AU648876B2 - Aluminium based, copper-cobalt alloy - Google Patents

Description

OPI DATE 77/08/9? AOJP DATE 01/10/92 APPLN. ID 12 717 9 2D PCT NUMBER DEMANDE DE BREVETS (PQT (51) Classification internationale des brevets 5 (11) Num~ro de publication internationale: WO 92/13111 .C22C 21/00, 2 1/12, C23C 30/00 Al (43) Date de publication internationale: 6 aoiit 1992 (06.08.92) (21) Numiro de la demande internationale: PCT/FR92/00030 (81) Etats d~sign~s: AT (brevet europ~en), AU, BE (brevet europ~en), CH (brevet europ~e DE (brevet europ~en), DK (22) Date de d~p6t international: 15 janvier 1992 (15.01.92) (brevet europeen), ES (brevet europ~en), FR (brevet europ~en), GB (brevet europ~en), GR (brevet europ~en), IT (brevet europ~en), JP, LU (brevet europ~en), MC Donn~es relatives i la priorit6: (brevet europ~en), NL (brevet europ~en), SE (brevet 92/00549 I8janvier 1991 (18.01.91) FR europ~en), US.

(71) Diposai (pour tous les Etats disig,:~s sauf US): CENTRE Publi~e NATIONAL DE LA RECHERCHE SCIENTIFIQUE Avec rapport de recherchie internationale.

[FR/FR); 15, quai Anatole-France, F-75700 Paris (FR).

(72) Inventeurs; et 1nvenleurs/D~posants (US seulement) DUBO IS, Jean-Marie [FR/FR]; 8, nie du Dr.-Zivr6, F-54340 Pompey (FR).

PIANELLI, Antoine [FR/FR]; 30, rue de Vainnes, F- 54 180 Heillecourt Ar 64 87 (74) Mandataires: SUEUR, Yvette etc. Cabinet Sueur L'Hel-A f goualch, 78, rue Carnot, F-95240 Cormeilles-en-Parisis (54)Title: ALUMINIUM ALLOYS, SUBSTRATES COATED WITH SAME AND THEIR APPLICATIONS (54)Titre: ALLIAGES D'ALUMINIUM, LES SUBSTRATS REVETUS DE CES ALLIAGES ET LEURS APPLICATIONS (57) Abstract Alloys, the essential constituent of which is aluminium, metal deposits using on said alloys, substrates coated with same and their application. The alloys of the present invention are characterized by having the following atomic composition Ala.

CubCob'(B, C)cMdNeIr, a b b' c e f 100onumber of atoms, a 50, 0 b 14, 0 b' 22, 0< b b' 0 c 5, 8 d 30, 0 e 4, f 2, M being one or more elements selected from Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Pd; N being one or more elements selected from W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge, the rare earths; I being the impurities inevitably formed during processing; and in that they contain at least 30 in mass of one or more qu asicrystal line phases.

(57) Abr~g6 La pr~sente invention concerne des alliages, dont le constituant essemtiel est aluminium, les d~p6ts m~talliques r~alis~s A partir de ces alliages, les substrats revktus de ces alliages et les applications de ces alliages, Les alliages de la pr~sente invention sont caract~ris~s en ce qu'ils pr~sentent la composition atomnique suivante: AlaCUbCOb'(B, C)cMdNclr, a b b' c d e f 100 en nombre d'atomes, a 50, 0 b 14, 0 b' 22, 0< b b' 30, 0 4 c 4 5, 8 d 30, 0 e 4.

f 2, avec M repr~sentant un ou plusieurs 616ments choisis parmi Fe, Cr, Mn, Ni, Ru, O~e, Mo, V, Mg, Zn, Pd; N rcpr~s 'ntant un ou plusieurs 616ments choisis parmi W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge, les terres rares; I repr~sentant les impuret~s d'61aboration in~vitables; et qu'ils contiennent au moins 30 en masse d'une ou. plusieurs phases qoasicristal lines.

PATENT APPLICATION CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE An invention of DUBOIS Jean-Marie PIANELLI Antoine

ABSTRACT

Aluminum alloys, substrates coated with these alloys and their applications.

The present invention relates to alloys in which the essential constituent is aluminum, metal deposits produced from these alloys, substrates coated with these alloys and the applications of these alloys.

The alloys of the present invention are characterized in that they have the following atomic composition AlaCubCOb, C) MdNaI (I) a b b' c d e f 100, expressed as number of atoms, a 50, 0 s b 14, 0 s b' s 22, 0 b b' 0 c 5, 8 s d s 30, 0 s e s 4, f 2, where M represents one or more elements chosen from Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn and Pd; N represents one or more elements chosen from W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths; I represents the inevitable production impurities; and they contain at least 30 by mass of one or more quasicrystalline phases.

I A Lu r iiC)

AN:

Aluminum alloys, substrates coated with these alloys and their applications.

The present invention relates to alloys in which the essential constituent is aluminum, substrates coated with these alloys and the applications of these alloys, for example for forming thermal protection elements.

Diverse metals or metal alloys, for example aluminum alloys, have found numerous applications to date because of their valuable properties and in particular their mechanical properties, their good thermal conductivity, their lightness and their low cost. Thus, for example, cooking implements and equipment, anti-friction bearings, equipment mountings or supports and diverse articles obtained by molding are known.

However, the majority of these metals or metal alloys have drawbacks for some applications, associated with their inadequate hardness and resistance to wear and with their low resistance to corrosion, in particular in an alkaline medium.

Various attempts have been made to obtain improved aluminum alloys. Thus, European Patent 100287 describes a family of amorphous or microcrystalline alloys having improved hardness which can be used as reinforcing elements for other materials or in order to produce surface coatings improving the resistance to corrosion or wear. However, a large number of the alloys described in this patent are not stable at temperatures higher than 200 0 C and during a heat treatment, in particular the treatment to which they are subjected in the course of deposition on a substrate, they change structure: return to the microcrystalline state if the alloys concerned are essentially amorphous, adt coarsening of the grains in the case of the essentially microcrystalline alloys which initially have a particle size of less than 1 micron. This change in crystalline or morphological structure gives rise to a change in the physical characteristics of the material, which essentially affects its density. This results in the appearance of microcracks, causing fragility, which have 7 2 an adverse effect on the mechanical stability of the materials.

Another family of alloys has been described in EP 356287. These alloys have improved properties. However, their copper content is relatively high.

Thermal stability is an indispensable property if an alloy is to be able to be used as a thermal barrier.

Thermal barriers are assemblies of one or more materials intended to restrict the heat transfer towards or from equipment parts and components in numerous domestic or industrial devices. For example, mention may be made of the use of thermal barriers in heating or cooking devices, irons at the attachment of the hot part to the casing and the thermal insulation; in cars, at several points, such as the turbocompressor, the exhaust silencer, insulation of the body, etc.; and in aeronautics, for example on the rear part of compressors and reactors.

Thermal barriers are sometimes used on their own in the form of a shield, but very often they are directly combined with the source of heat or with the part to be protected, for reasons of mechanical strength. Thus, use is made of mica sheets, ceramic sheets and the like in domestic household appliances, fitting them by screwing or sticking, or of sheets of agglomerated glass wool supported by a metal sheet. A particularly advantageous process for combining a thermal barrier with a part, in particular a metal part, consists in depositing the material constituting the barrier on a substrate in the form of a layer of predetermined thickness by a thermal spraying technique, such as plasma spraying for example.

Very often it is recommended to combine the thermal barrier with other materials aloo deposited in the form of a layer by thermal spraying. These other materials may be intended to ensure that the barrier is protected from external attack, such as, for example, mechanical shocks, a corrosive medium, and the like, or may serve as a sublayer for bonding to the substrate.

