research projects."

Jan 1, 2015

By D. J. H. Walker, W. H. Gibson

The inclination of any pit wall composed of stacks of benches is limited by the overall quality and structural complexity of the rock mass in which the slope is situated. For a bench stack angle that satisfies the stability criteria, various combinations of bench height, bench face angle and berm width can be used in the slope design. The bench face angle and berm width geometries must be chosen to fit the bench stack angle but must provide a berm that will be capable of catching the volume of failed wedge material from the bench faces above. Other considerations for bench height and berm width are equipment size, ore selectivity and blasting design. This paper studies the effects of different slope configurations on slope performance as it relates to wedge stability, volume of rock safely contained on berms, and rockfall. Optimisation of the geometry is carried out based on the need to minimise the volume of failed material which limits the effectiveness of the berm. This will reduce the number of rocks that can continue to fall further, reaching geotechnical safety berms or pit ramps, that put safety of personnel and equipment at risk. For general study it is most effective to investigate and compare the performances of each of a wide range of geometrical combinations of bench height, bench face angles and berm widths that fit a variety of different bench stack angles. These analyses were conducted for a predetermined bench stack height and three different bench stack angles.

Jan 1, 2006

By G. Coetzer

During galena flotation of Rosh Pinah milled material, metal ions and salts contents of various water resources (deionized, simulated circulated, lead concentrate thickener, lead tailing thickener and borehole) influenced mineral recoveries, upgrade ratios, selectivities, froth stability and flotation kinetics. The various water resources employed during galena flotation caused activation, depression or selectivity effects on minerals due to the presence of different ions in solution. Metal ions in these water resources were adsorbed by the ore, whilst ions associated with gangue minerals (dolomite and quartz) were released into the flotation pulp. Lead concentrate thickener water caused depression of sphalerite and pyrite, increased fast floating fractions for silver, copper minerals, sphalerite and quartz (unwanted), and improved slow floating rate selectivity against pyrite and sphalerite. Lead tailing thickener water enhanced sphalerite recovery during galena flotation (unwanted), and increased fast floating fractions of pyrite. Western borehole water did not affect galena recovery, but sphalerite and pyrite recoveries were unacceptably too high. Ions from copper, lead, and zinc salts tended to release high amounts of ions, such as calcium, magnesium, silicon, and manganese from gangue minerals (dolomite and quartz) during milling. During galena flotation, lead ions depressed sphalerite, pyrite and dolomite at a lead concentration of 400 ppm, but sphalerite was activated at a concentration of 800 ppm. Sphalerite was activated with copper ions (89% recovery, 2.09 upgrade ratio) and depressed with zinc ions (maximum recovery of 25%). This corresponds with findings in previous investigations. Dolomite and quartz were slightly activated with zinc ions. No evidence was found that lead and copper ions activated any gangue minerals during galena flotation. Keywords: galena, water resources, metal ions, activation, depression, selectivity.

Jan 1, 2003

By R A. Lynch, D A. Malovichko

The implementation of routine real-time micro-seismic monitoring of open pit mine slopes has been discussed. Some examples of seismic arrays have been given, and a recommendation of suitable seismic sensors made. Unfortunately near-surface sensors are required for good location accuracy, and the effects of reflection, mode conversion and surface waves must be accepted and compensated for during processing of the seismograms. It makes sense that mining at the base of a slope and levels of seismic activity within the slope should be related, and this is confirmed using both 2002-2003 and 2005 seismic data recorded at Navachab mine. An example of how seismic data can be used to gain information about seismically active geological structures has been described. The removal of broken rock, and not blasting nor the breaking of supporting rock, has been found to cause slope micro-seismicity. While the standard Brune source model is suitable for some 20% of the seismic events, unreasonable results are obtained for the rest. A moment tensor inversion has been performed after S-wave splitting and surface effects have been filtered out. This approach confirms a predominantly shear mechanism for a typical high frequency source.

