METHOD AND APPARATUS FOR PRODUCING A LIGHTWEIGHT METAL ALLOY

Abstract

A method of forming a metal alloy from a powder composition comprising first particles in a range of approximately 20-90% by weight of the powder composition, the remainder of the powder composition comprising approximately 95% by weight of second particles and 5% by weight of third particles, wherein the method includes the step of using rapid thermal processing (RTP) to sinter the powder composition.

Description

TECHNICAL FIELD

The present invention relates to a powdered metallurgy method and apparatus for producing a lightweight metal alloy suitable for instance in producing a automotive components and/or implantable medical components.

BACKGROUND OF THE INVENTION

The use of metal alloys is common in the manufacture of automotive components such as valves, valve seats, pistons and the like. Similarly, metal alloys have found commercial application in the field of implantable medical components and devices such as prosthetics and stents due to being relatively lightweight and having suitably durable properties.

Conventional processes and systems for commercial production of such metal alloy components have tended to involve relatively long sintering times in order for the metal alloy materials to exhibit suitable properties such as wear resistance, and hardness. Consequently, the relatively long sintering times tends to decrease overall production throughput and increase power consumption costs.

Additionally, metal alloy components which are manufactured in accordance with conventional processes and systems tend to require additional machining in order to produce suitable functional geometries. This also places a limitation upon overall manufacturing productivity and raises production costs.

SUMMARY OF THE INVENTION

The present invention seeks to alleviate at least one of the above-described problems.

The present invention may involve several broad forms. Embodiments of the present invention may include one or any combination of the different broad forms herein described.

In a first broad form, the present invention provides a method of forming a metal alloy from a powder composition comprising first particles in a range of approximately 20-90% by weight of the powder composition, the remainder of the powder composition comprising approximately 95% by weight of second particles and 5% by weight of third particles, wherein the method includes the step of using rapid thermal processing (RTP) to sinter the powder composition.

Preferably, the first particles include an inter-metallic compound. Typically, the inter-metallic compound includes TiAl₃ particles.

Preferably, the second particles include Aluminium particles. More preferably, the Aluminium particles include 6061 Aluminium particles.

Preferably, the third particles include Titanium particles.

Preferably, the step of using rapid thermal processing to sinter the powder composition includes heating the powder composition up to a temperature substantially within a range of 700-800° C.

More preferably, the step of using rapid thermal processing to sinter the powder composition includes initially heating the powder composition up to a sintering temperature within the range of approximately between 700-800° C. within a timeframe of between approximately 0-10 seconds. Thereafter, typically if the powder composition is heated up to a sintering temperature of substantially between 750-800° C., the sintering temperature is maintained for at least around 60 seconds. Alternatively, where the sintering temperature is substantially 700° C., the sintering temperature is maintained for at least around 90 seconds.

Preferably, sintering is ceased after a period of approximately 4 minutes.

Preferably, the present invention includes a step of cold-pressing the powder composition in to a mould before sintering the powder composition using rapid thermal processing.

Preferably, the present invention includes a step of mixing the powder composition before cold-pressing the powder composition. Typically, the step of mixing the power composition includes rotatably mixing the powder composition for at least 12 hours before being cold-pressed.

Typically, the TiAl₃ particles in the powder composition include diameters of approximately 50 μm before sintering.

Typically, the step of sintering the powder composition by rapid thermal processing causes the TiAl₃ particles to fragment into smaller particles of approximately 10 μm in diameter.

In a second broad form, the present invention provides a method of forming a Vanadium-containing metal alloy from a powder composition comprising first particles in a range of approximately 20-90% by weight of the powder composition, the remainder of the powder composition comprising approximately 95% by weight of second particles and 5% by weight of third particles, wherein the method includes the step of using rapid thermal processing (RTP) to sinter the powder composition.

In a third broad form, the present invention provides a powder composition adapted for processing by the method steps of the first or second broad forms to form a metal alloy.

In a fourth broad form, the present invention provides a metal alloy formed in accordance with the method steps of the first or second broad forms. Preferably, the metal alloy includes inter-metallic TiAl₃ particles of approximately 10 μm in diameter.