3 The material most frequently used in aeronautics to form thermal barriers is yttrium-containing zirconia, which withstands very high temperatures. The zirconia deposit is produced by plasma spraying using a conventional technique, using the powdered material as starting material. Zirconia has a low thermal diffusivity (a 10- 6 m 2 However, it has a relatively high specific mass d, which is a drawback for some applications; moreover, some of its mechanical properties, such as the hardness and the resistance to wear and to abrasion are poor.

Other materials are used as a thermal barrier.

Mention may be made of alumina, which -s a specific mass lower than that of zirconia and a diffusivity and a specific heat higher than those of zirconia, but has unsatisfactory mechanical properties. Mention may also be made of stainless steels and some refractory steels which offer thermal insulation properties, but which have a high specific mass.

The aim of the present invention is to provide a family of alloys having high hardness and thermal stability and improved ductility and corrosion resistance.

The present invention thus relates to a new family of alloys in which the essential constituent is aluminum.

The invention also relates to the metal coatings obtained from these alloys.

A further subject of the invention comprises the substrates coated with the said alloys.

Finally, a further subject comprises the applications of the said alloys.

The alloys of the present invention are characterized in that: r-s-ie- they have the following atomic composition AlCubCob, (B,C),MdNeIf

(I)

in which: ni N 4 a b b' c d e f 100, expressed as number of atoms a 2 0 b 14 0 b' s 22 0 b b' s 0 s c 5: 8 d s 0 ses 4 f 2 M represents one or more elements chosen from Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn and Pd; N represents one or more elements chosen from W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths; I represents the inevitable production impurities; and in that they contain at least 30 by mass of one or more quasicrystalline phases.

In the present text the expression "quasicrystalline phase" encompasses: 1) the phases having rotational symmetries normally incompatible with the translational symmetry, that is to say symmetries of the axis of rotation of the order of 5, 8, 10 and 12, these symmetries being revealed by-K--Ley-diffraction. By way of example, the icosahedral phase I of point group ml 5 (cf. D. Shechtman, I. Blech, D. Gratias, J.W. Cahn, Metallic Phase with Long-Range Orientational Order and No Translational Symmetry, Physical Review Letters, Vol. 53, No. 20, 1984, pages 1951-1953) and the decagonal phase D of point group 10/mmm (cf. L. Bendersky, Quasicrystal with One Dimensional translational Symmetry and a Tenfold Rotation Axis, Physical Review Letters, Vol. 55, No. 14, 1985, pages 1461-1463) may be mentioned. The X-ray diffraction diagram of a true decagonal phase has been published in "Diffraction approach to the structure of decagonal quasicrystals, J.M. Dubois, C. Janot, J. Pannetier, A. Pianelli, Physics Letters A 117-8 (1986) 421-427".

5 ci roxiiode- approximcted 2) The4eir---related- phases orAj-4act -rclatodcompounds which are true crystals to the extent that their crystallographic structure remains compatible with the translational symmetry, but which have, in the electron diffraction pattern, diffraction figures for which the symmetry is close to the axes of rotation 5, 8, or 12. Some of thesenea--t relted phases have been identified in compounds of the prior art. Others have been demonstrated in some alloys of the present invention.

Amongst these phases mention may be made, by way of example, of the orthorhombic phase characteristic of an alloy of the prior art having the atomic composition A1 5 Cu 20 Fe 10 Cr 5 for which the lattice constants are: 2.366, bo 1.267, c( 3.252 in nanometers.

This orthorhombic phase 01 is said to beA-aea-re-sfit relat to the decagonal phase. It is, moreover, so close that it is not possible to distinguish its X-ray diffraction diagram from that of the decagonal phase.

Mention may also be made of the rhombohedral phase having the constants a R 3.208 nm, a 360, present in the alloys having a composition close to Alg 4 Cu 24 Fe 12 in number of atoms Audier and P. Guyot, Microcrystalline AlFeCu Phase of Pseudo Icosahedral Symmetry, in Quasicrystals, Eds. M.V. Jaric and S. Lundqvist, World Scientific, Singapore, 1989).

This phase is a phase 4 naeCt rla-ted- to the icosahedral phase.

Mention may also be made of the orthorhombic O0 and 03 phases having the respective constants a0 2 3.83; bo 2 0.41; cO/ 2 5.26 and ao 3 3.25; bo 3 0.41; o 3 9.8 in nanometers, present in an alloy of composition Alg6Cu 1 7.Co 17 5 Si 2 in number of atoms, or else the 04 orthorhombic phase having constants ao 1 4 1 1.46; b 0 4 1.23; co 4 1.24 in nanometers, which forms in the alloy of composition A1 63 Cu 8 Fe 2 Cr,, in number of atoms, of the present invention. The qn -elatcd orthorhombic phases are described, for example, in C. Dong, V k*.i A 6 Dubois, J. Materials Science, 26 (1991), 1647.

Mention may also be made of a phase C, of cubic structure, very frequently observed in co-existence with thenoar or true quasicrystalline phases. This phase, which forms in some Al-Cu-Fe and Al-Cu-Fe-Cr alloys consists of a superstructure, by the effect of the chemical order of the alloying elements with respect to the aluminum sites, of a phase of typical structure Cs-Cl and lattice constant a, 0.297 nm.

A diffraction diagram of this cubic phase has been published Dong, J.M. Dubois, M. de Boissieu, C. Janot; Neutron diffraction study of the peritectic growth of the Al 5 Cu 2 0 Fe 15 icosahedral quasicrystal; J. Phys. Condensed Matter, 2 (1990), 6339-6360) for a sample of pure cubic phase of composition A1 65 Cu 20 Fe, 1 in number of atoms.

Mention may also be made of a phase H of hexagonal structure which derives directly from phase C, as is shown by the epitaxial relationships observed by electron microscopy between crystals of phases C and H and the simple relationships which link the constants of the crystal lattices, that is to say a s 3/7 a/J3- (to within 4.5 and cH 3/T al/2 (to within 2.5 This phase is isotypical of a hexagonal phase, designated )AlMn, discovered in Al-Mn alloys containing 40 by weight of Mn Taylor, Intermetallic phases in the Aluminum-Manganese Binary System, Acta Metallurgica 8 (1960) 256].

The cubic phase, its superstructures and the phases which are derived therefrom constitute a class of ap ro)cir ret1 J^>ephases' ea-rcst relatod toA quasicrystalline phases of closely related compositions.

Amongst the alloys of the present invention, mention may be made of those, designated (II) below, which have the abovementioned atomic composition in which 0 b s 5, 0 s b' s 22 and/or 0 c s 5 and M represents Mn Fe Cr or Fe Cr.

lei1 7 These alloys (II) are more particularly intended for coating cooking utensils.

Another particularly valuable family, designated (III) below, has the abovementioned atomic composition in whi.- 15 d 30 and M represents at least Fe Cr, with a Fe/Cr atomic ratio of 2.

These alloys (III) have a particularly high resistance to oxidation.

Moreover, amongst the alloys (III) it is possible to distinguish a family of alloys (IV) particularly resistant to corrosion: in a weakly acid medium (5 s pH 7) if b 6, b' 7 and e 1 0 where N is chosen from Ti, Zr, Rh and Nb, and in a strongly alkaline medium (up to pH 14) if b 2, b' 7 and e a 0.

Another family of alloys which are of interest because they offer an improved resistance to grain growth up to 700°C has the composition of the alloys where 0 e s 1, N being chosen from W, Ti, Zr, Rh, Nb, Hf and Ta.

Another family of alloys having an improved hardness, has the mposition of the alloys where b 5 and b' a 5, preferably b 2 and b' 7.

