High-plasticity and high-thermal-conductivity magnesium alloy plate and preparation method thereof

Abstract

The invention discloses a high-plasticity and high-thermal-conductivity magnesium alloy plate and a preparation method thereof, and relates to the technical field of magnesium alloy plates, and the preparation method comprises the steps of primary melting, smelting, refining, forming, thermal homogenization treatment, preheating and rolling. According to the high-plasticity and high-thermal-conductivity magnesium alloy plate and the preparation method thereof, through cooperative arrangement of aluminum, zinc and manganese in metal, second-phase particles distributed in a dispersed mode can be formed, the hardness and abrasion resistance of a matrix can be enhanced, dislocation movement can be hindered, the strength and plasticity of the material are further improved, and the lattice structure and the slip system starting capacity are improved; according to the magnesium alloy, the plasticity, the formability and the thermal conductivity are improved by activating a non-basal slip system, refining recrystallized grains, regulating and controlling a recrystallized structure and other mechanisms, meanwhile, the microstructure of the magnesium alloy can be optimized through the added yttrium, fine and uniform second-phase particles are further promoted to be separated out, and therefore the purpose of improving the plasticity and the thermal conductivity is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy plates, and more particularly to a high-plasticity and high-thermal-conductivity magnesium alloy plate and a preparation method thereof. Background Art

[0002] Magnesium alloy is a green and lightweight metal structural material with a density of only 1 / 4 of steel and 2 / 3 of aluminum alloy. It has the characteristics of high strength, good shock absorption, ability to shield electromagnetic radiation and environmental friendliness. It is widely used in aviation, aerospace, automobile, electronics, communication equipment and other fields.

[0003] The current magnesium alloys still have the following problems:

[0004] 1. Magnesium alloys have poor plasticity and toughness, and low deformation processing capabilities, which limit the manufacture of parts with complex shapes. This is because magnesium alloys have a hexagonal close-packed (HCP) crystal structure, which results in fewer slip systems in magnesium alloys and poor plastic deformation capabilities. Due to the limited slip system of magnesium alloys, their plastic deformation mainly depends on the twin deformation mechanism. Twin deformation will cause a large amount of residual stress inside the material, which in turn affects the overall plasticity and toughness of the material. At the same time, strong uneven deformation is likely to cause cracks at grain boundaries, phase boundaries, etc., leading to the fracture of magnesium alloys, which also greatly reduces the plastic deformation capacity of magnesium alloys.

[0005] 2. In order to solve the problems of poor plasticity and low strength, magnesium alloys are usually used after alloying. The addition of alloying elements not only improves the strength, but also introduces a large number of defects, such as solid solution atoms and second phases. The thermal conductivity of these second phases or compounds is usually poor and will become an obstacle to heat conduction, resulting in poor thermal conductivity of magnesium alloys and reducing the thermal conductivity of magnesium alloys.

[0006] Therefore, it is necessary to propose a high-plasticity and high-thermal conductivity magnesium alloy sheet and a preparation method thereof to solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to solve the problems raised in the above background technology and provide a high-plasticity and high-thermal-conductivity magnesium alloy sheet and a preparation method thereof.

[0008] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0009] A high-plasticity and high-thermal-conductivity magnesium alloy sheet and a preparation method thereof, comprising the following steps:

[0010] S1. Initial melting: preheat the crucible to 200°C, add 15kg of smelting agent into the crucible, add 2000kg of magnesium ingot after the smelting agent is dissolved, then add aluminum ingot, add magnesium-yttrium alloy when the temperature rises to 750°C-760°C, stir it with inert gas during melting, and obtain the initial molten metal after melting;

[0011] S2, smelting: the temperature of the primary molten metal is raised to 750°C-760°C, and the aluminum-manganese alloy is added, and the molten metal is stirred with an inert gas during smelting to make it fully fused, and then the zinc ingot is added when the molten metal is cooled to 700°C-705°C, and the molten metal is stirred with an inert gas for 10-15 minutes, and the molten metal is fully mixed and then allowed to stand for 35 minutes to obtain a magnesium alloy molten metal;

[0012] S3, refining: transporting the magnesium alloy molten metal from the crucible to the refining furnace through a low-pressure conduit. Before the magnesium alloy molten metal is introduced, the refining crucible should be preheated to 400°C. The specifications of the refining crucible are the same as those of the melting crucible. The magnesium alloy molten metal is heated to 760°C, and then 15 kg of refining agent is added to the refining furnace. After refining for 30 minutes, the refined molten metal is obtained;

