GB2527267A

GB2527267A - Method of producing metal

Info

Publication number: GB2527267A
Application number: GB1403090.2A
Authority: GB
Inventors: Kartik Rao; Lucy Grainger; James Deane; John Clifford; Ian Mellor
Original assignee: Metalysis Ltd
Current assignee: Metalysis Ltd
Priority date: 2014-02-21
Filing date: 2014-02-21
Publication date: 2015-12-23
Also published as: GB201403090D0

Abstract

A method of producing metal via the FFC process, comprising the steps of; (a) forming a blended feedstock powder comprising a plurality of discrete non-metallic particles and (b) Electrolytically reducing the blended feedstock powder so that the plurality of discrete non-metallic particles of the blended feedstock powder are reduced to a metallic powder comprising a plurality of discrete metallic particles. Step (a) involves providing a first non-metallic powder derived from a natural mineral or sand (ie rutile sand), the first non-metallic powder having a first overall composition, and mixing the first non-metallic powder with a second non-metallic powder having an overall composition different from the second non-metallic powder (ie ilmenite). The apparatus used may have a stainless steel cathode 20 with a carbon anode 30, located in a housing 40 which can comprise an electrolysis cell. The electrolyte 50 may comprise calcium chloride and calcium oxide. The powder may be arranged on the surface of the cathode 20.

Description

Method of Producinci Metal The invention relates to a method for producing metal, in particular a metallic powder suitable for subsequent consolidation using a selected powder metallurgy process.

Background

The present invention concerns a method for the production of a metallic powder by a process that includes the reduction of a blended feedstock powder, the blended feedstock powder formed by mixing at least two non-metallic powders comprising a plulality of non-metallic particles, such as oxide particles. As is known from the prior art, electrolytic processes may be used, for example, to reduce metal compounds or semi-metal compounds to metals, semi-metals, or partially reduced compounds, or to reduce mixtures of metal compounds to form alloys. In order to avoid repetition, unless otherwise indicated the term metal will be used in this document to encompass all such products, such as metals, semi-metals, alloys, intermetallics. The skilled person will appreciate that the term metal may, where appropriate, also include partially reduced products.

In recent years, there has been great interest in the direct production of metal by direct reduction of a solid feedstock, for example, a metal-oxide feedstock. One such direct reduction process is the Cambridge FFC®electrodecomposition process (as described in WO 99/64638). In the FF0 process, a solid compound, for example a metal oxide, is arranged in contact with a cathode in an electrolysis cell comprising a fused salt. A potential is applied between the cathode and an anode of the cell such that the compound is reduced.

In the FFC process, the potential that produces the solid compound is lower than a deposition potential for a cation from the fused salt.

Other reduction processes for reducing feedstock in the form of a cathodically connected solid metal compound have been proposed, such as the Polar® process described in WO 03/076690 and the process described in WO 03/048399.

Conventional implementations of the FF0 process and other solid-state electrolytic reduction processes typically involve the production of a feedstock in the form of a porous preform or precursor, fabricated from a sintered powder of the solid compound to be reduced. This porous preform is then painstakingly coupled to a cathode to enable the reduction to take place. Once a number of preforms have been coupled to the cathode, then the cathode can be lowered into the molten salt and the preforms can be reduced. During reduction of many metal oxides, for example titanium dioxide, the individual particles making up the preform undergo further sintering forming a solid mass of metal, which may have entrapped salt.

Solid state electroreduction processes may advantageously allow natural minerals to be reduced to metal directly, or with only minimal processing prior to reduction. The metal formed by such a direct reduction is usually impure, however, and unlikely to fall within a commercially acceptable specification. Furthermore, the variation in composition of natural minerals mined from different sources means that is difficult to consistently produce the same composition of metal by direct reduction of a natural mineral. Thus, metals produced by solid state electroreduction of natural mineral feedstocks typically require expensive additional processing to produce a saleable metallic product, e.g. by melting.

Summary of the Invention

The invention provides a method for producing metal as defined in the appended independent claims, to which reference should now be made. Preferred or advantageous features of the invention are set out in various dependent sub-claims.

Thus, a method of producing metal may comprise the steps of; (a) forming a blended feedstock powder comprising a plurality of disciete non-metallic particles by (i) providing a first non-metallic powder, the first non-metallic powder being a first mineral powder derived from a natural mineral or sand, the first non-metallic powder having a first overall composition, and (ii) mixing the first non-metallic powder with a second non-metallic powder, the second non-metallic powder having an overall composition different from the first non-metallic powder, and (b) electrolytically reducing the blended feedstock powder such that the plurality of discrete non-metallic particles of the blended feedstock powder are reduced to a metallic powder comprising a plurality of discrete metallic particles.

Individual powder particles making up the first non-metallic powder, which is a mineral powder derived from a natural mineral, for example a crushed ore or beneficiated mineral concentrate or sand, may display a wide variation in composition. Thus, considering an example in which the first non-metallic powder is a natural rutile sand, some individual powder particles making up the powder may be 100 % rutile and have a composition consisting essentially of titanium and oxygen, other powder particles may comprise titanium and oxygen and also high levels of other contaminant elements such as iron, still further powder particles may be non-rutile minerals and contain no titanium at all. There may be hundreds, or even thousands, of different particle compositions within a single batch of natural rutile sand. If the natural rutile sand was directly reduced to a metallic powder, the overall composition of the powder will be titanium-rich, but is also likely to contain high concentrations of other elements alloyed with the titanium. The overall composition of the powder may or may not have a commercially desirable composition that allows a metal formed from the powder to be of commercial value.

Even if the metallic powder formed by reduction of a natural rutile sand described in the paragraph above was of a commercially acceptable overall composition, the compositional variation between natural rutile sands from different sources, or even batches from the same source, means that it may be difficult to consistently produce a metallic product having the same composition. The same issues arise with powders derived from other natural minerals and ores.

The invention may solve problems associated with the manufacture of low cost, environmentally friendly, metal powders and products by providing that a non-metallic powder derived from a natural mineral or sand may be blended with one or more further non-metallic powders to provide a blended feedstock powder. The blended feedstock powder may be then directly reduced to form a metallic powder. Preferably the metallic powder has a pre-determined overall composition. The first non-metallic powder may be blended with one or more further non-metallic powders, any of which may be derived from a natural mineral or sand, to produce a blended feedstock powder having a predetermined overall composition, the pre-determined overall composition of the blended feedstock powder being such that it may be reduced directly to a metallic powder of a pre-determined overall composition. The method may include a step of determining an overall composition of the first and/or second non-metallic powders, and/or any further non-metallic powders included in the blend. For example, the overall composition of the first non-metallic powder may be determined, and then the first non-metallic powder may be blended with one or more further non-metallic powders of known composition to provide a blended feedstock powder of pre-determined composition. In a further example, all the non-metallic powders may be of known composition, and the powders may be blended in specific ratios to provide a powder of pre-determined overall composition.