Finally, the alloys (VII) having the composition and which have an improved ductility are those for which c 0, preferably 0 c s 1, and/or 7 s b' s 14.

The alloys of the present invention are distinguished from the alloys of the prior art, and in particular from those of EP 356 287, by their lower or even zero copper content. Because of this, the alloys are less susceptible to corrosion in an acid medium. Moreover, the low copper content is more favorable to the production of an improved ductility by the addition of other elements such as B or C. In the alloys of the present invention, copper may be completely or partially replaced by cobalt.

These alloys are then particularly valuable with regard 8 to the hardness, the ductility and the resistance to corrosion both in an alkaline medium and in an acid medium within the intermediate pH range (5 s pH The combination of these various properties offers a wide range of applications to the alloys of the present invention.

The alloys of the present invention may, for example, be used as wear-resistant surface or reference surface coating or to produce metal-metal or metal-ceramic joints. They are also suitable for all applications involving contact with foodstuffs.

The alloys of the invention, preferably those of group (VII), may also be used for shock-resistant surfaces.

For electrical or electrical engineering applications, or for high frequency he Lting, the alloys according to the invention of groups (III) and will preferably be used.

The alloys of group (III) will preferably be used to produce surfaces resistant to oxidation, whereas those of groups (III) and (IV) are particularly suitable for surfaces resistant to corrosion.

The alloys of groups (III), (IV) and (VII) are particularly suitable for the production of cavitationresistant or erosion-resistant surfaces.

The materials of the present invention, and more particularly those of group may be used to produce elements for thermal protection of a substrate, in the form of a thermal barrier or in the form of a bonding sublayer for thermal barriers consisting of conventional materials. They have good thermal insulation properties, good mechanical properties, a low epecific mass, good resistance to corrosion, especially to oxidation, and are very easy to use.

The materials of the present invention which can be used for the production of thermal protection elements according to the present invention have thermal diffusivity values a close to 10-6 m 2 which are very 9 comparable with the thermal diffusivity of zirconia.

Taking into account the lower specific mass d of these materials, the thermal conductivity A adCp in the vicinity of ambient temperature is not significantly different from that of zirconia. The quasicrystalline alloys of the present invention are therefore obvious substitutes for replacing numerous thermal barrier materials, and in particular zirconia, compared with which they have the advantages of low specific mass and excellent mechanical properties in respect of the hardness, the improved resistance to wear, to abrasion, to scratching and to corrosion.

The diffusivity of the materials forming the thermal protection elements of the present invention is reduced when the porosity of the materials increases. The porosity of a quasicrystalline alloy may be increased by a suitable heat treatment.

The materials forming the thermal protection elements of the present invention may contain a small proportion of heat-conducting particles, for example crystals of metallic aluminum. The heat conduction of the material will be dominated by the conduction properties of the matrix as long as the particles do not coalesce, that is to say as long as their proportion by volume remains below the percolation threshold. For particles which are approximately spherical and have a low radius distribution this threshold is at about 20 This condition implies that the material forming the thermal protection element contains at least 80 by volume of quasicrystalline phases as defined above. Preferably, therefore, use is made of materials containing at least of quasicrystalline phase, for their application as thermal barrier.

At temperatures below about 700 0 C, the thermal protection elements may be used as thermal barriers. Such temperature conditions correspond to the majority of domestic applications or applications within the S automobile sector. Moreover, they are very capable of k*" 10 resisting the stresses due to the expansion of the support and their coefficient of expansion is between that of metal alloys and that of insulating oxides.

Preferably, for temperatures higher than about 600 0 C, the quasicrystalline alloys forming the thermal barriers may contain stabilizing elements chosen from W, Zr, Ti, Rh, Nb, Hf and Ta. The stabilizing element content is less than or equal to 2 expressed as number of atoms.

The thermal barriers of the present invention may be multilayer barriers in which layers of materials which are good conductors of heat alternate with layers of materials which are poor conductors and which are quasicrystalline alloys. Abradable thermal barriers, for example, are structures of this type.

For applications in which the temperatures reach values higher than about 600 0 C, the thermal protection elements of the present invention may be used as bonding sub-layer for a layer serving as thermal barrier and consisting of a material of the prior art, such as zirconia. In these temperature ranges, the materials forming the thermal protection elements of the present invention become superplastic. They therefore meet the conditions of use required for the production of a bonding sublayer while being capable of themselves participating in insulation of the substrate. Thus, the thermal protection elements of the present invention may be used to within a few tens of degrees of the melting point of the material from which they are formed. This limit is at 950 0 C to 1200°C, depending on the composition.

The alloys according to the invention may be obtained by the conventional metallurgical production processes, that is to say processes which comprise a slow cooling stage AT/t less than a few hundred degrees). For example, ingots may be obtained by melting separate metallic elements or prealloys in a brasquelined graphite crucible under a blanket of protecting gas N "(argon, nitrogen), or a blanketing flow conventionally 11 used in production metallurgy, or in a crucible kept under vacuum. It is also possible to use crucibles made Coole of refractory ceramics or of Acopper with heating by high frequency current.

The preparation of the powders required for the metalization process may be carried out, for example, by mechanical grinding or by spraying liquid alloy in a jet of argon in accordance with a conventional technique. The alloy production and spraying operations may take place in sequence without requiring casting of intermediate ingots. The alloys produced in this way may be deposited in thin form, generally up to a few tens of micrometers thick, but also in thick form, which may attain several millimeters, by any metalization technique, including those which have already been mentioned.

The alloys of the present invention may be used in the form of a surface coating by deposition from a preproduced ingot or from separate ingots of the elements, taken as targets in a cathodic sputtering reactor, or else by deposition of the vapor phase produced by melting the solid material under vacuum. Other methods, for example those which use sintering of agglomerated powder, may also be used. The coatings may also be obtained by thermal spraying, for example with the aid of an oxy-gas torch, a supersonic torch or a plasma torch.

The thermal spraying technique is particularly valuable for the production of thermal protection elements.

The present invention will be explained in more detail with reference to the following nonlimiting examples.

The alloys obtained have been characterized in the raw production state by their X-ray diffraction pattern with a wavelength A 0.17889 nm (cobalt anticathode), supplemented, if need be, by electron diffraction diagrams recorded on a Jeol 200 CX electron microscope.

Some alloys were subjected to holding at temperature under secondary vacuum or in air in order to 12 evaluate their thermal stability and their capacity for resisting oxidation. The morphology of the phases and the grain size obtained in the raw production state were analyzed by optical micrography using an Olympus microscope.

The hardness of the alloys was determined using the Wolpert V-Testor 2 hardness tester under loads of and 400 grams.

An estimate of the ductility of some alloys was obtained by measuring the length of the cracks formed from the angles of the impression under a load of 400 grams. A mean value of this length and of the hardness was evaluated from at least 10 different impressions distributed over the sample. Another estimate of the ductility lies in the amplitude of the deformation produced before rupture during a compression test applied to a cylindrical testpiece 4.8 mm in diameter and 10 mm high machined with perfectly parallel faces perpendicular to the axis of the cylinder. An Instrom -{-eeie tensile/compression machine was used.

Finally, the coefficient of friction of a 100C6 steel ball on a substrate coated with an alloy of the present invention was determined using a CSEM tribological tester of the pin /disk type.

The electrical resistivity of the samples was determined at ambient temperature on cylindrical testpieces 20 mm long and 4.8 mm in diameter. The conventional method known as the 4-point method was used, with a constant measurement current of 10 mA. The voltage at the terminals of the inner electrodes was measured using a high precision nanovoltmeter. A determination was carried out as a function of the temperature with the aid of a specifically adapted furnace.