[0013] S4, molding: the refined molten metal is allowed to stand for 40 minutes, and then introduced into a crystallizer through a low-pressure stainless steel conduit for semi-continuous casting. A mold of a specific specification is placed in the crystallizer. The casting speed is 80 mm / min, the flow rate is 10 kg / min, and a magnesium alloy flat ingot of corresponding specifications is obtained after 3 hours;

[0014] S5, heat homogenization treatment: saw the magnesium alloy flat ingot, saw off the length of 300mm at the bottom and 150mm at the head, cut into required lengths, then mill the flat ingot with a gantry milling machine, the milling thickness is 20mm, chamfer the four corners by 45°, and then put it into a homogenization heat treatment furnace for 20 hours;

[0015] S6. Preheating: Put the heat-homogenized magnesium alloy flat ingot into a heating furnace, raise the furnace temperature to 460°C within 2 hours, and keep it at 460°C for 15 hours to prepare for rolling;

[0016] S7. Rolling: The magnesium alloy flat ingot to be rolled is firstly subjected to rough rolling, the plate thickness during rough rolling is 100 mm, then the temperature is controlled to 330° C. and intermediate rolling is performed, the intermediate rolling reduction is 22%, and finally finish rolling is performed to obtain magnesium alloy plates.

[0017] Preferably, the smelting agent in the initial melting step S1 is composed of the following raw materials in parts by mass: 45% magnesium chloride, 30% potassium chloride, 20% sodium chloride, and 5% barium chloride.

[0018] Preferably, the refining agent in the S3 refining step is composed of the following raw materials in parts by mass: 40% magnesium chloride, 35% potassium chloride, 15% sodium chloride, and 15% calcium fluoride.

[0019] Preferably, in the S1 initial melting step, the magnesium-yttrium alloy is composed of 30% yttrium (Y) and 70% magnesium (Mg), the addition amount of the magnesium-yttrium alloy is 1.65-1.70% of the total mass of the raw materials, and the addition amount of the aluminum ingot is 2.8-3.3% of the total mass of the raw materials.

[0020] Preferably, in the S2 smelting step, the aluminum-manganese alloy is composed of 10% manganese (Mn) and 90% aluminum (Al), the addition amount of the aluminum-manganese alloy is 3.2-4.1% of the total mass of the raw materials, and the addition amount of the zinc ingot is 0.8-1.2% of the total mass of the raw materials.

[0021] Preferably, the composition of the refined molten metal obtained in the S3 refining step is: aluminum (Al) 2.8-3.3%, zinc (Zn) 0.8-1.2%, manganese (Mn) 0.4-0.8%, yttrium (Y) 0.5%, silicon (Si) ≤0.05%, iron (Fe) ≤0.003%, calcium (Ca) ≤0.04%, copper (Cu) ≤0.01%, nickel (Ni) ≤0.001%, and magnesium (Mg) as the remainder.

[0022] Preferably, the crucible in the S1 initial melting step has a specification of φ1100*1850mm, the mold in the S4 molding step has a specification of 305 (width)*805 (length)*280 (height), the mold is made of a special copper alloy plate with a thickness of 10mm, and an inert gas is introduced into the crystallizer to protect the refined metal liquid.

[0023] Preferably, the step of heat homogenization is: firstly heating the flat ingot to 160 degrees within 2 hours, then keeping it warm for 3 hours, then heating the flat ingot to 220 degrees within 1 hour, then keeping it warm for 5 hours, and finally heating the flat ingot to 295 degrees within 1 hour, keeping it warm for 8 hours and then cooling it to room temperature.

[0024] Preferably, the performance parameters of the magnesium alloy sheet obtained in the S7 rolling step are thermal conductivity (w / mk) 120, tensile strength (MPa) 290, yield strength (MPa) 210, and elongation (%) 17.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Through the coordination of aluminum, zinc and manganese in the metal, dispersed second phase particles (Mg17Al12, Mg2Sn) can be formed. The uniformly distributed second phase particles can enhance the hardness and wear resistance of the matrix without sacrificing too much thermal conductivity, hinder dislocation movement, improve the strength and plasticity of the material, improve the lattice structure and slip system startup ability, activate non-basal slip system, refine recrystallized grains, regulate recrystallization structure and other mechanisms to improve plasticity, formability and thermal conductivity. At the same time, the added yttrium can optimize the microstructure of magnesium alloys and further promote the precipitation of fine and uniform second phase particles, thereby achieving the purpose of improving plasticity and thermal conductivity;

