CN111118315A

CN111118315A - Preparation method of nano-copper-tantalum homogeneous composite material and obtained composite material

Info

Publication number: CN111118315A
Application number: CN201911423167.8A
Authority: CN
Inventors: 戴姣燕; 徐金富; 鲍明东; 徐雪波; 吴泓均
Original assignee: Ningbo University of Technology
Current assignee: Ningbo University of Technology
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2020-05-08

Abstract

The invention relates to a preparation method of a nano-copper-tantalum homogeneous composite material and an obtained composite material, belonging to the technical field of metal materials. The preparation method comprises the following steps: and respectively cutting the copper and tantalum rod materials into sheet-shaped samples, stacking the sheet-shaped samples of the copper and the tantalum in a high-pressure twisting machine die, and pressurizing and twisting to obtain the copper-tantalum homogeneous composite material with the nano structure. Through simple high-pressure torsion, copper and tantalum which are not mutually soluble can be uniformly and dispersedly distributed in the material at low torsion rotating speed, and the grain size of the nano-structure of the obtained composite material is less than 100 nm.

Description

Preparation method of nano-copper-tantalum homogeneous composite material and obtained composite material

Technical Field

The invention relates to a preparation method of a nano-copper-tantalum homogeneous composite material and an obtained composite material, in particular to block material nanocrystallization and homogeneous compounding of immiscible components, and belongs to the technical field of metal materials.

Background

The copper-tantalum alloy is an important structural and functional material which is developed in recent years, and is considered to be a very promising material for military and nuclear power due to high strength, radiation resistance, no bubbling and high shock absorption performance. However, copper and tantalum are two metal elements which are not mutually soluble at any temperature, so that the conventional smelting method cannot obtain a uniform copper-tantalum alloy. The prior art mostly adopts a high-energy ball milling method to prepare the copper-tantalum alloy, such as the uniform amorphous copper-tantalum alloy which is researched by willow (willow, positive mixed heat system mechanical drive amorphization. Chinese non-ferrous metals academic report, 1994(1):50-53) and can be obtained by high-energy ball milling, but the single amorphous phase can be obtained only when the tantalum content is limited to 50-90 percent, the obtained material has a micron-sized structure, the inside of the structure has micropores, oxides are easy to mix, and the material performance cannot meet the requirement.

Generally, the internal microstructure of the material determines the external macroscopic properties of the material, and according to the Hall-Peltier formula, the finer the crystal grains of the material, the higher the yield strength of the material, and the toughness of the material is not reduced. In addition, the metal material with fine crystal grains generally has better mechanical properties, electrical properties, magnetic properties, thermal properties and the like, so the nano material has incomparable advantages compared with other materials. Chinese patent (publication No. CN 110144485A) adopts magnetron sputtering method to deposit and obtain Cu-Ta alloy with nano structure on silicon substrate, but only if Ta content is between 1-35%, the alloy has crystal structure and crystal grain is fine columnar nanocrystalline, and the thickness of the obtained Cu-Ta alloy is micron-sized, which is only suitable for micro-nano devices, and Cu-Ta alloy can only be formed on silicon substrate, thus greatly limiting the application field of alloy.

Disclosure of Invention

Aiming at the existing problems, the invention provides a simple preparation method of the nano copper-tantalum composite material, through the severe plastic deformation of a high-pressure twisting machine, the immiscible copper and tantalum elements are uniformly and dispersedly distributed in the material, and the obtained composite material has obvious grain refinement structure and stable grains.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a nano copper-tantalum homogeneous composite material comprises the following steps:

and respectively cutting the copper and tantalum rod materials into sheet-shaped samples, stacking the sheet-shaped samples of the copper and the tantalum in a high-pressure twisting machine die, and pressurizing and twisting to obtain the copper-tantalum homogeneous composite material with the nano structure.

In the present stage, because the properties of copper and tantalum metal are different, the copper and tantalum metal are difficult to alloy perfectly by the conventional process, the copper and tantalum metal are processed into copper sheets and tantalum sheets with required sizes by simple mechanical processing, the copper sheets and the tantalum sheets are loaded into a die of a high-pressure twisting machine, the high-pressure twisting process is carried out simultaneously by compression and twisting, and the friction resistance is changed into friction power under the condition of selecting certain process parameters, so that certain torsional deformation is realized, simple compressive deformation is realized, instability is not easy to occur in the compressive deformation process, and a larger strain can be obtained. Therefore, severe plastic deformation can be generated under high pressure through a high-pressure torsion method, so that copper and tantalum elements are dispersed and distributed, and crystal grains are in a nanometer size.