The blended feedstock powder may be electrolytically reduced such that the plurality of discrete non-metallic particles of the blended feedstock powder transform into a metallic powder comprising a plurality of discrete metallic particles. Each particle of the blended feedstock powder may be reduced to a corresponding particle of the first metallic powder -that is the chemical composition is essentially the same.

Despite the potentially large variation in the composition of individual non-metallic powder particles, the first non-metallic powder, the second non-metallic powder, and any further non-metallic powder, may be each classified by an overall composition. An overall composition may also be termed an average composition, and is representative of the composition of the non-metallic powder as a whole. The overall composition, or average composition, of the blended feedstock powder and the reduced metallic powder are likewise representative of the composition of each respective powder as a whole.

By mixing the first non-metallic powder and the second non-metallic powder it is possible to form a blended non-metallic powder that has a different overall composition to the first or second non-metallic powder. The mixing ratio of the first non-metallic powder to the second non-metallic powder may be controlled to provide a blended feedstock powder having a desired overall composition.

The skilled person will be aware of the many different ways in which an overall composition, or average composition, of a bulk powder material may be determined. \Mien forming a blended powder from two or more constituent powders the most important factor is that the overall composition of the constituent powders and the resulting blended powder are comparable. Thus, it is preferred that the analysis methods used to determine the overall composition of the blended powder and the constituent powders are, where possible, the same. The selection of the actual analysis technique used will depend on various factors such as the amount of material available and the degree of accuracy required. The skilled person will be aware of the different analysis methods and protocols for determining representative overall compositions of powdered materials. The following paragraphs provide some basic information regarding chemical analysis of powdered materials in general.

It is preferable that a sample of powder that is to be used for chemical analysis to determine an overall composition is truly statistically representative of the bulk material.

Natural minerals or (mineral derived metals) at typically processed commercially on a tonne scale, that is the bulk material may comprise a mass of many thousands of kilograms.

However, it is usually only feasible to take a bulk or gross sample in the region of 1-10kg, whilst lab samples are generally of the order of 1-10 grams. Furthermore, the actual measurement sample used in the measurement equipment may be of the order of just a few milligrams.

Powders and gianulated materials may be prone to segregation processes where differences in the size, density, shape and other properties of particles of which they are composed locally enhance or deplete some regions of a bulk material with respect to some of its components. This is particularly true of free flowing (non cohesive) natural mineral sands and ores.

Consequently great care should be must be exercised throughout any sampling and analysis procedure. Various methodologies and statistical techniques are described in the literature and are well known to those skilled in the art.

The mass of the sample and the number of samples taken are preferably such that one can demonstrate that they are statistically meaningful for the material being analyses. Also the sampling procedures and the sample size reduction equipment uses should be chosen to minimise sampling errors. Sampling of powders is discussed in C.H. Murphy, Handbook of Particle Sampling and Analysis Methods (Verlag Chemie, Deerfield Beach, 1984).

The following table provides some common powder sampling methods and provides some statistical indication of their reliability. The skilled person would be able to choose a sampling method to suit their particular purpose. ASTM B215-10 is one standard that deals with practices for sampling powders.

Relative reliability * Comparison of sampling devices based on a 60:40 sand mixture *AIlen 1981 Relative Estimated -. Standard Max.

Device Advantages Disadvantages deviation (%) Sample error ______ ______________ ____________ a (%)E Cone & Good for powders with Very operator-6 81 22 7 Quartering poor flow characteristics dependent Reliable for Particle segregation Scoop homogeneous and non-and non-flowing 5.14 17.1 Sampling __________ flowing powders powders _____________ ____________ Table Able to separate large Very dependent 2 09 7 0 Sampling quantity of material upon initial feed Can reduce powder Chute sample by 50% in one Operator bias 1.01 3.4 Splitting ___________ pass ____________________ _______________ ______________ Not efficient at Spin Reliable for free-flowing handling large 0.125 0.42 Riffling powder samples __________ ______________________ samples of powder _____________ ____________ Random 0.076 0.25 variation In addition to selecting an appropriate sampling method to provide a sample lepresentative of the overall powder, the skilled person would also select an appropriate analysis method.

The following are commonly used techniques for analysing powder materials.

* Traditional "wet" chemistry techniques. Titrations, gravimetry etc relying on chemical reactions to determine the concentration of elements.

* Atomic Absorption Spectrometry (AAS). Analyses the light absorbed by elements when excited to high temperatures.

* X-Ray Fluorescence spectrometry (XRF). Analyses the fluorescence radiation an element emits when exposed to X-rays.

* Inductively Coupled Plasma, Optical Emission Spectrometry (ICP-OES).

Analysed the light emitted by elements when excited at very high temperatures in a plasma.

* Inductively Coupled Plasma, Mass Spectrometry (ICP-MS). Analyses the atomic masses of a sample that has been ionised in a plasma.

* Glow Discharge, Mass Spectrometry (GDMS). Excites the sample by applying a potential across a vacuum tube where the sample forms the cathode. The resulting ions are passed to the mass spectrometer and the elemental composition determined.

Oxygen, nitrogen, hydrogen and carbon analysis. Metal samples are melted and the resulting gasses analysed for 0, N and C. The most preferred methods for bulk powder analysis are XRF or ICP-OES techniques. In practice, however, a full analysis providing the composition of a powdered material may use several of these techniques in conjunction.

The skilled person will be aware of suitable sampling and analysis techniques. When preparing blended powders, it is preferred that the sampling and analysis techniques used to determine the overall composition of the blended powder and each of the component parts of the blended powder are comparable. The exact technique used is of less significance, and would be chosen by the skilled person depending on his requirements.

The method of producing metal may be of particular use in forming a metallic powder of consistent overall composition using a non-metallic powder that is derived from a natural mineral as the predominant feedstock. For example, the predominant component of the blended feedstock powder may be the first non-metallic powder, which is derived from a natural mineral powder, for example a crushed ore or beneficiated mineral concentrate or sand. A further proportion of the blended feedstock powder may be the second non-metallic powder. The proportion of the second non-metallic powder that is added to the first non-metallic powder may be varied in order to produce a blended feedstock powder that has a substantially similar overall composition from batch to batch, irrespective of the overall composition of the first non-metallic powder. Thus, a blended feedstock powder may be produced that has a consistent batch-to-batch composition despite natural variation in the composition of the predominant non-metallic mineral powder. Such a blended feedstock may be reduced to provide a metallic product of consistent batch-to-batch composition.

