New ideas on the exploitation of copper,tin, gold,and lead ores in Bronze Age Britain: The mining,smelting, and movement of metal

ABSTRACT

Over the last 25 years, new evidence has emerged of the scale of prospection for copper and its mining during the Early-Middle Bronze Age in Britain. We know of 12 mines worked in the period 2100–1600BC, whilst the largest mine on the Great Orme continued until the Late Bronze Age, with perhaps its maximum output which may have been equivalent to 30+?tons of copper metal sometime between 1500 and 1300 BC. Bronze Age copper ores represent the now missing oxidized zones of many ore deposits, the enriched ores being easier to smelt. In this respect, the reasons why the richest ores in Cornwall were apparently not worked are discussed. The earliest tin extraction in Cornwall probably occurred during the Early Bronze Age, given the evidence for smelted tin and cassiterite; yet support for the antiquity of tin mining might be provided through the dating of some of the earliest mining artifacts, such as the antler pick from the Carnon streamworks. Yet other lines of research include paleoenvironmental investigations carried out within the tin streaming areas and isotopic provenancing of the tin in Bronze Age bronze. Alluvial gold may have been extracted from the Cornish tin streams more than 4000 years ago and could have been the main source of the gold used in Ireland and Britain during the Copper-Early Bronze Ages, a theory supported by recent lead isotope work carried out on gold artifacts and sources. However, finds of gold artifacts in areas with alluvial gold suggest that one source would not have been exclusive, particularly during the later Bronze Age. Although it sometimes tends to be invisible, lead has been used in small amounts since the Early Bronze Age, first for jewelry, and then from the Middle Bronze Age as rare artifacts, and for alloying in bronze to assist in casting. The earliest silver artifact also dates to this period. The Mendips in Somerset may have been a Late Bronze Age source of lead. Various models are examined for the exploitation of metals from the Copper Age to the Late Bronze Age, looking at the status of miners, the nature of exchange, resource protection, experimentation, prospection, and the discovery of ores. It seems possible also that the rapid development of the Bronze Age in Britain owes much to the early extraction of gold in South-West England and the discovery of tin.     

Microstructure development in Nb3Sn(Ti) internal tin superconducting wire

The authors have studied the phase formation sequences in a Nb₃Sn ‘internal tin’ process superconductor. Heat treatments were performed to convert the starting materials of tin, Ti–Sn, copper and niobium, to bronze and Nb₃Sn. Specimens were quenched at different points of the heat treatment, followed by metallography to identify the phases present and X-ray microtomography (XMT) to investigate the void volume and distribution. An unexpected observation of the microstructure development was the uphill diffusion of tin during the Cu–Sn reactive diffusion. Some defects likely to affect the superconducting performance of the wires were observed. Microscopy revealed the presence of a Ti–Sn intermetallic compound displacing the niobium filaments, and XMT revealed the formation of long pores in the longitudinal direction. Two types of pore formation mechanism, in addition to Kirkendall pores, are proposed. The phase and microstructure development suggests that low-temperature heat treatment (below 415 °C) will have significant influence on optimising the final superconducting properties.     

Ultrahigh-carbon “wootz” from crucible carburization of molten iron: Hypereutectoid steel from “Tamil Nadu Process” at Mel-siruvalur

ABSTRACT

As European and Mediterranean accounts indicate, India has been famed for the production of steel, apparently made by crucible processes. Late medieval traveler’s accounts record the making of “wootz” steel in several places in southern India. This material was used for the fabled Damascus swords, which were later found to be of ultrahigh-carbon steel. Whereas studies on Asian crucible steel making from India, Central Asia and Sri Lanka have discussed various processes ranging from co-fusion of cast iron and wrought iron to solid-state carburization of wrought iron, it has been difficult to find clear evidence relating to an end product of ultrahigh-carbon steel. In this light, the archeometallurgical evidence from Mel-siruvalur in Tamil Nadu, presented in this paper, is significant in that it shows unmistakable remnants in crucibles of ultrahigh-carbon, hyper-eutectoid steel, with a likely production mechanism of molten carburization of wrought iron to steel. The favorable comparison with ultrahigh-carbon steel finds dated to early historic or megalithic times in Tamil Nadu and southern India also suggest that this method of crucible steel manufacture, which may be described as the “Tamil Nadu process”, might have been earlier or more archaic than the co-fusion process.     