Jan 1, 2006

Power Point Presentation

Jan 1, 2007

By J. Utt

Recent developments in circulating fluidized bed (CFB) once-through supercritical technology (OTSC) have enabled this technology to be offered as a utility-scale alternative competing head-to-head with pulverized fuel (PF) OTSC offerings. One clear example is the CFB supercritical unit at the Lagisza Power Plant in Poland, owned by PoludniowyKoncernEnergetyczny SA (PKE). This unit has now been in commercial operation for three full years, exhibiting very good performance, and has validated Foster Wheeler?s performance model at this utility scale as well as for units in the 600 MWe and 800 MWe size ranges offering net efficiency of ~43 per cent (LHV basis). This operating unit has also proven the use of the world?s first FW/BENSON? vertical-tube OTSC low mass flux technology. Since the Lagisza original international tender specified OTSC PF technology, it is important to note that the alternative selection of CFB OTSC technology over conventional PF technology is of historic significance, not only for the validation of the CFB supercritical platform as a viable alternative to conventional PF technology, but it also positions the CFB OTSC with fuel flexibility for offering of sizes up to and including 800 MWe units. This paper explores the differences between CFB OTSC technology and standard PF OTSC in utility power generation. Selection criteria, fuel burning range in both technologies, and other selection drivers are discussed. Economic analysis of both technologies, based on existing cases, is also provided. Also discussed are the technical advantages and uses of each technology. Foster Wheeler has recently been awarded a contract for four units of CFB OTSC technology, which utilizes a 2 on 1 configuration of two 550 MWe CFB OTSC boilers on two single 1000 MWe turbines. Essentially this provides a fuel-flexible low-emissions alternative to a 2 × 1000 MWe solid fuel power block.

Jan 1, 2012

By J. F. Shao, G. Duveau, W. Z. Chen, O. Ozanam

In this paper, we present a sensitivity study for the numerical modelling of hydromechanical coupling around a shaft in partially saturated claystone. Two representative constitutive models have been used: an elastoplastic damage model (IDEPLML) and an elastic perfect plastic model based on the Hoek and Brown failure criterion (H&B). A series of comparative studies have been performed with respect to main parameters involved in coupling process (mechanical, hydraulic and hydric properties). The emphasis is put on the evaluation of induced plastic, damaged and failed zone due to excavation and drying process. Dans ce papier, nous présentons une étude numérique paramétrique du comportement hydromécanique couplé d’une argilite partiellement saturé, lors du creusement et de la maintenance d’un puit L’étude paramétrique porte à la fois sur le type de modèle et sur les principaux paramètres (mécaniques hydrauliques et hydriques) intervenant dans le couplage. L’accent est principalement porté sur l’évaluation des zones plastifiées autour de l’ouvrage lors de la désaturation. In unserem Beitrag geht es um eine digitale parametrische Untersuchung über das hydromechanische Verhalten eines teilweise durchtränkten Tons beim Abteufen und dem Betrieb von Schächten. Die parametrische Analyse konzentriert sich auf den Modelltypus und auf die wesentlichen bei der Verbindung wirksamen Parameter, d.h. die mechanischen, hydraulischen und hydrologischen. Der Schwerpunkt liegt auf der Bewährung der plastifizierten Bereiche des Bauwerkes während der Austrocknung.

Jan 1, 2003

By G. D. Buson

Driefontein Consolidated Limited has a proud history in the South African gold mining industry dating back to March 1945 with the formation of the West Driefontein Gold Mining Company. The reclamation gold plant at West Driefontein was originally built as a uranium recovery plant in 1970. With the collapse of the uranium oxide yellow cake market, the uranium plant was closed in 1988and successfully converted into a gold plant, recovering gold from repulped tailings dams1. The West Driefontein Reclaim plant utilized milling, leaching, conventional rotary vacuum filtration and cementation to recover the gold at a rate of 200,000 dry tons per month. The No. 1 tailings dam (at a head grade of 0.8 Au g/t) began to near the end of its life during 1996, and the next slimes dams to be treated, the No. 2tailings dam (at a lower head grade of 0.56 Au g/t) was found too marginal for reprocessing using the filtration technology. Alternate technologies were investigated, particularly the carbon-in-pulp (CIP) plant based on the Anglo-American Corporation (AAC) pump-cell technology at the Vaal Reefs Exploration and Mining Company?s East gold plant which was operating profitably at lower head grades2. The AAC pump-cell technology is based on the carousel mode of operation2. The suitability of CIP technology for the West Driefontein Reclaim plant was investigated using a pilot plant pump-cell supplied by Kemix The data gathered were utilized in sizing a full scale AAC pump-cell plant. This plant was motivated, built and commissioned on the 22nd of November 1996. Incorporating 6 eighty cubic metre AAC pump-cells. The West Driefontein Reclaim plant initially treated repulped slimes dam material. A subsequent change of feed material to current arisings (from the main gold plant) occurred in1997 in order to convert mills for waste rock treatment. Currently the reclaim plant treats a combination of current arisings and waste rock (milled at the reclaim site). The new CIP plant replaced twenty-seven rotary vacuum filters. A comparison between the filters and CIP in terms of operating costs was undertaken, as well as a performance analysis of the CIP plant to determine its flexibility in terms of variation of the throughput, pulp density, gold input, leaching efficiency prior to CIP, and the rate of carbon movement.

