A CNTs / Mg-6Zn magnesium-based composite plate with good plate shape and a rolling method thereof

Abstract

The application discloses a CNTs / Mg-6Zn composite material with good plate shape and a rolling method thereof, and the CNTs / Mg-6Zn composite material ingot is prepared by an ultrasonic semi-solid stirring assisted pressure casting method, then the CNTs / Mg-6Zn ingot is subjected to solid solution treatment, so that the dendritic segregation is eliminated, and eutectic compounds in the alloy are fully dissolved, the effect of eliminating internal stress and improving toughness and plasticity is achieved. Subsequently, the plate is preheated before rolling, the composition is more uniform, and the cracking phenomenon in the processing process is slowed down; finally, the composite material is rolled according to the specified reduction, rolling speed, rolling pass, preheating treatment between passes, and finally the CNTs / Mg-6Zn composite material rolled plate is obtained. The magnesium-based composite plate with excellent mechanical properties and good plate shape is obtained through the best matching of the solid solution process parameters, the preheating process parameters and the rolling process parameters, and the material manufacturing and the processing method used in the method are low-cost processes, and batch production is easy to realize.

Description

Technical Field

[0001] This invention belongs to the field of magnesium-based composite material processing technology, and particularly relates to a CNTs / Mg-6Zn magnesium-based composite plate with good plate shape and its rolling method. Background Technology

[0002] The density of magnesium and magnesium alloys ranges from 1.6 to 1.85 g / cm³. 3 Magnesium alloys possess high specific strength and specific stiffness, making them the lightest metallic structural materials currently available. However, their relatively low strength, hardness, and elastic modulus limit their industrial applications to some extent. Using discontinuous phases (particles, whiskers, microstructures, etc.) to reinforce magnesium matrix composites can effectively improve many shortcomings of magnesium alloys, such as low elastic modulus, low tensile strength, poor creep resistance, and low hardness. Compared to castings of magnesium matrix composites, deformed magnesium matrix composites processed through extrusion, rolling, and forging exhibit superior performance and can effectively eliminate casting defects. For magnesium alloy sheets, rolling is an economical and efficient processing method, which can improve the distribution of reinforcing phases and help refine the matrix structure, thereby efficiently improving the comprehensive performance of the composite material and meeting the requirements for magnesium sheet components under different working conditions. The patent applicant has prepared CNTs / Mg-6Zn composite ingots with good performance and low cost using semi-solid stirring technology. The ingots obtained by this method have a uniform distribution of reinforcement, fewer casting defects, and meet the microstructure requirements before rolling. To ultimately obtain composite materials with superior mechanical properties, it is particularly important to explore and develop rolling methods for CNTs / Mg-6Zn magnesium-based composite plates with good plate shape.

[0003] Zn is the most widely used alloying element in magnesium alloys after Al, playing a crucial role in plastic strengthening and improving mechanical properties, second only to Mg-Al alloys in practical application. However, due to the hexagonal packing structure (hcp) of magnesium, the strength and plasticity of Mg-Zn alloys and their composites at room temperature are still significantly lower than other alloys and composites, making it difficult to improve their mechanical properties through traditional plastic deformation processing. Even with thermoplastic deformation, problems such as complex equipment, complicated processes, stringent processing conditions, and high costs severely restrict the application and development of Mg-Zn alloys and their composites. Therefore, obtaining a low-cost, high-performance, and simple preparation method has become an urgent need for their industrial applications. Summary of the Invention

