A homogeneous casting method of a metal alloy / nanocarbon composite material with high fluidity and high plasticity

Abstract

The application discloses a kind of metal alloy / nano carbon composite material's homogeneous casting method giving consideration to high plasticity and high conductivity, belong to composite material preparation technical field.The application includes heating melting matrix metal, adding specific alloying element to obtain master alloy melt, under the temperature that carbon material and alloying element reaction power is enough, carbon material is added to melt surface, and high-speed vortex formed by stirring will carbon material be rolled into high-temperature melt, these elements react with defect sites of carbon material at high temperature to obtain carbide, so as to form metal-covalent heterojunction in high-temperature melt in-situ reaction process, after alloying element in melt and carbon material are fully reacted, keep stirring effect at the same time, realize negative pressure by vacuumizing, and directional solidification is carried out from bottom to top, and high plasticity and high conductivity metal alloy / carbon composite material homogeneous ingot is formed after cooling.The preparation method used in the application is simple, and the casting speed is fast, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and relates to a homogeneous casting method for a metal alloy / nano-carbon composite material with both high conductivity and high plasticity. Background Art

[0002] It is well known that nanocarbon materials with special crystal configurations (such as graphene, carbon nanotubes, carbon fibers, etc.) have extremely high electrical and thermal conductivity and other conductivity capabilities, and their theoretical conductivity performance is even much greater than that of metal materials. However, this special crystal configuration also determines that it does not have the same machinability as metal materials. Metal materials exhibit excellent plasticity due to the non-directionality of metal bonds. At the same time, the presence of a large number of free electrons also brings good conductivity. Combining metal alloys with nanocarbon is expected to give both high conductivity and high plasticity, and obtain ultra-high conductivity composite materials that can be processed and deformed. However, there are many difficulties in combining the two: the interface between metal and nanocarbon is not very compatible, the density difference is large in most cases, nanocarbon is difficult to disperse in the metal, and the ingot metallurgical quality of the composite material is poor.

[0003] At present, the methods for compounding metal materials with nanocarbon are mainly divided into two categories: solid-state method (represented by powder metallurgy) and liquid method (represented by traditional contact stirring casting). Among them, the powder metallurgy process (such as CN112779481A) has the disadvantages that the temperature cannot be higher than the melting point, the interface reaction is insufficient, the process is long, the cost is high and the efficiency is low. The metal alloy / carbon composite material prepared has poor performance and cannot take into account both high conductivity and high plasticity. The traditional contact stirring casting process has many disadvantages such as insufficient uniformity, the greater the viscosity, the worse the effect, difficulty in coordinating with directional solidification, easy pollution and high requirements for the stirring paddle material, and cannot achieve uniform dispersion of nanocarbon in the metal matrix. Patent CN110724887A discloses a method for coupling in-situ self-generated TiC particles with carbon fibers to reinforce aluminum-based composite materials. Continuous carbon fibers are clamped in a clamp to react in a melt, and then ultrasonic vibration and mechanical stirring are used to disperse the continuous carbon fibers. Although the dispersion effect of the continuous carbon fibers is improved, what is ultimately obtained is only a continuous fiber composite material with a directional arrangement (as can be seen in the accompanying drawings). The continuous fibers penetrate the matrix metal and do not achieve true uniform random dispersion. Subsequent deformation processing is likely to cause interface rupture, and subsequent processing performance is poor. In addition, it is mainly used to improve shear resistance, and does not mention the high conductivity that is the focus of this article. Summary of the Invention

[0004] To address these shortcomings, the present invention proposes a homogeneous casting method for a metal alloy / nanocarbon composite material that combines high conductivity with high plasticity. The key principle is to achieve a thorough in-situ interfacial reaction between the elements in the molten metal and the nanocarbon under non-contact, high-speed, continuous stirring. This is then combined with negative pressure and directional solidification techniques to produce a homogeneous ingot of excellent metallurgical quality. The preparation method employed in the present invention is simple, fast, and inexpensive.