Jan 1, 1999

By I. A. Mwamba

Titanium sponge, which is almost pure titanium, is extremely ductile and not easily processed into titanium powder. One method of producing powder is the hydride-dehydride (HDH) process, where titanium sponge is hydrided to form brittle titanium hydride (TiH2). Titanium hydride is easily milled to produce powder and is then dehydrided to form Ti powder. In this work, titanium hydride powder obtained from titanium sponge was used as a starting material for blending and mechanical alloying with elemental powders. Firstly, titanium hydride powder was blended with aluminium elemental powder to produce a homogenized powder, which was then compacted and sintered to produce powder metallurgy compacts. Secondly, titanium hydride powder was mechanically alloyed with aluminium elemental powder and then compacted. The mechanically alloyed powder was characterized in terms of particle size distribution, morphology and microstructure. In both blending and mechanical alloying, the green compacts were characterized by assessing the green density, while the sintered compacts were characterized by their sintered density, microstructure, and hardness. The two processes have resulted in the formation of TiA13 intermetallic compound. It was established that by simple mixing and homogenizing, titanium hydride can be used as a starting material to produce powder metallurgy components in which porosity is a benefit rather than a problem, much akin to metallic foams. From the products obtained in the TiHz-Al system, it appears that titanium hydride can be used as a precursor in mechanical alloying. However, the possible formation of complex hydrides may introduce detrimental properties, and needs to be further investigated. For the production of non-porous components, it would be advisable to dehydrogenate the TiH2 powder before milling i.e. producing titanium powder by the hydride-dehydride (HDH) method. Keywords Mechanical alloying, titanium hydride, titanium aluminide and blending

Jan 1, 2011

By S. P. Pereira

The mechanized mining cycle using loaders and shuttle cars had its peak in terms of usage in the mining industry during 1950 through 1960. In Brazil, this system is still used at underground coal mines in southern Santa Catarina coal basin. With the aim of investigating the benefits of a new mining scheme using the room and pillar method for these local mines, a computational simulator model was developed in order to investigate the mining cycle. This paper presents the methodology used to develop the simulator and the results that the simulation shows regarding impact of the proposed new scheme on mining productivity.

Jan 1, 2012

By S. P. Pereira

The mechanized mining cycle using loaders and shuttle cars had it speak in terms of usage in the mining industry during 1950 through 1960. In Brazil, this system is still used at underground coal mines in southern Santa Catarina coal basin. With the aim of investigating the benefits of a new mining scheme using the room and pillar method for these local mines, a computational simulator model was developed in order to investigate the mining cycle. This paper presents the methodology used to develop the simulator and the results that the simulation shows regarding impact of the proposed new scheme on mining productivity.

Jan 1, 2012

By B. K. Loveday, N. V. Ramlall

A study was carried out to evaluate various batch flotation models for the recovery of minerals in a UG2 platinum ore. The major minerals in a UG2ore can be grouped as platinum group minerals, chromite, and siliceous gangue. This study also examined the entrainment of minerals during flotation. The models were ranked using statistical methods and an analysis of model-fit residuals. Entrainment parameters obtained from model fitting were evaluated for logic using a simple mineral-to-water ratio versus time plot. The foremost conclusion from the study was the importance of entrainment modelling. The measurement of water recovery increased the size of the data-set, and the inclusion of a simple entrainment model was statistically significant. The overall fit to the data was improved, and the entrainment model provided logical information on the recovery of gangue minerals that were not considered to be floatable.