[0004] The technical objective of this invention is to provide a rolling method for CNTs / Mg-6Zn magnesium-based composite plates with good shape. Addressing the challenges of processing and cracking of cast CNTs / Mg-6Zn raw materials, this invention employs a heat treatment followed by rolling deformation, which significantly improves the shape and mechanical properties of the magnesium-based composite plate. This provides a solution to the problem of plastic deformation in magnesium-based composites and overcomes the technical obstacles in the rolling process of carbon nanotube-reinforced magnesium-based composites, while simultaneously reducing deformation costs. The rolling method for CNTs / Mg-6Zn magnesium-based composite plates prepared by this invention results in significantly refined grains, elimination of casting defects, and further enhanced mechanical properties. It can be used in the 3C digital field, supporting the urgent need for high-performance metal composite materials in this sector.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for rolling CNTs / Mg-6Zn magnesium-based composite plates with good plate shape, comprising the following steps: A method for rolling CNTs / Mg-6Zn magnesium-based composite plates with good plate shape, comprising the following steps:

[0006] Step 1: The CNTs / Mg-6Zn magnesium-based composite plate ingot prepared by semi-solid stirring-assisted pressure casting is subjected to solution treatment at a temperature of 350℃~360℃ for 12 hours.

[0007] Step 2: Cut the solution-treated billet into plates and grind and polish the surface of the plates.

[0008] Step 3: Preheat the polished sheet material before rolling at a temperature of 300℃~320℃ for 30 minutes.

[0009] Step 4: The preheated sheet is fed into the double rolls and rolled according to the set process flow. The rolling speed is 0.2-0.25m / s, and the reduction in pressure for each pass is 20%. Before each pass, the sheet is preheated at 300℃~320℃ for 30 minutes until the total deformation is controlled at 60%, thereby obtaining a CNTs / Mg-6Zn magnesium-based composite sheet with good sheet shape.

[0010] In step 1, the solution treatment temperature is 350℃~360℃, and the time is 12 hours.

[0011] The CNTs / Mg-6Zn magnesium-based composite plate ingot used in step 1 is cast using a semi-solid stirring method. The specific casting process is as follows: the Mg-6Zn magnesium alloy is heated to complete melting, and then cooled to the semi-solid temperature range. Preheated CNTs are added by mechanical stirring, with the stirring speed controlled at 600 rpm and the stirring time selected as 10-15 min. Then the melt is poured into the mold to obtain the CNTs / Mg-6Zn magnesium-based ingot.

[0012] The composition of Mg-6Zn magnesium alloy by mass percentage is: Zn = 5.8%, Si = 0.62%, and the remainder is Mg.

[0013] The physical parameters of the carbon nanotubes used are as follows: diameter of 30-50 nm, length of 5-10 μm, and purity of over 95%.

[0014] The added carbon nanotubes have a mass fraction of 0.5%. The carbon nanotubes need to be preheated before being added to the melt at a temperature of 350±10℃.

[0015] The cutting process in step 3 uses a wire EDM machine. After machining, the dimensions of the rolled plate are 10cm × 5cm × 1cm.

[0016] A CNTs / Mg-6Zn magnesium-based composite plate, obtained by the rolling method described in this invention, has alloy grains that are significantly deformed and elongated along the rolling direction, becoming flat. It has a yield strength of 278 MPa, a tensile strength of 348 MPa, and a fracture elongation of 6.3%. The alloy grains are significantly deformed and elongated along the rolling direction, becoming flat. The second phase distributed at the grain boundaries is crushed and dispersed in the composite matrix.

[0017] The CNTs / Mg-6Zn magnesium-based composite board can be used in the manufacture of 3C products.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] This invention proposes a rolling method for CNTs / Mg-6Zn magnesium-based composite plates with good plate shape. Addressing the poor deformation capacity of the matrix material at room temperature and the susceptibility to defects during the rolling of thin plates, this invention employs a heat treatment followed by rolling to improve material deformation and overall mechanical properties. By exploring the effects of solution temperature and holding time on grain size in CNTs / Mg-6Zn composites, and the effects of preheating temperature on plate shape and surface quality, combined with the influence of rolling reduction and rolling speed on the mechanical properties of CNTs / Mg-6Zn composites, this application determines the optimal process parameters, thereby preparing composite plates with superior performance. The rolled composite material produced by this proposed heat treatment and rolling process not only exhibits good plate shape, but also achieves a good match between the microstructure and properties of the CNTs / Mg-6Zn composite material. Its yield strength and tensile strength are significantly greater than those of the matrix Mg-6Zn alloy and most conventionally processed deformed magnesium alloys. In addition, due to its simple process, low-cost manufacturing method, and mature and reliable equipment, this patent can be applied to large-scale production.