In a fifth broad form, the present invention provides an apparatus adapted for performing the method steps in accordance with the first or second broad forms of the present invention.

In a sixth broad form, the present invention provides a metal alloy automotive component formed in accordance with the method steps of the first broad form.

In a seventh broad form, the present invention provides a metal alloy implantable medical component formed in accordance with the method of the second broad form.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the following detailed description of a preferred but non-limiting embodiment thereof, described in connection with the accompanying drawings, wherein:

FIG. 1A shows a table indicating proportions of TiAl3, Al and Ti particles by weight percentage used in four sample powder compositions;

FIG. 1B shows the relative composition (by weight percentage of Al and Ti particles) in the matrix of metal alloys formed from the four sample compositions;

FIG. 2 shows an exemplary SEM image of TiAl₃ particles (as received) magnified by a factor of ×800;

FIG. 3 shows an apparatus for sintering a cold-pressed sample powder composition using RTP in accordance with an embodiment of the present invention;

FIGS. 4A and 4B show SEM images (magnified by factors of ×800 and ×300 respectively) of the microstructure of a first sample after 15 seconds of sintering by RTP at a sintering temperature of approximately 800° C.;

FIGS. 5A and 5B show SEM images of the microstructure of the first sample magnified by factors of ×800 and ×300 respectively after 30 seconds of sintering by RTP at a sintering temperature of approximately 800° C.;

FIGS. 6A and 6B show SEM images of the microstructure of the first sample magnified by factors of ×800 and ×300 respectively after 1 minute of sintering by RTP at a sintering temperature of approximately 800° C.;

FIGS. 7A and 7B show SEM images of the microstructure of the first sample magnified by factors of ×800 and ×300 respectively after 2 minutes of sintering by RTP at a sintering temperature of approximately 800° C.;

FIGS. 8A and 8B show SEM images of the microstructure of the first sample magnified by factors of ×800 and ×300 respectively after 3 minutes of sintering by RTP at a sintering temperature of approximately 800° C.;

FIGS. 9A and 9B show SEM images of the microstructure of the first sample magnified by factors of ×800 and ×300 respectively after 4 minutes of sintering by RTP at a sintering temperature of approximately 800° C.;

FIG. 10 shows the results of a Vickers microhardness test upon the sintered first sample;

FIG. 11 shows the results of a thermo-mechanical analysis tests upon a metal alloy formed from the first sample composition in accordance with a first embodiment method;

FIG. 12 shows the results of a sliding wear test performed upon a metal alloy formed from the first sample composition in accordance with the first method;

FIG. 13 shows the results of a high temperature oxidation test performed upon a metal alloy formed from the first sample composition in accordance with the first embodiment method;

FIGS. 14A and 14B show SEM images, magnified by factors of ×800 and ×300 respectively, of the microstructure of the first sample which has been sintered by RTP at a sintering temperature of approximately 700° C. for approximately 90 seconds;

FIGS. 15A and 15B show SEM images, magnified by factors of ×800 and ×300 respectively, of the microstructure of the first sample which has been sintered by RTP at a sintering temperature of approximately 750° C. for approximately 60 seconds;

FIGS. 16A and 16B show SEM images of a second sample, magnified by factors of ×800 and ×300 respectively, after 90 seconds of sintering by RTP at a sintering temperature of approximately 700° C.;

FIGS. 17A and 17B show SEM images of the second sample, magnified by factors of ×800 and ×300 respectively, after 60 seconds of sintering by RTP at a sintering temperature of approximately 750° C.;

FIGS. 18A and 18B show SEM images of the second sample, magnified by factors of ×800 and ×300 respectively, after 60 seconds of sintering by RTP at a sintering temperature of approximately 800° C.;

FIGS. 19A and 19B show SEM images of a third sample, magnified by factors of ×800 and ×300 respectively, after 90 seconds of sintering by RTP at a sintering temperature of approximately 700° C.;

FIGS. 20A and 20B show SEM images of the third sample, magnified by factors of ×800 and ×300 respectively, after 60 seconds of sintering by RTP at a sintering temperature of approximately 750° C.;