[0027] 2. By carrying out a long-term heat homogenization step on the magnesium alloy flat ingot, when the temperature is gradually increased, it can be ensured that the elements inside the alloy gradually diffuse, avoiding local overheating or uneven cooling caused by excessive temperature gradient; the long-term insulation in each stage (3 hours, 5 hours, 7-8 hours) can provide enough time for the elements to fully diffuse, reduce or eliminate component segregation, and make the alloy composition more uniform, and provide enough time for the aluminum, zinc, manganese and yttrium elements in the magnesium alloy to fully diffuse, reduce component segregation, and make the alloy composition more uniform; long-term insulation at 295 degrees can promote the recrystallization and refinement of grains, and fine grains can improve the strength, plasticity and toughness of the material, and solve the problems of poor plasticity and toughness and low strength. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0029] Embodiment 1:

[0030] The addition amount of magnesium-yttrium alloy is 1.68% of the total mass of raw materials;

[0031] The amount of aluminum ingot added is 3.0% of the total mass of the raw materials;

[0032] The addition amount of aluminum-manganese alloy is 3.7% of the total mass of raw materials;

[0033] The addition amount of zinc ingot is 1.0% of the total mass of raw materials.

[0034] The preparation method comprises the following steps:

[0035] S1. Initial melting: preheat the crucible to 200°C, add 15kg of smelting agent into the crucible, add 2000kg of magnesium ingot after the smelting agent is dissolved, then add aluminum ingot, add magnesium-yttrium alloy when the temperature rises to 760°C, stir it with inert gas during melting, and obtain the initial molten metal after melting;

[0036] S2, smelting: the temperature of the primary molten metal is raised to 760°C, and the aluminum-manganese alloy is added, and the molten metal is stirred with an inert gas during smelting to make it fully fused, and then the zinc ingot is added when the molten metal is cooled to 705°C, and the molten metal is stirred with an inert gas for 15 minutes, and the molten metal is fully mixed and then allowed to stand for 35 minutes to obtain a magnesium alloy molten metal;

[0037] S3, refining: transporting the magnesium alloy molten metal from the crucible to the refining furnace through a low-pressure conduit. Before the magnesium alloy molten metal is introduced, the refining crucible should be preheated to 400°C. The specifications of the refining crucible are the same as those of the melting crucible. The magnesium alloy molten metal is heated to 760°C, and then 15 kg of refining agent is added to the refining furnace. After refining for 30 minutes, the refined molten metal is obtained;

[0038] S4, molding: the refined molten metal is allowed to stand for 40 minutes, and then introduced into a crystallizer through a low-pressure stainless steel conduit for semi-continuous casting. A mold of a specific specification is placed in the crystallizer. The casting speed is 80 mm / min, the flow rate is 10 kg / min, and a magnesium alloy flat ingot of corresponding specifications is obtained after 3 hours;

[0039] S5, heat homogenization treatment: saw the magnesium alloy flat ingot, saw off the length of 300mm at the bottom and 150mm at the head, cut into required lengths, then mill the flat ingot with a gantry milling machine, the milling thickness is 20mm, chamfer the four corners by 45°, and then put it into a homogenization heat treatment furnace for 20 hours;

[0040] S6. Preheating: Put the heat-homogenized magnesium alloy flat ingot into a heating furnace, raise the furnace temperature to 460°C within 2 hours, and keep it at 460°C for 15 hours to prepare for rolling;

[0041] S7. Rolling: The magnesium alloy flat ingot to be rolled is firstly subjected to rough rolling, the plate thickness during rough rolling is 100 mm, then the temperature is controlled to 330° C. and intermediate rolling is performed, the intermediate rolling reduction is 22%, and finally finish rolling is performed to obtain magnesium alloy plates.

[0042] The steps of heat homogenization are: first, heat the flat ingot to 160 degrees within 2 hours, then keep it warm for 3 hours, then heat the flat ingot to 220 degrees within 1 hour, then keep it warm for 5 hours, and finally heat the flat ingot to 295 degrees within 1 hour, keep it warm for 8 hours, and then cool it to room temperature.

[0043] Embodiment 2:

[0044] The addition amount of magnesium-yttrium alloy is 1.65% of the total mass of raw materials;

[0045] The amount of aluminum ingot added is 2.8% of the total mass of raw materials;

[0046] The addition amount of aluminum-manganese alloy is 4.1% of the total mass of raw materials;

[0047] The amount of zinc ingot added is 1.2% of the total mass of the raw materials.

[0048] The difference between Example 2 and Example 1 is that the addition amount of magnesium-yttrium alloy and aluminum ingot is reduced, and the addition amount of aluminum-manganese alloy and zinc ingot is increased, and the remaining steps remain the same as Example 1.

