EP2646587A2

EP2646587A2 - Process for producing an alscca alloy and also an aiscca alloy

Info

Publication number: EP2646587A2
Application number: EP11831814.6A
Authority: EP
Inventors: Frank Palm
Original assignee: EADS Deutschland GmbH
Current assignee: Airbus Defence and Space GmbH
Priority date: 2010-12-02
Filing date: 2011-11-30
Publication date: 2013-10-09
Anticipated expiration: 2031-11-30
Also published as: WO2012075993A2; US20130312876A1; DE102010053274A1; US9725790B2; EP2646587B1; US20170298477A1; WO2012075993A3

Abstract

The invention relates to a process for alloying calcium (14) to form an aluminium-scandium alloy (20) for producing an aluminium-scandium-calcium alloy (36), wherein aluminium (15), scandium (12) and calcium (14) are melted together and the joint melt (22) is quenched at a high rate.

Description

Process for producing an AIScCa alloy and AIScCa alloy

The invention relates to a method for adding calcium to a

Aluminum scandium alloy and an aluminum scandium-calcium alloy.

Due to its low density, aluminum is often used as a construction material, i. in applications where a low mass is desired, such as in means of transport, especially in the aerospace industry.

Although aluminum is a light metal and therefore interesting for the applications mentioned, it has the disadvantage that it is relatively soft and the tensile strength in the annealed state is only 30-50 MPa. The strength values of aluminum can be increased within a wide range by alloying with other metals, and other properties can also be influenced. This is advantageous for lightweight construction, since construction materials are required which have a high specific strength. For example, through

Addition of scandum, combined with a sufficiently rapid cooling after casting, in addition to the increased strength by solid solution formation a much greater strength increase by precipitation hardening over a fully or partially coherent Al ₃ Sc phase and / or by dispersoid hardening, ie if the A ^ Sc phases become more and more incoherent due to aging. However, since the density of scandium at 2.98 g / cm ^{3 is} higher than that of aluminum at 2.7 g / cm ³ , scandium increases the density of the material and thus also the thickness of the material

Total weight.

Aluminum scandium alloys are well known and their characteristics are described in the following publications, which by reference form part of this disclosure: AJ. Bosch, R. sending, W. Entelmann, M. Knüwer, F. Palm "Scalmalloy ^®: A unique high strength and corrosion insensitive AlMgScZr material concept", Proceedings of the 11 ^th International Conference on Aluminum Alloys

F. Palm, P. Vermeer, W. von Bestenbostel, D. Isheim, R. Schneider "Metallurg ical peculiarities in hyper-eutectic AISC and AlMgSc engineering materials prepared by rapid solidification processing", Proceedings of the 11 ^th International Conference on Aluminum Alloys ,

To lower the density of these aluminum scandium alloys, in addition to the addition of magnesium (density 1, 74 g / cm ³ ) described in the above publications, there is the possibility of lithium, which has a density of 0.5 g / cm ³ has zuzulegieren.

The production of aluminum-scandium-lithium alloys, however, is problematic to manufacture, since the melt must be handled under inert gas, such as argon. Furthermore, gutters and melting pots must be specially lined, for example with CeO, ZrO or other protective metal oxides. The melt easily reacts with fire or explosion in air and has therefore often been separated from the environment by a protective slag in earlier manufacturing processes.

US Pat. No. 5,211,910 describes an aluminum alloy which may contain scandium and / or calcium in an amount of 0.5 to 4% by weight.

WO 2007/102988 A2 discloses an aluminum alloy which may have calcium and / or scandium in a range of 0.01 to 6%. In the German Wikipedia is under the term "melt-spinning" one

Method described, with the melting, in particular molten metal, cooled at very high speeds, i. be deterred.

KBM AFFILIPS Master Alloys offers on its website aluminum base alloys, such as aluminum-magnesium alloys, aluminum-scandium alloys or aluminum-calcium alloys.

The object of the invention is to provide a simple and harmless method for producing a reduced-density aluminum-scandium alloy

propose.

