A new finite element model was developed to predict the density distribution in an Alumix 321 powder metallurgy compact. The model can predict the density distribution results of single-action compaction from 100 to 500 MPa compaction pressure. The model can also determine the amount of springback experienced by a compact upon ejection from the die at 100 and 300 MPa compaction pressure. An optical densitometry method, along with the creation of a compaction curve, was used to experimentally predict density distributions found within compacts, and found results that were consistent with both literature and finite element simulation. Further powder characterization included testing apparent density and flow rate of the powder. A literature review was also conducted and the results of which have been organized by three categories (powder type, material model, and finite element code) for easy reference by future powder researchers.

Nickel-based Superalloys are widely used in the steam turbine power generation and aerospace industries. They possess the desirable qualities of high-temperature strength, oxidation and corrosion resistance and can operate in some of the highest temperature ranges of the structural metals. The oxidation resistance of a Superalloy is achieved primarily through the formation of a dense alumina and/or chromia oxide layer(s) including spinels. This resistance has been further improved in wrought and cast alloys through the addition of reactive elements such as silicon, yttrium and lanthanum, although the exact effects of these elements have not been well defined. This project concentrated on a powder metallurgy ternary master alloy consisting of Ni-12Cr-9Fe (w/o) with additions of 6w/o aluminum, 0.5w/o Si, and 0.1w/o Y, in various combinations. Specifically, the primary goal was to produce and characterize a PM manufactured nickel-based Superalloy with minor additions of reactive elements and to assess the effectiveness of the Si and/or Y in improving the oxidation resistance. JMatPro modeling software was first used to help determine temperatures at which various events would occur in the alloys such as solutionizing and liquation temperatures. Subsequently green compacts were produced by a press (uni-axially) and sinter route to create transverse rupture strength bars (TRS bars). These bars were then thermomechanically deformed using a Gleeble tester to reduce porosity followed by a heat treatment to restore a microstructure better suited for high temperature oxidation. Sectioned TRS bars were then oxidized (static) 900?C in air for times up to 1000h and the influence of the Si/Y additions on oxidation resistance was determined via a combination of weight gain data and microstructural examination. Whereas JMatPro predicted solutionizing temperature of the compositions studied (1010°C quaternary; 1020°C quaternary + Si, respectively) these values were slightly lower than the results observed through DSC experiments (1045°C quaternary; 1065°C quaternary + Si, respectively). A w/o ?’ of approximately 25% was predicted by the modeling tool, but values of 58.3% to 61.7% were determined using a point count method. Finally, the addition of 0.5w/o Si to the quaternary Ni-Cr-Fe-Al PM system provided a measureable improvement in the oxidation resistance both in terms of thickness of oxide layer and in overall weight gain. Conversely, 0.1w/o Y provided little benefit, and was shown to be detrimental to alloys not containing Si.

The objective of this research was to design aluminum powder metallurgy (PM) alloys and processing strategies that yielded sintered products with thermal properties that rivaled those of the cast and wrought aluminum alloys traditionally employed in heat sink manufacture. Research has emphasized PM alloys within the Al-Mg-Sn system. In one sub-theme of research the general processing response of each PM alloy was investigated through a combination of sintering trials, sintered density measurements, and microstructural assessments. In a second, the thermal properties of sintered products were studied. Thermal conductivity was first determined using a calculated approach through discrete measurements of specific heat capacity, thermal diffusivity and density and subsequently verified using a transient plane source technique on larger specimens. Experimental PM alloys achieved >99% theoretical density and exhibited thermal conductivity that ranged from 179 Wm-1K-1 to 225 Wm-1K-1. Thermal performance was largely dominated by the amount of magnesium present within the aluminum grains and in turn, bulk alloy chemistry. Data confirmed that the novel PM alloys were highly competitive with even the most advanced heat sink materials such as wrought 6063 and 6061. Two methods of thermal analysis were employed in order to determine the thermal conductivity of each alloy. This first consisted of individual analysis of the specific heat capacity (Cp), thermal diffusivity (?) and density (?) as a function of temperature for each alloy. The thermal conductivity (K) was subsequently determined through the relationship: K=C_p ??. The second means of thermal analysis was a direct thermal conductivity measure using a transient plane source (TPS). The thermal diffusivity and density of samples were both found to decrease with temperature in a linear fashion. Conversely, the specific heat capacity was found to increase with temperature. The only measured thermal property that appeared to be influenced by the alloy chemistry was the thermal diffusivity (and subsequently the calculated thermal conductivity). Both means of thermal analysis showed high thermal conductivity in alloys with low concentrations of magnesium, demonstrating the significance of having alloying elements in solid solution with aluminum. Overall, several alloys were developed using a press and sinter approach that produced higher levels of thermal conductivity than conventional aluminum heat sink materials. The highest thermal conductivity was achieved by alloy Al-0.6Mg-1.5Sn with a calculated value of 225.4 Wm-1K-1. This novel aluminum PM alloy was found to exceed both wrought 6061 and 6063 (195 and 217 Wm-1K-1 respectively). Furthermore, PM alloy Al-0.6Mg-1.5Sn was found to have a significant advantage over die-cast A390 (142 Wm-1K-1).