[0005] The technical solutions of the present invention are as follows:

[0006] A homogeneous casting method for a metal alloy / nano-carbon composite material having both high conductivity and high plasticity is provided, comprising the following steps:

[0007] (1) melting a base metal, adding specific alloying elements to obtain a master alloy melt, and stirring the master alloy melt in a non-contact high-speed stirring environment to promote the high-speed flow of the master alloy melt to form a disordered turbulent flow;

[0008] (2) preparing nanocarbon, adding the nanocarbon to the surface of the master alloy melt at a stirring temperature at which the nanocarbon and the specific alloying element have sufficient reaction power, and using the large and small vortices in the disordered turbulence to draw the nanocarbon on the surface into the master alloy melt, so that the specific alloying element reacts with the defect sites of the nanocarbon to obtain carbides, forming a metal-covalent heterojunction, improving the interfacial affinity between the nanocarbon and the melt, and promoting the uniform and random dispersion of the nanocarbon under the action of non-contact high-speed stirring;

[0009] (3) while continuing to maintain the stirring effect, vacuum is drawn to achieve negative pressure, and directional solidification is performed from the bottom upward, which not only gradually discharges the gas involved in the melt from bottom to top, but also maintains the dispersion effect in the ingot, and the nano-carbon exceeding the critical content is interconnected in the matrix metal to form a flow-conducting network, thereby forming a homogeneous ingot of the metal alloy / nano-carbon composite material;

[0010] (4) The homogeneous ingot of the metal alloy / nanocarbon composite material is subjected to hot and cold working deformation. Since the nanocarbon is uniformly and randomly dispersed in the matrix metal, a coordinated effect between the nanocarbon and the matrix metal can be achieved during the deformation process, so the processing plasticity is good, thereby obtaining a metal alloy / nanocarbon composite material with both high conductivity and high plasticity.

[0011] Furthermore, the nanocarbon has a discontinuous nanostructure.

[0012] Furthermore, the specific alloying element refers to an alloying element that is slightly excessive and easily combines with carbon to form stable carbides, has a certain solid solubility in the matrix metal melt, and is easily de-melted from the matrix metal when the temperature is lowered.

[0013] Furthermore, the homogeneous ingot of the metal alloy / nano-carbon composite material in step (3) is a non-directionally arranged nano-carbon composite material.

[0014] Furthermore, the base metal is one of copper Cu, aluminum Al, iron Fe, magnesium Mg, titanium Ti, zinc Zn, lithium Li or an alloy thereof.

[0015] Furthermore, the specific alloying elements are one or more of chromium Cr, zirconium Zr, silicon Si, titanium Ti, molybdenum Mo, manganese Mn, and boron B.

[0016] Furthermore, the specific alloying element is added in the form of a master alloy.

[0017] Furthermore, in step (2), the stirring temperature is selected to be 100 degrees Celsius higher than the melting point of the master alloy to ensure the fluidity of the melt. To ensure the reaction kinetics of the carbon material and the alloying elements, the stirring temperature is not less than 800 degrees Celsius, the stirring speed is greater than 300 rpm, and the volume fraction of the nanocarbon is controlled between 0.1-30%.

[0018] Furthermore, in step (2), the stirring temperature is selected between 1000-1800 degrees Celsius, the stirring speed is greater than 800 rpm, and the volume fraction of the nanocarbon is controlled between 1-10%.

[0019] Furthermore, in the step (3), the vacuum pumping speed is greater than 5 L / min to ensure that the gas entrapped in the melt is released under negative pressure, thereby avoiding the occurrence of pores and porosity during the directional solidification process; the temperature gradient of the directional solidification is greater than 5 degrees Celsius / mm to refine the cast grain size and ensure that the nanocarbon is evenly distributed in the ingot.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are:

[0021] (1) During the casting process, the intrinsic structure of the nanocarbon will not be destroyed, thereby maintaining the high conductivity properties to the maximum extent. The interface reaction between the nanocarbon and the metal matrix is ​​sufficient, and the nanocarbon is evenly dispersed in the ingot, which can efficiently form a conductivity network.

[0022] (2) The obtained homogeneous ingot has low interfacial flow resistance and high bonding strength, and can still maintain a high bonding force during the subsequent plastic deformation process, thereby taking into account both processing capability and high flow conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the morphology of the original carbon fiber powder described in the present invention.