The second non-metallic powder may be a second mineral powder derived from a natural mineral, for example a crushed ore or beneficiated mineral concentrate or sand. The second non-metallic powder may alternatively be a synthetically produced or modified non-metallic powder such as a synthetic metal oxide powder.

Preferably, the step of electrolytically reducing the blended feedstock powder involves the steps of arranging a volume of the blended feedstock powder in contact with a molten salt within an electrolysis cell, the electrolysis cell comprising an anode and a cathode arranged in contact with the molten salt, and applying a potential between the anode and the cathode such that the plurality of discrete non-metallic particles of the blended feedstock powder are reduced to a metallic powder comprising a plurality of discrete metallic particles with essentially the same metallic content as the original non metallic particle.

Advantageously, the blended feedstock powder may be reduced by an electrodecomposition process, for example a process according to the FEC Cambridge process or the BHP Polar process. Some preferred methods of electrolytically reducing non-metallic powdered feedstocks are described in greater detail below.

Optionally, the first non-metallic powder may be additionally mixed with at least one further non-metallic powder in addition to the second non-metallic powder to form the blended feedstock powder. In this case, the, or each, further non-metallic powder would preferably have a different overall composition to the overall composition of the first non-metallic powder and the overall composition of the second non-metallic powder. If used, one or more of the at least one further non-metallic powders may be a powder derived from a natural mineral or sand. One or more of the at least one further non-metallic powders may be a pure metal oxide powder or a synthetically produced or modified metal oxide powder.

In some embodiments, the second non-metallic powder, or any further non-metallic powder, may be a metal oxide powder comprising oxygen and at least one metallic element selected from the list consisting of titanium, tantalum, zirconium, aluminium, vanadium, beryllium, boron, magnesium, silicon, scandium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, yttrium, zirconium, niobium, molybdenum, hafnium, tungsten, uranium, thorium and lanthanide group metals such as lanthanum, cerium, praseodymium, neodymium, and samarium. For example, the second non-metallic powder may be a synthetically produced or modified powder comprising a plurality of discrete particles of substantially uniform particle-to-particle composition.

Any mineral powder used, for example as the first non-metallic powder or the second non-metallic powder, may consist of, or comprise, one or more minerals selected from the list consisting of rutile, ilmenite, anatase, leucoxene, scheelite, loparite, perovskite, sphene, cassiterite, monazite, zircon, cobaltite, chromite, bertrandite, beryl, uranite, pitchblende, quartz, haematite, magnetite, corundum, pyrolusite, columbite, tantalite, and chrysoberyl.

Many natural sands will comprise more than one different mineral.

Preferably, the first non-metallic powder, the second non-metallic powder, and any further non-metallic powders, are mixed so as to produce a blended feedstock powder having a pre-determined overall composition. The pre-determined overall composition may be a composition specified for a particular purpose. The pre-determined overall composition may be a composition designed to be reduced to a metal product having a standard composition.

In order to facilitate the blending, the overall composition of the first non-metallic powder, the second non-metallic powder, and/or any further non-metallic powder may be measured. The measured value of overall composition may be used to determine the appropriate ratio of blending the respective powders. Wiere more than two powders are to be blended, for example 3 powders or 4 powders or even ten or more powders, the overall composition of each non-metallic powder may be measured and the appropriate mixing ratio calculated to achieve the blended metallic powder of pre-determined overall composition.

It may be particularly advantageous to use the method to produce metallic titanium powders and titanium metal products. Titanium is an allotropic element, that is it exists in more than one crystallographic form. The crystal structure of titanium at ambient temperature and pressure is close-packed hexagonal (hcp) a phase. At about 885°C, the titanium undergoes an allotropic transformation to a body-centred cubic (bcc) phase which remains stable to the melting temperature. It is common and convenient to classify commercial titanium alloys according to their crystallographic microstructure (ci, a + 3, 1) There are 5 widely recognised categories; (1) alpha alloys -which are essentially pure alpha phase & are not heat treatable, (2) alpha + beta alloys -which contain a mix of a + (typically 5-40 % I by volume) and are heat treatable to various degrees, (3) beta alloys -which are metastable and contain sufficient stabilisers to completely retain the I phase upon quenching and can be solution treated & aged to increase strength, (4) near alpha alloys -which contain limited amounts of phase, and (5) near beta alloys -which are metastable and tend to retain the j3 phase on initial cooling but precipitate secondary phases during heat treatment.

This transformation temperature from a + or from a to all 3 is known as transus temperature. Beta transus is defined as the lowest equilibrium temperature at which material is 100% 3. The 3 transus is critical in deformation processing and in heat treatment of a titanium alloy.

Some alloying elements raise the titanium alpha-to-beta transition temperature thereby increasing the temperature at which the a phase is stable (so called alpha stabilizers). Some titanium alloying elements exhibit low alpha phase solubility and readily dissolve in and stabilise the beta phase. These elements lower the transition temperature extending the stability of the I phase to lower temperatures (so called beta stabilizers). The transition and noble metals in general behave as beta stabilisers.

Elements that depress the transformation temperature can be further divided into two categories according to the mechanism by which they stabilise the crystal structure.

These are: (1) Beta phase -isomorphous elements, and (2) Beta phase -eutectoid elements. Isomorphous elements exhibit complete mutual solubility and miscibility with beta phase titanium. Eutectoid elements form eutectoid systems with titanium, with eutectoid temperatures over 100 ° C below the transformation temperature of unalloyed titanium.

Eutectoid elements have restricted solubility in beta titanium and form intermetallic compounds by eutectoid decomposition of the beta phase. Elements of the beta-eutectoid type can be further subdivided into fast and slow elements. Eutectoid decomposition of beta phase in former category can be so slow that intermetallic compound formation does not occur under noimal fabrication or operating conditions. Whereas, in fast eutectoid systems (e.g. Si & Cu) the beta phase decomposes to alpha and intermetallic compounds relatively quickly. As a result, controlled precipitation of the intermetallic compounds can be utilised to enhance the strength of titanium alloys containing appropriate concentrations of silicon or copper.

A few elements have extensive solid solubility in a and I phases and they do not strongly promote phase stability, they tend to retard the rates of transformation and are useful as strengthening agents in titanium alloys.

Common titanium alloying elements may be classified as having the following effects; Alpha phase stabilisers = Al, Ga, Ge, La, Ce, 0, N, C Beta phase (eutectoid) stabilisers = Fe, Cr, Ni, Co, Mn, Cu, U, Ag, Au, Pd, In, Pb, Si, TI, Si,

H

Beta phase (isomorphous) stabilisers = Mo, V, W, Nb, Ta, Re "Neutral" -i.e. only relatively slight stabilisation effect on either phase but tend to be predominantly alpha strengtheners = Zr, Hf, Sn, Si.