FIGS. 21A and 21B show SEM images of the third sample, magnified by factors of ×800 and ×300 respectively, after 60 seconds of sintering by RTP at a sintering temperature of approximately 800° C.;

FIGS. 22A and 22B show SEM images of a fourth sample, magnified by factors of ×800 and ×300 respectively, after 90 seconds of sintering by RTP at a sintering temperature of approximately 700° C.;

FIGS. 23A and 23B show SEM images of the fourth sample, magnified by factors of ×800 and ×300 respectively, after 60 seconds of sintering by RTP at a sintering temperature of approximately 750° C.;

FIGS. 24A and 24B show SEM images of the fourth sample, magnified by factors of ×800 and ×300 respectively, after 60 seconds of sintering by RTP at a sintering temperature of approximately 800° C.;

FIG. 25 shows a partially-formed cylinder liner which has been formed from a powder composition in accordance with the first embodiment method;

FIGS. 26A and 26B show SEM images of the cylinder liner microstructure in FIG. 25 magnified by factors of ×800 and ×300 respectively;

FIG. 27 shows a chart indicating weight percentages of Aluminium particles in Al—Ti based powder compositions suitable for processing by some embodiments of the present invention;

FIG. 28 shows a chart indicating the weight percentage of Vanadium particles in alternative suitable powder compositions plotted against suitable sintering temperatures;

FIG. 29 shows a chart indicating weight percentages of Vanadium, Aluminium and Titanium particles in alternative Vanadium-containing powder compositions suitable for processing in accordance with the first embodiment method of the present invention; and

FIG. 30 shows a flowchart of the first embodiment method steps.

PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the present invention will now be described below with reference to the accompanying drawings.

In accordance with a first embodiment of the present invention, a method is provided for forming a metal alloy from a powder composition comprising TiAl₃, Al and Ti particles. The proportion of inter-metallic TiAl₃ particles comprises between 20-90% by weight of the powder composition. The remainder of the powder composition is comprised approximately 95% by weight of Al particles and 5% by weight of Ti particles. FIG. 30 shows a flowchart representing method steps in accordance with the first embodiment method which will be described in further detail herein.

FIG. 27 shows a chart of weight percentages of Aluminium particles in the powder compositions suitable for use in forming a metal alloy in accordance with the first embodiment method charted against suitable sintering temperatures used to form the metal alloy.

A series of four sample powder compositions having different particle weight percentages falling within the above-described constituent parameters are processed using the first embodiment method with both the microstructures and the properties of the resulting metal alloys being subsequently observed and tested. FIG. 1A is a table indicating the proportions of TiAl3, Al and Ti particles by weight percentage in each of the four samples. In each of the sample powder compositions, 6061 Aluminium particles are used. Block 2700 in FIG. 30 represents the initial step of forming a sample powder composition using TiAl3, Al and Ti particles.

A JEOL JSM 820 model scanning electron microscope (SEM) operating at 20 kV is used to provide magnified images of the inter-metallic and matrix structures of the powder composition samples before and after sintering. The chemical compositions of the sintered samples are able to be measured by an Oxford Instruments INCA-200 energy dispersive spectrometer (EDX) installed in the SEM. FIG. 1B shows the relative composition (by weight percentage of Al and Ti particles) in the matrix of metal alloys formed from the different sample compositions obtained using energy dispersive X-ray (EDX) analysis.

FIG. 2 shows an exemplary SEM image of the TiAl3 particles (as received) magnified by a factor of ×800. It can be seen that the as received TiAl3 particles are substantially spherical in shape and have diameters of approximately 50 μm before sintering.

The TiAl3, Al and Ti particles in each of the sample powder compositions are rotatably mixed in a plastic container for at least 12 hours before being cold-pressed into moulds using a hydraulic press. It would of course be appreciated by a person skilled in the art that mixing time may vary from case to case. Blocks 2710 and 2720 of FIG. 30 respectively represent these steps of the first embodiment method.

After being cold-pressed into moulds, RTP is used to sinter the sample powder compositions. It would be understood by a person skilled in the art that RTP is able to be implemented by any number of specific techniques including for instance exposure to heat from high intensity quartz or halogen lamps, laser, induction heating, “heat dipping”, use of a tube furnace purged with Argon, or vacuum sintering.

