METHOD FOR MANUFACTURING A COMPOSITE MATERIAL WITH METAL MATRIX AND CARBON REINFORCEMENT

Abstract

The invention relates to a method for manufacturing a composite material (8) comprising a metal matrix reinforced by a carbon reinforcement, characterised in that the method is a continuous extrusion method which comprises friction-heating of a mixture (7) obtained from a mixture of powders comprising a metal-matrix powder and a carbon-reinforcement powder, by means of a movable extrusion wheel (2), in a passage formed between a groove (2a) of the wheel (2) and a stationary element referred to as shoe (3), followed by carrying the mixture (7) thus heated towards an extrusion die (4).

Claims

1. A process for manufacturing a composite including a metal matrix reinforced by a carbon reinforcement, said process comprising the steps of: a continuous extrusion process including the frictional heating of a mixture obtained from a mixture of powders having a metal matrix powder and a carbon reinforcement powder, using a movable extrusion wheel, in a passage formed between a groove of the wheel and a stationary element known as a shoe, then the conveying of the mixture thus heated to an extrusion die.

2. The process as claimed in claim 1, wherein the extruded composite is an electrical conductor for a cable, a wire rod or a wire intended for a mechanical reinforcement.

3. The process as claimed in claim 1, wherein the lower end of the passage is obstructed by an abutment (6).

4. The process as claimed in one of claims 1 to 3, wherein the entrance of the die is orthogonal to the lower end of the passage.

5. The process as claimed in claim 1, wherein the mixture comes from a hopper.

6. The process as claimed in claim 5, wherein the mixture introduced into the hopper is obtained by flocculation of the mixture of powders.

7. The process as claimed in claim 1, wherein the mixture is obtained by pre-extrusion of the mixture of powders.

8. The process as claimed in claim 7, wherein the pre-extrusion is carried out using a screw extruder.

9. The process as claimed in claim 1, wherein the elements of the metal matrix are selected from copper, aluminum, copper alloys and aluminum alloys.

10. The process as claimed in claim 9, wherein the mixture of powders comprises from 0.01% to 1.8% by weight of metal matrix when the metal matrix is copper or a copper alloy.

11. The process as claimed in claim 9, wherein the mixture of powders comprises from 0.03% to 6% by weight of metal matrix when the metal matrix is aluminum or an aluminum alloy.

12. The process as claimed in claim 1, wherein the mean size of the particles of metal matrix powder is between 10 nm and 1 mm.

13. The process as claimed in claim 1, wherein the carbon reinforcement is made of carbon nanotubes.

14. The process as claimed in claim 13, wherein the mean diameter of the carbon nanotubes is between 0.5 and 90 nm.

15. The process as claimed in claim 13, wherein the length of the carbon nanotubes is between 500 nm and 10 mm.

Description

[0035] Other features and advantages of the present invention will become more clearly apparent on reading the following description given by way of illustrative and non-limiting example and with reference to the appended FIG. 1 that schematically illustrates a device used in the process according to the invention.

[0036] As illustrated in FIG. 1, a continuous extrusion device 1 used in the invention comprises a frame, an extrusion wheel 2 and a shaping system. The shaping system comprises mainly a shoe 3 and an extrusion die 4. The frame supports the wheel 2 which is rotated by a motor. An endless groove 2a is formed at the periphery of the wheel 2 and receives a mixture that may come from a hopper 5. The mixture is a mixture of a powder of metal, typically of copper or aluminum, and a powder of carbon reinforcement, typically of carbon nanotubes.

[0037] In a first embodiment, the mixture of powders may be introduced into the hopper 5. In this case, the mixture of powders is advantageously subjected to a flocculation step, which makes it possible to form larger particles and to make the powder more manipulable for the introduction thereof into the extruder.

[0038] In a second embodiment, it is possible to place, upstream of the device, a screw extruder that will form a preformed rod 7, with a low density, but that will be sufficiently manipulable to be introduced directly into the device. In this second embodiment, the hopper 5 is of course not used.

[0039] A portion of the periphery of the wheel 2 is closely enveloped by the shoe 3, so that the groove 2a cooperates with the shoe 3 in order to delimit a passage. The mixture of powders from the hopper 5, or the mixture in the form of a preformed rod 7, enters into a first end of the passage and is rotated by the wheel 2. The other end of the passage is obstructed by an abutment 6 which is mounted on the shoe 3 and which intrudes into the passage. As the mixture is confined in the passage and since the wheel 2 continues to turn, the mixture is heated by friction with the groove 2a. The die 4 is mounted in a chamber formed directly downstream of the abutment 6. The heat supplied to the mixture enables extrusion thereof through the die 4.

[0040] Thus, the process according to the invention enables the rapid and economical manufacture of long products 8, such as conductive wires for a cable. Moreover, the process imparts a preferential orientation to the carbon nanotubes, which are oriented in the axis of the wire, which gives a better electrical conductivity.