DE1533242A1 - Process for improving the ductility of metal oxide composites or alloys in the disperse phase, in particular of aluminum-alumina composites - Google Patents

Description

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European Atoin Union (EURATOH)

Process for improving the ductility of "metal oxide" composites or alloys in the disperse phase, in particular of aluminum-alumina composite materials

The invention relates to a method for improving the ductility of metal oxide composites or alloys in the disperse phase and in particular of aluminum-alumina composite materials.

The aluminum-alumina composite material generally used is known to be sintered Al-AlpO ,, a metallurgical one Composition of the type of alloy in the disperse phase, which has multiple advantages for various Purposes, for example as a cladding material for fuel elements of certain types of nuclear reactors, offers.

This material is mainly produced as follows: Aluminum powder is partially oxidized to AlpO. The weight fraction of Al ₀ O ₃ in the oxidized bilver can vary between 2 % and 20%. The oxidized powder is first cold pressed and then sintered to form a block or billet.

Before sintering, the pressed powder is preferably degassed. The sintered block or billet is then made into at least one an extrusion process metallurgically processed to achieve the required properties of a semi-finished product or finished product.

From the production of nuclear fuel cladding using this Al ^ O ^ material, it is known that this material has good mechanical properties in terms of heat resistance, which has also been proven by long-term tests could.

However, the use of this material is currently limited to the production of a for lack of hot ductility Fuel element casing in the form of a rigid sleeve.

For example, led with samples of sintered Al-Al ^ O, at 45O ⁰ Cdurchgeführte I
following mean values.

at 45O ⁰ Cdurchgeführte tensile and creep tests to

example 1

(Extruded bars made of sintered Al-Al ^ O, with an alumina content of 4 %)

Tensile tests (fast train)

tensile strenght ι R. - 6 kg / mm 0.2% elongation Stretch limit : ⁸ 0.2 - 5th , 5 kg / mm ² Total elongation % <1 ₀ - 5 d _o ), V - 6 Creep attempts over 1000 h

50 ⁰ O

/ 2

Tensile strength Cf <i ä? 4 kg / mm

1000 h
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450 ⁰ O

Total elongation % (i _ft - 5 d _n ) Α _ς <^ ä 0.5%

1000 h

Example 2

(Extruded bars made of sintered Al-AIgO, with an alumina content of 7 % )

Tensile tests (faster to)

Tensile strength: B - 8kg / mm

0.2% elongation yield point; S _Q g "7kg / mm

Total elongation % (1 _Λ ■ 4 d _A ): _Ä y, ₀ /

Creep tests over 1000 h

<
czsz, 5 kg / mm  B 1000 h

450 ⁰ C

Total elongation% (1 _Q - 5 d _Q ) A ₅ <^ »0.7%

^^ R 1000 h

The elongation before breaking is about 0.5%

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Example 3

(Extruded helical finned tubes made of sintered Al-AlpO, with a clay content of 7%)
Tensile tests (fast train)

Tensile strength ι - 7th ρ
kg / mm E. - 8th, 5 ο
kg / mm Total elongation % (1 ^Α 5 - 4th % Burst attempt Burst voltage:

The value of the elongation at break A ₁ -, which is generally less than 1% for ΑΙ-ΑΐρΟ, materials even with different oxide contents, is typical for the very low creep ductility of the material

There is therefore an interest in this hot creep ductility, with which the above-mentioned good mechanical properties are nevertheless accompanied, to improve as far as it is the use of this material for core purposes relates to fuel element cladding from this material manufacture that have the shape and properties of resistant and stretchable casings.

It has been found that 2 to 20 wt .-% alumina containing composite material Al-Al ₀ O-, improved ductility, mainly hot-Kriechdehnbarkeit, can be produced by a method which thereby is characterized according to the invention is that a block, or Billet is made from Al-AlpCK powder or wire by spraying this or this onto a base body and then subjecting the billet to a metallurgical reshaping by mechanical processing in order to achieve the final

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to achieve mechanical properties for semi-finished or finished products. Oxidized Al-Al ₂ O, powder or semi-finished, sintered and hot-pressed composite material Al-AlpO can be used, the latter being reduced from the original diameter of a block, billet or rod by wire extrusion and subsequent wire drawing to form wire with a small diameter .