The object is achieved by a method having the features of claim 1.

An aluminum scandium-calcium alloy is the subject of

In addition claim.

Advantageous embodiments of the invention are the subject of the dependent claims.

A method of alloying calcium to an aluminum-scandium alloy to produce an aluminum-scandium-calcium alloy comprises the following steps:

a) melt-bringing together aluminum, scandium and calcium; and

b) quenching the common melt.

Calcium has a much lower density of 1.55 g / cm ³

Volume weight as aluminum and thus contributes to a zulegieren to one

Aluminum scandium alloy to reduce the overall density of the alloy at. A material made with such an alloy is lightweight and yet largely exhibits the strength properties of the aluminum scandium alloy.

The melt with calcium can be easily handled under atmospheric conditions, so that protective measures, such as

Lining of gutters and pots with oxides or the use of

Inert gas, not necessary.

The solubility of calcium in aluminum is very low, so far no significant amounts of alloy greater than 0.5 wt .-% were produced. However, if the melt, which contains the alloying partners elementary, quickly quenched and thus carried out a fast solidification process, calcium irj the solid phase remains largely in solution.

Thus, a high-strength, low-density aluminum alloy can be produced in a simple and harmless method.

Preferably, calcium is added at a level greater than 0.5% by weight. Thus, calcium is present with a significant proportion in the alloy and significantly reduces the weight of the alloy and also of the materials produced therefrom.

Preferably, calcium is added to the alloy in a proportion to the alloy that has a density less than 2.6 g / cm is reached. ³ Thus, the weight of the alloy can be reduced by about 5% over the aluminum scandium alloy.

It is advantageous for the common melt by means of a

Fast solidification process at a rate of more than 100 K / s, in particular 10,000 K / s to 10,000,000 K / s, quenched. Via a normal metallurgical manufacturing process, where after casting a casting Solidification with slow cooling conditions follows, so far it has been difficult to alloy calcium in significant amounts to an aluminum scandium alloy. Because it immediately forms an AI ₂ Ca phase, which is excreted and embrittles the alloy. However, when a fast solidification process is performed, the problem of limited solubility and unwanted premature coarse deterioration of calcium in aluminum alloys can be overcome and calcium remains largely in solution because rapid cooling prevents natural crystallization. This deprives the atoms of mobility before they become one

Can take crystal arrangement and thus A ^ Ca can be formed.

Processes that are suitable for this are all solidification processes in which the heat is quickly removed from the melt, for example the

Schmelzschleudem, the powder atomization by means of gas or in water, the

Thin strip casting or spray compacting, but also processes in which a melt is generated at short notice and this immediately solidifies again,

For example, welding methods for joining, surface modification or for the generative production of three-dimensional components, the so-called "layer manufacturing process" ("additive manufacturing").

Advantageous is the common melt by means of a nozzle as

Jet sprayed onto a substrate, wherein the substrate is cooled and rotated during the application of the common melt. The substrate may be, for example, a water-cooled copper wheel. The cooling results in a temperature difference between the common melt and the substrate, so that a temperature transfer from the melt takes place on the substrate. The higher the temperature difference, the faster the temperature is transferred to the substrate and dissipated by the cooling. Next depends the cooling rate and thus the presence of a rapid solidification

Prevent the AI ₂ Ca phase formation from the rate at which the Melt impinges on the substrate and the rotational speed of the rotated substrate.

If the substrate is preferably rotated so fast that the quenched common melt is thrown off the substrate from an impingement area of the jet on the substrate, the substrate is automatically freed from the solid alloy already formed by quenching and stands for subsequently sprayed common melt Cooling available. An accumulation of alloy material on the substrate, which precludes rapid temperature transfer from the common melt to the substrate, is thus advantageously prevented. The centrifuged common melt forms a band which can be further processed in subsequent process steps.

For example, the belt is first chopped small, processed into granules or powder and then compacted into bolts in a pressing and outgassing / annealing process. The bolts, i. the particulate starting material, then can

Extruded extrusions with different cross sections are extruded.