Jan 1, 2015

By H. Yavuz

Physical modelling is one of the research tools in the understanding of the failure mechanisms and the deformations likely to be experienced by the strata during mining operations. Success of the physical models to predict the strata behaviour depends on satisfaction of the scaling requirements in modelling material used. This paper gives results from a laboratory work carried out into the factors influencing the strength and elastic properties of a physical model material to satisfy the scaling requirements determined from application of dimensional analysis to the pertinent variables affecting the deformation and failure of the underground structures. It was found that the conditions for preparing the material over its composition had a great influence on the final properties. The effect of different water quantities, sand size and mixing time upon the properties of modelling material was studied and water requirement for different proportions of sand/plaster to prepare the material was optimized. Various sand/plaster ratios of compositions were cured at three different levels of oven temperatures. Curing at low temperature produced material within the average modulus ratios ranging from 290 to 432, which are common to most rock types according to Deere?s rock classification, whilst curing at high temperature produced material within the low modulus ratios ranging from 64 to 140 depending on its composition. A combination of low and high temperature curing resulted with an increase in modulus ratio compared to high temperature curing. Curing the material at low temperature compared to other curing temperatures provided a satisfactory range of strength ratio. It has been shown that the relative amount of filler to plaster in the mix controls the frictional properties of the material and results with an increase in strength and modulus ratio of the material provided that suggested preparation and curing conditions were applied. Model material developed by curing at low temperature simulated modulus ranging from 241 to 343 and strength ratios ranging from 11.6 to14.8 of a coal mine rocks, satisfactorily.

Jan 1, 2003

By D. J. Young

Alloys used at high temperature must resist both creep and corrosion. Design for corrosion resistance is based on the formation of a slow-growing, protective oxide scale by selective oxidation of an appropriate alloy component, usually chromium or aluminium. A successful scale will exclude other corrodents, notably carbon, which can otherwise cause extremely rapid corrosion at high temperatures. Selective oxidation of an alloy component necessarily lowers the concentration of that metal in the alloy subsurface region. Under thermal cycling conditions, mechanical damage to the scale leads to renewed oxide growth and accelerated alloy depletion. Eventually, a point is reached where diffusion of a corrodent into the alloy becomes competitive with the outward diffusion of alloy metal to repair the protective scale. Two examples of alloy failure by carbon attack are considered. In the steam cracking (pyrolysis) process, centrifugally cast tubes of heat-resisting alloy are exposed to a gas stream of hydrocarbon and steam, at a carbon activity of unity. Formation and repair of the surface chromia scale causes alloy depletion, Kirkendall void formation, and subsequent internal precipitation of chromium-rich carbides. Their formation makes chromia scale formation much more difficult, and generates internal stress. Eventually, the tubes fail by creep rupture. In other processes (e.g. steam reforming, heat treatment), synthesis gases are supersaturated with carbon at intermediate temperatures. Once the alloy's protective scale is breached, carbon attacks the depleted substrate. In the case of ferritic alloys, it forms a surface scale of Fe3C. As this scale thickens, the supersaturated carbon precipitates as graphite within its outer regions. The resulting volume expansion causes disintegration of the cementite in a process known as metal dusting. In the case of austenitic alloys, no metal carbide is formed. Instead, carbon dissolves in the depleted metal to diffuse inward and precipitate as graphite within the metal matrix. Again, volume expansion causes disintegration of the alloy, and metal dusting results. Dusting occurs at an extraordinarily rapid rate, and leads to failure by section loss or even penetration.

Jan 1, 2013

By T. Gerritsen, A. Matyas, F. Stober, I. Candy

This paper describes developments in ferro-nickel furnace technology, specifically improvements to cooling methods, furnace controls, and high voltage furnace operating regime. The evolution of these technologies is briefly presented, as context for describing the current state of the art that has enabled ferro-nickel furnace operation at over 75 MW and specific energy consumption of less than 400 kWh/t dry ore. Examples from existing operations are used to illustrate present best practices, and potential future trends are discussed. The paper begins with an overview of the fundamental aspects of pyrometallurgical treatment of lateritic ores that drive ferro-nickel furnace design. Furnace wall cooling methods are related to the requirements resulting from specific furnace process conditions, including slag and metal compositions, as well as arc and bath power. The benefits of high productivity and low specific energy consumption resulting from high voltage (shielded-arc) operating practice are discussed, along with the furnace controls and electrical power train that enable such operation even with captive power generation.

Jan 1, 2004

By D. W. Dew

Billiton Process Research has carried out extensive research over the past four years to develop new process technology using bioleaching for extraction of copper and nickel from their sulphide concentrates. Continuous pilot scale and laboratory batch testwork has been carried out with adapted mesophile bacterial cultures at40°C?45°C, moderate thermophile cultures at 50°C?55°C and thermophile cultures at 65°C?85°C. Pilot scale work has demonstrated the commercial viability of mesophile cultures for bioleaching of secondary copper sulphide and nickel sulphide concentrates. Moderate thermophiles offer benefits in terms of reduced cooling requirements for commercial reactors and, in the case of bioleaching of nickel concentrates, some selectivity over bioleaching of pyrite. Continuous pilot scale testwork has shown that thermophiles achieve efficient bioleaching of primary copper sulphide and nickel sulphide concentrates, giving much higher recoveries than achieved by bioleaching with a mesophile or moderate thermophile culture.