[0049] Embodiment 3:

[0050] The addition amount of magnesium-yttrium alloy is 1.70% of the total mass of raw materials;

[0051] The amount of aluminum ingot added is 3.3% of the total mass of raw materials;

[0052] The addition amount of aluminum-manganese alloy is 3.2% of the total mass of raw materials;

[0053] The amount of zinc ingot added is 0.8% of the total mass of the raw materials.

[0054] The difference between Example 3 and Example 1 is that the addition amount of magnesium-yttrium alloy and aluminum ingot is increased, and the addition amount of aluminum-manganese alloy and zinc ingot is reduced, and the remaining steps remain the same as Example 1.

[0055] Embodiment 4,

[0056] The addition amount of magnesium-yttrium alloy is 1.70% of the total mass of raw materials;

[0057] The amount of aluminum ingot added is 3.3% of the total mass of raw materials;

[0058] The addition amount of aluminum-manganese alloy is 4.1% of the total mass of raw materials;

[0059] The amount of zinc ingot added is 1.2% of the total mass of the raw materials.

[0060] The difference between Example 4 and Example 1 is that the addition amount of magnesium-yttrium alloy, aluminum ingot, aluminum-manganese alloy and zinc ingot is increased, and the other steps remain the same as Example 1.

[0061] Comparative Example:

[0062] Conventional raw materials are used, which are 8%-10% zinc ingot, 5.5%-6% aluminum ingot, and the balance is Mg and inevitable impurity elements;

[0063] The manufacturing method comprises the following steps:

[0064] S1. Initial melting: preheat the crucible to 200°C, add 15kg of smelting agent into the crucible, add 2000kg of magnesium ingot after the smelting agent is dissolved, raise the temperature to 760°C, stir it with inert gas during melting, and obtain the initial molten metal after melting;

[0065] S2. Smelting: Raise the temperature of the primary molten metal to 760°C, add aluminum ingots, stir them with inert gas during smelting to make them fully fused, then cool the molten metal to 705°C, add zinc ingots, and stir them with inert gas for 15 minutes. After the molten metal is fully mixed, let it stand for 35 minutes to obtain magnesium alloy molten metal.

[0066] The remaining steps remain the same as in Example 1.

[0067] The heat homogenization steps are as follows: firstly, the flat ingot is heated to 250 degrees within 2 hours, then kept warm for 2 hours, then the flat ingot is heated to 500 degrees at a heating rate of 50 degrees Celsius / min, then kept warm for 4 hours, and finally cooled to room temperature.

[0068] The difference between the comparative example and the embodiment 1 is that the added magnesium-yttrium alloy and aluminum-manganese alloy are removed, and the heat homogenization is changed into a conventional step, and the other manufacturing steps remain unchanged.

[0069] The following is a comparative analysis of Example 1, Example 2, Example 3, Example 4 and Comparative Example 1, and the parameters of the comparison are thermal conductivity, tensile strength, yield strength and elongation:

[0070] Table 1 Performance comparison

[0071]

[0072] It can be seen from Table 1 that the thermal conductivity and elongation of Example 1 are better than those of other magnesium alloy sheets. At the same time, the tensile strength and yield strength are close to those of Example 4. More magnesium-yttrium alloy is added to Examples 3 and 4 than to Examples 1 and 2, so that the tensile strength and yield strength of Examples 3 and 4 are better than those of Example 1, Example 2 and the comparative example, but the thermal conductivity and elongation are reduced.

[0073] The performance of Examples 1, 2, 3 and 4 using this production method is better than that of the control example using the conventional production method, and the thermal conductivity, tensile strength, yield strength and elongation of the product can be improved.

[0074] It can be seen that the method for preparing high-plasticity and high-thermal conductivity magnesium alloy sheets using the ratio of the present application can enhance the thermal conductivity, tensile strength, yield strength and elongation of the magnesium alloy sheets, solve the problems of poor plasticity and low strength of the magnesium alloy sheets, and improve their quality.

