DE3313478A1 - Composite material and production process therefor - Google Patents

Abstract

A composite material consists of at least one component with shape-memory properties (shape-memory component) and at least one further component with different composition and different physical properties from the shape-memory component. The composite material is to be improved as regards its electrical conductivity. For this purpose, it is provided for the shape-memory component to be firmly bonded to a component which has a higher electrical conductivity than the shape-memory component. The production of such a composite material is expediently carried out by joining the two components by means of a metallurgical joining process, in particular by pressure welding.

Description

A 919

Composite material and manufacturing process for this

The invention relates to a composite material, consisting of at least one component with shape memory properties (shape memory component) and at least one further component with a composition different from that of the shape memory component and different physical properties. In addition, there are advantageous process steps for the production of such a composite material specified.

By various publications are alloys became known after appropriate treatment

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change their shape depending on the temperature due to structural changes (see for example J. Perkins, "Shape Memory Behavior and Thermoelastic Martensitic Transformations", Materials Science and Engineering 1981, 51, 181-192). Such alloys are called shape memory or memory alloys called rungs.

Essential prerequisite for the shape memory effect is a martensitic phase transition, where the involved phases have the smallest possible volume difference and ordered lattice structures have to. The irreversible shape memory effect (one-way effect) means that after a deformation in the martensitic state only once the high-temperature form is accepted on heating and then retained on cooling. A reversible one Shape change (two-way effect) can be achieved by appropriate Treatment can be induced, with the alternating ■ heating and cooling the high temperature again or the low-temperature form. of the fitting adjusts.

Since the change in shape with a relatively large work capacity expires, shape memory alloys have generated a great deal of practical interest and

appear to open up a wide range of applications Suitable wherever temperature-dependent switching operations are carried out almost suddenly should. Shape memory alloys can replace thermal bimetallic elements in many applications, whose temperature deflection characteristic is linear, so that mostly complex adjustment work required are. It is true that abrupt changes in shape can be made on the basis of Thermobimeta 11, for example -Achieve with snap disks, but these have various disadvantages, which in the practical Application cause additional additional costs.

When using shape memory alloys, the thermally active fitting is either indirectly through an additional heating element or heated by direct passage of current, especially in the latter case the electrical conductivity is of great importance.

The types of alloys known for practical purposes, namely NiTi or Ni / Ti / X (X = third element), Cu / Zn / Al or Gu / Zn / Al / Y (Y = fourth element) and Cu / Al / Ni show a relatively low electrical conductivity overall. For use in electrical circuit technology there is therefore a need for shape memory components with relatively high electrical Conductivity.

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The invention is based on the task of creating new composite materials on the basis of shape memory alloys indicate · which the advantageous, almost sudden change in shape is more appropriate with the application combine electrical conductivity. Both shape memory alloys with disposable as well as can be used with two-way effect.

This problem is solved in that the shape memory component is fixed to one component is connected, which compared to the shape memory component has an increased electrical conductivity (conductivity component). The electrical conductivity of the material of the conductivity component should be expediently be at least 6 times higher than the electrical conductivity of the material of the shape memory component.

Useful further bi! Fertilizers of the composite material are in -ν included in claims 2-8. These claims concern the metallurgical connection of the two components, the formation of the conductivity component as an adhesive coating on the shape memory component, the use of a metal intermediate layer, as well as conductivity components made of copper or silver. In addition, a sandwich-like arrangement of the components and a training is claimed, in which the shape memory component and the

• Conductivity component as shell or core material

'are connected in a tubular arrangement.

j A convenient method of making a sol-

I chen composite material can according to claims 9-12

j 5 are carried out in that the two components

j · connected by a metallurgical joining process

j ^ den be. As a metallurgical joining process

j are plating, welding, soldering, powder metallurgy

J and other procedures according to the appropriate

I 10 intended use.

; For this purpose, a melting or powder metallurgy ^{manufacturing:} asked FormgedächtnisIegierung by rolling in strip form are produced, at least one band portion ■ metallurgically bonded to a tape section from the conductivity component 15 and further wherein the shape memory properties are generated by treatment of the component made of composite material.

The metallurgical connection can be advantageously carried out by Pressure welding carried out at a temperature above 500 C 20, it can also be useful before Connect the components with a diffusion barrier layer in the form of a galvanically or vapor-deposited one . metallic surface coating of the shape memory component apply.

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A composite material of the specified type can, however, also be produced by gluing the components together. Essential it is that there is a solid mechanical connection between the shape memory component and the conductivity component is achieved. Composite materials produced in this way can be used in sheet metal, strip, rod, • Wire, pipe or profile shape are available and then to the individual components, e.g. to contact carriers, are processed.

Embodiment I.

