A heat treatment free high-strength and high-toughness die-casting magnesium alloy and a preparation process thereof

Abstract

The application relates to the alloy technical field and discloses a heat-treatment-free high-strength and high-toughness die-casting magnesium alloy and a preparation process thereof, which is prepared from 90-95 parts of magnesium, 2-8 parts of aluminum, 0.2-0.5 parts of manganese, 0.4-0.8 parts of zinc and 1-3 parts of a powder reinforcing phase as raw materials through a heat-treatment-free process, wherein the powder reinforcing phase is a ball-milling mixture of three-dimensional porous carbon nanotubes and metal yttrium; the three-dimensional porous carbon nanotubes and the magnesium alloy matrix form a buckle type stable structure; the magnesium alloy is effectively strengthened by combining the advantages of the carbon nanotubes; the strength and the toughness of the magnesium alloy are effectively improved; and in addition, the heat-treatment-free process can greatly save the cost and reduce the energy consumption.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, specifically to a heat-treasure-free high-strength and high-toughness die-cast magnesium alloy and its preparation process. Background Technology

[0002] Magnesium alloys possess advantages such as light weight, high specific strength, and high thermal conductivity, and are among the lightest engineering metal structural materials, thus being considered one of the most promising green engineering materials of the 21st century. With continuous technological advancements, various industries have increasingly higher requirements for the strength and toughness of magnesium alloys. Currently, obtaining higher strength magnesium alloys often requires appropriate heat treatment processes. Heat treatment processes include steps such as solution treatment, machining, and failure treatment. These processes are energy-intensive and costly, and can lead to defects such as deformation or blistering in magnesium alloys, reducing their consistency and stability and negatively impacting their performance. Therefore, the casting process for magnesium alloys still has its limitations.

[0003] Currently, most methods circumvent the aforementioned problems by optimizing the magnesium alloy formulation or heat treatment process. For example, the invention patent with application number CN202210604213.X discloses a high-strength cast magnesium alloy and its preparation method. By adding rare earth metals La and Ce, a high-strength Mg-Zn-Al-Mn-RE cast magnesium alloy is obtained, which can improve the absolute strength and toughness of the magnesium alloy. However, this method still cannot avoid the problems of high energy consumption and low cost of heat treatment process. Therefore, it is of great significance to develop a heat treatment-free die-cast magnesium alloy with high strength and good toughness. Summary of the Invention

[0004] The purpose of this invention is to provide a heat-free high-strength and high-toughness die-cast magnesium alloy and its preparation process. By designing and synthesizing a powder reinforcing phase, the problem of insufficient strength and toughness of magnesium alloys caused by the absence of heat treatment is solved.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A heat-treatable, high-strength, high-toughness die-cast magnesium alloy, comprising the following raw materials by weight: 90-95 parts magnesium, 2-8 parts aluminum, 0.2-0.5 parts manganese, 0.4-0.8 parts zinc, and 1-3 parts powdered reinforcing phase;

[0007] The powder reinforcement phase is a ball-milled mixture of three-dimensional porous carbon nanotubes and yttrium.

[0008] Furthermore, the preparation method of the powder-reinforced phase includes the following steps:

[0009] Step 1: Mix multi-walled carbon nanotubes with purified water, disperse evenly by ultrasonication, add acidifying reagent and sodium hydroxide, mix mechanically, and keep warm and stir at 60-70℃ for 4-6 hours. Separate the solid, wash and dry it to obtain carbon nanotube intermediate.

[0010] Step 2: Mix the metal chloride with purified water and stir until completely dissolved. Add the carbon nanotube intermediate and ultrasonically disperse it evenly. Heat the mixture in a reaction vessel to 100-120℃ and maintain the temperature for 6-12 hours. Then, cool the mixture and discharge it. Separate the product to obtain the carbon nanotube-zinc ion crosslinking intermediate.

[0011] Step 3: Place the carbon nanotube-zinc ion crosslinking intermediate in a tube furnace, control the temperature in the tube furnace to 200-300℃, maintain for 1-3 hours, then take out the material and soak it in hydrochloric acid solution for 4-8 hours to separate the material and obtain three-dimensional porous carbon nanotubes.

[0012] Step 4: Mix the three-dimensional porous carbon nanotubes with yttrium powder, place them in a high-energy ball mill, evacuate the ball mill, and ball mill under nitrogen protection. After ball milling, discharge the material to obtain the powder-reinforced phase.

[0013] Furthermore, in step one, the acidifying agent is any one of chloroacetic acid, bromoacetic acid, or 3-chloropropionic acid.