Claims

1. A method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet, characterized in that: The preparation method comprises the following steps: S1. Initial melting: preheat the crucible to 200°C, add 15kg of smelting agent into the crucible, add 2000kg of magnesium ingot after the smelting agent is dissolved, then add aluminum ingot, add magnesium-yttrium alloy when the temperature rises to 750°C-760°C, stir it with inert gas during melting, and obtain the initial molten metal after melting; S2, smelting: the temperature of the primary molten metal is raised to 750°C-760°C, and the aluminum-manganese alloy is added, and the molten metal is stirred with an inert gas during smelting to make it fully fused, and then the zinc ingot is added when the molten metal is cooled to 700°C-705°C, and the molten metal is stirred with an inert gas for 10-15 minutes, and the molten metal is fully mixed and then allowed to stand for 35 minutes to obtain a magnesium alloy molten metal; S3, refining: transporting the magnesium alloy molten metal from the crucible to the refining furnace through a low-pressure conduit. Before the magnesium alloy molten metal is introduced, the refining crucible should be preheated to 400°C. The specifications of the refining crucible are the same as those of the melting crucible. The magnesium alloy molten metal is heated to 760°C, and then 15 kg of refining agent is added to the refining furnace. After refining for 30 minutes, the refined molten metal is obtained; S4, molding: the refined molten metal is allowed to stand for 40 minutes, and then introduced into a crystallizer through a low-pressure stainless steel conduit for semi-continuous casting. A mold of a specific specification is placed in the crystallizer. The casting speed is 80 mm / min, the flow rate is 10 kg / min, and a magnesium alloy flat ingot of corresponding specifications is obtained after 3 hours; S5, heat homogenization treatment: saw the magnesium alloy flat ingot, saw off the length of 300mm at the bottom and 150mm at the head, cut into required lengths, then mill the flat ingot with a gantry milling machine, the milling thickness is 20mm, chamfer the four corners by 45°, and then put it into a homogenization heat treatment furnace for 20 hours; S6. Preheating: Put the heat-homogenized magnesium alloy flat ingot into a heating furnace, raise the furnace temperature to 460°C within 2 hours, and keep it at 460°C for 15 hours to prepare for rolling; S7. Rolling: The magnesium alloy flat ingot to be rolled is firstly subjected to rough rolling, the plate thickness during rough rolling is 100 mm, then the temperature is controlled to 330° C. and intermediate rolling is performed, the intermediate rolling reduction is 22%, and finally finish rolling is performed to obtain magnesium alloy plates.

2. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The smelting agent in the initial melting step S1 is composed of the following raw materials in parts by mass: 45% magnesium chloride, 30% potassium chloride, 20% sodium chloride, and 5% barium chloride.

3. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The refining agent in the S3 refining step is composed of the following raw materials in parts by mass: 40% magnesium chloride, 35% potassium chloride, 15% sodium chloride, and 15% calcium fluoride.

4. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: In the S1 initial melting step, the magnesium-yttrium alloy is composed of 30% yttrium (Y) and 70% magnesium (Mg), the addition amount of the magnesium-yttrium alloy is 1.65-1.70% of the total mass of the raw materials, and the addition amount of the aluminum ingot is 2.8-3.3% of the total mass of the raw materials.

5. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: In the S2 smelting step, the aluminum-manganese alloy is composed of 10% manganese (Mn) and 90% aluminum (Al), the addition amount of the aluminum-manganese alloy is 3.2-4.1% of the total mass of the raw materials, and the addition amount of the zinc ingot is 0.8-1.2% of the total mass of the raw materials.

6. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The composition of the refined molten metal obtained in the S3 refining step is: aluminum (Al) 2.8-3.3%, zinc (Zn) 0.8-1.2%, manganese (Mn) 0.4-0.8%, yttrium (Y) 0.5%, silicon (Si) ≤0.05%, iron (Fe) ≤0.003%, calcium (Ca) ≤0.04%, copper (Cu) ≤0.01%, nickel (Ni) ≤0.001%, and magnesium (Mg) as the remainder.

7. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The crucible specification in the S1 initial melting step is φ1100*1850mm, the mold specification in the S4 molding step is 305 (width)*805 (length)*280 (height), the mold is made of a special copper alloy plate with a thickness of 10mm, and an inert gas is introduced into the crystallizer to protect the refined metal liquid.

8. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The steps of heat homogenization are: firstly heating the flat ingot to 160 degrees within 2 hours, then keeping it warm for 3 hours, then heating the flat ingot to 220 degrees within 1 hour, then keeping it warm for 5 hours, and finally heating the flat ingot to 295 degrees within 1 hour, keeping it warm for 8 hours and then cooling it to room temperature.

9. The method for preparing a high-plasticity and high-thermal-conductivity magnesium alloy sheet according to claim 1, characterized in that: The performance parameters of the magnesium alloy plate obtained in the S7 rolling step are thermal conductivity (w / mk) 120, tensile strength (MPa) 290, yield strength (MPa) 210, and elongation (%) 17.

10. High plasticity and high thermal conductivity magnesium alloy sheet, characterized in that: The product is prepared by the preparation method described in claim 1.

Images