FIG. 3 shows an exemplary apparatus (300) in accordance with a further embodiment of the present invention which may be used for sintering sample powder compositions cold-pressed into moulds by RTP in accordance with the first embodiment method steps. The apparatus includes a cold-wall chamber (310) in which the mould (320) containing the cold-pressed powder composition (330) is mounted on a support (340) and edge-ring (350). Arrays of quartz lamps (360) are disposed above and beneath the mould to provide rapid thermal processing of the powder composition. Quartz windows are disposed between the lamps and the sample. A pyrometer is also provided for non-contact measurement of the thermal radiation of the sample.

First Sample Composition—50% TiAl₃, 50% of (95% Al+5% Ti)

A first sample powder composition is processed in accordance with the first embodiment method in which TiAl₃ particles comprise approximately 50% by weight of the powder composition, and, the remainder of the sample powder composition is comprised of approximately 95% by weight of Al particles and 5% by weight of Ti particles.

RTP is applied to the first sample powder composition whereby the sample powder composition is initially sintered up to a temperature of approximately 800° C. in less than 10 seconds. The step of initially ramping up the sintering temperature of the first sample powder composition is represented by block 2730 in FIG. 30.

The sintering temperature is then maintained at approximately 800° C. for a duration of at least approximately 60 seconds. The step of maintaining the sintering of the first sample powder composition is represented by block 2740 in FIG. 30.

FIGS. 4A and 4B show SEM images (magnified by factors of ×800 and ×300 respectively) of the first sample after 15 seconds of sintering at a sintering temperature of approximately 800° C. There are two main constituents of the metal alloy microstructure after sintering—that is, the inter-metallic hard TiAl₃ particles (400) and the matrix (410) consisting of Al and Ti particles. It can be seen that cracks (420) have started to appear at the interface between the TiAl₃ particles and the matrix at around 15 seconds of sintering at approximately 800° C.

As shown in FIGS. 5A and 5B, after 30 seconds of sintering using RTP at a sintering temperature of approximately 800° C., cracks (500) within the TiAl₃ particles (510) have developed as the TiAl₃ particles fragment into smaller uniform particles (510) of approximately 10 μm in diameter. It can also be seen from FIGS. 5A and 5B that porosity has remained relatively high at this stage of sintering.

FIGS. 6A and 6B are SEM images magnified by factors of ×800 and ×300 respectively in which it can be seen that after 1 minute of sintering, the TiAl₃ particles within the matrix (600) have now substantially fragmented into relatively smaller and finer particles (610) of approximately 10 μm in diameter. It is also evident from FIGS. 6A and 6B that the degree of porosity remains relatively high at this stage of sintering by RTP.

FIGS. 7A-7B, 8A-8B and 9A-9B are magnified SEM images of the first sample after 2 minutes, 3 minutes and 4 minutes of sintering by RTP respectively at 800° C. Surprisingly, it can be seen that between 2 to 4 minutes of sintering, the original 50 μm diameter of the TiAl₃ particles have now substantially fragmented into relatively smaller and finer TiAl₃ particles (700,800,900) of approximately 10 μm diameter and have become increasingly dispersed in a relatively uniform manner in the matrix (710,810,910) which assists in strengthening the resulting metal alloy.

Also surprisingly, an analysis of the images between 2 to 4 minutes of sintering reveals that there is no indication of re-growth in size of the TiAl₃ particles size. The interfaces between the fragmented TiAl₃ particles (700,800,900) and the matrix (710,810,910) also remain substantially continuous and the porosity of the metal alloy appears to be become negligible.

In this embodiment, sintering is ceased after approximately 4 minutes as it is observed that substantial grain growth of the TiAl₃ particles occurs which may reduce the strength of the metal alloy. The sintered sample is cooled as fast as practicable by switching off the quartz lamps heaters and continuously purging the chamber with argon gas directly from argon gas bottles. The argon flow rate used is 1210 milli-litre/minute which assists in halting any further microstructure changes after the prescribed sintering time.

