Preparation method for spiral laminate composite using compressive torsion

Abstract

Disclosed is a preparation method for a composite which comprises the following steps: (a) preparing unit metal pieces comprising two or more types of different metals; (b) circumferentially arranging the two or more types of unit metal pieces in a mold comprising upper and lower dies; (c) applying compressive stress to the loaded metal pieces using the upper and lower dies; and (d) rotating the upper and lower dies in one or two directions to apply torque in the pressed state.

Claims

1. A method of preparing a laminate composite, comprising: (a) preparing two types of unit metal specimens comprising different metals; (b) circumferentially arranging the two types of unit metal specimens in a mold having upper and lower dies, wherein the two types of unit metal specimens are circumferentially arranged in an A-B-A-B pattern; (c) applying compressive stress to the loaded metal specimens using the upper and lower dies; and (d) rotating either or both of the upper and lower dies to apply torque to the metal specimens which are pressed and forming the laminate composite having a spiral laminate structure in a thickness direction.

2. The method of claim 1, wherein properties of the composite are controlled by adjusting the number of loaded unit metal specimens in (b).

3. The method of claim 1, wherein properties of the composite are controlled by adjusting the number of rotations in (d).

4. The method of claim 1, wherein A is copper or a copper alloy, and B is aluminum or an aluminum alloy.

5. The method of claim 1, wherein the unit metal specimens have a shape of a circular sector or a semicircular shape.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a flowchart illustrating a process of preparing a composite according to the present invention;

(2) FIG. 2 is a schematic view illustrating a process of preparing the composite according to the present invention;

(3) FIG. 3 is a schematic view illustrating a serial sectioning process; and

(4) FIG. 4 is a view illustrating results of the composite prepared in the present example as analyzed by the serial sectional process of FIG. 3.

MODE FOR INVENTION

(5) Hereinafter, a detailed description will be given of a method of preparing a composite according to preferred embodiments of the present invention with reference to the appended drawings, but these embodiments are not construed as limiting the present invention. Therefore, it is apparent to those having ordinary knowledge in the art that the present invention be variously modified within a scope that does not depart from the spirit of the invention.

(6) As illustrated in FIG. 1, the process of preparing the composite according to the present invention includes preparing metal specimens (S10), loading the specimens (S20) and performing compressive shear deformation of the specimens (S30).

(7) As illustrated in FIG. 2, preparing the metal specimens (S10) is a step of cutting bulk metal to a fan shape (division in four, six, etc. equal parts) or a semicircular shape (division in two equal parts) so that specimens comprising different types of metals are adjusted to form a cylindrical shape and then loaded in a mold. The type of metal specimen for a composite is not limited, and a variety of metals, including two, three, four, etc. types of metals, may be made into a composite depending on the properties required of the composite. Also, the composite-making method according to the present invention adopts a compressive torsion process. This process is advantageous because a large deformation may be easily applied and brittle metal may be processed, and thereby not only good ductile metal but also somewhat brittle metal may be made into a composite.

(8) As illustrated in FIG. 2, loading the specimens (S20) is a step of circumferentially loading different types of metal specimens in a periodic pattern such as A-B-A-B, A-B-C-A-B-C or A-B-C-D or in an aperiodic pattern such as A-B-B-C-A to ensure a total cylindrical shape. The lamination period and the type of metal to be laminated are not limited, but may be adjusted so as to be adapted for required properties because the properties of the resultant composite may vary depending on the lamination period and the type of metal to be laminated.

(9) Performing compressive shear deformation (S30) is a step of applying torque to the loaded specimens which are pressed using the upper and lower dies to undergo shear deformation. As such, the surfaces of the upper and lower dies are preferably provided with recesses (), so as to prevent movement of the specimens when torque is applied thereto. Also, torque may be applied by rotating either of the upper and lower dies or by rotating both of them in different directions. Because the structure of the composite in a thickness direction may significantly vary depending on the number of rotations, the number of rotations is preferably adjusted so as to attain required properties. Furthermore, upon compressive shear deformation, grain refinement may occur through dynamic recrystallization. Thus, the method of preparing the composite according to the present invention may result in improved properties by grain refinement in coincidence with the composite-making process.

(10) Thereby, the composite having a spiral structure is afforded, thus obtaining unique electrically conductive properties or elastic properties which cannot result from conventional simple multilayered composites.

EXAMPLE

(11) Specifically, bulk copper (A metal) and A606 aluminum alloy (B metal) were processed, thus manufacturing metal specimens having a fan shape resulting from dividing a circle in four equal parts, as illustrated in FIG. 2. Subsequently, the copper-aluminum alloy unit specimens were circumferentially alternately arranged in an A-B-A-B pattern in a cylindrical mold having an upper die and a lower die. The surfaces of the upper die and the lower die were provided with recesses () for inserting specimens, so that the arranged specimens were easily fixed. On the other hand, the shape of the composite structure may be controlled by adjusting the size of the loaded specimens.

(12) Subsequently, the specimens were pressed by the upper and lower dies at a pressure of 2.5 GPa, and then torqued and thus distorted. As such, the number of distortion rotations was adjusted, making it possible to control the interlayer interval of the resulting composite and the amount of deformation. In the present example, the number of distortion rotations was set to 1.

(13) The compressive distortion process according to the present example is advantageous because the composite-making process may be very easily implemented, a large deformation may be easily applied, and light brittle metal may undergo the composite-making process.

(14) In order to analyze the internal structure and the bondability of the composite prepared in the present example, serial sectioning was used. As illustrated in FIG. 3, serial sectioning was executed in such a manner that the cross-section of a specimen was polished at a predetermined interval and then photographed, after which the serial 2D photos were converted into actual 3D images by means of an image processing operation.

(15) Specifically, while the composite specimen was polished to a thickness of 0.05 mm, individual 2D photos were obtained through scanning, and then 3D visualized by image analysis processing using AMIRA program. FIG. 4 shows the analyzed image. Also, phenomena such as interfacial separation, etc., could not be observed in the course of polishing the composite specimen, and thus the interfacial integrity of the composite according to the present invention was evaluated to be good.

(16) As illustrated in FIG. 4, the composite prepared in the present example has a spiral laminate structure in a thickness direction, which means that it has a continuous structure between heterogeneous composite metals compared to conventional simple laminate structures, and also that electrically conductive properties or elastic properties which were difficult to ensure in conventional composites can be attained.