Ordinary nanocrystalline grains can cause internal instability due to the existence of high grain boundary volume fraction, and can spontaneously transform to coarse grains at normal temperature. The copper and the tantalum adopted by the invention are solid insoluble elements, and the insoluble elements can be distributed in the grain boundary, so that the free energy can be reduced, the grain growth can be slowed down, and the insoluble elements can play a pinning role in the grain boundary. Therefore, the nano-size of the crystal grains of the copper-tantalum alloy system obtained by high-pressure torsion stably exists.

Preferably, the diameter of the selected copper and tantalum bars is 10-20 mm; more preferably, the copper and tantalum rod have the same diameter; therefore, the sheet-shaped samples of copper and tantalum formed by cutting have the same diameter, and can form uniform tissues in the pressurizing and twisting process, so that the situation that the periphery of the composite material is a single element is avoided.

The thickness of the cut copper and tantalum sheet samples is 0.2-2mm, and the thickness is too large, so that the copper and tantalum sheet samples are not beneficial to the dispersion distribution of copper and tantalum elements. The thickness of the sheet samples of copper and tantalum can be selected at will within the above range, and different thicknesses can form copper-tantalum composite materials with different proportions.

The cut copper and tantalum sheet samples can be subjected to simple polishing, oil stain removal and oxide skin treatment before high-pressure torsion, so that the surfaces of the sheet samples are smooth and free of impurities, and the formed alloy composite material has uniform phase and good performance.

Preferably, the high-pressure torsion processing parameters are as follows: the rotating speed of the pressure head is 1-3 r/min, and the pressure is 3-9 GPa. Preferably, the number of turns of the high-pressure twister is 2 to 200 turns, and more preferably 20 to 80 turns.

The rotating speed, the pressure and the number of turns of torsion are important parameters influencing the dispersion distribution effect of the copper-tantalum element, the pressure is too small, the number of turns of torsion is too small, the copper-tantalum element is not uniformly dispersed, the plastic deformation of the material is increased along with the increase of the pressure and the number of turns, the dispersion effect of the copper-tantalum element is better, but the further increase of the pressure and the number of turns of torsion can cause the fine crystal grains to dynamically recover so as to increase the crystal grains.

After high-pressure torsion, the thickness of the obtained copper-tantalum homogeneous composite material is 0.1-1 mm.

In order to achieve the other purpose, the invention adopts the following technical scheme:

the nano copper-tantalum homogeneous composite material obtained by the preparation method comprises a vol.% of Cu and b vol.% of Ta, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, and a + b is equal to 100; the grain size of the composite material is less than or equal to 100 nm.

Compared with the prior art, the invention has the following advantages:

(1) the invention can lead the copper and tantalum elements which are not mutually dissolved to be evenly and dispersedly distributed in the material under the low torsion rotating speed through simple high-pressure torsion, and the obtained composite material has the nano-structure grain size of less than 100nm and stable grain size, and can be used as structural material and functional material in the fields of military industry, nuclear power and the like.

(2) The components of the copper-tantalum homogeneous composite material obtained by high-pressure torsion can be unlimited, the copper-tantalum content can be changed between 0 and 100 percent according to the performance and the organization requirements of different service conditions, and the copper-tantalum homogeneous composite material has a wider application range.

(3) The preparation method has simple raw materials, directly takes the rod-shaped pure copper and the pure tantalum as raw materials, and does not need to carry out special complex processes such as powder preparation, sintering and the like.

Drawings

FIG. 1 is a schematic diagram of the present invention for preparing a copper-tantalum homogeneous composite material by high-pressure torsional deformation;

FIG. 2 is a transmission electron microscope image of the copper-tantalum homogeneous composite material obtained in example 1 of the present invention;

FIG. 3 is a graph showing the cross-sectional hardness distribution of the copper-tantalum homogeneous composite material obtained in example 1 of the present invention;

in the figure, 1, a rotating platform; 2. a fixed platform; 3. an upper die; 4. and (5) a lower die.

