WO2011039469A1

WO2011039469A1 - Method for producing a part including aluminium

Info

Publication number: WO2011039469A1
Application number: PCT/FR2010/052045
Authority: WO
Inventors: Samuel Kenzari; Vincent Fournee
Original assignee: Ateliers Cini; Centre National De La Recherche Scientifique; Institut National Polytechnique De Lorraine; Universite Henri Poincare - Nancy 1
Priority date: 2009-10-02
Filing date: 2010-09-29
Publication date: 2011-04-07
Also published as: FR2950826B1; FR2950826A1

Abstract

The invention relates to a method for producing a part including aluminium, characterised in that the method includes a step of selective laser sintering a mixture including a polymer powder and a powder of a quasicrystalline aluminium alloy, the weight of the alloy not exceeding 80% of the overall weight of the mixture.

Description

PROCESS FOR PRODUCING A WORKPIECE COMPRISING

ALUMINUM

The present invention relates to a process for producing functional parts comprising aluminum. It also relates to the parts obtained using the method.

It is known to obtain rigid functional parts having a cast aluminum metallic appearance, to subject a mixture of crystalline aluminum powders and a polyamide matrix to a selective laser sintering process. Such parts are, for example, sold under the name DuraForm® AF by the company 3D SYSTEMS or under the name ALUMIDE® by the company EOS.

When the mixture is sintered under the action of the laser, the parts have the disadvantage of having a high degree of porosity, and therefore not being sealed under pressure. It is thus necessary, in order to obtain a satisfactory seal, to cover the material with a layer of waterproof coating, typically with a layer of resin, which makes the process of making the pieces longer and more complex.

The present invention aims to overcome these disadvantages.

The invention proposes a simplified method, making it possible to quickly obtain functional parts of complex shape having a metallic appearance and which have a very good seal.

The present invention thus relates to a process for producing a part comprising aluminum.

The method according to the invention comprises a step of selective laser sintering of a mixture comprising a polymer powder and a powder of a quasi-crystalline aluminum alloy, the weight of the alloy not exceeding 80% of the total weight of the mixture.

The weight of the alloy is less than or equal to 80% of the total weight of the mixture. The quantity of alloy powder is thus chosen so that the volume fraction of the alloy, after the sintering step, does not exceed 50% of the total volume of the workpiece. Selective laser sintering (SLS), also known as Selective Laser Sintering (SLS), is a process that allows a part to be shaped by successive additions of material in the form of powders.

This method uses a laser to transform a material in the form of powders, comprising a mixture of metal powders and polymer, into a solid object by selective sintering without external pressure.

It is known that selective sintering by laser makes it possible to produce parts without form stress, with a high accuracy (± 0.2 mm), but with a high degree of porosity.

The Applicant has discovered that, surprisingly, when the process is carried out using a mixture of powders comprising a limited content of quasi-crystalline aluminum alloy, the part obtained had a very low porosity rate, and therefore a higher seal than when the process is implemented from crystalline aluminum powder. It has also found that by using a quasi-crystalline aluminum alloy the part obtained had improved mechanical properties, in particular of wear, friction and hardness.

The powder mixture may be composed of polymer powder and quasi-crystalline aluminum alloy powder.

The part obtained by the process of the invention is a composite material comprising a polymer matrix and an optionally multiphase complex mechanical alloy.

The quasi-crystalline aluminum alloy may be a complex metal alloy comprising an atomic percentage of aluminum greater than 50%.

The process of the invention is carried out from a powder of a quasi-crystalline aluminum alloy. In the present text, "quasicrystalline alloy" refers to an alloy that includes one or more quasicrystalline phases that are either quasicrystalline phases in the strict sense or approximate phases. The quasicrystalline phases in the strict sense are phases exhibiting symmetries of rotation normally incompatible with the translational symmetry, that is to say rotational axis symmetries of order 5, 8, 10 or 12, these symmetries being revealed by diffraction techniques. By way of example, mention may be made of the icosahedral moment group phase m3 5 and the phase group decagonal phase 10 / mmm.

The approximate phases or approximate compounds are true crystals insofar as their crystallographic structure remains compatible with symmetry of translation, but which exhibit, in the diffraction pattern of electrons, diffraction patterns whose symmetry is close to a symmetry of order 5, 8, 10 or 12. These are phases characterized by an elementary cell containing several tens, or even several hundred atoms, and whose local order presents arrangements of almost icosahedral or decagonal symmetry similar to the quasi-crystalline parent phases.