The melting points of a few alloys were determined on heating at a rate of 5 0 C/min. by differential thermal analysis on a Setaram 2000C apparatus.

The crystallographic structure of the alloys was defined by analysis of their X-ray diffraction pattern 13 and their electron diffraction patterns.

Example 1 Production of quasicrystalline alloys A series of alloys has been produced by melting the pure elements in a high frequency field under an argon atmosphere in a chilled copper crucible. The total mass produced in this way was between 50 g and 100 g of alloy. The melting point, which depends on the composition of the alloy, was always found in the temperature range between 950 and 12000C. While keeping the alloy in the molten state, a solid cylindrical testpiece 10 mm 0.5 mm in diameter and a few centimeters high was formed by drawing liquid metal into a quartz tube. The rate of cooling of this sample was ulose to 250°C per second. This sample was then cut using a diamond saw to shape the metallography and hardness testpieces used in the examples below. Part of the testpiece was broken up for thermal stability tests and one fraction was ground to a powder for X-ray diffraction analysis of each alloy. An analogous assembly was used to obtain cylindrical testpieces 4.8 mm in diameter intended for the electrical resistivity. The rate of cooling of the testpiece was then close to 1000 0 C per second.

Table 1 below gives the quasicrystalline phase content of the alloys according to the invention obtained, as well as the melting point of some of these.

The X-ray diffraction patterns and the electron diffraction patterns were recorded for the quasicrystalline alloys indicated in Table 1. Study of these alloys enabled the crystallographic nature of the phases present to be determined. Thus, for example, alloys nos. 2, 5, 7, 8, 9, 19 and 22 contain predominantly phase 01 and alloy 1 contains predominantly phase C. Alloy 3 contains predominantly phase H. Alloy 6 consists essentially of phase H, as well as a small fraction of phase C. The other alloys contain variable proportions of phases C, 01, 03 and 04 (and H in the case of 23).

14 '~55 TABLE 1 Alloy composition by mass Melting No. of quasi- point of crystalline the alloy phase 1 Al, 4 CUj 2 Fe.Cr.Ni 8 Co 4 >90 2 Al 70 Cu 9 FejO.

5 CrjO.

5 >95 1040 3 Al 70 CojOFe 13 Cr 7 >95 1180 4 Al6 9 Cu 4 Fej 0 Cr 7 Mnj 0 Al,,CuFel 2 Cr 2 >8 0 1080 6 Al, 5 Co,,Cr 8 Fea >95 1165 7 Al7 2 Cu.

4 Co 4 Fej 0 Cr 0 z>:6 0 8 A1 75 Cu 5 Fej 0 Crj 0 >:80 1030 9 A1 71 4 Cu 4 5 Fe 1 2 Cr 12

B

0 1 A1 73

CU

4 3 CoFelCr 8 5 Ti 0 7 S1,I 11 Al 74 6

CU

4 Fej 4 Cr 7

C

0 3 12 A1 75 Cu 9 Co 1 6 0 13 A1 75 CugMn, 6 6 0 14 Al, Cu.Fe 16 8 0 lb A17.

7 CUO, GFeqMn6B 0 5 :50 1060 16 Al74CU 2 Co 6 Fe 8 Cr 8 Ni 2 -e70 1090 17 A1 74

CU

2 5 Fe 12 Cr 12

B

0 5 18 A1 69 3

CU

9 2 Fel 1 0 6 CrjO.

6

BO,

3 19 .7l 67 3

CU

8 Fej 1 0 2 Crj 1 0 3

B

33 A1 6 2 2

CU

9 2 Fe 10 .CrjO.

6 8 0 Zr 0 3 21 Al 68 1 Cuq 9 jFej 1 4 Zr 2 30 1080 22 Alrq, 3

CU

9 2 Fel 0 5 Crj 10 6 :80 1100 0 4 15 TABLE 1 (continuation) loy Composition by mass Melting No. of quasi- point of crystal- the alloy line phase 23 Al 66 BCu 1 Co 4 Mn 6 Fel 2 Crl,- 24 Al 69 BCu 1 C o 7 Fe 12 Cr 10

B

0 2 Cu 3 Co.Fe 12 Crl,B, 24 0 1090 26 Al 6 9 CoBFel 2 Cr,B 0 2 27 A1 66 GCo 4 5 Mn 6 5 Fe 12 Crj 0 B02 28 A1 69 5 Cu 9 Fej,. 5 Cr 0 5 HfO, 5 195 29 Al 695 Cu 9 FejO.

5 Cr 10 5 TaO, 5 A1 69 5 CugFe 1 0 5 Cr 1

W

0 5 31 A1Eq, 5 Coj 0 Fe 13 Cr 7 Hf 0 5 32 Al 69 5 Coj 0 Fe 13 Cr 7 Ta, 5 >95 1155 33 Al 6 9 C ojFe 13Cr 7

W

0 5 34 Al 67 CuqFe 10 5 Cr,.

5 Si 3 A1 6 3 5 CUB, Fe 1 Cr 1 0 ,Si,2 5

B

5 36 Al 62 Co 16 Fe8Cr 6 MnNiHf 4 37 Al 6 ,Col 6 Fc 6 CrMnNi 1 Nb 4 38 Al 66 Co 1 4 Nil 4 Mn 2 Hf 4 47 A1 7 0 Co 1 5 Ni 1 5 Example 2 Pr~rnictiaf nnef .a nuii.i-crvsta1 1 n all rv in a larcre auantitv A one hundred (100) kilogram bath of an alloy producing a mass fraction of more than 95 of quasicrystalline phase was produced. The nominal composition of the alloy was A1 67 Cu 9 5 Fe 12 Crjj* 5 expressed as number of atoms (alloy 39). This composition was produced from 16 industrial metal components, that is to say aluminum a Cu-Al-Fe alloy containing 19.5 Al by weight, 58.5 Cu by weight and 21.5 Fe by weight. These elements and alloys were introduced cold into an alumina-lined graphite crucible. They were melted under a blanketing flow which was maintained until the end of the operation.

A 125 kW high-frequency current generator was used. After melting this batch and homogenizing its temperature at 1140 0 C, pure iron, in the form of bars 8 mm in diameter, and then Al-Cr briquettes containing 74 by weight of chromium and 14 by weight of flux were added to obtain the nominal composition of the alloy. After homogenization, all of the melt was cast to give 2-kg ingots. Two samples taken, respectively, at the middle of casting and at the end, were analyzed by a wet method and gave two very close compositions of A1 66 .gCug.

4 Fe 12 .Cr 11 Mn 01 expressed as number of atoms. The proportion of impurities, carbon and sulfur, was found to be less than 0.1 at. X-ray diffraction examination of several Ingot samples, reduced to powder form, shows diffraction Ae. aCpProxftw+re patterns corresponding to- phase 01,-eae rel-a-ted- to the true decagonal phase.