Detailed Description

The technical solutions of the present invention will be further described and illustrated below by means of specific examples and drawings, however, these embodiments are exemplary, the disclosure of the present invention is not limited thereto, and the drawings used herein are only for better illustrating the disclosure of the present invention and do not have a limiting effect on the scope of protection. Unless otherwise specified, the raw materials used in the following specific examples of the present invention are those commonly used in the art, and the methods used in the examples are those conventional in the art.

The schematic diagram of the preparation of the copper-tantalum homogeneous composite material through high-pressure torsional deformation is shown in figure 1, a sample is placed between an upper die (3) and a lower die (4), the dies are positioned on a fixed platform (2), and a rotating platform (1) above the dies acts on the dies under the pressure of a plurality of GPa, so that the sample is subjected to torsional compression deformation.

The invention is carried out in the following embodiment using a Lion HPT4 high pressure torque device.

Example 1

Cutting a copper rod and a tantalum rod with the raw material purity of 99.99 wt% and the diameter of 10mm into round pieces with the diameters of 1.4mm and 0.6mm respectively, performing simple polishing, removing oil stains and oxide skin, and then stacking the round pieces in a die of a high-pressure twisting machine. The copper-tantalum homogeneous composite material with the nano structure is obtained through high-pressure torsional severe plastic deformation, and the high-pressure torsional processing parameters are as follows: the rotation speed of the pressure head is 1 r/min, the pressure is 5GPa, and the number of turns is 25. A homogeneous composite of 70 vol.% Cu to 30 vol.% Ta with a nano-structure of 0.8mm thickness was finally obtained.

Fig. 2 is a microscopic image of a tem obtained from example 1, wherein the black area is a Ta-rich area, and the white area is a Cu-rich area, and it can be seen that 70 vol.% Cu to 30 vol.% Ta homogeneous composite is a nano material with a grain structure less than 100nm, and the tantalum grains are uniformly and dispersedly distributed in the copper matrix.

The nanocrystalline grains of pure copper are unstable, tend to grow inevitably at normal temperature, and are difficult to maintain within 100 nm. But the grain size after Cu-Ta compounding is stabilized within 100 nm. This is because the grain growth is hindered by the pinning action of Ta atoms to grain boundaries and the barrier action to the diffusion of copper atoms.

FIG. 3 is a graph of the cross-sectional hardness distribution of the copper tantalum homogeneous composite obtained in example 1, and it can be seen that the hardness distribution of the 70 vol.% Cu-30 vol.% Ta homogeneous composite is uniform, greater than HV310, and significantly higher than that of annealed pure copper. The high hardness results from the fine grain strengthening and the nail rolling of tantalum atoms to dislocations.

Example 2

Cutting a copper rod and a tantalum rod with the raw material purity of 99.99 wt% and the diameter of 15mm into round pieces with the diameters of 1.0mm and 1.0mm respectively, and stacking the round pieces in a die of a high-pressure torsion machine after removing oil stains and oxide skins through simple polishing. The copper-tantalum homogeneous composite material with the nano structure is obtained through high-pressure torsional severe plastic deformation, and the high-pressure torsional processing parameters are as follows: the rotation speed of the pressure head is 1.5 r/min, the pressure is 6GPa, and the number of turns is 45 turns. A homogeneous composite of 50 vol.% Cu to 50 vol.% Ta with a nano-structure of 0.8mm thickness was finally obtained.

Example 3

The copper rod and the tantalum rod with the raw material purity of 99.99 wt% and the diameter of 18mm are respectively cut into round pieces with the diameter of 0.6mm and 1.4mm, and the round pieces are stacked in a die of a high-pressure twisting machine after being simply polished and subjected to oil stain and oxide skin removal. The copper-tantalum homogeneous composite material with the nano structure is obtained through high-pressure torsional severe plastic deformation, and the high-pressure torsional processing parameters are as follows: the rotation speed of the pressure head is 1.2 r/min, the pressure is 4GPa, and the number of turns is 55 turns. A homogeneous composite of 30 vol.% Cu to 70 vol.% Ta with a nano-structure of 0.8mm thickness was finally obtained.