The wire for metal spraying obtained from the blocks, the diameter of which is normally between 70 and 20 mm has a diameter between 1 and 10 mm.

The metal spraying is done in a range between 50 and 250 mm fluctuating distance to the base body.

The spray direction can be perpendicular to parallel to the axis of the base body, the parallel direction being preferred will.

The injection process must be at a temperature of at least 800 ⁰ O and in well defined spraying times of a few seconds or preferably less than one second.

The prepared billet is subjected to thermal degassing and oxide stabilization in a vacuum furnace.

These operations are to be carried out at temperatures between 550 and 625 ⁰ O and a residual pressure between 10 and 10 ~ ^ Torr over a period of 10 to 30 hours, preferably from 20 to 24 hours.

The semi-finished or finished products, such as Rods, smooth or ribbed casings (with transverse, longitudinal or

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helical ribs) are in particular by known metallurgical production processes, such as Extrusion and possibly drawing with intermediate annealing.

The invention is explained below with the aid of four exemplary embodiments.

EXAMPLES Λ and 2 (4 % Ai-Ai ₂ O ₅ J 7 % Ai-Ai ₂ O ₅ )

A block or billet made in the normal production process from sintered ΑΙ-ΑΐρΟ -, - material with 4% or 7% alumina and a diameter of 70 mm was ^{extruded through a press nozzle at a temperature of about 57O 0} O to form bars with a diameter of 5 mm which were then drawn at room temperature to produce 3 mm thick wires in three or four passes.

These wires were sprayed with a metal spray gun (Brand "Netco") to make a new billet.

Metal spraying took place under the following working conditions:

Flow rate, oxygen »50 l / min Flow rate, acetylene: 50 l / min Compressed air pressure: 4.5 kg / cm

Spray distance: about 100 mm

Spray direction: at right angles to

Axis of the billet to be produced.

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The injection process was canceled when a stick of was made about 2 cm thick, sufficient to produce a perfectly cylindrical surface on the lathe.

After cylindrical turning or grinding, injection molding was continued until a billet about 70 mm in diameter was completed. This "billet was turned on a lathe to a diameter of 68.4 mm and then ^{degassed in an oven under a high vacuum of 10 *" * 7} Torr by heating to a temperature of 600 ^° C. for a period of 20 hours.

The degassed billet was then passed through a Preös nozzle at 250 ° C extruded to make bars 20mm in diameter.

Extrusion data:
Container diameter: 70 mm container temperature ί ⁰

Nozzle temperature ί 480 ⁰ C

Extrusion ratio ι 12.3
Extrusion speed t 7 »58 m / min

In the case of the 4% Al-Al ₂ O, the tensile and creep ^{tests were carried out at 450 °} C. and the following mean values were obtained:
Zugytrsuoh (Faster To)

tensile strenght in % - 5th I. R. ο
* 6 kg / mm 0.2 limit : ^S 0.2 "5» 5 kg / mm Total stretch : - 15% -

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Creep test over 1000 h tearing stressö '

450 ⁰ O

E 1000 h

Total elongation in % (1 ■ 5 dJ A c

«4 kg / mm ⁴

15 %

K 1000 h

That the hot strength transactions seigen W From these results it can be seen were maintained at the above-mentioned values, while creep and tensile elongation have become much higher, in particular the value of A, - the creep elongation was increased from less than 1% to about 15%.

In the case of the 7% Al-Al ₂ O *, the creep ^{tests were carried out at 450 °} C. and the following mean values were obtained »

Creep test over 1000 h

Tensile strength

450 ⁰ O

B 1000 h

5 | 2 kg / mm *

Total elongation in % (1 «5 d) A, -

450 ° C

E 1000 h

4.5%

It can be seen from these results that the high temperature strength properties were maintained at the above-mentioned values, while the creep elongation was increased considerably, namely from less than 1% to about 4.5 % .