Transformation studies and mechanical properties of melt-quenched amorphous titanium-silicon alloys

The formation, stability and decomposition characteristics of the amorphous phase in binary titanium-silicon alloys rapidly quenched from the molten state have been investigated. Electron microscopy and diffraction coupled with X-ray diffraction techniques suggested that the amorphous phase could be obtained in alloys containing 15 to 20 at% silicon. The transformation of the amorphous phase to the equilibrium phases took place in two stages. A metastable b c c titanium solid solution, containing silicon in excess of the equilibrium value, formed initially, followed by the precipitation of the Ti₅Si₃ intermetallic compound. Microstructural features at various stages of decomposition have been described and interpreted in terms of the constitution of the alloys. Mechanical properties of the amorphous alloys have also been investigated.     

Characteristics Study on Bi-Pb Based Alloys Quenched from Melt

Three different bismuth-lead systems namely,Wood's alloy(Bi50Pb25Sn12.5Cd12.5),Newton's alloy(Bi50Pb31.2Sn18.8) and Rose's alloy(Bi50Pb28Sn22),with one used as fusible alloys were quenched from melt by melt spinning technique.Thermal analysis,structure and mechanical properties of all alloys have been studied and analyzed.From X-ray diffraction analysis,an intermetallic compound phase,designated Pb7Bi3 is detected.The formation of an intermetallic compound phase causes a pronounced increase in the electrica...     

Glass formation adjacent to the intermetallic compounds in Cu-Zr binary system

On the contrary to the common belief that glass formation is unfeasible near terminal intermetallic compound due to fast crystallization kinetics, here we present our findings that bulk metallic glasses are readily formed near intermetallic compounds, far away from the traditional region of glass forming near eutectics. While the intermetallic compounds themselves are not possible glass formers, bulk metallic glasses can be quenched compositionally neighboring the intermetallic compounds as close as 0.5 at.%. Taking binary Cu-Zr as a model system, the phenomenon of two optimum glass forming compositions sandwiching the corresponding intermetallic compounds (Cu₅₁Zr₁₄, Cu₁₀Zr₇, CuZr, CuZr₂ and Cu₈Zr₃) is observed consistently. This new scenario of “intermetallic glass” is verified by the thermodynamic principle that the alloy liquids neighboring the intermetallic compounds possess lower Gibbs free energy than that of the compounds themselves. Furthermore, the sluggish crystallization behavior of these liquids provides an additional kinetic explanation.     

Characterizing the formation and growth of intermetallic compound in the solder joint

A solder/intermetallic layers/copper joint assembly was prepared by the dipping process and then aged thermally for an accelerating aging test. The phase transformation of the assembly was compared to the phase diagram of binary alloy, Cu–Sn, and it showed an agreement with the resultant intermetallic phases formed between the pure tin and pure copper. Two theoretical models proposed by Gösele and Shatynski were developed and then employed to characterize the assembly. The Gosele's model was used to predict whether the intermetallic layers grew or shrank during aging, while the Shatynski's model was employed to estimate the related reactive thicknesses and hence the ratios of the interdiffusivities in the joint assembly. After a series of calculations, the Gösele's model predicted that Cu6Sn5 and Cu3Sn intermetallic layers became thicker; the orders of the intermetallic interdiffusivities were also proven to approach theoretical values from the Shatynski's model.     

Experiments on interaction of liquid tin with solid copper

Abstract

The reaction of liquid tin with solid copper has been studied by heating small volumes ofpure tin on copper coupons at various temperatures and times, and evaluating the resulting reaction metallographically. Three reaction temperatures were used:260,400,and450 ° C. Specimen geometry was chosento simulate a typical solder joint. The reaction was observed to occur in two stages: an initial fast stage with copper/liquid tin interface movement rates from 0.2 μm s^-1 at260 ° C to 0.8 μm s^-1 at 450 ° C, followed by a much slower stage. It was concluded that the first stage corresponds to direct dissolution of copper in liquid tin up to or beyond the liquidus concentration for the reaction temperature used.This is followed by the formation of an intermetallic compound layer atthe copper/liquid interface. Subsequent copper dissolution then occurs by solid state diffusion through the compound layer, a much slower process than direct dissolution.     