In conventional sintering methods where sintering times may typically be measured in the order of hundreds of minutes, inter-metallic particle size in a metal alloy tends to increases rather than decrease. However, the phenomenon observed in the microstructure of the metal alloy formed in accordance with the first embodiment would appear to be counter-intuitive to the understanding of a person skilled in the art based on conventional methods.

Vickers Micro-Hardness Testing

Vickers microhardness tests are applied to the first sample composition when exposed at 800° C. for different sintering times. Hardness (H) is a measure of a material's resistance to localized plastic deformation. The Vickers microhardness test is a non-destructive test in which a micro-sized diamond indenter having pyramidal geometry is pressed into a flat surface of the sintered sample.

Specifically, the test is carried out on the as-cast samples with a Matsuzawa MXT-α7 digital microhardness tester with the load set at 100 gf (=0.98 N). The as-cast samples do not have to be annealed in this embodiment, however, annealing may take place if so desired. The microhardness tester is first calibrated with a standard calibration block with hardness 281 Hv and the accuracy of the measurement is determined to be within approximately 6%.

At intervals of 30 seconds, 2 minutes and 4 minutes into the sintering process, hardness measurements are taken at 10 randomly selected points upon the sintered sample. For each sintering time, the microhardness is taken as the average of the 10 hardness readings. Based on the results of the test shown in FIG. 10, the average measured hardness of the sintered sample is shown to increase with the heating time.

The hardness of A390.0, a very typical aluminium alloy for automotive cylinder block applications, ranges from Brinell Hardness 100-150*(approximately equal to Vickers Hardness 105-160*) depending on the heat-treatment applied. Furthermore, the hardness of 319.0 alloy, which is used for making an automotive cylinder head, is in the range HB70-95. In contrast, the optimal hardness of the metal alloy embodiment is in the range HV150-190 (FIG. 10), which is substantially higher than that of A390.0 and 319.0 alloys. Accordingly, it would be appreciated by a person skilled in the art that the hardness of the metal alloy embodiment should satisfy the hardness requirements for automotive components.

Thermo-Mechanical Analysis

Thermo-Mechanical Analysis (TMA) tests are performed by applying forces of 5 g, 75 g and 150 g upon the sintered sample while being subjected to temperature increases at a constant rate of 20 K/min. The results of the TMA tests are shown in FIG. 11 in which it can be seen that the softening point of the sintered sample is approximately between 650 to 680° C. The softening points, ˜650 to 680° C., of the formed metal alloy embodiment are comparable to those of typical cast aluminium alloys (e.g. A390.0) with liquidus temperature of 650° C., for automotive applications. It would therefore be appreciated by persons skilled in the art that the metal alloy embodiment is suitable for applications where cast alumunium alloys are currently employed.

Wear Testing

A sliding wear test using a pin-on-disk configuration is performed upon the first sample composition which has been sintered in a tube surface at 800° C. for 1 minute. The unlubricated disk has a diameter of 75 mm and a thickness of 10 mm and is cleaned ultrasonically before and after performing the wear test. A pin of 3 mm in diameter and 13 mm in length is pressed against the surface of the disk by a pneumatic system under a normal load of 30 N. The disk rotation speed is set at 30 rpm which at a radius of 25 mm results in a sliding velocity of 0.07 m/s.

The weight loss of the sample is measured every hour over a total period of eight hours during this test. The chart shown in FIG. 12 indicates the extent of weight loss resulting from the wear test. The linear relationship between the wear weight loss and wear test time (distance) indicates that the main cause of wear is attributable to abrasive wear rather than through fracturing or chipping off of relatively large pieces of tested surface.

High Temperature Oxidation Test

FIG. 13 shows the mass change of the sintered sample versus time of oxidation at a constant temperature of 550° C. over a test duration of 4 hours. The initial loss of mass is attributed to loss of water vapour and/or impurities in the sample. After the initial 40 minutes of testing, the sample weight appears to remain relatively steady throughout the test which indicates that there is no substantial oxidation of the sintered sample at 550° C. In view of the minute weight change after being exposed to 550° C. for 4 hours, which is already close to the softening temperature, the metal alloy embodiment would be understood to be highly oxidation resistant at high temperatures. This would appear to be at least partially due to the protective nature of the aluminium oxide and titanium oxide layers formed on the surface of the test sample during the initial stage of the oxidation test.