The process is preferably carried out under atmospheric conditions, in particular under air contact. Thus, measures to protect the common melt against the atmosphere are no longer necessary, it may be based on the use of inert gas, vacuum conditions, protection device and

Similar be dispensed with. This significantly simplifies and reduces the cost of the process compared to adding lithium.

Particularly preferably, step a) comprises the step of melt-bringing an aluminum-magnesium base alloy. Magnesium has a density of 1.74 g / cm ³ . At the same time it controls and reduces the density of the corresponding alloy. The more magnesium in the alloy, the lower the density. The alloying of magnesium to aluminum is up to a proportion of 10% by weight makes sense. Due to the similar melting points of aluminum and magnesium, production of an aluminum-magnesium base alloy is particularly easy to produce.

Aluminum scandium alloy is a generic term for all alloys containing aluminum and scandium. This includes all compositions having the formula AIScM ¹ M ² M ³ M ⁴ , where M ^{1 is} a metal selected from the group consisting of

which contains copper, magnesium, manganese, silicon, iron, beryllium, lithium, chromium, zinc, silver, vanadium, nickel, cobalt and molybdenum, and wherein M ^{2 is} a metal selected from the group consisting of copper .

Magnesium, manganese, silicon, iron, beryllium, lithium, chromium, zinc, silver, vanadium, nickel, cobalt and molybdenum.

M ³ comprises the group of elements which have a certain compatibility with the Al ₃ Sc phase, ie metal-physical similarity (exchangeability), and can therefore form the tertiary phase Al ₃ Sc ₁ -xM ₃ x. Primarily, these are zirconium, niobium, tantalum, hafnium and titanium.

M ⁴ comprises the group of the so-called rare earths {element numbers 39 and 57 to 71), which in principle are very similar to scandium. Therefore, Sc is often wrongly attributed to the rare earths. They too can be alloyed to a considerable extent in addition to the scandium of the alloy and then, in addition to the solid solution hardening alone or with scandium, form a hardening phase with comparable stoichiometry as Al ₃ Sc ₁ -xM ₃ x.

Further preferably, in step a) an aluminum scandium master alloy is melted. Scandium has a much higher melting point than aluminum, which is why it takes a long time to form an alloy

must be complied with. This is complicated, which is why it is advantageous if, instead of the pure elements, a master alloy is used in which the scandium already "melted down" and thus a lower holding time must be maintained to form the aluminum scandium-calcium alloy.

Preferably, an aluminum-calcium master alloy is further melted in step a). Also, calcium has a much higher melting point (842 ° C) than aluminum, and by the pre-alloy is needed

Melting point and thus the holding time preferably reduced.

An aluminum-scandium-calcium alloy has a calcium content of more than 0.5% by weight. Thus, the density of the aluminum-scandium alloy can be reduced by containing an easily available and easy-to-handle metal as an alloying component in the alloy.

Preferably, the alloy comprises from 0.2% to 3%, preferably from 0.4% to 1, 5%, by weight scandium. If scandium is included in the specified amounts in the alloy, it increases the strength of the alloy but does not contribute so much to increasing the density of the alloy that a material made from it would be too heavy for lightweight construction. Alternatively, instead of scandium, ytterbium can also be alloyed in the stated proportions of the alloy. Ytterbium is cheaper than scandium, but has the disadvantage of not improving the strength of the alloy as well as scandium.

Advantageously, the alloy comprises from 0.1% to 5% by weight, more preferably from 0.2% to 0.75% by weight of zirconium. Zirconium in such a proportion in the alloy (ratio Zr / Sc about Α to about Vi) facilitates the temperature-enhanced further processing of the alloy and stabilizes it thermally, i. It reduces the tendency to "age", which is equivalent to an unwanted one

Coarsening of the curing phase A Sc by formation of an Al ₃ ScZr phase.