A systematic investigation of the Mössbauer parameters of some intermetallic compounds and electroplated alloys of tin

The Mössbauer parameters of specific intermetallic binary compounds of tin are reported, together with those of electroplated tin-nickel, tin-copper and tin-cobalt alloys. These are interpreted on the basis of the band theory previously proposed (et al., [24]). In addition a tentative correlation between the observed parameters and the known properties of electroplates is proposed.     

Evolution behavior of δ phase in Cu12Sn2Ni alloy and the corresponding effects on alloy property

With the increase of tin content in tin bronze, the rise of δ phase made the strength, hardness of tin bronze increase and the ductility decrease sharply, that difficult to process. In this paper, the Cu12Sn2Ni alloy was prepared by centrifugal casting, the microstructure and phase formation before and after heat treatment were observed by x-ray diffraction, scanning electron microscope, and transmission electron microscope. The results showed that the as-cast sample microstructure was composed of equiaxed grains rather than coarse dendrites. centrifugal casting inhibits tin diffusion to form metastable phase β′-Cu_13.7Sn. The as-cast sample had good deformability and its tensile strength and elongation were 381.9 MPa and 12.4 %, respectively, which are higher than the mechanical properties of gravity casting. The tensile strength and elongation of the sample after furnace cooling at 620 °C/8 min are 439.5 MPa and 24.4 %, respectively, the increase was 16.6 % and 85.07 %, compared with the as-cast samples, due to the solid solution strengthening, the second phase strengthening and the homogenization of the microstructure.     

Particle break-up during heat treatment of 3000 series aluminium alloys

Abstract

In wrought aluminium alloys, the fragmentation of coarse, iron bearing intermetallic particles by hot rolling is an important development in industrial processing. Here a model 3000 series alloy is used to show that fragmentation can occur prior to hot rolling, during the homogenisation heat treatment. Some fragmented particles display a curved morphology of break-up that results from matrix wetting of two phase (or 'duplex') interfaces in Al₆(Fe,Mn) particles partially transformed to an α-Al–(Fe,Mn)–Si phase. In contrast, samples rapidly heated to temperature in a fluidised bath show an angular break-up indicative of tensile stresses induced by thermal expansion mismatch between the intermetallic particles and aluminium matrix. Although this break-up should not be industrially significant, the transformation induced break-up by wetting may be. More generally, internal boundaries resulting from the transformation to α-Al–(Fe,Mn)–Si phase may be mechanically weak fracture initiation points during hot rolling.     

Comparative Thermodynamic Analysis of Nanocrystalline and Amorphous Phase Formation in Nb/Al and Nb/Sn Systems During Mechanical Alloying

Elemental powders of niobium–tin and niobium–aluminum were mechanically alloyed by Spex ball mill, respectively, in order to fabricate disordered nanocrystalline Nb₃Sn and Nb₃Al. The solid solution phase transitions of MA powders before and after heat treatment were characterized using X-ray diffraction (XRD) analysis. The microstructural analysis was performed using scanning electron microscopy (SEM). Results showed that mechanical alloying (MA) of Nb₇₅Sn₂₅ for 28 h led to the formation of the Nb₃Sn intermetallic phase, while mechanical alloying of Nb₇₅Al₂₅ until 41 h did not show formation of the intermetallic phase. A thermodynamic analysis was performed based on the semiempirical theory of Miedema. The theory’s results showed that the intermetallic phase has a minimum Gibbs free energy compared to solid solution and amorphous states in both systems. Therefore, the most stable phase is intermetallic compound. But in case of the Nb/Al, the Nb₃Al intermetallic compound was not formed during milling and needs heat treatment.     