Example 4

Cutting a copper rod and a tantalum rod with the raw material purity of 99.99 wt% and the diameter of 12mm into round pieces with the diameters of 0.2mm and 1.8mm respectively, and stacking the round pieces in a die of a high-pressure torsion machine after removing oil stains and oxide skins through simple polishing. The copper-tantalum homogeneous composite material with the nano structure is obtained through high-pressure torsional severe plastic deformation, and the high-pressure torsional processing parameters are as follows: the rotation speed of the pressure head is 1.8 r/min, the pressure is 7GPa, and the number of turns is 62 turns. A homogeneous composite of 10 vol.% Cu to 90 vol.% Ta with a nano-structure of 0.8mm thickness was finally obtained.

Example 5

The copper rod and the tantalum rod with the raw material purity of 99.99 wt% and the diameter of 20mm are respectively cut into wafers with the diameter of 1.8mm and 0.2mm, and the wafers are stacked in a die of a high-pressure twisting machine after being simply polished and subjected to oil stain and oxide skin removal. The copper-tantalum homogeneous composite material with the nano structure is obtained through high-pressure torsional severe plastic deformation, and the high-pressure torsional processing parameters are as follows: the rotation speed of the pressure head is 2 r/min, the pressure is 8GPa, and the number of turns is 23. A homogeneous composite of 90 vol.% Cu to 10 vol.% Ta with a nano-structure of 0.8mm thickness was finally obtained.

Comparative example 1

Comparative example 1 is different from example 1 only in that the number of turns of the high pressure twister of comparative example 1 is 5 turns.

Comparative example 2

Comparative example 2 is different from example 1 only in that the number of turns of the high pressure twister of comparative example 2 is 10 turns.

Comparative example 3

Comparative example 3 is different from example 1 only in that the number of turns of the high pressure twister of comparative example 2 is 100 turns.

Comparative example 4

Comparative example 4 differs from example 1 only in that comparative example 4 has a high pressure twister ram speed of 0.5 rpm.

Comparative example 5

Comparative example 5 differs from example 1 only in that comparative example 5 has a high pressure twister ram speed of 5 revolutions per minute.

The composite materials prepared in examples 1 to 5 and comparative examples 1 to 5 were subjected to property measurement, and alloy samples were measured for micro Vickers hardness using a Micromet-5101 micrometer indenter, with an applied load of 250mN for a hardness test of 15s for 10 times, and the hardness of each alloy sample was averaged. The grain size was determined by a quantitative metallographic method using an Axio Imager M2M positive full-automatic material microscope. The results are shown in table 1:

table 1: composite hardness and grain size of examples 1-5 and comparative examples 1-5

	Hardness (HV)	Average grain size (nm)
			Example 1	312	91
Example 2	320	83
			Example 3	396	75
Example 4	405	72
			Example 5	270	96
Comparative example 1	245	330
			Comparative example 2	272	305
Comparative example 3	269	166
			Comparative example 4	235	345
Comparative example 5	266	179

The processing parameters of the high-pressure twister have great influence on the performance of the composite material, and the high-pressure twister parameters adopted in comparative examples 1-5 are not matched, so that the obtained composite material has poorer performance compared with example 1.

The technical scope of the invention is not exhaustive and new solutions formed by equivalent replacement of single or multiple technical features in the embodiments are also within the scope of the invention; meanwhile, in all the embodiments of the invention, which are listed or not listed, each parameter in the same embodiment represents only one example (i.e., a feasible solution) of the technical scheme.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims

1. The preparation method of the nano copper-tantalum homogeneous composite material is characterized by comprising the following steps of:

2. The method of claim 1, wherein the copper and tantalum flake sample has a diameter of 10 to 20mm and a thickness of 0.2 to 2 mm.

3. The production method according to claim 1 or 2, wherein the sheet-like test pieces of copper and tantalum have the same diameter.

4. The method of manufacturing of claim 1, wherein the high pressure twist machining parameters are: the rotating speed of the pressure head is 1-3 r/min, and the pressure is 3-9 GPa.

5. The method of claim 1, wherein the high pressure twister is twisted for 2 to 200 turns.

6. The method of claim 1, wherein the high pressure twister is twisted for 20-80 turns.

7. The method of claim 1, wherein the copper-tantalum homogeneous composite material obtained has a thickness of 0.1-1 mm.

8. A nanocopper-tantalum homogeneous composite material obtained by the method of claim 1, wherein said composite material comprises a vol.% Cu and b vol.% Ta, wherein 0 < a < 100, 0 < b < 100, and a + b 100;

the grain size of the composite material is less than or equal to 100 nm.