[0014] Furthermore, in step two, the metal chloride is either cobalt chloride or zinc chloride.

[0015] Furthermore, in step three, the mass concentration of the hydrochloric acid solution is 10-20%.

[0016] Furthermore, in step four, the mass ratio of the three-dimensional porous carbon nanotubes to yttrium powder is 1:3-6.

[0017] Furthermore, in step four, the ball milling time is 48-72 hours, the ball-to-material ratio is 10-50:1, and the rotation speed is 200-500 r / min.

[0018] In the above technical solution, after multi-walled carbon nanotubes are modified with an acidifying agent, their surfaces contain a large number of carboxyl functional groups, thus obtaining a carbon nanotube intermediate. Using metal ions as nodes, they coordinate with the carboxyl groups on the surface of the carbon nanotube intermediate to form a three-dimensional carbon nanotube-zinc ion crosslinking intermediate. During high-temperature calcination, zinc ions further form zinc oxide, which is then further etched away by hydrochloric acid, thereby forming a three-dimensional porous carbon nanotube with a rich pore structure. After high-energy ball milling with yttrium powder, the yttrium powder flows into the pores of the three-dimensional porous carbon nanotube during the ball milling process, ultimately forming a ball-milled mixture of three-dimensional porous carbon nanotubes and metallic yttrium, i.e., a powder-reinforced phase.

[0019] A process for preparing a heat-treasure-free high-strength and high-toughness die-cast magnesium alloy includes the following steps:

[0020] Step 1: Weigh out each ingredient in the specified weight proportions and set aside.

[0021] Step 2: Add magnesium, aluminum, manganese and zinc to the furnace in sequence, raise the furnace temperature to 750-760℃, and after the raw materials are melted evenly, let it stand for 20-40 minutes, add the powdered reinforcing phase, and let it stand for 10-20 minutes to obtain magnesium alloy melt.

[0022] Step 3: Pour the molten magnesium alloy into a mold and perform vacuum die casting. After the die casting is completed, refine and remove impurities from the magnesium alloy to obtain the die-cast magnesium alloy.

[0023] The beneficial effects of this invention are:

[0024] This invention prepares die-cast magnesium alloys without heat treatment, avoiding the huge energy consumption of heat treatment and effectively reducing costs. To compensate for the strength and toughness loss caused by the absence of heat treatment, a powdered reinforcing phase is added during the metal raw material smelting process. Since the molten metal forms a liquid fluid, it flows into the pores and three-dimensional gaps of the three-dimensional porous carbon nanotubes in the powdered reinforcing phase, forming a snap-fit ​​tenon-and-mortise stable structure. This allows the carbon nanotubes to effectively bond with the magnesium alloy matrix, avoiding the problem of delamination between the two phases and the resulting decrease in mechanical properties. Therefore, by combining the advantages of carbon nanotubes, the magnesium alloy is strengthened, effectively improving its strength and toughness. Furthermore, during the smelting process, the molten metal flows into the pores of the porous carbon nanotubes and can combine with yttrium in the pores. The presence of yttrium not only optimizes the nucleation density of the magnesium alloy at that location, giving it an ultrafine grain structure, but also maintains good toughness and plasticity, making the snap-fit ​​structure more stable and further enhancing the strength and toughness of the magnesium alloy.

[0025] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a scanning electron microscope image of the powder-reinforced phase in an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The powder-reinforced phase used in the following examples was prepared by the following steps:

[0030] Step 1: Mix 2g of multi-walled carbon nanotubes with purified water, disperse evenly by ultrasonication, add 1.2g of bromoacetic acid and 0.5g of sodium hydroxide, mix mechanically, and keep warm and stir at 65℃ for 6h. Separate the solid, wash and dry it to obtain the carbon nanotube intermediate.

[0031] Step 2: Mix 3.5g of zinc chloride with purified water and stir until completely dissolved. Add 1.8g of carbon nanotube intermediate, disperse evenly by ultrasonication, place in a reaction vessel, heat to 110℃, maintain the temperature for 9 hours, cool down and discharge the material, separate the product, and obtain carbon nanotube-zinc ion crosslinking intermediate.

[0032] Step 3: Place 2.5g of carbon nanotube-zinc ion crosslinking intermediate material in a tube furnace, control the temperature in the tube furnace to 280℃, maintain for 2 hours, take out the material, soak it in a 20% hydrochloric acid solution for 4-8 hours, separate the material, and obtain three-dimensional porous carbon nanotubes.