[0024] Figure 2This is the as-cast structure of the copper alloy / carbon fiber composite material in Example 1 of the present invention.

[0025] Figure 3 This is the hot-rolled structure of the copper alloy / carbon fiber composite material in Example 1 of the present invention.

[0026] Figure 4 This is the as-cast structure of the copper alloy / carbon fiber composite material in Example 3 of the present invention.

[0027] Figure 5 This is the morphology of the original carbon nanotube powder described in the present invention.

[0028] Figure 6 This is the morphology of the original graphene powder described in the present invention.

[0029] Figure 7 This is the cast structure of the aluminum alloy / carbon fiber / carbon nanotube / graphene composite material in Example 3 of the present invention.

[0030] Figure 8 This is the as-cast structure of the magnesium-lithium alloy / carbon fiber composite material in Example 4 of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] An embodiment of the present invention provides a homogeneous casting method for a copper alloy / carbon fiber composite material having both high conductivity and high plasticity, comprising the following steps:

[0034] (1) Pure Cu, CuCr master alloy, and CuZr master alloy are melted at a high temperature of 1800 degrees Celsius to obtain a Cu-0.5Cr-1Zr master alloy melt;

[0035] (2) Lower the melt temperature to 1400 degrees Celsius and add 5 vol.% carbon fiber (such as Figure 1 As shown, the average diameter of the carbon fiber is 10 μm, the length is 200 μm, the intrinsic thermal conductivity is 1200 W / (m·K), and the stirring speed is 1000 rpm;

[0036] (3) After the Cr and Zr in the melt fully react with the carbon fiber, while maintaining the stirring effect, vacuum is applied to achieve a negative pressure of 0.1 Pa, and directional solidification is performed from the bottom upward. The temperature gradient of directional solidification is 30 degrees Celsius / mm. After cooling, the required copper alloy / carbon fiber composite material homogeneous ingot is formed (the cast structure is as follows Figure 2 The ingot was hot rolled at 900 degrees Celsius with a deformation of 75% (the longitudinal section SEM image is shown in Figure 2). Figure 3 The ingot was subjected to a cold rolling test with a deformation amount of 75%, and then a stress relief annealing at 300 degrees Celsius for 5 hours was performed after cold rolling.

[0037] Comparative sample 1: The same process is used without adding alloying elements Cr and Zr.

[0038] Comparative sample 2: The same process is used without adding the alloying element Zr.

[0039] Comparative sample 3: using the same process, the stirring speed is lower than 200 rpm.

[0040] Comparative sample 4: Using the same process, normal pressure replaces negative pressure.

[0041] Comparative sample 5: Using the same process, casting is used instead of directional solidification.

[0042] Its performance data is shown in Table 1.

[0043] Table 1 Performance data of copper-carbon fiber composite material in Example 1

[0044]

[0045] Analysis of results: In comparative example 1, there is no alloying element, which cannot change the incompatibility between copper and carbon. Under the same process conditions, the content of carbon material entering into the copper melt and dispersing is very limited, and the ingot is close to pure copper. In comparative example 2, only the alloying element Cr is added, which can form excessive chromium carbide on the surface of the carbon fiber, which has a certain effect, but the performance is not as good as the combined addition of Cr and Zr. In comparative example 3, the stirring speed is low, and the melt mainly flows horizontally rather than turbulently. The stirring and dispersion effects are limited and the effect is not good. In comparative sample 4, normal pressure is used instead of negative pressure, and the gas entrapped in the ingot is not easy to discharge, and the performance is reduced. In comparative sample 5, casting is used instead of directional solidification. After casting, the melt cannot maintain the stirring effect, the carbon material floats to a certain extent, and the performance of the ingot is reduced.