Extensive computer predictions have been carried out by the author to study flow, addition dispersion and particle motion during central gas injection into cylindrical vessels. In conjunction with numerical computations, experiments were conducted in a 0.30 scale water model of a 150 ton steel processing ladle, using a Froude number scaling criterion. Two typical gas injection configurations (i.e., conventional central injection and C.A.S. alloy addition procedure) were investigated. / Flow visualization studies were carried out using a suspended network of silken threads, mean velocity vectors and overall flow patterns were determined by video recording techniques, while mean velocity vectors and associated turbulence level were also measured with laser doppler velocimetry. These measurements show very reasonable agreement with equivalent numerical predictions. / To simulate the subsurface motion of additions, spherical wooden balls of various densities were dropped from typical heights, and their subsurface trajectories, immersion times, etc., recorded by means of a video recorder. Frame by frame analysis of the video tapes showed trends which are in good accord with computed trajectories. / Mixing times of simulated molten additions were measured by the conductivity measurement technique. These were compared with prediction from an equivalent tracer dispersion model and excellent agreement achieved. / For industrial application, flow, particle motion, and mixing times in a 150 ton steel processing ladle have been predicted and their technological significance discussed.

The main object of this thesis is to reassess critically the nature and development of the earliest metallurgy of the Greek mainland in the Late Neolithic and Early Bronze Age periods (c. 4800 - c. 1900), both in its technological and socio-economic context. The aims of the research are thus to: 1) show whether or not the LN finds represent the beginnings of autonomous mainland metallurgy or whether they simply represent artefacts imported from contemporary neighbouring cultures involved in metalworking. Diffusionists regard the development of EBA metallurgy as some revolutionary break. Accumulating evidence should put the Greek mainlandindustries more into line with those from the Aegean; 2) show whether the LN industry was ancestral in some way to that of the EBA or if the development of the EBA industry was due to external influence; 3) make some chronological assessment of the initial progress of technological ability as well as the structure and organisation of metallic mineral acquisition. This will further provide data on the degrees of communication between communities and metalworking sites; and, 4) examine the socio-economic context which permitted the development of metallurgy. To achieve these aims it will be necessary to demonstrate the potential availability of copper, tin and other minerals and to show clearly through analytical techniques the range of technical skills known and mastered (especially smelting and alloying). Evidence on the relationship between metalwork, settlement, sources and the role of foreign influence will also be required. The first step was to compile a fully up-to-date catalogue of metal finds and evidence for metalworking. This was done from published material, museum collections in Greece and Britain, tracing artefacts referred to in publications but never fully described and obtaining information on artefacts from recent excavations and finds (until end 1986). This work had the effect of doubling the number of artefacts to come under study and justified taking a fresh look at the state of the industry, the range of types and techniques, and, through them, the evidence for foreign or internal relations. This was a necessary preliminary to the analytical study and the study of the contexts of the metals. No single typological study had been devoted specifically to the LN and EBA material and so one was made, devising at the same time a standard typology and comparing previous classification systems. The typological affinities of the artefacts from every sub-phase of the LN-EBA period were then studied and discussed. This study brought out the range of local types, the continuity of some types from the LN to the EBA and the evidence of foreign influence. The next task was to demonstrate that this large collection of metals could have been produced from local sources, the geological evidence for metallic minerals in Greece was reviewed and a visit was made to one of the richest mineral areas in Greece to assess the types of deposits with which we were dealing. It was demonstrated that the