The starting point is a shape memory alloy produced by melt metallurgy with the following composition:

. Cu 75.5 wt

". Zn 15.0 wt .- #

Al .8.0
■ - ■ ■ Ni 1.5

electrical conductivity at room temperature 3 χ 10 -

A plate having 10 mm thickness is produced by cold rolling in (<A + ß) -Gefügezustand and corresponding intermediate annealing at 500 ⁰ C. Between two such Cu / Zn / Al / Ni plates, which are used in advance to create a diffusion barrier. side / galvanically with a 4 m thick nickel layer in a Watts bath at 6O ⁰ C

^ J

- 10 -

are coated, a 4 mm thick copper plate is placed and the shaped piece is pressure-welded with the aid of two 10yum thick eutectic Cu / Ag foil sections at about 790 ° C. and then rolled out to a thickness of 2.4 mm. Are prepared molded pieces having dimensions of 2.4 x 5 χ 60 mm, solution heat treated at 83O ⁰ C in air, and quenched in water. A two-way effect is induced by a strong bending deformation of these fittings, which is about 0.8 $ in the outermost Cu / Zn / Al / Ni layers.

The inserted copper slices cause a fourfold Increase in electrical conductivity in comparison with corresponding fittings without a copper intermediate layer. Additional tests with Cu / Zn / Al / Ni fittings of the same dimensions without a copper intermediate layer have shown that the copper interlayer, which increases the conductivity, is not worth mentioning Influencing the two-way effect.

Embodiment II

The starting point is a NiTi alloy produced by melt metallurgy with the composition:

Nickel 54.5 wt .- ^ Titanium 45.5 wt .- / *

f Conductivity at low temperature 1.2 χ 10

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This shape memory alloy is produced by hot extrusion Processed in bar form at 850 C and from a diameter of 80 mm to 50 mm and then to formed an Eohr with an inner diameter of 30 mm and a wall thickness of 7 ram. By cold drawing and intermediate annealing at 650 ° C., a tube • with an inner diameter of 3.7 mm and a wall thickness is finally produced of 3.2 mm. A copper wire with a diameter of 3.5 mm is inserted into this tube

and the molding with intermediate 6Ou at ⁰ C to a diameter of 2.5 mm cold-drawn. Fittings of 20 mm length are cut from this wire. After a one hour solution annealing in protective gas at 900 C and quenching in cold water, a training process follows through torsional stress, which has a two-way effect with elongations of about 0.6% in the main directions of stress (tension and pressure).

A comparison with NiTi toision bars of the same size without a copper core leaves no significant influence of the Detect copper core on the two-way effect. The material with a copper core, however, shows an electrical conductivity about 6.5 times higher than the corresponding one NiTi torsion bar without copper core. .

The invention is of course not restricted to the examples mentioned. Rather, through opti-

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mated arrangement and thickness of the layer or layers with high or very high electrical conductivity (conductivity component) the electrical conductivity of the semi-finished product or the fitting can be determined in wide areas. For many applications the overheating • Risk for the forum memory component reduced and opened up an expansion of their application possibilities. With a sandwich-like layer structure with at least three layers, the conductivity component is expediently in the range of the lower Deformation, i.e. placed between the shape memory components. The conductivity component forms accordingly in the case of a sheathed wire design, expediently the core.

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Claims (1)

Dr .-! Ng. Herbert Moser Patent attorney 75Karlsruhe, NoYJaokBTilagei6 Expectations / Iy composite material, consisting of at least one component with shape memory properties (shape memory component) and at least one further component with different composition and different physical properties compared to the shape memory component,. _v da "'Ü" ui ^} r ' ^} c ' ^{ nil indicates that the * Fornrgedächtnisllomponente is fixed with a component ^{? i} % er, bunde, n, which has an increased electrical conductivity (conductivity component) compared to the shape memory component. 2. Composite material according to claim 1, characterized characterized in that the two components are metallurgically connected. 3. Composite material according to claim 1, characterized characterized in that the conductivity component forms an adhesive coating on the shape memory component. 4. Composite material according to claim 3, characterized characterized in that there is a metallic intermediate layer between the two components is arranged. 5. Composite material according to claim 1, dadurc h characterized in that the conductivity component Copper is. 6. Composite material according to claim 1, characterized characterized in that the conductivity component Silver is. 7. Composite material according to claim 1, characterized in that the shape memory component and the conductivity component are sandwiched, the conductivity component lies in the area of lower deformation. 8. Composite material according to claim 1, characterized in that the shape memory component and the conductivity component as a cladding or core material in a tubular arrangement are connected. .9. Process for the production of a composite material consisting of at least one shape memory com- - - S. J J component and at least one conductivity component, in particular according to claim 1, characterized in that the two components be joined by a metallurgical joining process. .10. Method according to claim 9, characterized in that a melting or shape memory alloy produced by powder metallurgy is produced by rolling in strip form, that at least one band section with a band section from the conductivity component metallurgically is connected, and that the shape memory properties through treatment of the component made of composite material. 11. A composite material according to claim 10, characterized labeled in ze ic hne t that the metallurgical bonding is performed by pressure welding at a temperature above 500 ⁰ C. 12. The method according to claim 9, characterized in that before connecting the Components a diffusion barrier in the form of an electroplated metal surface coating the shape memory component is generated.