Hard magnetic phase in rapidly quenched Zr-Co-B alloys

In order to identify a hard magnetic phase in rapidly quenched Zr-Co-B alloys and clarify its magnetic properties, Zr-Co-B ribbons, Zr-Co ribbons, and Zr-Co ingots were studied. The hard magnetic phase is interpreted as a Zr₂Co₁₁ intermetallic compound. This compound has a Curie temperature of 500°C and uniaxial magnetic anisotropy with an anisotropy field of 34 kOe. The magnetization of this compound was estimated to be 67 emu/g at 15 kOe. In addition to the hard magnetic phase, the low and high T_c phases appear in both binary and ternary alloys. The low T_c phase is FCC Zr₆Co₂₃ with T_c=180°C. The magnetization of Zr₆Co₂₃ was estimated to be 44 emu/g at 15 kOe. The high T_c phase is cobalt including a small amount of zirconium. In Zr-Co-B alloys, suitable boron addition is shown to enhance the coercive force. On the other hand, the addition increases the magnetization. While the boron addition produces cobalt, it reduces Zr₆Co₂₃ or quenches its ferromagnetism     

Initiation of voiding at second-phase particles in a quaternary Al–Li alloy

Abstract

The intermetallic phases within an as-cast and rolled Al–Li–Cu–Mg alloy have been characterized using quantitative X-ray microanalysis and back-scattered electron imaging. An Al–Cu–Mg eutectic and an Al/Cu-rich intermetallic resembling A1₆( Fe, Cu) are the principal constituents of the as-cast alloy. During homogenization and fabrication, the eutectic dissolves but the iron-rich phase is broken up into stringers which lie along the high-angle grain boundaries. Void initiation at the particles during deformation of the wrought material has been observed and quantified. Voids nucleate following either particle cracking or particle/matrix decohesion. Evidence for particle cracking caused by coplanar slip band impingement is presented based on electron microscopical observations of specimens deformed conventionally and in situ.

MST/569     

Characteristics on Bi-Pb Based Alloys Quenched from Melt

Three different bismuth-lead systems namely, Wood's alloy (Bi50Pb25Sn12.5Cd12.5), Newton's alloy (Bi50Pb31.2Sn18.8) and Rose's alloy (Bi50Pb28Sn22), with one used as fusible alloys were quenched from melt by melt spinning technique. Thermal analysis, structure and mechanical properties of all alloys have been studied and analyzed. From X-ray diffraction analysis, an intermetallic compound phase, designated Pb7Bi3 is detected. The formation of an intermetallic compound phase causes a pronounced increase in the electrical resistivity. The Wood's alloy containing-cadmium exhibits mechanical properties superior to both the Newton's and Rose's alloys. The presence of cadmium in Wood's alloy decreases its melting point. Wood's alloy has better properties, which make it useful in various applications such as in protection shields for radiotherapy, locking of mechanical devices and welding at low temperature.     

Unalloyed copper inclusions in ancient bronze artefacts

Ancient bronze artifacts, that represent a considerable part of the archeological finds, have been largely studied because of their complex degradation phenomena taking place in the long time span that have not been fully understood. One of the peculiar features of ancient bronzes is the presence of inclusions of copper unalloyed with tin. Unalloyed Copper Inclusions (UCI) have been observed in buried archaeological bronze artefacts by several authors, but each paper reports only on a limited number of cases. In our extensive studies on bronze artefacts, UCI have been observed in many bronze artefacts with very different features and purposes. Both as-cast and wrought artefacts were studied, so that the influence of the manufacturing process and the composition of the artefacts on the formation of UCI might be evaluated. The microstructure and composition of these artefacts were studied and the features of UCI have been related with those of the surrounding phases. The results have been discussed and compared with those obtained by other authors. The presence of UCI in buried archaeological bronze artefacts could indicate some unusual corrosion processes that might need to be accounted for when designing conservation treatments.     

Influence of third elements on growth of Nb3Sn compounds and on global pinning force

The crystal growth of Nb₃Sn by the bronze method has been investigated by using diffusion couples consisting of niobium and bronze with the addition of third elements. When the specimens were annealed at temperatures between 973 and 1073 K, the time-dependence of layer thickness was represented approximately by the function ofd=kt ^m . The time exponent changed from 1/3 to unity depending on the annealing condition as well as on the nature of the third element. By the addition of titanium, hafnium, zirconium, indium and galium to the bronze, the growth rate of the compound layer increases. Faster layer growth corresponds to a larger time exponent. The following three processes are suggested to be important for controlling layer growth: diffusivity of tin atoms through grain boundaries in the compound layer, diffusivity of tin atoms through the matrix of the compound, and the rate of the chemical reaction to form the compound. Essentially these combined processes control the overall rate of layer growth. The grain size is found to be the most effective structural parameter to affect directly the maximum global pinning force. The critical current at a magnetic field of 5T can be scaled by both the layer thickness and the inverse grain size.     