[0033] Step 4: Mix 1.5g of three-dimensional porous carbon nanotubes with 5g of yttrium powder, place them in a high-energy ball mill, evacuate the ball mill, set the ball-to-material ratio to 40:1 and the rotation speed to 500r / min, and ball mill for 72h under nitrogen protection. Then discharge the material to obtain the powder-reinforced phase.

[0034] Figure 1 The image shows a scanning electron microscope (SEM) image of the powder-reinforced phase. As can be seen from the image, the powder-reinforced phase has a rich porous structure, and yttrium metal is densely deposited in the pores.

[0035] Example 1

[0036] A heat-treatable, high-strength, high-toughness die-cast magnesium alloy comprises, by weight, the following raw materials: 90 parts magnesium, 2 parts aluminum, 0.2 parts manganese, 0.4 parts zinc, and 1 part powdered reinforcing phase;

[0037] The preparation method of this die-cast magnesium alloy includes the following steps:

[0038] Step 1: Weigh out each ingredient in the specified weight proportions and set aside.

[0039] Step 2: Add magnesium, aluminum, manganese and zinc to the furnace in sequence, raise the furnace temperature to 750℃, and after the raw materials are melted evenly, let it stand for 20 minutes, add the powdered reinforcing phase, let it stand for 10 minutes, and the magnesium alloy melt can be obtained.

[0040] Step 3: Pour the molten magnesium alloy into a mold and perform vacuum die casting. After the die casting is completed, refine and remove impurities from the magnesium alloy to obtain the die-cast magnesium alloy.

[0041] Example 2

[0042] A heat-treasure-free high-strength and high-toughness die-cast magnesium alloy comprises the following raw materials by weight: 92 parts magnesium, 5 parts aluminum, 0.4 parts manganese, 0.6 parts zinc, and 2 parts powdered reinforcing phase.

[0043] The preparation method of this die-cast magnesium alloy includes the following steps:

[0044] Step 1: Weigh out each ingredient in the specified weight proportions and set aside.

[0045] Step 2: Add magnesium, aluminum, manganese and zinc to the furnace in sequence, raise the furnace temperature to 760℃, and after the raw materials are melted evenly, let it stand for 30 minutes, add the powdered reinforcing phase, let it stand for 20 minutes, and the magnesium alloy melt can be obtained.

[0046] Step 3: Pour the molten magnesium alloy into a mold and perform vacuum die casting. After the die casting is completed, refine and remove impurities from the magnesium alloy to obtain the die-cast magnesium alloy.

[0047] Example 3

[0048] A heat-treatable, high-strength, high-toughness die-cast magnesium alloy, comprising the following raw materials by weight: 95 parts magnesium, 8 parts aluminum, 0.5 parts manganese, 0.8 parts zinc, and 3 parts powdered reinforcing phase;

[0049] The preparation method of this die-cast magnesium alloy includes the following steps:

[0050] Step 1: Weigh out each ingredient in the specified weight proportions and set aside.

[0051] Step 2: Add magnesium, aluminum, manganese and zinc to the furnace in sequence, raise the furnace temperature to 760℃, and after the raw materials are melted evenly, let it stand for 40 minutes, add the powdered reinforcing phase, let it stand for 20 minutes, and the magnesium alloy melt can be obtained.

[0052] Step 3: Pour the molten magnesium alloy into a mold and perform vacuum die casting. After the die casting is completed, refine and remove impurities from the magnesium alloy to obtain the die-cast magnesium alloy.

[0053] Comparative Example 1

[0054] A heat-free, high-strength, high-toughness die-cast magnesium alloy comprises the following raw materials by weight: 92 parts magnesium, 5 parts aluminum, 0.4 parts manganese, 0.6 parts zinc, and 2 parts carbon nanotubes.

[0055] The preparation method of this die-cast magnesium alloy includes the following steps:

[0056] Step 1: Weigh out each ingredient in the specified weight proportions and set aside.

[0057] Step 2: Add magnesium, aluminum, manganese and zinc to the furnace in sequence, raise the furnace temperature to 760℃, and after the raw materials are melted evenly, let it stand for 30 minutes, add carbon nanotubes, and let it stand for 20 minutes to obtain magnesium alloy melt.

[0058] Step 3: Pour the molten magnesium alloy into a mold and perform vacuum die casting. After the die casting is completed, refine and remove impurities from the magnesium alloy to obtain the die-cast magnesium alloy.

[0059] Comparative Example 2

[0060] A heat-free, high-strength, high-toughness die-cast magnesium alloy comprises the following raw materials by weight: 92 parts magnesium, 5 parts aluminum, 0.4 parts manganese, and 0.6 parts zinc.