The specific heat of the alloy was determined in the temperature range 20-80 0 C using a Setaram scanning calorimeter. The thermal diffusivity of a pellet of this alloy 15 mm thick and 32 mm in diameter was deda'. from the temperature/time curve measured on one face of the pallet knowing that the opposite, previously blackened face has been irradiated by a laser flash of calibrated power and form. The thermal conductivity is deduced from the above two determinations, knowing the specific mass of the alloy, which has been determined using Archimedes' method by immersion in butyl phthalate kept at 30 0

C

0.1 0 C) and found to be 4.02 g/cm 3 Example 3 Comparative Production of alloys of the prior art By way of comparison, a series of alloys known from the prior art was produced using the process of o I 17 Example 1. These compositions are collated in Table 2 below. The alloys contained at most 30 by mass of quasicrystalline phase, except for that for which the atomic copper content was higher than 18 TABLE 2 Alloy No. Composition by mass of quasi-crystalline phase Al 5 s, Cu, 1 ,Fe.Cr 8 41 AlsFel 5 42 AlgsCr 1 s 43 A1 85 Cu 15 0 44 AlasMo 1 i 0 AlsCu 3 Fez 0 46 Alg 9 CusFes 0 Example 4 Thermal stability The thermal stability of a few alloys of the present invention has been evaluated. The alloys selected were subjected to holding at various temperatures for durations ranging from a few hours to several tens of hours. Fragments extracted by breaking the ingots produced according to Example 1 were placed in quartz ampoules sealed under secondary vacuum. The volume of these fragments was of the order of 0.25 cm 3 The ampoules were placed in a furnace pr ,heated to the treatment temperature. At the end of the treatment, they were cooled under vacuum to ambient temperature by natural convection in air or at a controlled rate. The fragments were then ground for examination by X-ray diffraction.

Examinations by electron diffraction were also carried out. The experimental conditions of the heat treatments are summarized in Table 3 below.

18 TABLE 3 Treatment Alloy Holding Holding Cooling in No. No. temp. period air or coolin hours ing rate T2 2 9500C 5 air T3 5 800 0 C 6 0.5 0 C/min T4 5 950 0 C 5 7 8000C 30 0.5 0 C/min T6 8 950 0 C 5 T7 9 800 0 C 6 0.5 0 C/min The structural development of the alloys during isothermal treatment in the present example was assessed by comparison with the X-ray diffraction patterns recorded, respectively, before and after the heat treatment. It is surprising to find that these patterns show no major modification, either in respect of the number of diffraction lines or in their relative intensities. However, thinning of the diffraction lines is observed, which is due to the well-known phenomenon of grain coarsening at high temperature.

The alloys of the present invention are stable to heat in the sense that their structure, as characterized by the appropriate diffraction patterns, is not essentially changed during isothermal heat treatments at temperatures which can reach the melting point of the alloys. In other words, the mass fraction of quasi-crystalline phase present in the raw production state is not reduced during holding at temperature.

Example Resistance to oxidation Fragment samples identical to those described in Example 4 were subjected to heat treatment in a furnace open to the air, under the conditions summarized in Table 4 below.

Y

19 TABLE 4 a. i' Treatment Alloy Holding Holding No. No. temp. period T9 2 400 0 C 75 hrs 23 500 0 C 24 hrs Ti1 28 500 0 C 24 hrs T12 29 500 0 C 24 hrs T13 30 500 0 C 24 hrs T14 31 500°C 24 hrs 32 500 0 C 24 hrs T16 33 500 0 C 24 hrs Comparison of the diffraction patterns of the samples before treatment with those recorded at the end of the heat treatments in air shows that the samples have not undergone any alteration. More precisely, no trace of grain coarsening is detectable from the widths of the diffraction lines, which have remained identical to those of the patterns characteristic of the raw production state.

Example 6 Morphology and grain size The alloys of the present invention, produced by the method of Example 1, are polycrystalline materials, the morphology of which was studied by optical microscopy using a conventional metallographic technique. For this purpose, pellets 10 mm in diameter (produced by the method of Example 1) were finely polished and then etched with a suitable metallographic reagent. The metallographic images were photographed using an Olympus optical microscope, working in white light. The grain size observed is between a few micrometers and a few tens of micrometers.

i 20 The same method of characterization was applied to the samples treated in air in the temperature range from 400°C to 500°C as described in Table 4 of the above example. On the metallographic images thus obtained it was found that the alloys have not undergone grain coarsening at the end of these heat treatments. It follows that the polycrystalline morphology of these materials, which determines numerous thermomechanical properties, in particular the macroscopic hardness (Hv 400 the coefficients of friction, the elastic limit and the resilience, is not sensitive to holding at temperatures which may reach at least 500 0 C for at least several tens of hours, including in the presence of air.

Example 7 Hardness and ductility at ambient temperature The Vickers hardnesses of the alloys of the present invention and of some alloys of the prior art were determined at ambient temperature on fragments of alloys produced by the process of Example 1, embedded in a resin for metallographic use and then finely polished.

Two microhardness tester loads of, respectively, 30 g and 400 g were used. The results are given in Table 5 below.

The Vickers hardnesses observed for the alloys of the present invention are particularly high in comparison with the Vickers hardnesses under a load of 400 grams recorded for the alloys of the prior art produced as in Example 3 (samples 41 to 46).

The presence of cobalt in the alloys of the present invention singularly increases the hardnesses observed since some values exceed HV 400 800.

In general, the ductility of the alloys having a high hardness is relatively low. However, it is found, surprisingly, that the alloys of the present invention containing cobalt have a higher ductility. In the case of the alloys of the present invention which do not contain cobalt, it is possible to improve the ductility by virtue of additions, for example of boron or of carbon. For simple assessment of the effect of such additions on the 21 ductility of some alloys, the mean length of the cracks which form from the angles of the Vickers impressions under a load of 400 grams were measured. This length is the shorter the more ductile the alloy. A few results are reported in Table TABLE 1.

Alloy No. H 308 HV 400 Mean length of crack (Am) 2 530 650 54 3 655 840 4 670 700 540 540 6 845 46 7 700 770 46 8 430 620 9 450 660 360 660 16 610 775 17 570 620 18 520 660 33 19 460 690 560 680 22 540 730 23 650 795 24 610 715 25 550 775 26 825 39 28 510 700 37 29 410 710 43 510 690 22 TABLE 5 (continuation) Alloy No. HV30S HV 00 Mean length of crack (Am) 31 580 830 32 520 830 33 530 820 41 41 210 42 340 43 170 44 310 45 110 46 170 In addition a compression test was carried out with alloy 2 of Example 1, which does not contain boron, and alloy 19, modified by the addition of 3.3 atomic of boron. Th,. st was carried out at ambient temperature, under increasing load, on cylindrical testpieces 4.8 mm in diameter and 10 mm high. The surfaces of the cylinder to which the load is applied were very carefully machined to be perfectly parallel to one another and perpendicular to the axis of the cylinder. According to the deformation-compression stress curves which were recorded during deformation of testpieces of alloys 2 and 19 (as produced by the method of Example it was found that the addition of boron doubles the deformation obtained at break, which reaches about 2 and the breaking point, which exceeds 1000 MPa.

Example 8 Electrical resistivity at ambient temperature Resistivity determinations were carried out for the alloys according to the invention and, by way of comparison, for compositions of the prior art. In all cases cylindrical testpieces prepared by the method of 23 Example 1 were used.

The results obtained are collated in Table 6 below.

Compositions 41 to 46 and 40 are alloys of 'he prior art; the others are alloys according to the invention.

The compositions of the prior art have an electrical resistivity at ambient temperature which is between a few pn cm and a few tens of pO cm. However, an exception is observed in the case of alloy 42, which has the composition Alg 5 Cr 15 expressed as number of atoms and has a resistivity of 300 pn cm. This value is to be related to the presence of a proportion of quasicrystalline phase which is fairly close to, although less than, 30 by mass. However, this state is metastable and has been produced only by virtue of the high cooling rate which characterizes the production method for the present testpieces.

TABLE 6 Alloy No. Mass fraction of quasicrystalline phase Electrical lesistivity at ambient temp. in gp cm 41 <10 22 42 530 300 43 0 4 44 0 32 0 6 46 0 11 >95 230 2 >95 575 3 >95 520 4 :50 590 7 >60 395 8 >80 380 24 TABLE 6 (continuation) Alloy No. Mass fraction of Electrical resisquasicrystallina tivity at ambient phase temp. in po cm 16 a70 370 17 >90 530 23 >60 330 24 a40 420 25 &40 460 The characteristic values of the electrical resistivity of the alloys of the present invention are between 300 and 600 po cm. Such high values make the quasicrystalline alloys of the present invention suitable for all applications where this property must be put to use, such as, for example, heating by the Joule effect, resistances with high calorific dissipation, and electromagnetic coupling, which may be high frequency.