Further advantageously, the alloy contains 1, 0 wt .-% to 8.0 wt .-%, more preferably 2.5 wt .-% to 6.0 wt .-%, magnesium. Magnesium sets the Density of an aluminum alloy down. The alloying of magnesium to aluminum, however, makes sense only up to certain amounts, since otherwise negative properties such as brittleness and corrosion sensitivity increase greatly. Therefore, magnesium is preferably contained in the stated proportions in the alloy.

Further preferably, the alloy also has other admixtures, also in multiple form, of the elements mentioned in M ¹ , M ² , M ³ and M ⁴ with the proportions of 0.2 to 2.0 wt .-%, the mechanical, physical or chemical

Improve properties of the alloy. Unavoidable is that

Presence of unwanted impurities of both metallic and non-metallic nature such as oxides, nitrides, dissolved gases, etc. in

negligible quantities, i. with a sum of less than 0.5% by weight) in the alloy.

Preferably, the alloy has a density less than 2.6 g / cm ³ . Thus, the alloy is particularly well suited as a basic material for lightweight construction.

In a preferred embodiment, the alloy has substantially the same strength and essentially the same elastic modulus as the pure aluminum scandium alloy in which no alloyed calcium is contained. Thus, the alloy has the positive properties of the aluminum scandium base alloy, i. substantially the same strength and modulus of elasticity, but is denser reduced by the presence of calcium and thus easier.

An aluminum scandium-calcium material has more than 0.5 wt .-% calcium. Such a material is characterized by particularly good strength values and a high modulus of elasticity, but has a reduced density and is therefore particularly suitable for lightweight construction. An embodiment of the invention will be explained in more detail with reference to the accompanying drawings. It shows:

Figure 1 is the common in-melt aluminum, scandium and calcium.

FIG. 2 shows the quenching of the common melt by spraying onto a cooled, rotating substrate; FIG.

Fig. 3 is a rear view of the substrate; and

4 shows the formation of an alloy strip;

Fig. 1 shows how in a common crucible 10, the metals scandium 2 and calcium 14 to an aluminum 15 and magnesium 16 containing

Aluminum-magnesium base alloy 17 are added. The crucible 10 has on its underside a nozzle 18, which is separated by a closing device 19 of the crucible 10.

In order to achieve the lowest possible holding times, scandium 12 is added as aluminum scandium master alloy 20 and calcium 14 as aluminum calcium master alloy 21. For melting, the mixture is heated with an induction heater 23. However, there are other suitable heating options for in

Melting of metals 12, 14, 15, 16 possible. After the in the

Crucible 10 input metals 12, 14, 15, 16 are melted, a common melt 22 has emerged.

In Fig. 2 it is shown how the common melt 22 is sprayed onto a rotating substrate 24. For this purpose, the closing device 19 is opened between the nozzle 18 and the crucible 10, so that the common melt 22 can flow into the nozzle 18. The nozzle 18 sprays the common Melt 22 in a nozzle jet 30 on a landing area 32 on a surface 33 of the substrate 24. The substrate 24 is cooled on the side opposite to the impact area 32 via a cooling device 34. The substrate 24 is rapidly rotated about the axis 35 in the direction of the arrow O.

The common melt 22 solidifies on the cooled substrate 24 at a high cooling rate to an aluminum-scandium-calcium alloy 36. The rapid rotation of the substrate 24 and the resulting forces, the resulting aluminum-scandium-calcium alloy 36 of the Surface 33 of the substrate 24 thrown away, so that an alloy strip 40 is formed.

FIG. 3 shows the substrate 24 from a rear side 42 that is opposite to the surface 33. Here, the cooling device 34 is arranged in the form of a cooling coil 44. Water can be passed through the cooling coil 44, for example in the direction of the arrow, so as to cool the substrate 24. However, it is also possible to use, for example, liquid nitrogen or other lower-than-water-melting media for cooling so as to achieve a greater temperature difference between the impinging jet 30 and the substrate 24.