Typical ranges of alloying elements in titanium alloys, and the effect on the microstructure, may be as set out below.

Element range wt % effect on microstructure Aluminium 2-8 Alpha stabiliser Tin 2 -11 more typically 2-6 Alpha strengthener Vanadium 2-20 Beta Stabiliser Molybdenum 2-20 Beta Stabiliser Chromium 2-12 Beta Stabiliser Iron 0.01-7 Beta Stabiliser Copper 0.1-6 more typically 0-3 Beta Stabiliser Zirconium 2-8 Alpha & beta strengtheners Silicon 0.1 -1 weak beta stabiliser Improves creep resistance Manganese 0 -8 more typically 2-8 Tin 2-12 Nb 0.1-4 Ta 0.1-4 The main alloying element that promotes the alpha phase is aluminium and it is now common practice to relate the stabilising elects of the other alpha stabilisers to the equivalent amount of aluminium as proposed by Rosenberg according the foimula: Aluminium equivalent (wt%) = Al + 1/3 Sn + lI6Zr + 10(0 + C + 2N) Wherein the respective chemical symbols represent the amounts of the respective elements in weight percent based on the total weight of the alloy.

For a stable alpha alloy the Aleq should not exceed about 9 wt% otherwise other phases (e.g. Ti3X) tend to precipitate.

In the case of beta alloys a similar convention has been developed (by P. Bania, Beta Titanium Alloys in the 1990's, TMS, Warrendale, 1993) based the Molybdenum equivalent (MOeq). where the stability of the beta phase is expressed as the sum of the weighted averages of the beta stabilising elements in the alloy according the following formula; MOeq =1.OOMo+O.2BNb+O.22Ta÷O.67V÷1.43Co+1.6OCr+O.77Cu+2.90Fe +1.54Mn+1.11 Ni+0.44W-1.OOAL Wherein the respective chemical symbols represent the amounts of the respective elements in weight percent based on the total weight of the alloy.

In beta alloys aluminium is a stabilizer having a reverse effect to that of Mo and it can be substituted by gallium, carbon, germanium or boron.

Tin, Hafnium and Zirconium are known to lower the beta transus, however the effect is so weak that these elements are generally considered to be neutral additions. US Air Force Technical Report AFML-TR-75-41 however suggests that combined Sn, Hf & Zr do have a small Mo equivalent effect of 0.25.

Hence a modified form of the equation may be used in blends derived from feeds that contain appreciable amounts of zircon and cassiterite: MOeq.1.OOMo+O.28Nb+O.22Ta+O.67V+1.43Co+1.6OCr+O.77Cu÷2.9OFe+1.54Mn+1.11 Ni+ 0.44W+O.25(Sn+Zr+Hfl-1.OOAI Readily available minerals such as rutile and ilmenite are titanium bearing minerals. It would be desirable to directly reduce natural rutile powders and ilmenite powders to form titanium metal. By using the method set out herein it may be possible to produce titanium powders of an overall composition that will produce, when consolidated and thermally homogenised (i.e. diffusional homogenisation), a titanium metal having a pre-determined microstructure. For example, a blended feedstock powder may be formed having a composition such that, once reduced to metallic powder, consolidated and homogenised, (e.g. by manipulating the sintering process conditions (time & temp) to effect thermal diffusional homogenisation), a solid item of predominantly titanium composition is formed. The composition of the blended feedstock powder used as a feedstock for electrolytic reduction may be controlled to produce a specific type of titanium alloy, such as an alpha plus beta phase titanium alloy, a beta phase titanium alloy, or a near beta phase titanium alloy.

Thus, it may be preferred that the method is a method of producing a titanium alloy and the first non-metallic powder is a powder derived from a natural titanium-bearing mineral or sand, such as rutile or ilmenite. The first non-metallic powder may be mixed with the second non-metallic powder, and any further non-metallic powder, in a pre-determined proportion to produce a blended feedstock powder of pre-determined overall composition. When reduced, consolidated and homogenised, the blended feedstock powder may produce a titanium item having a pre-determined microstructure.

In preferred embodiments, the first non-metallic powder may be natural rutile, or may be derived from rutile, and the second non-metallic powder may comprise one or more non-metallic material selected from the list consisting of natural rutile, natural ilmenite, synthetic rutile, rutile slag, and synthetic titanium dioxide, the metallic powder that results after reduction being a titanium powder, or a titanium-rich powder.

In preferred embodiments, the first non-metallic powder may be synthetic rutile, or a chemically leached ilmenite, and the second non-metallic powder may comprise one or more non-metallic material selected from the list consisting of natural rutile, natural ilmenite, synthetic rutile, rutile slag, and synthetic titanium dioxide, the metallic powder that results after reduction being a titanium powder, or a titanium-rich powder.

An advantageous embodiment of the invention may be a method for producing an alpha phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended feedstock powder, reduction of the blended feedstock powder producing a metallic powder having an overall composition that is essentially titanium with between 2 and 10 wt % of elements that act as alpha stabilisers in titanium, preferably alloying elements selected from the list consisting of aluminium Ga, Ge, La, Ce, 0, N, C, and less than a total of 2 wt % more preferably less than 1.0 wt % of elements that act as beta stabilisers in titanium, preferably alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Cu, Mo, V, W, Nb, Ta, U, Ag, Au, Bi, TI, Si, & H. . The overall composition of the metallic powder may contain between 2 and 8 wt % Al, 10-4000 ppm 0, and 10-2000 ppm C. and optionally between 0.01 -18 wt % Zr, Hf, & Sn.

A further advantageous embodiment of the invention may be a method for producing an near alpha phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended feedstock powder, reduction of the blended feedstock powder producing a metallic powder having an overall composition that is essentially titanium with between 2 and 10 wt % of elements that act as alpha stabilisers in titanium, preferably alloying elements selected from the list consisting of aluminium Ga, Ge, La, Ce, 0, N, C, and between 1 and 4 more preferably 1-2 wt% of elements that act as beta stabilisers in titanium, prefelably alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Cu, Mo, V, W, Nb, Ta, U, Ag, Au, Bi, TI, Si, & H.. The overall composition of the metallic powder may contain between 2 and 8 wt % Al, 10-4000 ppm 0, and 10-2000 ppm C. and optionally between 0.001 -18 wt % Zr, Hf, & Sn.