Among these phases, there may be mentioned by way of example the orthorhombic phase O _{l 5} characteristic of an alloy having the atomic composition Al ₆₅ Cu ₂ _O Fei ₀ Cr ₅ , whose parameters of mesh in nm are: a ₀ ⁽¹⁾ = 2.366, b ₀ ⁽¹⁾ = 1, 267, c ₀ ⁽¹⁾ = 3.252. This orthorhombic phase Oi is said to approximate the decagonal phase. The nature of the two phases can be identified by transmission electron microscopy.

We can also mention the rhombohedral phase of parameters at _R = 3.208 nm, a = 36 °, present in the alloys of atomic composition close to Al ₆₄ Cu ₂₄ Fei ₂ . This phase is an approximate phase of the icosahedral phase.

There may also be mentioned orthorhombic O ₂ and O ₃ phases of respective parameters in nm at ₀ ⁽²⁾ = 3.83; b ₀ ⁽²⁾ = 0.41; c ₀ ⁽²⁾ = 5.26 and ₀ ⁽³⁾ = 3.25; b ₀ ⁽³⁾ = 0.41; c ₀ ⁽³⁾ = 9.8, present in an alloy of atomic composition Al ₆₃ Cui _{7; 5} Coi _{7; 5} Si ₂ or the orthorhombic phase O4 of parameters in nm at ₀ ⁽⁴⁾ = 1, 46; b ₀ ⁽⁴⁾ = 1, 23; c ₀ ⁽⁴⁾ = 1, 24, which is formed in the alloy whose atomic composition is Al ₆₃ Cu ₈ Fei ₂ Cr ₁₇ .

We can also mention a phase C, of cubic structure, very often observed in coexistence with the approximate or quasi-crystalline phases true. This phase, which is formed in certain Al-Cu-Fe and Al-Cu-Fe-Cr alloys, consists of a super-structure, by the chemical effect of the alloying elements with respect to the aluminum sites, of a typical Cs-Cl structure phase and lattice parameter ai = 0.297 nm. A diffraction pattern of this cubic phase has been published for a pure cubic phase sample and atomic Al ₆₅ Cu ₂₀ Fei ₅ atomic composition.

We can also mention a phase H of hexagonal structure which derives directly from the phase C as demonstrated by the epitaxial relationships observed by electron microscopy between crystals of the C and H phases and the simple relations that link the parameters of the crystal lattices, namely a _H =

(to within 4.5%) and c _H = 3-jal (to within 2.5%). This phase is isotype of a hexagonal phase, noted ΦΑΙΜη, found in Al-Mn alloys containing 40% by weight of Mn. The cubic phase, its superstructures and the phases derived from them constitute a class of approximate phases of quasi-crystalline phases of neighboring compositions.

The quasi-crystalline alloys of the Al-Cu-Fe system and the Al-Fe-Co-Cr system are particularly suitable for carrying out the process of the present invention. Mention may in particular be made of alloys which have one of the following atomic compositions: Al ₆₂ Cu _25; Fei _2; 5, Al ₅₉ Cu ₂ 5 _, Fe _2, B ₃ , Al ₇₁ Cu _9, Fe ₈ , ₇ Cr ₁₀ , ₆ , and Al _71, Fe ₈ , Co _{2, 8} Cr _{7, 8} . These alloys are marketed by Saint-Gobain. In particular, the alloy Al ₅₉ Cu _25; Fei _{2; 4} B ₃ is marketed under the name Cristome Fl, the alloy Al ₇₁ Cu _{9; 7} Fe ₈ , ₇ Cr ₁₀ , ₆ is marketed under the name Cristome Al , and the alloy

is marketed under the name Cristome BT1. These complex alloys have the advantage of having tribological properties (friction and wear), surface (low surface energy), mechanical properties (hardness, yield strength and Young's modulus), thermal conductivity and electrical properties (high resistivity). , different from those of crystalline aluminum alloys.

The polymer may for example be chosen from thermoplastic organic polymers such as polyamides (for example nylon 6, nylon 11, nylon 12), amide copolymers (for example nylon 6-12), polyacetates, polyethylenes, as well as polyetheretherketone, designated by the acronym PEEK (PolyEtherEtherKetone in English).

Preferred polymers are polyamides and polyetheretherketone.

The mixture of quasi-crystalline aluminum alloy powder and polymer powder may contain from 4 to 80% by weight of alloy, more preferably from 30 to 65%.

The volume fraction of the alloy can easily be calculated by those skilled in the art from the mass and density of the various constituents of the mixture.

In the mixture of powders used for carrying out the process, the alloy particles preferably have an average particle size of between 1 and 90 μηι, more particularly between 10 and 75 μηι, and the polymer particles preferably have a particle size distribution. average between 1 and 90 μηι, more particularly between 40 and 70 μηι.