Fig. 4 shows a view of the surface 33 of the substrate 24. The substrate 24 is rotated in the direction of arrow P so fast that the solidified aluminum scandium calcium alloy 36 as by the resulting forces

Alloy band 40 is thrown off the surface 38.

The following example describes the preparation of an AIScCa alloy semi-finished product.

An AIGg5.4 Sc1, 2ZrO, 6MnO, 5 alloy is added to 2.0% by weight of calcium as described above. The alloy ribbon is chopped into granules and then placed in a heatable device at 290 to 300 ° C under alternating rinsing with vacuum degassed at about 10 to 2 mbar and supply of dry nitrogen and repeated vacuum suction. Of the

Degassing process is carried out five times and the granules are compacted by means of a hydraulic press into a stud with 98% gross density and 31 mm diameter at 25 -30 mm length.

This bolt is then turned over to 30 mm and subsequently in one

Extruding device with a compression ratio of 25: 1 at 325 to 335 ° C to a 6 mm rod pressed. Standard round tensile specimens EN 0001 B6 x 30 are taken from the round bar and the strength tested. In addition, the microstructure hardness can be determined using the Brinell hardness test method (HB2, 5 / 6.5) on small disks from the 6 mm rod

The lower the material density, the greater is the lightweight construction potential, this is a fixed design size with otherwise constant strength properties.

Fabric-based lightweight construction requires high strength, low density construction materials, i. high specific strength, also called breaking length.

High-strength AlMgSc alloys have a density of 2.62 to 2.86 g / cm ³ and an Mg content of 6.0 to 2.5 wt .-%. AlMg materials in their

American Al alloy key composition all written in field AA5XXX are widely used because of their relatively low densities and are very popular because of their good strength and processing properties. The magnesium content of the alloy partly controls the strength via solid-solution hardening, but at the same time also determines the density of the corresponding alloys, since magnesium 16 has a density of 1.74 g / cm ³ . This should be as low as possible, especially from a lightweight construction point of view. The more magnesium 16 in the alloy, the lower the density. It is known that the alloying of magnesium 16 to aluminum 15, and thus the associated reduction in density, makes sense only up to certain amounts, since otherwise other negative properties such as brittleness and

Corrosion sensitivity increase sharply. For this reason, generally established, ie industrially used, high-magnesium aluminum materials have a magnesium content of less than 6% by weight (eg AA5059 or AA5083). The alloying of lithium is state of the art, the alloying of calcium 14 in AlMgSc alloys not. The alternative to lowering the density, ie the alloying of lithium with a density of 0.52 g / cm ³ , was already developed in the 20s of the last century and technically implemented in Russia especially from the late 70s. Thus, a further density reduction by addition of lithium (0.5 g / cm ³ ) or only calcium 14 (1, 55 g / cm ³ ) is possible. The alloying of scandium 12, combined with a sufficiently rapid cooling after casting or during solidification, allows by means of defined heat conduction, eg

downstream aging in the temperature range between 250 and 400 ° C, in these materials, a further increase in strength of

Precipitation hardening via a fully or partially coherent A ^ Sc phase and / or dispersoid hardening, when the A ^ Sc phase becomes increasingly incoherent due to overaging.

The density of AlMgSc sheet and more of extruded sections is determined by the amount of magnesium 16 which is added to this type of solid solution for solid solution hardening. This results in a limited minimum density for higher-strength AlMgSc alloys. The alloying of calcium 14 with a density of 1.55 g / cm ³ and in an amount of more than 0.5% by weight is hitherto used in high-strength aluminum-magnesium-scandium alloy concepts for applications in the traffic or air & Space area not available.

Since the solubility of calcium 14 in aluminum 5 is very low, the use of calcium 14 as a standard alloying element with significant amounts of alloy greater than 0.5 wt.% Is out of the question. However, this applies only to the normal metallurgical production route, in which after melting a Casting or solidification with slow cooling conditions follows and immediately an AI ₂ Ca phase precipitates, which embrittles the alloy.