[0020] The advantage of this method lies in the fact that the heat treatment process is carried out in a conventional electric resistance furnace, while the rolling process is carried out on a common twin-roll mill. Significant improvements in the performance of rolled composite material sheets can be achieved simply by controlling the solution heat treatment temperature and time before rolling, the preheating temperature and time before rolling, and the rolling reduction and rolling speed. Compared to the cold rolling process for magnesium alloy sheets, which involves small single-pass reduction, numerous reduction passes, large required deformation force, and many defects in the rolled sheet, this patented process is simple, controllable, and low-cost, effectively solving the problem of difficulty in rolling and deforming magnesium alloy sheets.

[0021] The CNTs / Mg-6Zn composite material plate prepared by this invention has a good plate shape and does not exhibit defects such as warping, cracking, or camber. Compared with the metallographic structure of the plate without rolling deformation, the finished rolled plate with 60% reduction shows that the alloy grains are significantly deformed and elongated along the rolling direction, and are flattened, with a significant grain refinement effect. The second phase distributed at the grain boundaries is crushed and dispersed in the composite material. To investigate the effect of rolling process on the mechanical properties of materials, tensile specimens were designed according to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature". The results show that the rolled composite material exhibits higher yield strength and tensile strength than the cast composite material. After rolling deformation, the yield strength of the composite material increased by 191 MPa, an increase of 220%, and the tensile strength increased by 139 MPa, an increase of 67%. At the same time, the elongation at break of the composite material remained at 6.3%. The method described in this application reduces the production cost of magnesium alloy sheets, simplifies the production process, and to some extent solves the problem of difficult plastic processing of magnesium alloys and their composite materials, thus promoting the development of rolling deformation technology for such materials and their application in the 3C field. Attached Figure Description

[0022] Figure 1 This is a process route diagram for rolling CNTs / Mg-6Zn composite materials.

[0023] Figure 2 The images show the metallographic structure of the CNTs / Mg-6Zn composite material before and after rolling.

[0024] Figure 3 This refers to the standard tensile specimen size.

[0025] Figure 4 The diagram shows the yield strength, tensile strength, and elongation of the composite material at each process stage. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, but is not limited to the following embodiments.

[0027] A rolling method for CNTs / Mg-6Zn magnesium-based composite plates with good shape is proposed. Using carbon nanotube-reinforced magnesium-based composite material as a deformed billet, CNTs / Mg6Zn composite material plates with good shape are prepared by heat treatment and rolling deformation processes. After rolling, not only can plates with high appearance quality be obtained, but the comprehensive performance of the plates is also excellent, which effectively broadens the application of magnesium-based composite materials in the 3C electronics field.

[0028] refer to Figure 1The ingot used in this invention is a CNTs / Mg-6Zn composite material ingot, which exhibits high plasticity at room temperature. To prepare rolled plates with superior performance, the ingot must first undergo solution treatment and machining, followed by preheating and rolling. During rolling, the preheating temperature and time, the reduction per pass, and the roll speed must be controlled. The final product is a rolled plate with good shape, high yield strength, and high tensile strength.

[0029] Example 1:

[0030] The rolling process of the magnesium-based composite material prepared in this example is carried out according to the following steps:

[0031] Step 1: Alloy smelting of magnesium ingots and zinc ingots. The temperature of the resistance furnace is raised to the melting temperature of magnesium alloy. After the alloy is completely melted, the temperature of the melt is cooled to the semi-solid stirring temperature and carbon nanotubes are injected for stirring. After stirring, ultrasonic vibration is performed. Then the mixture is poured into a preheated mold for cooling to obtain composite material ingots.