Microstructure and kinetic analysis of the properties and behavior of nickel (Ni) nano-particle doped tin–zinc–bismuth (Sn–8Zn–3Bi) solders on immersion silver (Ag)-plated copper (Cu) substrates

In order to identify the effect on the properties and behavior of tin–zinc–bismuth (Sn-8 wt% Zn-3 wt% Bi or Sn-13.6 at.% Zn-1.6 at.% Bi) based solders produced by adding nickel (Ni) nano-particles, the interfacial microstructure between plain and composite solders with newly developed immersion silver (Ag) plated copper (Cu) substrates has been investigated as a function of reaction time, at various temperatures. For plain Sn–8Zn–3Bi solder joints, a scallop-shaped Cu–Zn–Ag intermetallic compound layer was found to adhere to the surface of the immersion Ag-plated Cu substrate. However, after addition of Ni nano-particles into the Sn–8Zn–3Bi solder, Cu–Zn–Ag (at the bottom) and (Cu, Ni)–Zn (at the top) intermetallic compound layers were observed at the interfaces. In addition, these intermetallic compound layer thicknesses increased substantially with increases in the temperature and reaction time. In the solder ball region, needle-shaped α-Zn rich phase and spherically-shaped Bi-particles appeared to be homogeneously distributed throughout a beta-tin (β-Sn) matrix. However, after the addition of Ni nano-particles, needle-shaped α-Zn rich phase appeared that exhibited a fine microstructure, due to the heterogeneous nucleation of the Ni nano-particles. The calculated activation energy for the Cu–Zn–Ag intermetallic compound layer for the plain Sn–8Zn–3Bi solder/immersion Ag-plated Cu system was 29.95 kJ/mol—while the activation energy for the total [Cu–Zn–Ag + (Cu, Ni)–Zn] intermetallic compound layers formed in the Sn–8Zn–3Bi–0.5Ni (Sn-13.6 at.% Zn-1.6 at.% Bi ~1 at.% Ni) composite solder/immersion Ag-plated Cu system was 27.95 kJ/mol. Addition of Ni nano-particles reduces the activation energy which enhanced the reaction rate as we know that lower the activation energy indicates faster the reaction rate.     

Microstructure of as-cast aluminium bronze containing iron

Abstract

The morphology, crystallography, and chemistry of phases present in an as-cast commercial aluminium bronze containing iron, of nominal composition (wt-%) Cu–10Al–2·5Fe (BS 1400: AB1), and the development of microstructure on cooling from elevated temperatures, have been studied using optical and electron microscopic techniques. The as-cast microstructure consists of α-phase, martensite, and iron-rich intermetallic precipitates. The α-phase is fcc copper-rich solid solution and exhibits a Widmanstätten morphology. The martensitic phase, which is derived from the high-temperature β-phase, has the 9R crystal structure. The intermetallic particles are based on Fe₃Al and have the Do₃ structure. These iron-rich particles are precipitated in the β-phase and cause a refinement of the microstructure by providing sites for the nucleation of the β-phase, to some extent, by impeding the growth of the α-phase.

MST/150     

Microstructural Features and Mechanical Properties Induced by the Spray Forming and Cold Rolling of the Cu-13.5 wt pct Sn Alloy

Copper alloys with high strength and high conductivity are an important functional material with full of potential applications. In the present investigation, a bronze with higher tin content （Cu-13.5 wt pct Sn） was prepared successfully by spray forming, the feasibility of cold roiling this alloy was investigated, and the cold roiling characteristics of this alloy have also been discussed. The results indicate that the spray-formed Cu-13.5 wt pct Sn alloy, compared with the as-cast ingot, shows a quite fine and homogeneous single-phase structure, and, therefore shows an excellent workability. It can be cold-roiled with nearly 15% reduction in the thickness per pass and the total reduction can reach 80%. The classical border between the wrought and cast alloys is shifted to considerably higher tin contents by spray forming. After proper thermo-mechanical treatment, spray-formed Cu-13.5 wt pct Sn alloy exhibits excellent comprehensive mechanical properties. Particularly, it shows a low elastic modulus （-88 GPa） and a high flow stress （over 800 MPa） after cold forming. This combination of properties is unique in the domain of metallic materials and could open new possibilities in spring technology field.