[0046] Example 2

[0047] An embodiment of the present invention provides a homogeneous casting method for a copper alloy / carbon fiber composite material having both high conductivity and high plasticity, comprising the following steps:

[0048] (1) Pure Cu, CuCr master alloy, and CuZr master alloy are melted at a high temperature of 1800 degrees Celsius to obtain a Cu-1Cr-2Zr master alloy melt;

[0049] (2) Lower the melt temperature to 1500°C, add 10 vol.% carbon fiber (with an average diameter of 10 μm and a length of 200 μm), and stir at 2500 rpm;

[0050] (3) After the Cr and Zr in the melt have fully reacted with the carbon fiber, while maintaining the stirring effect, vacuum is drawn to achieve a negative pressure of 0.1 Pa, and directional solidification is carried out from the bottom upward. The temperature gradient of directional solidification is 30 degrees Celsius / mm. After cooling, the required copper alloy / carbon fiber composite material homogeneous ingot (such as Figure 4 The ingots were subjected to a hot rolling test at 900 degrees Celsius with a deformation of 75%, and a cold rolling test at 75% with a deformation of 75%. After the cold rolling, stress relief annealing was performed at 300 degrees Celsius for 5 hours.

[0051] Its performance data is shown in Table 2.

[0052] Table 2 Performance data of copper-carbon fiber composite material in Example 2

[0053]

[0054] Example 3

[0055] An embodiment of the present invention provides a homogeneous casting method for an aluminum alloy / carbon fiber / carbon nanotube / graphene composite material having both high conductivity and high plasticity, comprising the following steps:

[0056] (1) Melting 5005 aluminum alloy and AlSi master alloy at a high temperature of 1500 degrees Celsius to obtain a 5005Al-1Si master alloy melt;

[0057] (2) Add 5 vol.% of carbon fiber (the average diameter of carbon fiber is 10 microns and the length is 200 microns), 1 vol.% of carbon nanotubes (such as Figure 5 As shown, the carbon nanotubes have an average diameter of 200 nm and a length of 20 μm) and 0.3 vol.% graphene (as Figure 6 As shown, the average graphene diameter is 10 microns), the stirring speed is 1500 rpm, a high-speed vortex is formed in the melt, and the melt stirs and disperses the carbon fibers, carbon nanotubes and graphene in the form of turbulence;

[0058] (3) After the Si in the melt fully reacts with the carbon material, while maintaining the stirring effect, vacuum is applied to achieve a negative pressure of 0.1 Pa, and directional solidification is performed from the bottom upward. The temperature gradient of directional solidification is 20 degrees Celsius / mm. After cooling, the desired 5005Al-Si / carbon fiber / carbon nanotube / graphene composite material homogeneous ingot (such as Figure 7 The ingots were subjected to a hot rolling test at 450 degrees Celsius with a deformation of 75%, and a cold rolling test at 75% with a deformation of 75%. After the cold rolling, stress relief annealing was performed at 200 degrees Celsius for 5 hours.

[0059] Its performance data is shown in Table 3.

[0060] Table 3 Performance data of aluminum-carbon composite material in Example 3

[0061]

[0062] Example 4

[0063] An embodiment of the present invention provides a homogeneous casting method for a magnesium-lithium alloy / carbon composite material having both high conductivity and high plasticity, comprising the following steps:

[0064] (1) melting the Mg-10Li alloy and the MgZr master alloy at a high temperature of 1200 degrees Celsius to obtain a Mg-10Li-1Zr master alloy melt;

[0065] (2) Add 5 vol.% carbon fiber (with an average diameter of 10 μm and a length of 200 μm) and stir at a speed of 2000 rpm to form a high-speed vortex in the melt. The melt stirs and disperses the carbon fiber in the form of turbulent flow.

[0066] (3) After the Zr in the melt fully reacts with the carbon material, while maintaining the stirring effect, vacuum is applied to achieve a negative pressure of 0.1 Pa, and directional solidification is performed from the bottom upward. The temperature gradient of directional solidification is 20 degrees Celsius / mm, and after cooling, the desired MgLiZr / carbon fiber composite material homogeneous ingot is formed (such as Figure 8 The ingots were subjected to a hot rolling test at 400 degrees Celsius with a deformation of 75%, and a cold rolling test at 75% with a deformation of 75%. After the cold rolling, stress relief annealing was performed at 200 degrees Celsius for 5 hours.

[0067] Its performance data is shown in Table 4.