[0032] Step 2: Spread graphite powder evenly on tin foil, then place the composite material ingot that needs to be heat treated on the graphite powder. After the alloy is completely covered by graphite, wrap it further with tin foil. Place the CNTs / Mg-6Zn composite material ingot into a box-type resistance furnace for solution treatment. Set the target temperature of the box-type resistance furnace to 350℃. After the furnace temperature reaches the set temperature, start heat preservation for 12 hours.

[0033] Step 3: Cut a 10mm×50mm×1mm slab from the composite material casting billet and use a polishing machine to grind and polish the upper and lower surfaces of the sample.

[0034] Step 4: Place the prepared rolled plate into a box-type resistance heating furnace for preheating, heat to 300℃ and hold for 30 minutes;

[0035] Step 5: Place the product into a twin-roll mill for rolling. Set the rolling speed to 0.2 m / s and the reduction per pass to 20%. Remove the product after completion.

[0036] Step 6: Place the rolled plate with a reduction of 20% into a box-type resistance heating furnace for preheating, heat to 300℃ and hold for 30 minutes;

[0037] Step 7: Take out the rolled plate and put it into a twin-roll mill for rolling. The rolling speed is set to 0.2m / s. Based on the existing size, the reduction per pass is set to 20%. After completion, a rolled plate with a reduction of 40% is obtained.

[0038] Step 8: Place the rolled plate with a reduction of 40% into a box-type resistance heating furnace for preheating, heat to 300℃ and hold for 30 minutes;

[0039] Step 9: Take out the rolled plate and put it into a twin-roll mill for rolling. Set the rolling speed to 0.2m / s. Based on the existing dimensions, set the reduction per pass to 20% to obtain a rolled plate with a reduction of 60%, thus completing the rolling process of the plate.

[0040] In step 3, the twin-roll mill used has a diameter of 175mm, a roll length of 260mm, and a maximum roll opening and closing degree of 20mm. During the preparation process, the temperature of the plate surface is measured by a handheld infrared thermometer.

[0041] No obvious edge cracks or macroscopic cross sections were observed in the composite rolled sheet obtained by this invention, and the shape and size of the sheet met the expected goals.

[0042] Depend on Figure 2 It can be seen that when the reduction is 60%, the composite material grains are flat along the rolling direction, and a large number of twins exist inside the grains, exhibiting a parallel state. Compared with the unrolled plate, when the reduction is increased to 60%, the composite material plate shows an elongation phenomenon, the grain size is significantly refined, and the deformed grains gradually transform into recrystallized grains.

[0043] To investigate the effect of rolling process on the mechanical properties of materials, tensile specimens were designed according to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature" standard. (See attached document.) Figure 3 This invention tests the tensile properties of CNTs / Mg-6Zn magnesium-based composite plates: at least three standard tensile specimens were prepared from cast composite material, solution-treated composite material, rolled composite material with 20% reduction, rolled composite material with 40% reduction, and rolled composite material with 60% reduction, and the tensile properties were tested using an electronic universal testing machine. Detailed mechanical property data for each material are as follows: Figure 4 As shown in Table 1.

[0044]

[0045]

[0046] Table 1

[0047] Example 2:

[0048] The rolling process of the magnesium-based composite material prepared in this example is carried out according to the following steps:

[0049] Step 1: Add high-purity magnesium ingots and zinc ingots into a stainless steel mold placed in a resistance furnace and raise the temperature of the resistance furnace. After they are completely melted, lower the temperature to a semi-solid temperature to obtain a semi-solid "jelly" melt. Start the stirring device. After a 2cm deep vortex is generated on the surface of the melt, add preheated carbon nanotube particles into the melt and continue stirring the mixture. Then pour the uniformly dispersed semi-solid mixture into the mold to obtain a composite ingot.