Weight Testing

The measured densities of two tested samples of the metal alloy embodiment (formed from a powder composition comprising 50% TiAl3, 50% of (95% Al+5% Ti) which has been sintered at 800° C. for 90 sec) are 2.55 and 2.53 g/cm3, while the density of solid aluminium is 2.71 g/cm3 and that of A390.0 is 2.73 g/cm3.

First Sample Composition—Sintered at 700-750° C.

The first sample composition is also sintered by RTP up to alternative sintering temperatures in less than 10 seconds and exposed to the alternative sintering temperatures for alternative sintering times in order to allow observation of the resulting microstructures.

FIGS. 14A and 14B show SEM images (magnified by factors of ×800 and ×300 respectively) of the microstructure of the first sample composition which has been sintered up to a sintering temperature of approximately 700° C. in less than 10 seconds and then held at this sintering temperature for approximately 90 seconds.

FIGS. 15A and 15B show SEM images (magnified by factors of ×800 and ×300 respectively) of the microstructure of the first sample composition which has been sintered up to a sintering temperature of approximately 750° C. in less than 10 seconds and then held at this temperature for approximately 60 seconds.

It can be seen that under these alternative processing conditions the microstructures of the samples indicate the formation of relatively smaller and refined TiAl3 particles (1400,1500) dispersed within their respective matrixes (1410,1510).

Second Sample Composition—30% TiAl₃, 70% of (95% Al+5% Ti)

A second sample powder composition comprising 30% of TiAl3 particles by weight, with the remainder of the composition comprising 95% Al particles by weight and 5% Ti particles by weight, is sintered using RTP up to alternative sintering temperatures in less than 10 seconds and exposed to the sintering temperatures for alternative sintering times to enable observation of the resulting microstructures.

FIGS. 16A and 16B show SEM images of the second sample composition (magnified by factors of ×800 and ×300 respectively) after 90 seconds of sintering at a sintering temperature of approximately 700° C.

FIGS. 17A and 17B show SEM images of the second sample composition (magnified by factors of ×800 and ×300 respectively) after 60 seconds of sintering at a sintering temperature of approximately 750° C.

FIGS. 18A and 18B show SEM images of the second sample composition (magnified by factors of ×800 and ×300 respectively) after 60 seconds of sintering at a sintering temperature of approximately 800° C.

It can be seen that the microstructures of the samples indicate the formation of relatively smaller and refined TiAl3 particles (1600,1700,1800) dispersed within their respective matrixes (1610,1710, 1810).

Third Sample Composition—70% TiAl₃, 30% of (95% Al+5% Ti)

A third sample powder composition consisting of 70% TiAl3 particles by weight, with the remainder of the composition comprising 95% Al particles by weight and 5% Ti particles by weight is sintered using RTP up to alternative sintering temperatures in less than 10 seconds and maintained at the temperatures for alternative sintering times in order to allow observation of the resulting microstructures.

FIGS. 19A and 19B show SEM images of the third sample composition (magnified by factors of ×800 and ×300 respectively) after 90 seconds of sintering at a sintering temperature of approximately 700° C.

FIGS. 20A and 20B show SEM images of the third sample composition (magnified by factors of ×800 and ×300 respectively) after 60 seconds of sintering at a sintering temperature of approximately 750° C.

FIGS. 21A and 21B show SEM images of the third sample composition (magnified by factors of ×800 and ×300 respectively) after 60 seconds of sintering at a sintering temperature of approximately 800° C.

It can also be seen that the microstructures of the samples indicate the formation of relatively smaller and refined TiAl3 particles (1900,2000,2100) dispersed within their respective matrixes (1910,2010, 2110).

Fourth Sample Composition—80% TiAl₃, 20% of (95% Al+5% Ti)

A fourth sample powder composition comprising 80% TiAl3 particles by weight, with the remainder comprising 95% Al particles by weight and 5% Ti particles by weight, is sintered using RTP up to alternative sintering temperatures in less than 10 seconds and held at the temperature for alternative sintering times in order to allow observation of the resulting microstructures.