A further advantageous embodiment of the invention may be a method for producing a beta phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended feedstock powder, reduction of the blended feedstock powder producing a metallic powder having an overall composition that is essentially titanium with a total of less than 5 and more preferably less than 4 wt % of elements that act as alpha stabilisers in titanium, preferably alloying elements selected from the list consisting of aluminium Ga, Ge, La, Ce, 0, N, C, and between 2 and 25 wt% of elements that act as beta stabilisers in titanium, preferably alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Cu, Mo, V, W, Nb, Ta, U, Ag, Au, Bi, TI, Si, & H. A further advantageous embodiment of the invention may be a method for producing a mixed alpha and beta phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended feedstock powder, reduction of the blended feedstock powder producing a metallic powder having an overall composition that is essentially titanium with a total of between 1 and 7 wt % of elements that act as alpha stabilisers in titanium, preferably alloying elements selected from the list consisting of aluminium, Ge, La, Ce, 0, N, C, between 4 and 8 wt% of elements that act as beta stabilisers in titanium, preferably alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Cu, Mo, V, W, Nb, Ta, U, Ag, Au, Bi, TI, Si, & H. , and optionally between 0.01 and 8 wt % of elements that act as alpha strengtheners in titanium, preferably alloying elements selected from the list consisting of zirconium, hafnium and tin.

Although this discussion has focused on the production of a titanium material from a blended feedstock powder comprising a naturally occurring titanium-bearing mineral, it is clear than the same considerations may apply to the formation of other metals from other feedstocks.

Advantageously the metallic powder resulting from reduction of the blended feedstock may be used in a powder metallurgy process. For example, the metallic powder may be consolidated to form a solid metallic item, for example a billet, bar, sheet or net-shape product. The metallic powder may comprise a plurality of discrete metallic particles having varied individual compositions but one overall composition, the method further comprising steps of consolidating and thermally treating the metallic powder to form a solid metallic item, the item having a substantially uniform composition that is the same as the overall composition of the metallic powder.

The metallic powder may be consolidated by processes such as cold isostatic pressing (CIP), hot isostatic pressing (HIP), vacuum hot pressing (VHP) or roll compaction I consolidation. Any solid metallic item formed may be heat treated, during or after consolidation, for example by vacuum or inert atmosphere sintering (e.g. in argon), to produce an item in which the composition is that of the overall composition of the metallic powder used to form the item.

Preferred methods of electrolytically reducing the blended feedstock powder will now be discussed. The blended feedstock powder may be used as the feedstock powder in any of the reduction methods described below.

A method for reducing a non-metallic powder (the feedstock powder), comprising a plurality of non-metallic particles, to form a metallic powder may comprise the steps of; arranging a cathode and an anode in contact with a molten salt within an electrolysis cell, arranging a volume of the feedstock powder comprising the plurality of non-metallic particles within the electrolysis cell, causing a molten salt to flow through the volume of feedstock powder, and applying a potential between the cathode and the anode such that the feedstock powder is reduced to a metal powder.

A method for reducing a non-metallic powder (the feedstock powder), comprising a plurality of non-metallic particles, to form a metallic powder may comprise the steps of; arranging a cathode and an anode in contact with a molten salt within an electrolysis cell, an upper surface of the cathode supporting the feedstock powder comprising the plurality of non-metallic particles, and a lower surface of the anode being vertically spaced from the feedstock powder and the cathode, and applying a potential between the cathode and the anode such that the feedstock powder is reduced to metal powder.

A method for reducing a non-metallic powder (the feedstock powder), comprising a plurality of non-metallic particles, to form a metallic powder may comprise the steps of; arranging a cathode and an anode in contact with a molten salt within an electrolysis cell, an upper surface of the cathode supporting a free-flowing feedstock powder comprising the plurality of discrete non-metallic particles, and a lower surface of the anode being vertically spaced from the feedstock powder and the cathode, and applying a potential between the cathode and the anode such that the feedstock powder is reduced to a plurality of discrete metal particles.

The following preferred or advantageous features may be used in conjunction with any method for reducing a non-metallic powder disclosed above. Preferred and advantageous features may be combined in any permutation or combination.

It is preferred that the feedstock powder is a free-flowing non-metallic powder comprising a plurality of separate discrete particles of non-metallic material. The use of free-flowing particles, for example free-flowing powder particles, as a feedstock powder may provide considerable advantage over prior art electro-decomposition methods that have required a powdered non-metallic feedstock to be formed into a porous perform or precursor prior to reduction. Preferably, individual particles in the feedstock powder are reduced to individual particles of metal powder. Preferably, there is substantially no alloying between separate particles. Preferably, there is substantially no sintering between adjacent feedstock particles during reduction.

Particles of powder material, and particularly particles of sand, are rarely perfect spheres. In practice individual powder particles may have different lengths, widths, and breadths. For convenience, however, powder particle sizes are usually stated as a single diameter, which is approximately correct providing the particles do not have an excessively high aspect ratio.

Powder particles may be described by a single average particle size for the purposes of this invention.

Preferably, a feedstock powder suitable for use in an embodiment of the invention substantially comprises free-flowing particles of between 40 more preferably 62.5 microns and 4 mm in diameter. Average particle size may be determined by a number of different techniques, for example by sieving, laser diffraction, dynamic light scattering, or image analysis. While the exact value of the average particle size of powder may differ slightly depending on the measurement technique used to determine the average value, in practice the values will be of the same order providing the particles do not have an excessively high aspect ratio. A particularly preferred feedstock powder may comprise a non-metallic powder having an average particle diameter of between 40-60 microns and 2 mm, preferably between 100 microns and 1.75 mm, for example between 250 microns and 1.5 mm.

It is preferred that the average particle diameter is determined by laser diffraction. For example, the average particle size could be determined by an analyser such as the Malvern Mastersizer Hydro 200DM U. It may be desirable to specify the range of particle size in a feedstock powder. A feedstock powder containing particles that vary in diameter over a wide range may pack more densely than a feedstock powder in which the majority of the particles are of substantially the same particle size. This may be due to smaller particles filling interstices between adjacent larger particles. It may be desirable that a volume of a feedstock powder has sufficient open space or voidage for a molten salt to flow freely through a bed formed by the feedstock powder during reduction. If the feedstock powder packs too densely, then the molten salt flow-path through the feedstock powder may be inhibited.

Particle size range may be determined by laser diffraction. For example, the particle size range could be determined by an analyser such as the Malvern Mastersizer Hydro 2000MU.

It may be convenient to select a feedstock powder size range by a process of sieving. The selection of size ranges or size fractions of particles by sieving is well known. It is preferred that the feedstock powder comprises free-flowing particles within a size range of between 40 microns, more preferably 63 microns, and 1 mm as determined by sieving. It may be particularly preferred that the feedstock powder comprises free-flowing particles within a size range of between 100 microns, more preferably 150 microns, and 212 microns as determined by sieving.