copper, arsenic, gold, silver and lead supplies of the mainland were more than adequate to meet the needs of the local industries in the LN and EBA. Tin was not locally availably and so an extensive review of all possible sources was carried out and two potential supply areas were designated -Yugoslavia and north west Anatolia. The analytical programme presented the chemical and lead-isotope results of over seventy mainland artefacts, attempting to interpret these results for both the technological and chronological information which they could give, formed the main part of the programme. The actual analyses were carried out, in the main, by Dr N H Gale (Oxford). To assist the interpretation of the results a review was made of the metallurgical processes used in the manufacture of copper, arsenical copper, tin bronze, lead, silver and gold. The historical background of the metal technology of the Old World was reviewed, in particular the beginnings of melting, smelting and the origins and development of alloying,in order to provide a reference with which to compare the status of the Greek mainland metallurgical industries. A brief review of the analytical techniques used then led to a full interpretation of the results themselves. The results of the lead-isotope programme demonstrated that several sources were used by both the LN and EBA metallurgies three sources were used in the LN and EBA periods - so there was some continuity of tradition. A new source was identified in the lead-isotope diagrams, though it was not geographically located. This source was used only by mainland communities and, on present evidence, it is highly likely that it is a local source. The chemical results for the mainland artefacts demonstrated that all the main techniques current in the Aegean were known and practiced on the mainland. These include smelting, alloying with arsenic tin and even lead, casting in single and double moulds, cupelling silver from lead and smelting lead as well as working gold. The Greek LN metal industry was not simply an offshoot of the Balkan industries and the EBA industry was in no way backward compared with the other industries of the Aegean. Over 200 chemical results mainly from the EBA Aegean were computed in order to obtain some new information regarding the status of the mainland industry and also to attempt a new approach to provenancing. All the computing work was carried out by Dr M Pollard (Oxford). First of all, the character of the mainland industry was assessed and then it was compared, using various computer techniques, with the industries of the Troad, the Cyclades and Crete. The result was that the mainland industry was basically quite distinct from the other three industries, though it did share several common techniques (or possibly sources) with other areas in the Aegean. Provenancing metals by chemical analyses has had little success in the past and so an attempt was made to utilise the vast bulk of chemical results available for the Aegean by devising a new approach to provenancing, employing the results themselves, lead isotope results (where available), computer cluster dendrograms and typological information, While the approach does not claim to be a general panacea for provenancing problems it did, when applied, offer a few insights into the problem and will become more effective when more lead-isotope data becomes available One of the advantages of the approach is that it provides a much needed check on the lead-isotope technique. A study of the temporal, spatial and socio-economic context of metals and the evidence for metalworking during the LN and EBA periods was quite revealing. The dating of artefacts showed that there were two main periods of increased metallurgical activity -the LN and the EBA II. Metalworking started in northern and southern Greece at roughly the same time, though there is more evidence for metals in northern Greece during the LN and in central and south west Greece during the EBA II and III. The relative distribution of different types of metals demonstrated that copper was always the main metal used, though lead and silver were restricted to southern Greece and gold was found mainly in northern Greece. The distribution of different types showed that weapons were most often found in central Greece, tools in northern Greece and tools and jewellery in southern Greece. Both artefacts and the evidence for metalworking tended always to be located on land routes or close to the sea. Most of the finds come from settlement sites, with grave finds being important only in central Greece.

No description available.

No description available.

No description available.