[0068] Table 4 Performance data of magnesium-lithium-carbon composite material in Example 4

[0069]

[0070] The embodiments of the present invention are described in detail, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. A homogeneous casting method for a metal alloy / nano-carbon composite material having both high conductivity and high plasticity, characterized in that: The following steps are involved: (1) melting a base metal, adding specific alloying elements to obtain a master alloy melt, and stirring the master alloy melt in a non-contact high-speed stirring environment to promote the high-speed flow of the master alloy melt to form a disordered turbulent flow; (2) preparing nanocarbon, adding the nanocarbon to the surface of the master alloy melt at a stirring temperature at which the nanocarbon and the specific alloying element have sufficient reaction power, and using the large and small vortices in the disordered turbulence to draw the nanocarbon on the surface into the master alloy melt, so that the specific alloying element reacts with the defect sites of the nanocarbon to obtain carbides, forming a metal-covalent heterojunction, improving the interfacial affinity between the nanocarbon and the melt, and promoting the uniform and random dispersion of the nanocarbon under the action of non-contact high-speed stirring; (3) while continuing to maintain the stirring effect, vacuum is drawn to achieve negative pressure, and directional solidification is performed from the bottom upward, which not only gradually discharges the gas involved in the melt from bottom to top, but also maintains the dispersion effect in the ingot, and the nano-carbon exceeding the critical content is interconnected in the matrix metal to form a flow-conducting network, thereby forming a homogeneous ingot of the metal alloy / nano-carbon composite material; (4) The homogeneous ingot of the metal alloy / nanocarbon composite material is subjected to hot and cold working deformation. Since the nanocarbon is uniformly and randomly dispersed in the matrix metal, a coordinated effect between the nanocarbon and the matrix metal can be achieved during the deformation process, so the processing plasticity is good, thereby obtaining a metal alloy / nanocarbon composite material with both high conductivity and high plasticity.

2. A homogeneous casting method for a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 1, characterized in that: The nanocarbon has a discontinuous nanostructure.

3. The homogeneous casting method of a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 1, characterized in that: The specific alloying element refers to an alloying element that is slightly excessive and easily combines with carbon to form a stable carbide, has a certain solid solubility in the matrix metal melt, and is easily de-melted from the matrix metal when the temperature is lowered.

4. The homogeneous casting method of a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 2, characterized in that: The homogeneous ingot of the metal alloy / nano-carbon composite material in step (3) is a non-directionally arranged nano-carbon composite material.

5. The homogeneous casting method of a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 1, characterized in that: The base metal is one of copper Cu, aluminum Al, iron Fe, magnesium Mg, titanium Ti, zinc Zn, lithium Li or an alloy thereof.

6. The homogeneous casting method of a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 3, characterized in that: The specific alloying elements are one or more of chromium Cr, zirconium Zr, silicon Si, molybdenum Mo, manganese Mn, and boron B.

7. A homogeneous casting method for a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 6, characterized in that: The specific alloying elements are added in the form of a master alloy.

8. The homogeneous casting method of a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 1, characterized in that: In the step (2), the stirring temperature is selected to be 100 degrees Celsius higher than the melting point of the master alloy to ensure the fluidity of the melt. To ensure the reaction kinetics of the carbon material and the alloying elements, the stirring temperature is not less than 800 degrees Celsius and the stirring speed is greater than 300 rpm. The volume fraction of the nanocarbon is controlled between 0.1-30%.

9. The homogeneous casting method of a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 1, characterized in that: In the step (2), the stirring temperature is selected between 1000-1800 degrees Celsius, the stirring speed is greater than 800 rpm, and the volume fraction of the nanocarbon is controlled between 1-10%.

10. The homogeneous casting method of a metal alloy / nano-carbon composite material having both high conductivity and high plasticity according to claim 1, characterized in that: In the step (3), the vacuum pumping speed is greater than 5 L / min to ensure that the gas entrapped in the melt escapes under negative pressure, thereby avoiding the occurrence of pores and looseness during the directional solidification process; the temperature gradient of the directional solidification is greater than 5 degrees Celsius / mm to refine the cast grain size and ensure that the nanocarbon is evenly distributed in the ingot.

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