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Execution example 3
(7% strength sprayed onto an Al-Hohr

The forming of the starting material into wire and the working conditions in metal spraying are the same as in Embodiments 1 and 2 of the invention. Instead of a core rod that rotates at 10 to 70 rpm on a solid billet core, the composite material was sprayed onto a rotating aluminum tube at 10 to 70 rpm until a billet with an outside diameter of about 70 mm was produced. This billet was then turned to 68.4 mm outside diameter and 25.75 mm inside diameter. In addition, the billet was degassed for 20 hours at a temperature of 600 ⁰ in a vacuum furnace (ΙΟ " ^-3 mm hg).

The degassed billet tube was then extruded through a die at 573 ° O to produce a helically finned tube.

Extrusion data:

Container diameter: 70 mm

Container temperature χ 55O ° O

Nozzle temperature ι 540 ° C

Extrusion ratio: 25
Extrusion speed t 25 m / min

The mechanical tests were ^{carried out at 450 0} O and resulted in the following mean values:

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- 10
Tensile test (fast train)

tensile strenght in % (1 _O - 5 d ₀ ): Ö « E. 4th - 9 kg / mm Total elongation Rapid burst attempt at 450 ⁰ O: Embodiment H - 4th % Bursting stress - 8th kg / mm

(7% Al-AIpO injected parallel to the axis of the chopper)

In this case, too, the same applies to wire extrusion and the working conditions during spraying as specified above Data. However, while in the .Exemplary examples 1 to 3 injection was carried out perpendicular to the stick axis, it was done in in this case, parallel to this axis, on a disk that rotates at 30 rpm. In this way it became a massive one Made billets of 70 mm in diameter and 120 mm in length. This billet was turned to 68.4 mm in diameter and 100 mm in length and then turned in the same manner as in FIG other cases degassed.

The reshaping of the billet into a bar with a diameter of 20 mm also took place in accordance with the data given for exemplary embodiments 1 and 2.

The creep tests then carried out at 450 ^° C. gave the following mean values:

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Creep test (300 h)

Tensile strength Ό <^ ί = »5» 3 kg / mm

H 300 h

Total elongation in % (1 * 5 d) A ₁ - <^ "s = ^ 4 %

R 300 h

The elongation before break was about 2.5 %

It can be seen from these results that the high-temperature strength properties of the material were also retained in Examples 3 and 4, while the creep elongation became much higher. The value A ₁ . increases from less than 1 % to about 4%, the elongation before breakage being much higher than that of normal extruded Al-Al ^ O ^ bars.

The invention is not limited to those described above Embodiments, rather it is also applicable to other compounds, such as magnesium talc earth compositions, applicable.

Claims ·.

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Claims (6)

Claims 1. Decay to improve the ductility of metal oxide composites or alloys in the disperse phase, in particular of aluminum-alumina composite materials with 2 P up to 20 wt.% Alumina content, characterized in that a block or billet of Al-Al ₂ O, powder or wire is produced by spraying this or this onto a base body, and the billet is then metallurgically formed is subjected to mechanical processing in order to achieve the final mechanical properties for semi-finished or finished products. 2. The method according to claim 1, characterized in that the metal spraying from a lying between 50 and 250 mm Distance from the base body is carried out and the spray direction with respect to the axis of the base body from . the vertical to the parallel direction can be changed can, whereby the parallel direction is preferred. 3. The method according to claim Λ and 2, characterized in that the metal spraying is carried out at a temperature of at least 800 ⁰ C and within precisely limited spray times of a few seconds or preferably less than one second. 4. The method according to claim 1, 2 or J, characterized in that the billet produced is subjected to thermal degassing and oxide stabilization in a vacuum furnace «, 009809/0494 5 × The method according to claim 4, characterized in that the degassing and oxide stabilization at temperatures between 55O ⁰ O and 625 C and a Hestdruck between 10 "* and 10" - ⁷ Torr for a period of 10 to 30 hours, preferably from 20 to 24 hours. 6. The method according to claim 1 or one of the claims following it, characterized in that the Al-AlpO ^ wire from a rod or a block or billet of _M ΑΙ-ΑΙρΟ, composite material, which is normally ™ as a sintered, hot-pressed ΑΙ-ΑΐρΟ, composite material is produced. Ur / 17 486 "original inspected 009809/0494 '~ * ~