[0050] Step 2: Place the CNTs / Mg-6Zn composite material billet into a box-type resistance furnace for solution treatment. Set the target temperature of the box-type resistance furnace to 360℃. After the furnace temperature reaches the set temperature, start heat preservation for 12 hours.

[0051] Step 3: Cut a 10mm×50mm×1mm slab from the composite material casting billet and use a polishing machine to grind and polish the upper and lower surfaces of the sample.

[0052] Step 4: Place the sample in a box-type resistance heating furnace for preheating. Heat to 320°C and hold for 30 minutes.

[0053] Step 5: Place the product into a twin-roll mill for rolling. Set the rolling speed to 0.25 m / s and the reduction per pass to 20%. Remove the product after completion.

[0054] Step 6: Place the rolled plate with a reduction of 20% into a box-type resistance heating furnace for preheating, heat to 320℃ and hold for 30 minutes;

[0055] Step 7: Take out the rolled plate and put it into a twin-roll mill for rolling. The rolling speed is set to 0.25m / s. Based on the existing size, the reduction per pass is set to 20%. After completion, a rolled plate with a reduction of 40% is obtained.

[0056] Step 8: Place the rolled plate with a reduction of 40% into a box-type resistance heating furnace for preheating, heat to 320℃ and hold for 30 minutes;

[0057] Step 9: Take out the rolled plate and put it into a twin-roll mill for rolling. Set the rolling speed to 0.25m / s. Based on the existing dimensions, set the reduction per pass to 20% to obtain a rolled plate with a reduction of 60%, thus completing the rolling process of the plate.

[0058] In step 3, the rolling mill used in Example 1 is used, and the temperature of the plate surface is measured by a handheld infrared thermometer during the preparation process.

[0059] No obvious edge cracks or macroscopic cross sections were observed in the composite rolled sheet obtained by this invention, and the shape and size of the sheet met the expected goals.

[0060] When the reduction is 60%, the recrystallized grains in the composite material increase significantly. The grains are deformed along the rolling direction, changing from polygonal to flat. The second phase that accumulates at the grains is crushed and no longer accumulates at the grain boundaries. Fine eutectic compounds also exist within the grains.

[0061] This invention tests the tensile properties of CNTs / Mg-6Zn magnesium-based composite sheets: at least three types of CNTs / Mg-6Zn composite sheets are processed from cast composites and rolled composites with 60% reduction. Figure 3 The tensile specimens shown were tested using an electronic universal testing machine. Detailed mechanical property data for various materials are shown in Table 2.

[0062]

[0063] Table 2

[0064] Example 3:

[0065] The rolling process of the magnesium-based composite material prepared in this example is carried out according to the following steps:

[0066] Step 1: Place magnesium ingots and zinc ingots into a mold inside the resistance furnace and raise the temperature of the resistance furnace to the melting point. After melting, lower the temperature to the semi-solid range to obtain a semi-solid melt. Then, start the stirring device and add preheated carbon nanotube particles into the melt. Continue stirring the mixture until it is evenly dispersed and then pour it into the mold to obtain a composite ingot.

[0067] Step 2: Place the CNTs / Mg-6Zn composite material billet into a box-type resistance furnace for solution treatment. Set the target temperature of the box-type resistance furnace to 355℃. After the furnace temperature reaches the set temperature, start heat preservation for 12 hours.

[0068] Step 3: Cut a 10mm×50mm×1mm slab from the composite material casting billet and use a polishing machine to grind and polish the upper and lower surfaces of the sample.

[0069] Step 4: Place the sample in a box-type resistance heating furnace for preheating. Heat to 310°C and hold for 30 minutes.

[0070] Step 5: Place the product into a twin-roll mill for rolling. Set the rolling speed to 0.23 m / s and the reduction per pass to 20%. Remove the product after completion.