Jan 1, 2000

By J. Utt

Recent developments in circulating fluidized bed (CFB) once-through supercritical technology (OTSC) have enabled this technology to be offered as a utility-scale alternative competing head-to-head with pulverized fuel (PF) OTSC offerings. One clear example is the CFB supercritical unit at the Lagisza Power Plant in Poland, owned by PoludniowyKoncernEnergetyczny SA (PKE). This unit has now been in commercial operation for three full years, exhibiting very good performance, and has validated Foster Wheeler's performance model at this utility scale as well as for units in the 600 MWe and 800 MWe size ranges offering net efficiency of -43 per cent (LHV basis). This operating unit has also proven the use of the world's first FW/BENSONTM vertical-tube OTSC low mass flux technology. Since the Lagisza original international tender specified OTSC PF technology, it is important to note that the alternative selection of CFB OTSC technology over conventional PF technology is of historic significance, not only for the validation of the CFB supercritical platform as a viable alternative to conventional PF technology, but it also positions the CFB OTSC with fuel flexibility for offering of sizes up to and including 800 MWe units. This paper explores the differences between CFB OTSC technology and standard PF OTSC in utility power generation. Selection criteria, fuel burning range in both technologies, and other selection drivers are discussed. Economic analysis of both technologies, based on existing cases, is also provided. Also discussed are the technical advantages and uses of each technology. Foster Wheeler has recently been awarded a contract for four units of CFB OTSC technology, which utilizes a 2 on 1 configuration of two 550 MWe CFB OTSC boilers on two single 1000 MWe turbines. Essentially this provides a fuel-flexible low-emissions alternative to a 2 x 1000 MWe solid fuel power block.

Jan 1, 2012

By E. Kapilashrami, S. Seetharaman

Refractory/metal interactions and associated reactions are significant during casting as they can lead to inclusion formation. High-temperature interactions between aluminosilicate refractories and molten steel were studied in the present investigation using the sessile drop method. The changes in the contact angles between molten iron with well-defined oxygen levels and substrates of silica, mullite (3Al2O3?2SiO2) as well as commercial refractories were measured in the dynamic mode. In all cases, the reaction led to slag formation. The experiments were performed under isothermal conditions at 1823 and 1873 K. A known and constant oxygen partial pressure was imposed above the iron drop, through appropriate CO-CO2-Ar mixtures. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen was imposed on to the system. When a critical level of oxygen was reached, slag started forming at the drop/substrate interface and at this stage, the contact angle dropped suddenly. Subsequent behaviour of silica and mullite was observed to be different, with SiO2showing a non-wetting behaviour. In the case of SiO2substrate, there were also deep erosions along the periphery of the drops and there was slag accumulation at the sides of the metal drop, probably due to Marangoni flow and/or SiO(g) formation. SEM and EDS analysis of the substrates revealed that the formed slag was fayalite. The thermodynamic criteria for slag formation and possible mechanisms of the reaction are discussed in the light of the experiments. Key words: silica, mullite, fayalite, corundum, slag formation, sessile drop.

Jan 1, 2004

By M. Sibanda

The diffusion of carbon in Co-5% Fe alloy was studied in a belt-type pressure system at temperatures of up to 1330°C and press loads or nominal pressures of 7 020 tons or 42±3 kbar. Under these conditions, this alloy is in the solid state. Discs of graphite and prealloyed Co-5%Fe were used to make up the diffusion couple. The diffusion coefficient increased with increasing press load due to the tendency of the low density graphite to dissolve in the metallic phase reducing the overall volume and increasing the density of the system. Furthermore, inhomogeneous plastic deformation may have promoted diffusion by creating defects in the alloy. Diffusion couples treated at atmospheric pressure exhibited graphite particles in the metal, while those treated at high pressures exhibited carbide in the form of Widmanstatten laths. Carbon analyses indicated increased carbon solubility with increasing pressure. This was confirmed from calculated high-pressure phase diagrams.

Jan 1, 2005