FIGS. 22A and 22B show SEM images of the fourth sample composition (magnified by factors of ×800 and ×300 respectively) after 90 seconds of sintering at a sintering temperature of approximately 700° C.

FIGS. 23A and 23B show SEM images of the fourth sample composition (magnified by factors of ×800 and ×300 respectively) after 60 seconds of sintering at a sintering temperature of approximately 750° C.

FIGS. 24A and 24B show SEM images of the fourth sample composition (magnified by factors of ×800 and ×300 respectively) after 60 seconds of sintering at a sintering temperature of approximately 800° C.

It can again be seen that the microstructures of the samples indicate the formation of relatively smaller and refined TiAl3 particles (2200,2300,2400) dispersed within their respective matrixes (2210,2310, 2410).

Based on an analysis of the resulting microstructures of samples indicated in the magnified SEM images for various conditions outlined above, a person skilled in the art would appreciate that it is feasible to form relatively homogeneous and fine distributions of TiAl₃ particles of approximately 10 μm in diameter within the matrix where TiAl₃ particles comprise between 30%-80% by weight of the powder composition and the remainder of the powder composition comprises 95% by weight of Al particles and 5% by weight of Ti particles when processed in accordance with the first embodiment method. Furthermore, based on the results of tests and the analysis of the microstructures under varying conditions, a person skilled in the art would reasonably expect that a powder composition comprising between 20%-90% by weight of TiAl₃ particles and the remainder comprising 95% by weight of Al particles and 5% by weight of Ti particles may achieve the same microstructure through cold-pressing and sintering using RTP.

Vanadium-Containing Powder Compositions

It would be appreciated by a person skilled in the art that in alternative embodiments, a Vanadium-containing powder composition is able to be processed in accordance with the first embodiment method to form a metal alloy having a substantially similar microstructure and properties as described above in relation to non-Vanadium containing powder compositions.

By way of example, the chart depicted in FIG. 28 indicates the weight percentage of Vanadium particles in suitable alternative Vanadium-containing powder compositions plotted against suitable sintering temperatures in accordance with a further embodiment method of the present invention. The chart depicted in FIG. 29 further provides an indication of the relative weight percentages of Vanadium, Aluminium and Titanium particles in various Vanadium-containing powder compositions suitable for use.

Commercial Applications and Advantages

The first embodiment method herein described assists in fragmenting the relatively large TiAl₃ particles within the powder composition into relatively fine TiAl₃ particles having diameters of approximately 10 μm which tend to disperse more uniformly within the matrix. Advantageously, based on the above testing, the resulting metal alloy is not only relatively lightweight, but also exhibits relatively high mechanical strength, wear resistance, thermal stability and resistance to high temperature oxidation.

It would be further appreciated by a person skilled in the art that because a cold-pressed powder composition is processed in accordance with the first embodiment method, it lends itself well to the formation of products of moderately complex geometries such as valve seats, pistons, piston cylinders and the like which may particularly benefit from the above-described properties of the resulting metal alloy. In view of the test results of the microstructure and properties of the metal alloy embodiment formed, it would be appreciated by a person skilled in the art that the metal alloy embodiment material should be suitable for application in automotive applications. Moreover, because such products are formed by sintering a cold-pressed moulded powder composition, the need for machining of the products is alleviated. Consequently, the costs and labour associated with machining processes, as well as the typical wastage of manufacturing materials associated with machining processes, may conveniently be reduced.

It would further be appreciated by a person skilled in the art that because rapid thermal processing is used to sinter powder compositions in accordance with the first embodiment method, this assists in substantially reducing the overall manufacturing time and associated power consumption in comparison to pre-existing manufacturing processes used in a similar context in which relatively lengthy sintering times and sintering temperatures are required.

By way of example, FIG. 25 shows a partially-formed cylinder liner (2500) which has been formed from a powder composition in accordance with the first embodiment method. The constituent particle weight percentages of the powder composition falls within the parameters described herein and has been cold-pressed and sintered at a sintering temperature of approximately 700° C. for 2 minutes.