Moreover, a representative alloy of family (III) has a low temperature coefficient of the electrical resistivity (1/p dp/dT). The relative variation in the electrical resistivity with temperature was determined for a testpiece of alloy 2. This testpiece was prepared from a strip 0.1 mm thick and 1.2 mm wide produced by quenching the liquid alloy on a copper drum, the surface of which was rotating at a speed of 12 m/s (technique known as melt spinning). The ingot heated to the liquid state had been produced by the method of Example 1. The testpiece was heated at a constant rate of 5°C/min and kept in contact with four platinum wires in accordance with the method of determination known as the four-point method. The gap between potential electrodes was 20 mm and the voltage was measured using a precision nanovoltmeter. A constant current of 10 mA circulated in the testpiece through the other two electrodes. The measuring device was kept under a protective argon flow in an i appropriate furnace. It was found that the variation in r' s- 0u 25 resistance is linear, which demonstrates that there is no transformation of the sample either during the determination or during the subsequent heating cycle, confirming the high thermal stability of the alloys (Example The temperature coefficient derived from the (1/p(20 0 0 C)/AT curve is -3.10-4. This low value distinguishes the alloy for applications where it is preferable to retain the characteristics of the material within a narrow range as a function of the temperature, such as, for example, heating by electromagnetic induction.

Example 9 Corrosion resistance The dissolution of some alloys of the present invention, and that of an alloy of the prior art, in various media was determined.

The samples tested are: alloy No. 40 of the prior art containing 18.5 of Cu alloy No. 2 of the invention containing 9 of Cu alloy No. 3 of the invention containing 10 of Co and 0 of Cu alloy No. 6 of the invention containing 18 of Co and 0 of Cu.

To determine the degree of dissolution, a testpiece 10 mm in diameter and 3 mm thick, produced by the method of Example 1, was immersed for 30 h in a corrosive solution at various temperatures. The solution was stirred throughout the immersion period and kept at temperature by means of a thermostat-controlled bath.

After 30 hours, the loss in weight of each testpiece was determined.

The results are collated in Table 7 below. The figures given represent the loss in weight of the sample in gm' 2 h- 1 N.D. denotes "not detected".

26 TABLE 7 Medium 10 20 Pure Pure

HNO

3

HNO

3 NaOH KOH pH=5 pH=4 Sample 20 0 C 35 0 C 200C 700C 200C 20 0

C

No. 40 30 25 35 230 No. 2 N.D. N.D. 7 No. 3 N.D. N.D.

No. 6 N.D. N.D.

It is well-known that the addition of copper reduces the corrosion resistance of alur Inum alloys (Chapter 7 of Aluminum, Vol. I, Ed. K.R. Van Horn, American Society for Metals). In a dilute acid medium, for example, aluminum alloys have a high degree of dissolution which usually falls as the acid content increases. In the proximity of 100 acid concentration, this, degree of dissolution again increases vory substantially. Conversely, on the alkaline side, the behavior of aluminum alloys is satisfactory until the pH rises above pH=12. The passivating alumina film which protects them is then able to go into solution and aluminum alloys usually have very low resistance to corrosion in a highly alkaline medium.

The above tests show that the present invention provides alloys which have excellent resistance to corrosion in an acid medium (No. 2, having a Cu content higher than 5 atomic or in a strongly alkaline medium (Nos. 3 and 6, having a cobalt content higher than atomic Thus, the quasi-crystalline alloys of the present invention combine several properties which single them out very particularly for numerous applications in the form of surface coatings: high hardness, low but not negligible ductility, stability to heat and high resistance to corrosion. The following example will show that these alloys retain these properties after their use IV 27 as surface coating. They then have a surprisingly low coefficient of friction, which adds to the range of valuable properties already mentioned.

Example Use of an alloy of the present invention for the production of a surface deposit A two-kilogram ingot of the alloy produced according to Example 2 was reduced to powder by grinding using a carbon steel concentric pebble mill. The powder thus obtained was sieved so as to retain only the particle fraction having a size between a minimum of 25 ym and a maximum of 80 pm. A 0.5 mm thick deposit was then produced by spraying this powder onto a sheet of previously sandblasted mild steel. This spraying was carried out using a Metco flame torch fed by a mixture containing 63 of hydrogen and 27 of oxygen. The operation was carried out under a protective atmosphere of nitrogen containing 30 hydrogen, so as to prevent any oxidation of the sample. After removal of the surface roughness by mechanical polishing, examination by X-ray diffraction showed that the alloy deposited consisted of at least of icosahedral phase. The testpiece, consisting of the steel substrate provided with its quasicrystalline coating, was then divided into two parts by sectioning and one of these parts was subjected to a heat treatment at 500 0 C in air as indicated in Example 4. A study of the X-ray diffraction pattern recorded for the treated sample shows no major modification in the structure after holding at temperature for 28 hours and confirms the very high thermal stability of the alloy, including after the surface metalization operation. Table 8 below summarizes the results of the hardness determtinations carried out, as in Example 7, before and after heat treatment. The value determined for the ingot before reduction to powder is also given.

28 TABLE 8 Raw production ingot (Ex. 2) Deposit before treatment Deposit after treatment 28 h 500 0

C

air Vickers hardness Hv 30 640 525 550 510 610 Coefficient of friction Brinell 100C6 0.26-0.30 0.23-0.25 ball In addition, the coefficient of friction of a s-6-el usge 1for Brinell ball, made of 100C6A tools, on the deposit of the present example was determined using a CSEM tribological tester of the pin -disk type. A normal force Fn 5N was applied to the friction piece normal to the plane of the deposit. The force of resistance to the movement of the friction piece Ft(N), measured (in newtons) tangentially to the movement, gives the coefficient -f friction i Ft(N)/Fn, under constant normal force, which is given in Table 8. It should be noted that the values in Table 8 are comparable to, or even substantially better than, the values obtained for other materials used in tribological applications.

Example 11 Thermal diffusivity at ambient temperature.

The thermal diffusivity a, the specific mass d and the specific heat Cp were determined in the vicinity of ambient temperature for several samples prepared according to Example 1 and a sample prepared according to Example 2. The samples produced by the method of Example 1 are pellets 10 mm in diameter and 3 mm thick.

The sample of Example 2 is a pellet 32 mm in diameter and mm thick.

The opposite faces of each pellet were polished Smechanically under water, taking great care to guarantee I" 29 their parallelism. The structural state of the testpieces was determined by X-ray diffraction and by electron microscopy. All of the samples selected contained at least 90 by volume of quasi-crystalline phase according to the definition given above.

The thermal conductivity is given by the product A=adCp.

The thermal diffusivity a was determined using a laboratory apparatus combining the laser flash method with a Hg-Cd-Te semiconductor detector. The laser was used to supply pulses having a power of between 20 J and J and a duration of 5.10 4 s to heat the front face of the testpiece, and the semiconductor thermometer served to detect the thermal response on the opposite face of the testpiece. The thermal diffusivity was derived from experiments carried out in accordance with the method described in Degiovanni, High Temp. High Pressure, 17 (1985) 683".

The specific heat of the alloy was determined in the temperature range 20-80 0 C using a Setaram scanning calorimeter.

The thermal conductivity A is derived from the above two determinations, knowing the specific mass of the alloy, which was determined by the Archimedes method by immersion in butyl phthalate kept at 30 0 C 0.1"C).