When a fast solidification process, e.g. The problem of the very limited solubility of calcium 14 in aluminum 15 and aluminum-magnesium alloys 17 can be overcome and calcium 14 remains largely in solution. Sufficiently solidified, with scandium 12 between 0.3 and 1, 5 wt .-% alloyed and thus high to very solid aluminum-magnesium materials with a magnesium content between 1 and 10 wt .-% can by addition of calcium 14 in a Range between 0.5 and 5% by weight are further reduced in density and so increase their attractiveness as lightweight materials because of the high specific strength for all types of weight-driven applications, such as aircraft, vehicle construction, etc.

Thanks to the rapid cooling and solidification from the liquid phase, which is necessary in order to be able to dissolve increased amounts of scandium 12 in the aluminum material, it is now possible to give the aluminum-magnesium-scandium alloys the alkaline earth element calcium 14 with a density of 1, 54 g / cm ³ and thus further reduce the density of these attractive high-strength aluminum materials. High-strength aluminum-magnesium scandium materials with a reduced density of less than 2.6 g / cm ³ can be obtained as profiles, but also high-strength aluminum-magnesium scandium materials with a reduced density of less than 2.6 g / cm ³ as directly generated (eg remelted by laser) close-net shape components, the components are more efficient lightweight structures with high longevity. List of Reference Numerals: 10 crucible

12 Scandium

14 calcium

15 aluminum

16 mg

17 aluminum-magnesium base alloy 18 nozzle

19 closing device

20 aluminum scandium master alloy

21 aluminum-calcium master alloy

22 common melt

23 induction heating

24 substrate

30 jet

32 impact area

33 surface

34 cooling device

25 axis

36 aluminum scandium-calcium alloy 40 alloy strip

42 back side

44 cooling coil

O arrow

P arrow

Claims

claims

A method of alloying calcium (14) to an aluminum scandium alloy (20) to produce an aluminum scandium-calcium alloy (36) comprising the steps

a) to melt together aluminum (15), scandium (12) and calcium (14); and

b) quenching the common melt (22),

wherein calcium (14) is alloyed in an amount to the alloy to achieve a density of less than 2.6 g / cm ³ .

2. The method according to claim 1,

characterized in that calcium (14) is added in an amount of more than 0.5% by weight.

3. Method according to one of the preceding claims,

characterized in that the common melt (22) is quenched by means of a rapid solidification process at a rate of more than 100 K / s.

4. Method according to one of the preceding claims,

characterized in that the common melt (22) is sprayed onto a substrate (24) by means of a nozzle (18) as a jet (30), wherein the substrate (24) is cooled and rotated during the application of the common melt (22).

5. The method according to claim 4,

characterized in that the substrate (24) is rotated so fast that the quenched common melt (22) originates from an impact area (32) of the jet (30) on the substrate (24) from the substrate (24) is thrown off.

6. The method according to any one of the preceding claims,

characterized in that the process is carried out under atmospheric conditions.

7. The method according to any one of the preceding claims,

characterized in that step a) the step

and / or melted an aluminum-scandium master alloy (20) and / or melted an aluminum-aluminum master alloy (21).

8. aluminum scandium-calcium alloy (36) having a calcium (14) content of more than 0.5 wt .-%, wherein the alloy has a density of less than 2.6 g / cm ³ .

9. An alloy according to claim 8,

characterized in that the alloy contains from 0.2% to 3% by weight of scandium (12).

10. Alloy according to one of claims 8 or 9,

characterized in that the alloy is 0.1% by weight to 1.5% by weight

Contains zirconium and / or that the alloy contains from 1.0% to 8.0% by weight

Magnesium (16) and / or admixtures and undesirable impurities.

11. An alloy according to any one of claims 8 to 10,

characterized in that the alloy is 2.5% to 6.0% by weight

Contains magnesium (16).

12. Aluminum scandium-calcium material, wherein the material contains more than 0.5 wt .-% calcium (14) and has a density of less than 2.6 g / cm ³ .