Homogenization of alloying elements is desired during sintering of powder metallurgy components. The redistribution processes such as penetration of liquid phase into the interparticle/grain boundaries of solid particles and subsequent solid-state  diffusion of alloy element(s) in the base powder, are important for the effective homogenization of alloy element(s) during liquid phase sintering of the mixed powders. The aim of this study is to increase the understanding of alloy element redistribution processes and their effect on the dimensional properties of the compact by means of numerical and experimental techniques. The phase field model coupled with Navier-Stokes equations is used for the simulations of dynamic wetting of millimeter- and micrometer-sized metal drops and liquid phase penetration into interparticle boundaries. The simulations of solid particle rearrangement under the action of capillary forces exerted by the liquid phase are carried out by using the equilibrium equation for a linear elastic material. Thermodynamic and kinetic calculations are performed to predict the phase diagram and the diffusion distances respectively. The test materials used for the experimental studies are three different powder mixes; Fe-2%Cu, Fe-2%Cu-0.5%C, and Fe-2%(Cu-2%Ni-1.5%Si)-0.5%C. Light optical microscopy, energy dispersive X-ray spectroscopy and dilatometry are used to study the microstructure, kinetics of the liquid phase penetration, solid-state diffusion of the Cu, and the dimensional changes during sintering. The wetting simulations are verified by matching the spreading experiments of millimeter-sized metal drops and it is observed that wetting kinetics is much faster for a micrometer-sized drop compared to the millimeter-sized drop. The simulations predicted the liquid phase penetration kinetics and the motion of solid particles during the primary rearrangement stage of liquid phase sintering in agreement with the analytical model. Microscopy revealed that the C addition delayed the penetration of the Cu rich liquid phase into interparticle/grain boundaries of Fe particles, especially into the grain boundaries of large Fe particles, and consequently the Cu diffusion in Fe is also delayed. We propose that the relatively lower magnitude of the sudden volumetric expansion in the master alloy system could be due to the continuous melting of liquid forming master alloy particles. / <p>QC 20140515</p>

Aspects of early Greek extractive iron metallurgy are investigated here, for the first time, with particular emphasis on Macedonia, Greece's most metals-rich province. The subject is approached experimentally by considering equally the ores, slag and artefacts of iron in Macedonia, through the analytical examination of archaeological slag and artefacts, the experimental smelting of Macedonian ores and subsequent analytical investigation of the slag and blooms produced. The mineral resources geology of Macedonia is presented. The historical background to mining and metal working in Macedonia from the Early Iron Age (tenth century BC) to the turn of the present century is documented. The literature on the introduction of iron into Greece, and the East Mediterranean more generally, is critically reviewed, and in the light of results obtained, especially from Thasos, it is argued that the origins of iron making in Macedonia, if not elsewhere in Greece, should be sought locally during the Late Bronze Age. Despite the absence of excavated furnace remains, it has been possible, through analytical examination of metallurgical waste, to trace the operation of the bloomery in Macedonia continuously for nearly thirty centuries. That a considerable variety of iron ores were exploited was elucidated by the analysis of slag inclusions in a large number of iron artefacts from Vergina and from sites on Thasos and the East Macedonian Mainland, spanning chronologically the Early Iron Age to the Byzantine period. The titanium-rich magnetite sands on Thasos and at Vrontou on the Mainland were shown to have been worked from the Hellenistic/Roman to the turn of this century. A second century BC nickel-rich bloom found at the Hellenistic site at Petres in West Macedonia testified, for the first time, to the smelting of nickel-rich iron laterites in Greece, while the manganese-rich iron deposits in Palaia Kavala district were worked for their precious metals content, probably during Ottoman times and perhaps as early as the Classical period. It is suggested that the Skapte Hyle of the classical texts may be located in the Palaia Kavala district. A fresh appraisal of the depiction of furnaces on Black and Red Figure Attic vases of the sixth and fifth centuries BC suggests that the bloomery process may have developed at that time to a level not previously suspected. The classical texts, the function of the cauldron on the furnace top and experimental meltings carried out in the process of this work all point to the production of wrought iron/steel through the decarburisation of high carbon iron in a fining hearth. It is argued that the furnaces depicted on the vases are themselves fining hearths, the cauldron sealing the furnace top in order for the air blast to be directed over the molten mass.