One standard way of defining the particle size distribution in a powder is to refer to D10, D50 and D90 values. 010 is the particle size value that 10% of the population of powder particles lies below. D50 is the particle size value that 50 % of the population lies below and 50% of the population lies above. D50 is also known as the median value. D90 is the particle size value that 90 % of the population lies below. A feedstock powder sample that has a wide particle size distribution will have a large difference between 010 and 090 values. Likewise, a feedstock powder sample that has a narrow particle size distribution will have a small difference between DiG and D90.

Particle size distribution may be determined by laser diffraction. For example! the particle size distribution, including D10, D50 and D90 values, could be determined by an analyser such as the Malvern Mastersizer Hydro 2000MU.

It may be preferable that 010 for any feedstock powder is greater than 40 microns, or 60 microns, and D90 is lower than 3 mm. It may be preferable that D90 is no more than 200% greater than D10, preferably no more than 150% greater than 010, or no more than 100% greater than D10. It may be beneficial if the feedstock powder has a size distribution in which D90 is no more than 75% greater than 010 or no more than 50% greater than DiG.

D10 is preferably between 0.25 and 1 mm. D90 is preferably between 0.5 mm and 3 mm.

One embodiment of a feedstock powder may have a population of particles in which 010 is 1 mm and 090 is 3 mm. Another embodiment of a feedstock powder may have a population of particles in which Dl 0 is 1.5 mm and D90 is 2.5 mm. Another embodiment of a feedstock powder may have a population in which 010 is 250 microns and 090 is 400 microns.

Another embodiment may have a population in which 010 is 0.5 mm and D90 is 0.75 mm.

The reduction time used is preferably as low as possible, to limit or prevent sintering of individual particles of the metal powder product. The metal powder product may be, for example, the first metallic powder or the second metallic powder. Advantageously, the reduction time may be lower than 100 hours, preferably lower than 60 hours or lower than 50 hours. Particularly preferably the reduction time is lower than 40 hours.

The molten salt temperature is preferably as low as possible, to limit or prevent sintering of individual particles of the metal product. Preferably, the molten salt temperature during reduction of the non-metallic powder is maintained to be lower than 1100°C, for example lower than 1000°C, or lower than 950°C, or lower than 900°C.

The reduced feedstock powder may form a friable mass of individual metallic particles.

Advantageously, such a friable mass may be easily broken up to form a free-flowing metallic powder. Preferably, substantially every particle forming the metallic powder corresponds to a non-metallic particle from the feedstock.

Some reduction processes may only operate when the molten salt or electrolyte used in the process comprises a metallic species (a reactive metal) that forms a more stable oxide than the metallic oxide or compound being reduced. Such information is readily available in the form of thermodynamic data, specifically Gibbs free energy data, and may be conveniently determined from a standard Ellingham diagram or predominance diagram or Gibbs free energy diagram. Thermodynamic data on oxide stability and Ellingham diagrams are available to, and understood by, electrochemists and extractive metallurgists (the skilled person in this case would be well aware of such data and information).

Thus, a preferred electrolyte for an electrolytic reduction process may comprise a calcium salt. Calcium forms a more stable oxide than most other metals and may therefore act to facilitate reduction of any metal oxide that is less stable than calcium oxide. In other cases, salts containing other reactive metals may be used. For example, a reduction process according to any aspect of the invention described herein may be performed using a salt comprising lithium, sodium, potassium, rubidium, caesium, magnesium, calcium, strontium, barium, or yftrium. Chlorides or other salts may be used, including mixture of chlorides or other salts.

By selecting an appropriate electrolyte, almost any metal oxide particles may be capable of reduction using the methods and apparatuses described herein. Naturally occurring minerals containing one or more such oxides may also be reduced. In particular, oxides of beryllium, boron, magnesium, aluminium, silicon, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, yttrium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, uranium, thorium and the lanthanides including lanthanum, cerium, praseodymium, neodymium, samarium, may be reduced, preferably using a molten salt comprising calcium chloride.

The skilled person would be capable of selecting an appropriate electrolyte in which to reduce a particular metal oxide, and in the majority of cases an electrolyte comprising calcium chloride will be suitable.

Preferably, the reduction occurs by an electro-decomposition or electro-deoxidation process such as the FF0 Cambridge process or the BHP Polar process and the process described in Specific embodiment of the invention Specific embodiments of the invention will now be described with reference the accompanying drawings, in which; Figure 1 is a schematic diagram illustrating an electrolysis apparatus arranged to reduce a blended feedstock powder to a metallic powder, Figure 2A is a schematic cross-sectional view illustrating additional detail of the cathode structure of the electrolysis apparatus of figure 1, Figure 2B is a plan view of the cathode illustrated in figure 2A, A specific method for reducing a blended feedstock powder will now be described with reference to the figures.

Figure 1 illustrates an electrolysis apparatus 10 configured for use in performing a reduction on a blended feedstock powder comprising a plurality of non-metallic particles. The blended feedstock powder comprises a non-metallic powder that is a mineral powder derived from a natural mineral or sand and at least one other non-metallic powder. The apparatus comprises a stainless steel cathode 20 and a carbon anode 30 situated within a housing 40 of an electrolysis cell. The anode 30 is disposed above, and spatially separated from, the cathode 20. The housing 40 contains 500 kg of a calcium chloride based molten salt electrolyte 50, the electrolyte comprising Cad2 and 0.4 wt % CaO, and both the anode 30 and the cathode 20 are arranged in contact with the molten salt 50. Both the anode 30 and the cathode 20 are coupled to a power supply 60 so that a potential can be applied between the cathode and the anode.

The cathode 20 and the anode 30 are both substantially horizontally oriented, with an upper surface of the cathode 20 facing towards a lower surface of the anode 30.

The cathode 20 incorporates a rim 70 that extends upwards from a perimeter of the cathode and acts as a retaining barrier for a blended feedstock powder 90 supported on an upper surface of the cathode. The rim 70 is integral with, and formed from the same material as, the cathode. In other embodiments, the rim may be formed from a different material to the cathode, for example from an electrically insulating material.

The structure of the cathode may be seen in more detail in Figure 2A and Figure 2B. The rim is in the form of a hoop having a diameter of 30 cm. A first supporting cross-member 75 extends across a diameter of the rim. The cathode also comprises a mesh-supporting member 71, which is in the form of a hoop having the same diameter as the rim 70. The mesh-supporting member has a second supporting cross-member 76 of the same dimensions as the supporting cross-member 75 on the rim 70. A mesh 80 is supported by being sandwiched between the rim 70 and the mesh-supporting member 71 (the mesh 80 is shown as the dotted line in Figure 2A). The mesh 80 comprises a stainless steel cloth of mesh-size 100 that is held in tension by the rim 70 and the mesh-supporting member. The cross-member 75 is disposed against a lower surface of the mesh 80 and acts to support the mesh. An upper surface of the mesh 80 acts as the upper surface of the cathode.