FIGS. 26A and 26B show SEM images of the cylinder liner (2500) microstructure magnified by factors of ×800 and ×300 respectively in which it can be seen that TiAl₃ particles (2600) of approximately 10 μm in diameter are relatively uniformly distributed throughout the matrix (2610) to form a relatively fine, homogenous microstructure.

Furthermore, embodiments of the present invention in which metal alloys are formed from Vanadium-containing powder compositions are particularly well-suited for application in the manufacture of prosthetics, stents and other implantable medical component due to the resulting metal alloy being lightweight, robust, suitably adapted for formation into the requisite geometries, and biocompatible.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described without departing from the scope of the invention. All such variations and modification which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope of the invention as broadly hereinbefore described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps and features, referred or indicated in the specification, individually or collectively, and any and all combinations of any two or more of said steps or features.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge.

Claims

1. A method of forming a metal alloy from a powder composition comprising first particles in a range of approximately 20-90% by weight of the powder composition, the remainder of the powder composition comprising approximately 95% by weight of second particles and 5% by weight of third particles, wherein the method includes the step of using rapid thermal processing (RTP) to sinter the powder composition.

2. A method as claimed in claim 1 wherein the first particles include an inter-metallic compound.

3. A method as claimed in claim 2 wherein the inter-metallic compound includes TiAl3 particles.

4. A method as claimed in claim 1 wherein the second particles include Aluminium particles.

5. A method as claimed in claim 4 wherein the Aluminium particles include 6061 Aluminium particles.

6. A method as claimed in claim 1 wherein the third particles include Titanium particles.

7. A method as claimed in claim 1 wherein the step of using rapid thermal processing to sinter the powder composition includes heating the powder composition up to a temperature substantially within a range of 700-800° C.

8. A method as claimed in claim 7 wherein the step of using rapid thermal processing to sinter the powder composition includes heating the powder composition up to within the range of approximately 700-800° C. within a timeframe of between approximately 0-10 seconds.

9. A method as claimed in claim 7 wherein after initially heating the powder composition up to a sintering temperature within the range of approximately 750-800° C., the powder composition is maintained at that sintering temperature for at least around 60 seconds.

10. A method as claimed in claim 7 wherein after initially heating the powder composition up to a sintering temperature of approximately 700° C. the powder composition is maintained at that sintering temperature for at least around 90 seconds.

11. A method as claimed in claim 1 wherein sintering is ceased after approximately 4 minutes of sintering.

12. A method as claimed in claim 11 wherein after sintering is ceased, the sintered powder composition is rapidly cooled.

13. A method as claimed in claim 1 including the step of cold-pressing the powder composition in to a mould before sintering the powder composition using rapid thermal processing.

14. A method as claimed in claim 13 including a step of mixing the powder composition before cold-pressing the powder composition.

15. A method as claimed in claim 14 wherein the step of mixing the power composition includes rotatably mixing the powder composition for at least 12 hours before being cold-pressed.

16. A method as claimed in claim 3 wherein the TiAl3 particles in the powder composition include diameters of approximately 50 μm before sintering.

17. A method as claimed in claim 3 wherein sintering of the powder composition by rapid thermal processing causes the TiAl3 particles to fragment into smaller particles of approximately 10 μm in diameter.

18. A method of forming a Vanadium-containing metal alloy from a powder composition comprising first particles in a range of approximately 20-90% by weight of the powder composition, the remainder of the powder composition comprising approximately 95% by weight of second particles and 5% by weight of third particles, wherein the method includes the step of using rapid thermal processing (RTP) to sinter the powder composition.

19. A powder composition adapted for processing by the method steps of claim 1 to form a metal alloy.

20. A metal alloy formed in accordance with the method steps of claim 1.

21. A metal alloy as claimed in claim 20 including inter-metallic TiAl3 particles of approximately 10 μm in diameter.

22. An apparatus adapted for performing the method steps in accordance with claim 1.

23. A metal alloy automotive component formed in accordance with the method of claim 1.

24. A metal alloy implantable medical component formed in accordance with the method of claim 18.