[0061] The preparation method of this die-cast magnesium alloy includes the following steps:

[0062] Step 1: Weigh out each ingredient in the specified weight proportions and set aside.

[0063] Step 2: Add magnesium, aluminum, manganese and zinc to the furnace in sequence, raise the furnace temperature to 760℃, and after the raw materials are melted evenly, let it stand for 30 minutes to obtain magnesium alloy melt.

[0064] Step 3: Pour the molten magnesium alloy into a mold and perform vacuum die casting. After the die casting is completed, refine and remove impurities from the magnesium alloy to obtain the die-cast magnesium alloy.

[0065] The magnesium alloys prepared in Examples 1-3 and Comparative Examples 1-2 of this invention were subjected to performance tests, and the test results are recorded in the table below:

[0066]

[0067] Analysis of the test results shows that the magnesium alloys prepared in Examples 1-3 of this invention have high strength and good toughness. In contrast, the magnesium alloys prepared in Comparative Examples 1 and 2 have significantly reduced strength and toughness. Since carbon nanotubes were added to the magnesium alloy prepared in Comparative Example 1, its performance is slightly better than that of the magnesium alloy prepared in Comparative Example 2.

[0068] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0069] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A heat treatment free high strength high toughness die cast magnesium alloy, characterized in that, By weight parts, including the following raw materials: magnesium 90-95 parts, aluminum 2-8 parts, manganese 0.2-0.5 parts, zinc 0.4-0.8 parts, powder reinforcing phase 1-3 parts; The powder reinforcing phase is a ball-milled mixture of three-dimensional porous carbon nanotubes and metal yttrium; The preparation method of the powder reinforcing phase comprises the following steps: Step one: mix multi-walled carbon nanotubes with purified water, uniformly ultrasonic dispersed, then add acidifying reagent and sodium hydroxide, mechanically mix uniformly, keep stirring at a temperature environment of 60-70 DEG C for 4-6h, separate the solid, wash and dry to obtain carbon nanotube intermediate; Step two: mix zinc chloride with purified water, stir until completely dissolved, add carbon nanotube intermediate, ultrasonic disperse uniformly, place in a reaction kettle, heat to 100-120 DEG C, keep constant temperature for 6-12h, then cool down and discharge, separate the product to obtain carbon nanotube-zinc ion crosslinked intermediate; Step three: place the carbon nanotube-zinc ion crosslinked intermediate in a tube furnace, control the temperature of the tube furnace to be 200-300 DEG C, keep for 1-3h, then take out the material, soak in a hydrochloric acid solution for 4-8h, separate the material to obtain three-dimensional porous carbon nanotubes; Step four: mix the three-dimensional porous carbon nanotubes with yttrium powder, place in a high-energy ball mill, vacuumize the ball mill, ball mill under nitrogen protection, after ball milling, discharge, then the powder reinforcing phase is obtained.

2. The heat treatment free high strength and high toughness die casting magnesium alloy according to claim 1, characterized in that, In step one, the acidifying reagent is any one of chloroacetic acid, bromoacetic acid or 3-chloropropionic acid.

3. The heat-treatment free high-strength and high-ductility die-casting magnesium alloy according to claim 1, characterized in that, In step three, the mass concentration of the hydrochloric acid solution is 10-20%.

4. The heat-treatment free high-strength and high-ductility die-casting magnesium alloy according to claim 1, characterized in that, In step four, the mass ratio of the three-dimensional porous carbon nanotubes to yttrium powder is 1:3-6.

5. The heat-treatment free high-strength and high-ductility die-casting magnesium alloy according to claim 1, characterized in that, In step four, the ball milling time is 48-72h, the ball-to-material ratio is 10-50:1, and the rotation speed is 200-500r / min.

6. The process for preparing a heat treatment free high strength high toughness die casting magnesium alloy according to claim 1, characterized in that, Comprise the following steps: First step: weigh each raw material according to weight parts, and reserve; Second step: add magnesium, aluminum, manganese and zinc into a melting furnace in turn, raise the temperature of the melting furnace to 750-760 DEG C, after the raw materials are uniformly melted, stand for 20-40min, add the powder reinforcing phase, stand for 10-20min, then the magnesium alloy melt is obtained; Third step: pour the magnesium alloy melt into a mold, vacuum die casting is carried out, after die casting is completed, refine the magnesium alloy to remove impurities, then the die cast magnesium alloy is obtained.

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