The stainless steel cloth forming the mesh 80 is fabricated from 30 micrometre thick wires of 304 grade stainless steel that have been woven to form a cloth having square holes with a micrometre opening. The mesh 80, cross-member 75 and rim 70 that form the cathode are all electrically conductive. In other embodiments, the mesh may be the only electrically conductive component of the cathode.

Example I

A first non-metallic powder was prepared by sieving natural rutile sand particles, excavated from a specific source of natural rutile, and selecting the fraction of sand particles falling between meshes of 63 microns and 212 microns. The natural rutile used was Sibelco's Cruzor premium, produced at Pinkenba, Queensland, Australia. This rutile has approximately 96.2 wt % Ti02, 0.5 wt % A1203, 1.5 wt % SiO, and various Fe bearing components. If the oxygen was removed, the first non-metallic powder could be expected to form a reduced powder having an overall composition of approximately 97.5 wt % Ti, 0.46 wt % Al, 1.42 wt % Si and 0.41 wt % Fe.

A second non-metallic powder was prepared by sieving synthetic rutile particles, produced by beneficiating a natural ilmenite powder, and selecting the fraction of synthetic rutile particles falling between meshes of 63 microns and 212 microns. The synthetic rutile used was Iluka's Carpel synthetic rutile, premium grade. This synthetic rutile has approximately 91.75 wt % Ti02, 1.45 wt % A1203, 1.3 wt % SiC, and various Fe bearing components. If the oxygen was removed, the second non-metallic powder could be expected to form a reduced powder having an overall composition of approximately 90.5 wt % Ti, 1.0 wt % Al, 1.21 wt % Si and 6.52 wt % Fe.

A proportion of the first non-metallic powder was thoroughly mixed with a proportion of the second non-metallic powder to form a blended feedstock powder. The mixing ratio was 50:50 by weight.

About 3 kg of the blended feedstock powder 90 was arranged on the upper surface of the cathode 20 and in contact with the molten salt 50 (which consisted of CaCI2 and 0.4 wt % CaO). Thus, the blended feedstock powder 90 was supported by the mesh 80 of the cathode and retained at a depth of approximately 2 cm by the cathode-rim 70.

The molten salt was maintained at a temperature of about 1000 °C and a potential was applied between the anode and the cathode. Thermal currents and gas lift effect generated by the buoyancy of the gases (which are predominantly CO and CC2) generated at the anode cause the molten salt to circulate within the cell and generate flow through the bed of natural rutile supported on the cathode. The cell was operated in constant current mode, at a current of 400 A, for 52 hours. After this time, the cell was cooled and the cathode removed and washed to free salt from the metallic powder, which was the product formed by reducing the blended feedstock powder.

The reduced product was removed from the cathode as a friable lump or cake of metallic powder particles that could be separated using light manual pressure. The lumps of material were tumbled in a barrelling tumbler containing alumina balls, and the material separated out into individual powder particles. These powder particles were then dried. The resulting metallic powder was a titanium-rich powder having 36 to 39 wt % Ti and 3.5 wt % Fe.

The metallic powder was consolidated by hot isostatic pressing and was annealed to homogenise the composition. On cooling to room temperature the consolidated powder had formed a titanium billet with a near-alpha microstructure.

Example 2

A first non-metallic powder was prepared by sieving natural ilmenite particles, and selecting the fraction of particles falling between meshes of 150 microns and 212 microns. This ilmenite has approximately 61 to 65 wt % TiC2 and approximately 22 to 33 wt % Fe203.

Other oxides present in the ilmenite at low levels includes A12O3, ZrO2, V2O5, MgO, Cr2O3, and P205. If the oxygen was removed, the first non-metallic powder could be expected to form a reduced powder having an overall composition of approximately 63 wt % Ti and 31 wt % Fe.

A second non-metallic powder was prepared by sieving a granulated pigment grade Ti02 and selecting the fraction of particles falling between meshes of 200 microns and 300 microns. If the oxygen was removed, the second non-metallic powder could be expected to form a reduced powder having an overall composition of approximately pure Ti.

The first non-metallic powder was blended with the second non-metallic powder in a 7:3 ratio to form a blended feedstock powder. That is, 7 parts by weight of the first non-metallic powder were blended with 3 parts by weight of the second non-metallic powder. 30g of the blended feedstock powder was then reduced in 1kg of a molten salt comprising Cad2 and 0.6 wt % CaO at 1000 DC for l6hrs. The blended feedstock was reduced under constant current conditions.

After reduction, the reduced metal was recovered from the salt, washed, and then pressed into pellets of approximately ig using 1 tonne pressing force. The pellets were then sintered in a vacuum furnace at 1100°C for 2 hrs.

SEM-EDS analysis was carried out using a JEOL 6490LV SEM with an Inca energy EDS.

The theoretical composition of the reduced powder was approximately 76 wt % Ti and 20 wt % Fe. The results showed that the actual composition was about 17.5wt % Fe with the balance being Ti. The slight reduction in levels of Fe, compared with a theoretical predication, is believed to be due to loss of Fe by leaching into the molten salt during reduction.