The values obtained are given in Table 9. By way of comparison, this table contains the values relating to a few materials of the prior art (samples 5 to 13), some of which are known to be thermal barriers (samples to 8).

In Table 9 the letter symbols in the last column have the meaning given above.

4-^ 30 TABLE 9 Alloy Composition a d Cp A=ad Cp by No. m 2 s .10 6 k Jkg Wkg' mass of m k K quasicrystalline phase 28 31 33 34 36 37 38 39 47 100 110 120 130 A1,70CuFe 10 5 Crjb, Al, 0 ColoFe 1 3 Cr A1, 69 Cu 4 FejoCrMnjo Al 6 5 Co 1 8Cr.Fep Al 2 Cu 4 Co 4 Fe 10 Cr 1 o Al 5 Cu 5 FejoCrjo Al1, 4 Cu 4 5 ,Fe 12 Cr 1 2 Bo. 1 Al, .7Cuo. aFeMnrCr%-

B

0 Al 69 5 CuFe 10 5 Crj 0 .5- Al 6 9 5 CuFeo, Crjo 5- Al 6 9 5 CojoFej 3 CrHf 0 ,5 Al 69 5 CojoFe 13 CrWo.

A1 67 CuFejO 5 Crjo.sSi 3 Al 6 3 5 Cu 8 5 Fe 1 0 CrjO- Si2,5B5.5 Al 62 Col 6 Fe8CrMn 1 Ni Hf4 Al 6 2 Co1 6 Fe8Cr8Mn 1 Nij- Nb 4 Al,,Co 1 4 Ni 1 4 Mn 2 Hf 4 A1 6 7 Cu, sFeiCrnts A17 0 Co 1 5 Ni, 5 Al fcc A1 2 0 3 stainless steel Zr02-Y 2 0 3 8 Al 6 Mn A1 13 Si 4 Cr 4 Al.Ti 2 Cu AlCu 2 Fe Al 2 Cu 0.75 1.55 0.75 1.5 1.10 1.65 0.85 1.4 1.35 0.93 1, 0 1.25 0.80 1.10 1.35 2.0 2.3 1.015 1.55 90-100 8.5 4 0.8 5.4 7.4 6.2 14-17 3940 400 3950 3800 3980 4000 4100 4870 4690 4830 4020 4100 2700 3800 7850 5700 620 625 675 670 680 630 670 600 600 900 1050 480 400 1.8 3.9 2.9 4.2 2.0 3.0 2.45 230 34 2 >95 >95 50 >95 >90 >90 >95 >90

O/D

C/H

O/D

C/H

O/D

O/D

O/D

O/D

>90 O/D >95 O/D >95 C/H >90 C/H >95 O/D >90 O/D >90 C/H >70 C/H >60 D >95 0 >95 D These results reveal that, at ambient temperature, the thermal conductivity of the quasi-crystalline alloys forming the protection elements of the present invention is considerably lower than that of the metallic materials (aluminum metal or tetragonal A12Cu), given by way of comparison. It is two orders of magnitude lower than that of aluminum and one order of magnitude lower gf A I' 31 than that of stainless steel, which is usually considered to be a good thermal insulator. Moreover, it is lower than that of alumina and entirely comparable with that of zirconia doped with Y 2 0 3 considered to be the archetypal thermal insulator in the industry.

By way of comparison, the thermal diffusivity of alloys 90, 100, 110, 120 and 130 was determined. These alloys, which form defined aluminum compounds, have compositions close to those of the quasi-crystalline alloys which can be used for the protection elements of the present invention. However, they do not have the quasi-crystalline structure defined above. In all cases, their thermal diffusivity is higher than 5.10- 6 m 2 that is to say well above that of the alloys used for the present invention.

Example 12 Thermal diffusivity as a function of the temperature The values of a were recorded as a function of the temperature up to 900C.

The thermal diffusivity was determined using the method of Example 11. Each testpiece was placed under a flow of purified argon in the center of a furnace heated by the Joule effect; the rate of rise in temperature, programmed by computer, varied linearly at 5 0 C/min. All of the samples according to the present invention show an approximately linear increase in a with the temperature.

The value of a determined at 700 0 C is close to twice that determined at ambient temperature. Similarly, the specific heat increases with the temperature and reaches 800 to 900 J/kgK at 700°C. The specific mass falls by the order of 1 to 2 %t as is indicated by thermal expansion or neutron diffraction determinations,. Consequently, the thermal conductivity remains below 12 W/mK, that is to say below the thermal conductivity of stainless steels which are used for some thermal insulation applications.

Figures 1, 2 and 3 show, respectively, the change in a as a function of the temperature for alloys 28, 31 and 33. The measurements recorded during heating are

S

32 represente- by A4-sI.qyaz-- and those recorded during cooling by.citz quareS [sieG].

Example 13 The variation in the thermal expansion of alloy 2 was determined. The thermal expansion curve shows that th2 coefficient of expansion shows very slight dependence on the temperature and is 9.10- 6 O C, a value close to -t of stainless steel.

Example 14 The superplastic behavior of some alloys capable of forming the thermal protection elements of the present invention was studied. Cylindrical testpieces 4 mm in diameter and 10 mm long, having strictly parallel faces, were produced by the same method as those of Example 1 using alloys 34 and 35. These testpieces were subjected to mechanical tests under compression in an Instrom-Ea-3machine. Tests were carried out up to a load of 250 MPa, at a speed of movement of the beam of 50 ym/min, the temperature being kept constant at between 600 and 850 0

C.

The two alloys show superplastic behavior from 600 0

C.

Example Production of thermal protection elements according to the invention and according to the prior art.

A first series of testpieces was produced. The substrate was a solid copper cylinder having a diameter of 30 mm and a height of 80 mm and the coating was applied using a plasma torch in accordance with a conventional technique. Teetpiece CO is the uncoated copper cylinder. Testpiece C1 was coated over its entire surface with a 1 mm thick layer of alloy 2 and testpiece C2 was coated with a 2 mm thick layer of alloy 2. Testpiece comprises a layer of alloy 2 forming the thermal protection element of the present invention serving as bonding layer and a layer of yttrium-containing zirconia. Testpieces C3 and C4, which serve for comparison, comprise, respectively, a layer of yttrium-containing zirconia and a layer of alumina. Another series of testpieces was S produced using, as support, a stainless steel tube having 33 a length of 50 cm, a diameter of 40 mm and a wall thickness of 1 mm (testpieces AO to A2). In each case, the support tube is coated at one of its ends over a length of 30 cm. In the latter case, the deposits were produced using an oxy-gas torch. Table 10 below shows the nature and the thickness of the layers for the various testpieces. The accuracy in respect of the final thicknesses of the deposits was 0.3 mm.

All of the testpieces were provided with Chromel-Alumel thermocouples of very low inertia. Figure 4 shows a testpiece of the type comprising a copper cylinder 1 carrying a coating 2 and provided with a central thermocouple 3 and a lateral thermocouple 4, the two being inserted to half the length of the cylinder. Figure shows a hollow tube 5, into which a flow of hot air 6 is passed and which is fitted with three thermocouples denoted, respectively, by Ti, T2 and T3, the first two being inside the tube and placed, respectively, at the start of the coated ea and at the end of the coated area, and the third being on the outer surface of the coating.

Example 16 Use of protection elements as protection with regard to a flame.

Testpioces CO, Cl, C2, C3, C4 and C5 were placed with their base on a refractory brick. Successive heat pulses of 10 s duration were applied to each testpiece at intervals of 60 s and the response of the thermocouples was recorded. These pulses were produced by the flame of a torch placed at a constant distance from the testpiece and facing the thermocouple close to the surface. The flow rate of the combustion gases was carefully controlled and kept constant throughout the experiment. Two series of experiments were carried out: one using testpieces initially at 20°C and the other using testpieces initially at 650 0

C.