Selective laser sintering is preferably computer assisted. In a particular embodiment, the mixture of powders is heated to a temperature of a few degrees Celsius lower than the melting temperature of the polymer, for example to a temperature of 1 to 10 ° C. lower than the melting point. of the polymer. The energy required for fusion is then provided by the laser.

The invention also relates to a part comprising aluminum obtained by a method described above. The parts obtained may have a volume porosity of less than 5%, and especially less than 3%, and more particularly less than 1%.

Equivalently, the apparent density equal to the mass / volume ratio of the part may be greater than or equal to 95% of the theoretical density of the part, and in particular greater than or equal to 97% of the theoretical density of the part, and more particularly greater than or equal to 99% of the theoretical density of the part.

The method of the invention is particularly useful for the rapid prototyping of lightweight pieces with an apparent density of between 1 and 3 g / cm ³ and without any form stress. Selective laser sintering allows easy and nontoxic elaboration of parts that have the desired complex shape. The use of a quasi-crystalline aluminum alloy allows the development of parts having a greater seal than those obtained with crystalline aluminum.

The parts obtained also have remarkable mechanical properties, and in particular the properties of wear, friction and hardness which are better than those of the parts obtained with crystalline aluminum. They are also easily recyclable.

The present invention will be described in more detail by means of the following examples, to which it is however not limited, the description being made with reference to FIG. 1, which schematically illustrates a device making it possible to implement the method according to FIG. 'invention.

Example 1

Preparation of the powder

A composite powder comprising at least two different types of powder (polymer and complex metal alloy) was prepared. Each grade of powder is accurately weighed so as to obtain a volume fraction of complex metal alloy in the final composite part of 30%. The powders are preferably mixed homogeneously using a turbulat, which will obtain parts with homogeneous mechanical properties and sealing. About ten to fifteen minutes are needed to mix 20 kg of powders.

Manufacture of composite parts

Several composite parts were prepared by selectively laser sintering the powder mixture consisting of 65% by weight of a powder of an AlCuFeB alloy having a particle size of between 10 and 75 μηι and 35% by weight of a polyamide powder which is a nylon 12 powder having an average particle size of 60 μηι. The AlCuFeB alloy is a quasi-crystalline alloy of nominal atomic composition Al ₅₉ Cu ₂ 5 _; 5Fei _{2; 5} B3, sold under the name Cristome Fl by the company Saint-Gobain. This alloy consists of the phase of complex structure (icosahedral i) isostructural at the phase z-Al ₆₂ Cu ₂ 5 _{; 5} Fei _2; And from an isostructural cubic phase to -Al ₅₀ (CuFe) ₅ o.

Selective laser sintering can be implemented using a device 1 as illustrated in FIG.

The selective laser sintering device 1 comprises a powder supply tank 2 in which the mixture is placed, a powder supply and distribution roller 3, and a laser 4.

The laser 4 is, for example, a CO ₂ laser of power 35 W. The laser beam is directed via a mirror 5 towards the powder zone that it is desired to sinter, under a preferably neutral atmosphere, for example under a nitrogen atmosphere. .

The process uses a manufacturing platform heated to a temperature close to the melting point of the polymer. The laser traces the layer-by-layer form and locally supplies, to each successive layer of the initial powder mixture, sufficient thermal energy to bring the polymer to a temperature causing it to melt. Unsintered powders naturally provide support for the following layers. The mobile work platform descends from the thickness of a layer, the displacement of the vertical part being provided by a piston 6. A new layer of powder is then spread by the roller 3 and the cycle starts again to build the part layer by layer from bottom to top. Instead of the roller 3, another mechanical system could be used, such as a scraper.

Properties of the obtained parts

The parts obtained after sintering have a homogeneous shrinkage of 2 ± 0.2% along the horizontal x and y axes, and of 1.3 ± 0.2% along the vertical axis z. The density Apparently measured by the mass / volume ratio of the workpiece is always greater than or equal to 99% of the theoretical density, which implies a porosity of less than 1% volume. The parts obtained are sealed under a minimum pressure of 8 bar, from room temperature up to 100 ° C. The gain in wear volume compared to the crystalline aluminum reinforced polyamide matrix is about 70%. The coefficient of friction measured using a pin-type tribometer on the disk (load 10N, sliding speed 16cm / s, cavity diameter lcm) shows a gain of the order of 30%. The average Shore D hardness is 79 ± 1.

EXAMPLE 2 The procedure of Example 1 was repeated, but using a mixture of powders consisting of 52% by weight of a powder of crystalline aluminum alloy (1000 series aluminum) and 48% by weight of a polyamide powder which is a nylon 12 powder.