[0071] Step 6: Place the rolled plate with a reduction of 20% into a box-type resistance heating furnace for preheating, heat to 310℃ and hold for 30 minutes;

[0072] Step 7: Take out the rolled plate and put it into a twin-roll mill for rolling. The rolling speed is set to 0.23m / s. Based on the existing size, the reduction per pass is set to 20%. After completion, a rolled plate with a reduction of 40% is obtained.

[0073] Step 8: Place the rolled plate with a reduction of 40% into a box-type resistance heating furnace for preheating, heat to 310℃ and hold for 30 minutes;

[0074] Step 9: Take out the rolled plate and put it into a twin-roll mill for rolling. Set the rolling speed to 0.23 m / s. Based on the existing size, set the reduction per pass to 20% to obtain a rolled plate with a reduction of 60%, thus completing the rolling process of the plate.

[0075] In step 3, the twin-roll mill used is the same as the one used in Example 1. During the preparation process, the temperature of the plate surface is measured by a handheld infrared thermometer.

[0076] No obvious edge cracks or macroscopic cross sections were observed in the composite rolled sheet obtained by this invention, and the shape and size of the sheet met the expected goals.

[0077] Table 3

[0078]

[0079] This invention tests the tensile properties of CNTs / Mg-6Zn magnesium-based composite sheets: at least three types of CNTs / Mg-6Zn composite sheets are processed from cast composites and rolled composites with 60% reduction. Figure 3 The tensile specimens shown were tested using an electronic universal testing machine. Detailed mechanical property data for various materials are shown in Table 3.

Claims

1. A method for rolling CNTs / Mg-6Zn magnesium-based composite plates with good plate shape, characterized in that, Includes the following steps: Step 1: The CNTs / Mg-6Zn magnesium-based composite plate ingot prepared by semi-solid stirring-assisted pressure casting is subjected to solution treatment. The specific casting process is as follows: The Mg-6Zn magnesium alloy is heated to complete melting, and then cooled to the semi-solid temperature range. Preheated CNTs are added by mechanical stirring at a speed of 600 rpm for 10-15 min. The melt is then poured into a mold to obtain the CNTs / Mg-6Zn magnesium-based ingot. The physical parameters of the CNTs used are as follows: tube diameter of 30-50 nm, length of 5-10 μm, and purity higher than 95%. The mass fraction of the added CNTs is 0.5%. The carbon nanotubes need to be preheated before being added to the melt at a temperature of 350±10℃. The solution treatment temperature is 350℃-360℃ for 12 hours. Step 2: Cut the solution-treated billet into plates and grind and polish the surface of the plates. Step 3: Preheat the polished sheet material before rolling at a temperature of 300℃~320℃ for 30 minutes. Step 4: The preheated sheet is fed into the double rolls and rolled according to the set process flow. The rolling speed is 0.2-0.25m / s, and the reduction in pressure for each pass is 20%. Before each rolling pass, the sheet is preheated at 300℃~320℃ for 30 minutes until the total deformation is controlled at 60%, thereby obtaining a CNTs / Mg-6Zn magnesium-based composite sheet with good sheet shape.

2. The rolling method for CNTs / Mg-6Zn magnesium-based composite plates with good plate shape according to claim 1, characterized in that, The composition of Mg-6Zn magnesium alloy by mass percentage is: Zn=5.8%, Si=0.62%, and the remainder is Mg.

3. The rolling method for CNTs / Mg-6Zn magnesium-based composite plates with good plate shape according to claim 1, characterized in that, The dimensions of the double rollers in step 4 are 175cm × 260cm, and the maximum opening and closing degree of the rollers is 20mm.

4. A CNTs / Mg-6Zn magnesium-based composite board, characterized in that, The alloy grains obtained by the rolling method described in any one of claims 1 to 3 have a yield strength of 278 MPa, a tensile strength of 348 MPa, and a fracture elongation of 6.3%. The alloy grains are significantly deformed and elongated along the rolling direction, and are flattened. The second phase distributed at the grain boundaries is crushed and dispersed in the composite matrix.

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