Testpieces CO to C5 enable three parameters to be defined which summarize the results of the experiment, 34 that is to say the maximum difference P in temperature between the two thermocouples, AT/At, the rate of rise in temperature of the lateral thermocouple 4 during the pulse, and the increase in temperature AT produced in the center of the testpiece (thermocouple These data are given in Table 10. It was found that the zirconia layer of testpiece C3 did not resist more than three pulses and was cracked from the time of the first pulse. Sample C2 did not start to crack until the sixth pulse and sample Cl resisted more than 50 pulses. These results show that the protection elements of the present invention, used as thermal barrier, show performances which are at least equivalent to those of zirconia.

Example 17 Use of the protection elements according to the invention as sub-layer for a thermal barrier.

In testpiece C5 the thermal protection element of the present invention forms a sub-layer. It was found that the zirconia layer of testpiece C3 did not resist more than three heat pulses and was cracked from the time of the first pulse. For testpiece C5, which was also subjected to a series of heat pulses, the surface temperature of the zirconia deposit, measured by a third thermocouple placed in contact with the deposit at the end of the tests, stabilized at 1200 0 C. The experiment extended to 50 pulses and testpiece C5 resisted these without apparent damage, although the coefficient of expansion of copper is close to twice that of the quasicrystalline alloy, which would imply high shear stresses at the substrate/deposit interface if the material of the sub-layer did not become plastic. The thermal protection elements of the present invention are therefore suitable for the production of bonding sub-layers, in particular for thermal barriers.

35 TABLE 100 0

C

650 550 Coating AT AT/At P AT AT/At P material ±0.5C OC/s ±0.5 0 C ±0.5 0 C OC/s OC oC oC oC CO None 27 2.85 5.4 22 2.3 <1 Cl A1 70 CuqFeos, 5 24 2.8 3.8 11 1.1 6 1 mm C2 A1 70 CugFeo,5- 18 1.3 0 25 0.3 4.7 Cro 1 ,5 2 mm A1 70 CugFe 0 5 23 2.6 4.2 13 1.2 Cr 10 ,s0.5 mm ZrO 2

-Y

2 0 3 8% 1 mm C3 Yttrium-contain- 24 2.75 4.7 14 1.5 2.3 ing zirconia 1 mm C4 Alumina 1 mm 27 2.7 6.5 25 3.0 8.2 AO None Al A1 6 5 Co 18 CrFe mm A2 A, 70 CuFejo.,Cro.

5 mm EXAMPLE 18 Application of a thermal protection element of the present invention for the insulation of a reactor.

Testpieces AO, Al and A2 were used to assess the suitability of the alloys of the invention for the thermal insulation of an apparatus. The testpieces were each provided with 3 thermocouples T1, T2 and T3 as shown on Figure 5. A stream of hot air at constant flow rate was passed through the stainless steel tube forming the substrate of each testpiece. The air temperature at the inlet, measured using thermocouple T1, was 300t2 C. The surface temperature, measured using thermocouple T3, was recorded as a function of time from the time the hot air generator was switched on. Thermocouple T2 made it possible t.

V '(r 1. 36 to verify that the transient conditions for establishment of the flow of hot air were identical for all determinations.

Figures 6 and 7 show the change in the surface temperature of each of the testpieces AO, Al and A2 as a function of time. At equilibrium, the surface temperature of testpiece AO (without coating) is about 35 0 C higher than that of testpiece A2 and 270C higher than that of testpiece Al. The thermal protection elements of the present invention give interesting results with regard to thermal insulation.

I 92) d, y

Claims (28)

1. Alloys in which the essential constituent is alum- inum, characterized in that they have the following atomic composition AlaCubCo, C) MdN,I (I) a b b' c d e f 100, expressed as number of atoms a 0 b 14 0 b' 5 22 0 b b' 8 s d f 2 M represents one or more elements chosen from Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn and Pd; N represents one or more elements chosen from W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths; I represents the inevitable production impurities; and they contain at least 30 by mass of one or more quasi-crystalline phases.

2. Alloys according to claim 1, characterized in that they h'ave the atomic composition where 0 r b 0 s b' 5 22 and/or 0 s c s 5, M representing Mn Fe Cr or Fe Cr.

3. Alloys according to claim 1 A characterized in that they have the atomic composition where 15 d s M representing at least Fe Cr, with a Fe/Cr atomic ratio of 2. c I or clafim or

4. Alloys according toAclaim 3, characterized in that b 6, b' 7 and e 0 and N is chosen from Ti, Zr, Rh and Nb.

Y a on C.0eF cf( w Io Alloys according to.-3tai4--r characterized in that b s 2, b' 7 and e 0. <'vl 01e of C[IS I4T s

6. Alloys according toAle-3am--7 characterized in that 0 e s 1, N being chosen from W, Ti, Zr, Rh, Nb, Hf and Ta.

7. Alloys according to claim 1, characterized in that S b 5 and b' z i j a 38

8. Alloys according to claim 7, characterized in that b 2 and b' 7.

9. Alloys according to claim 1, characterized in that 0 c 5 1 and/or 7 5 b' s 14.

10. Alloys according to any one of claims 1 to 9, characterized in that they are obtained in the form of a solid part.

11. Alloys according to any one of claims 1 to 9, characterized in that they are obtained in the form of a deposit on a substrate.

12. Substrates coated with an alloy according to any one of claims 1 to 9.

13. Application of an alloy according to any one of claims 1 to 9 in the production of wear-resistant and/or friction-resistant surfaces, shock-resistant surfaces, reference surfaces, cavitation-resistant or erosion-re- sistant surfaces or a surface resistant to oxidation or to corrosion.

14. Application of an alloy according to any one of claims 1 to 9 in the production of metal-metal joints or metal-ceramic joints.

Application of an alloy according to any one of claims 1 to 9 in the coating of utensils intended for contact with foodstuffs.

16. Electrical engineering applications of the alloys according to any one of claims 1 to 9.

17. Application according to claim 16, in the production of heating elements operating by electromagnetic induction.

18. Application of an alloy according to any one of claims 1 to 9 ia the production of elements for thermal protection of substrate.

19. Application according to claim 18, characterized in that the thermal protection element consists of a quasicrystalline material essentially consisting of the said alloy, deposited on the substrate.

Application according to claim 19, characterized in that the said quasicrystalline material is deposited on the substrate by thermal spraying.

21. Application according to claim 18, characterized in that the said quasicrystalline material contains at least 80% by volume of at least one quasicrystalline phase.

22. Application according to claim 18, characterized in that the said quasicrystalline material has a porosity of more than

23. Application according to claim 18, characterized in that the thermal protection element forms a thermal barrier at temperatures below 8000C.

24. Application according to claim 23, characterized in that the said quasi- crystalline material also contains stabilizing elements, in a content of less than 2% expressed as number of atoms, chosen from W, Zr, Ti, Rh, Nb, Hf and Ta.

Application according to claim 18, characterized in that the thermal protection element is used in the form of an intermediate bonding layer between a support and a thermal barrier, the surface temperature of the said barrier optionally being able to exceed 8000C.

26. Application according to claim 25, characterized in that the thermal protection element consists of layers of quasicrystalline material alternating with layers of materials which are good conductors of heat.

27. Alloys according to claim 1, substantially as herein described with reference to the accompanying drawings.

28. Alloys according to claim 1, substantially as herein described with reference to any one of Examples 1, 2, and 4 to 18. DATED this 9th day of February 1994. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE By their Patent Attorneys: CALLINAN LAWRIE