Claims

Claims 1. A method of producing metal comprising the steps of; (a) forming a blended feedstock powder comprising a plurality of discrete non-metallic particles by (i) providing a first non-metallic powder, the first non-metallic powder being a first mineral powder derived from a natural mineral or sand, the first non-metallic powder having a first overall composition, and (ii) mixing the first non-metallic powder with a second non-metallic powder, the second non-metallic powder having an overall composition different from the first non-metallic powder, and (b) electrolytically reducing the blended feedstock powder such that the plurality of discrete non-metallic particles of the blended feedstock powder are reduced to a metallic powder comprising a plurality of discrete metallic particles.
2. A method of producing metal according to claim 1 in which the step of electrolytically reducing the blended feedstock powder involves the steps of arranging a volume of the blended feedstock powder in contact with a molten salt within an electrolysis cell, the electrolysis cell comprising an anode and a cathode arranged in contact with the molten salt, and applying a potential between the anode and the cathode such that the plurality of discrete non-metallic particles of the blended feedstock powder are reduced to a metallic powder comprising a plurality of discrete metallic particles.
3. A method according to claim 1 or 2 in which the second non-metallic powder is a metal oxide powder.
4. A method according to claim 1, 2, or 3 in which the first non-metallic powder is blended with the second non-metallic powder and one or more further non-metallic powders to form the blended feedstock powder, for example with two, or three or four further non-metallic powders, each further non-metallic powder having a different overall composition.
5. A method according to any preceding claim in which the second non-metallic powder, or any further non-metallic powder, is a metal oxide powder comprising oxygen and at least one metallic element selected from the list consisting of titanium, tantalum, zirconium, aluminium, vanadium, beryllium, boron, magnesium, silicon, scandium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, yttrium, zirconium, niobium, molybdenum, hafnium, tungsten, uranium, thorium, lanthanum, cerium, praseodymium, neodymium, and samarium.
6. A method according to claim 5 in which the second non-metallic powder, or any further non-metallic powder, is a synthetically produced or modified powder comprising a plurality of discrete particles of substantially uniform particle-to-particle composition.
7. A method according to any preceding claim in which the second non-metallic powder, or any further non-metallic powder, is a mineral powder derived from a natural mineral or sand.
8. A method according to any preceding claim in which the first non-metallic powder is mixed with the second non-metallic powder, and optionally one or more further non-metallic powder, to produce a blended feedstock powder of predetermined overall composition, the blended feedstock powder being reduced to form a metallic powder having a predetermined overall composition.
9. A method according to claim 8 in which the overall composition of the second non-metallic powder, and optionally the overall composition of any further non-metallic powder, is selected so as to combine with the first non-metallic powder to produce a blended feedstock of predetermined overall composition.
10. A method according to claim 8 or 9 in which the ratio of the first non-metallic powder and the second non-metallic powder, or optionally the ratio of the first non-metallic powder to each further non-metallic powder, is selected to produce a blended feedstock of predetermined overall composition.
11. A method according to any preceding claim in which the first mineral powder comprises one or more minerals selected from the list consisting of rutile, ilmenite, anatase, leucoxene, scheelite, loparite, perovskite, sphene, cassiterite, monazite, zircon, cobaltite, chromite, bertrandite, beryl, uranite, pitchblende, and quartz, haematite, magnetite, corundum, pyrolusite, columbite, tantalite and chrysoberyl.
12. A method according to any of claims 2 to 11 in which a loose volume of the blended feedstock powder is arranged in contact with the cathode and the molten salt.
13. A method according to any preceding claim in which the blended feedstock powder is reduced by an electrodecomposition process, for example according to the FFC Cambridge process or the BHP Polar process.
14. A method according to any preceding claim in which the first non-metallic powder is natural rutile, or is derived from rutile, and the second non-metallic powder comprises one or more non-metallic material selected from the list consisting of natural rutile, natural ilmenite, synthetic rutile or chemically leached ilmenite, rutile slag, and synthetic titanium dioxide, the resulting metallic powder being a titanium powder, or a titanium-rich powder.
15. A method according to any preceding claim in which the first non-metallic powder is synthetic rutile, or chemically leached ilmenite, and the second non-metallic powder comprises one or more non-metallic material selected from the list consisting of natural rutile, natural ilmenite, synthetic rutile, rutile slag, and synthetic titanium dioxide, the resulting metallic powder being a titanium powder, or a titanium-rich powder.
16. A method according to any preceding claim in which the metallic powder is consolidated to form a solid metallic item of greater than 95% theoretical density, for example a billet, bar, sheet, or net-shape product.
17. A method according to any preceding claim in which the metallic powder comprises a plurality of discrete metallic particles having varied individual compositions but one overall composition, the method further comprising steps of consolidating and thermally treating the metallic powder to form a solid metallic item, the item having a substantially uniform composition that is the same as the overall composition of the metallic powder.
18. A method according to claim 16 or 17 in which the metallic powder is consolidated by cold isostatic pressing, hot isostatic pressing, vacuum hot pressing, or roll consolidation.
19. A method according to claim 16, 17 or 18 in which the consolidated powder preform is sintered in a vacuum or in an atmosphere of argon or helium, preferably at a temperature of between 1000-1660 °C more preferably 1100-1300 °C.
20. A method according to any of claims 16 to 19 in which the solid metallic item is a titanium alloy, preferably an alpha plus beta phase titanium alloy, a beta phase titanium alloy, or a near beta phase titanium alloy.
21. A method according to any preceding claim which is a method for producing an alpha phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended non-metallic powder having an overall composition that can be electiolytically reduced to a metallic powder having an overall composition consisting of titanium with between 2 and 10 wt % of alloying elements selected from the list consisting of Al, Ga, Ge, La, Ce, 0, N and C and less than a total of 1 wt % of alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Mo, V, W, Nb, Ta, Si, Cu and H.
22. A method according to claim 21 in which the overall composition of the metallic powder contains between 2 and 8 wt % Al, 10-4000 ppm 0, and 10-2000 ppm C.
23. A method according to claim 20 or 21 in which the overall composition of the blended metallic powder contains between 0.01 -18% total content of Zr, Hf, and Sn.
24. A method according to any of claims ito 20 which is a method for producing an near alpha phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended non-metallic powder having an overall composition that can be electiolytically reduced to a metallic powder having an overall composition consisting of titanium with between 2 and 10 wt % of alloying elements selected from the list consisting of Al, Ga, Ge, La, Ce, 0, N and C, and between 1 and 4 wt% and more preferably 1-2 wt% of alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Mo, V, W, Nb, Ta, Si, Cu and H.
25. A method according to claim 24 in which the overall composition of the metallic powder contains between 2 and 8 wt % Al, 10-4000 ppm 0, and 10-2000 ppm C.
26. A method according to claim 24 or 25 in which the overall composition of the blended metallic powder contains between 0.01 -18% total content of Zr, Hf, and Sn.
27. A method according to any of claims ito 20 which is a method for producing a beta phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended non-metallic powder having an overall composition that can be electiolytically reduced to a metallic powder having an overall composition consisting of titanium with a total of less than 5 wt % more preferably less than 4 wt % of alloying elements selected from the list consisting of Al, Ga, Ge, La, Ce, 0, N and C, and between 2 and 25 wt% of alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Mo, V, W, Nb, Ta, Si, Cu and H
28. A method according to any of claims ito 20 which is a method for producing a mixed alpha and beta phase titanium alloy, the method comprising the steps of mixing the first non-metallic powder and the second non-metallic powder, and any further non-metallic powder, to form a blended non-metallic powder having an overall composition that can be electrolytically reduced to a metallic powder having an overall composition consisting of titanium with a total of between i and 7 wt % of alloying elements selected from the list consisting of Al, Ga, Ge, La, Ce, 0, N and C, between 4 and Bwt% of alloying elements selected from the list consisting of Fe, Cr, Ni, Co, Mn, Mo, V, W, Nb, Ta, Si, Cu and H and optionally between 0.01 and 8 wt % of alloying elements selected from the list consisting of zirconium, hafnium and tin.