The pieces obtained after sintering have a homogeneous shrinkage of 2 ± 0.2% along the x and y axes and 1.3 ± 0.2% along the z axis. The density measured is always less than or equal to 80% of the theoretical density, which implies a porosity rate greater than 20%. The parts are not waterproof without impregnation of resin on the surface. The tribological properties of abrasion-wear and friction are poor. The average Shore D hardness is 72 ± 2. Example 3

The procedure of Example 1 was repeated, but each grade of powder was accurately weighed so as to obtain a volume fraction of complex metal alloy in the final composite part of 15%. The powder mixture consists of 44% by weight of a powder of AlCuFeB alloy of Example 1 and 56% by weight of a nylon powder which is a nylon 12 powder.

The parts obtained after sintering have a homogeneous shrinkage of 2 ± 0.2% along the x and y axes and 1.3 ± 0.2% along the z axes. The density measured is always greater than or equal to 98% of the theoretical density, which implies a volume porosity rate of less than 2%. The pieces obtained are waterproof. The tribological and hardness properties are improved over those of the parts of Example 2.

Example 4 The procedure of Example 1 was repeated, but using a mixture of powders consisting of 61.5% by weight of a powder of an AlCuFeCr alloy and 38.5% by weight of a polyamide powder which is a nylon 12 powder. AlCuFeCr alloy is a complex metal alloy of nominal atomic composition Al ₇₁ Cu ₉ FeioCr ₁₀ . This alloy consists of the orthorhombic phase Ol-Al ₆₅ Cu ₂ oFeioCr ₅ and an isostructural quadratic phase at the phase ω-Al ₇ oCu ₂ oFe ₁₀ .

The pieces obtained after sintering have a homogeneous shrinkage of 2 ± 0.2% along the x and y axes and 1.3 ± 0.2% along the z axis. The density measured is always greater than or equal to 99% of the theoretical density, which implies a volume porosity of less than 1%. The pieces obtained are waterproof. The tribological and hardness properties are improved over those of the parts of Example 2.

EXAMPLE 5 The procedure of Example 1 was repeated, but using a mixture of powders consisting of 40% by weight of a powder of the AlCuFeCr alloy of Example 4 and 60% by weight of a powder. polyamide which is a nylon 12 powder.

The pieces obtained after sintering have a homogeneous shrinkage of 2 ± 0.2% in x and y and 1.3 ± 0.2% in z. The density measured is always greater than or equal to 97% of the theoretical density, which implies a volume porosity of less than 3%. The pieces obtained are waterproof. The tribological and hardness properties are improved over those of the parts of Example 2.

Claims

1. A process for producing a part comprising aluminum, characterized in that it comprises a step of selective laser sintering of a mixture comprising a polymer powder and a powder of an alloy of aluminum. quasi-crystalline minium, the weight of the alloy not exceeding 80% of the total weight of the mixture.

2. Method according to claim 1, characterized in that the quasi-crystalline aluminum alloy is a complex metal alloy comprising an atomic percentage of aluminum greater than 50%.

3. Method according to claim 2, characterized in that the quasi-crystalline aluminum alloy is selected from Al ₆₂ Cu _25; Fei _2; 5 Al ₅₉ Cu ₂ of 5, Fe _{12 _5; 5} B3, Al ₇₁ Cu ₉ Fe ₇ _8; ₁₀ ₇ Cr, Al ₆ and _{71; 3} _{8 Fe,} Co ₁ _{12; 8} Cr _{7; 8.}

4. Method according to one of claims 1 to 3, characterized in that the polymer is a thermoplastic organic polymer selected from polyamides, amide copolymers, polyacetates, polyethylenes, polyetheretherketone.

5. Method according to one of claims 1 to 4, characterized in that the mixture of quasi-crystalline alloy powder and polymer contains from 4 to 80% by weight of alloy.

6. Method according to one of claims 1 to 5, characterized in that the alloy particles have a mean particle size of between 1 and 90 μηι, and the polymer particles have a mean particle size of between 1 and 90 μηι.

7. Method according to one of claims 1 to 6, characterized in that the selective laser sintering is computer assisted.

8. Method according to one of claims 1 to 7, characterized in that the mixture of powders is heated to a temperature of 1 to 10 ° C below the melting temperature of the polymer, and in that the energy necessary for fusion is provided by the laser.

9. Part comprising aluminum, characterized in that it is obtained by a method according to one of claims 1 to 8.

10. Part according to claim 9, characterized in that the apparent density equal to the mass / volume ratio of the workpiece is greater than or equal to 95% of the theoretical density of the workpiece.