Aluminum-containing high strength-to-toughness soluble magnesium alloy and method of making

Abstract

The application provides a high-temperature-resistant high-toughness soluble magnesium alloy and a preparation method thereof, wherein the soluble magnesium alloy comprises the following components in percentage by weight: Al 3-9%, Mn 0.1-1%, Zn 1-3%, Zr 0.1-1.0%, Ni 0.1-3%, and the rest is Mg. The soluble magnesium alloy according to the application maintains high plasticity under high strength, and meanwhile, the manufacturing cost is reduced. The high-temperature-resistant high-toughness soluble magnesium alloy can achieve that the elongation after breaking is greater than 10% under the strength greater than 300 MPa.

Description

Technical Field

[0001] This invention relates to magnesium alloys and their manufacturing processes, and more particularly to a low-cost, high-strength, soluble magnesium alloy containing aluminum and its manufacturing method. Background Technology

[0002] Currently, soluble materials mainly include biodegradable polymers and biodegradable metals. Soluble magnesium alloys (abbreviated as soluble magnesium alloys) are materials that can automatically degrade and disappear within a certain period of time in both thermodynamic and kinetic terms. Since 2014, soluble magnesium alloys have been used in the development and application of well completion tools for oil and gas fields. This type of magnesium alloy has a density of 1.80-1.96 g / cm³, a strength of 250-300 MPa, and an optimal operating temperature of 20-200℃. It has advantages such as controllable degradation rate, no need for chemical additives, and suitability for low pH environments. Fracturing balls developed using this alloy can achieve a maximum working differential pressure of 70 MPa and can completely degrade within hours or days.

[0003] However, soluble magnesium alloys currently face several problems: (1) they require the presence of certain rare earth elements (see Chinese Patent Application Publication CN 109797361A), which results in excessively high costs, low production efficiency, and significant difficulties in subsequent deformation processing, leading to high secondary processing costs; (2) they struggle to achieve high toughness while maintaining high mechanical strength. These issues have hindered the widespread application of soluble magnesium alloys, making them a bottleneck for large-scale application.

[0004] Among commonly used magnesium alloys, the AZ80 series, with its high aluminum content, exhibits high strength and a lower cost advantage due to its absence of rare earth elements. However, its low elongation limits its applications. Grain refinement offers a method to simultaneously increase the strength and elongation of metallic materials. Commonly used grain refiners for magnesium alloys include hexachloroethane, tin, and Zr. Zr is the most effective and successful grain refiner for aluminum-free magnesium alloys; however, because Zr and aluminum produce the intermediate compound Al3Zr, which has a high density, it sinks to the bottom of the crucible in liquid magnesium alloys, thus losing its grain-refining effect in aluminum-containing magnesium alloys.

[0005] Therefore, adding Zr to aluminum-magnesium alloys to prepare low-cost, high-strength magnesium alloys can rapidly promote the application of magnesium alloys. Summary of the Invention

[0006] Given the current problems of high cost and poor toughness under high strength in soluble magnesium alloys, this invention provides a high-temperature resistant, high-strength, and high-toughness soluble magnesium alloy, which adds Zr element to aluminum-containing magnesium alloy to achieve high plasticity under high strength while reducing manufacturing costs.

[0007] According to one aspect of the present invention, a high-temperature resistant, high-strength, and high-toughness soluble magnesium alloy is provided, comprising the following components by weight percentage: Al 3-9%, Mn 0.1-1%, Zn 1-3%, Zr 0.1-1.0%, Ni 0.1-3%, with the remainder being Mg.

[0008] Preferably, the high-temperature resistant, high-strength, and tough soluble magnesium alloy according to the present invention has the following composition by weight percentage: Al 7%, Zr 0.8%, Mn 0.5%, Zn 1%, Ni 2%, with the remainder being Mg.

[0009] Preferably, the high-temperature resistant, high-strength, and tough soluble magnesium alloy according to the present invention has the following composition by weight percentage: Al 8%, Zr 0.5%, Mn 1%, Zn 3%, Ni 2%, with the remainder being Mg.

[0010] Preferably, the high-temperature resistant, high-strength, and tough soluble magnesium alloy according to the present invention has the following composition by weight percentage: Al 9%, Zr 1%, Mn 0.7%, Zn 2%, Ni 0.8%, and the remainder being Mg.

[0011] According to another aspect of the present invention, a method for preparing a high-temperature resistant, high-strength, and high-toughness soluble magnesium alloy is provided. The soluble magnesium alloy comprises the following components by weight percentage: Al 3-9%, Mn 0.1-1%, Zn 1-3%, Zr 0.1-1.0%, Ni 0.1-3%, with the remainder being Mg. The preparation method includes the following steps:

[0012] Step 1: Place the magnesium ingot and the first flux into a container and heat to 650°C to 750°C to melt the magnesium ingot;

[0013] Step 2: After the magnesium ingot is melted, pure metals, intermediate alloys, or compounds other than Zr are added to the container in the above percentages to carry out alloying.

[0014] Step 3: After alloying, add a second flux to the container and refine for a certain period of time;

[0015] Step 4: After refining, the molten alloy is transferred to an intermediate ladle and Mg-Zr intermediate alloy is added for casting to obtain a high-temperature resistant, high-strength, and tough soluble magnesium alloy billet.

[0016] Preferably, in the method for preparing soluble magnesium alloy according to the present invention, in step 2, after the magnesium ingot is melted, pure zinc, pure aluminum, pure manganese or anhydrous manganese chloride, pure nickel or Mg-Ni master alloy are added to the container in sequence for alloying, wherein the manner of adding each metal is such that the previously added metal is melted before the next metal is added to fully achieve alloying.

[0017] Preferably, in the method for preparing soluble magnesium alloy according to the present invention, in step 3, flux is added to the container for refining for 20-30 minutes, and after refining, the mixture is left to stand for 2 to 4 hours.

[0018] Preferably, in the method for preparing the soluble magnesium alloy according to the present invention, in step 4, the Mg-Zr master alloy added to the intermediate ladle is preheated.

[0019] Preferably, in the method for preparing soluble magnesium alloy according to the present invention, the intermediate ladle is equipped with a stirring device, and while transferring the alloy liquid into the intermediate ladle, the Mg-Zr intermediate alloy is added to the intermediate ladle and the stirring device is turned on to stir the alloy liquid.

[0020] Preferably, according to the method for preparing soluble magnesium alloy of the present invention, the prepared magnesium alloy billet is heated to 350-450°C and placed in an extruder for extrusion.

[0021] In the series of magnesium alloys described above according to the present invention, Al can form a solid solution with magnesium, which can significantly improve the strength of the magnesium alloy. Mn mainly forms compounds with impurity iron and settles to the bottom of the smelting crucible during the smelting process, improving the purity of the magnesium alloy. Zr acts as a grain refiner, refining the magnesium alloy grains, thereby increasing the strength and plasticity of the magnesium alloy.

[0022] According to the present invention, a high-temperature resistant, high-strength, and high-toughness soluble magnesium alloy is prepared by adding Zr to a high-aluminum magnesium alloy, thereby achieving high ductility while maintaining high strength and reducing manufacturing costs. The high-temperature resistant, high-strength, and high-toughness soluble magnesium alloy of the present invention can achieve an elongation at break of greater than 10% even with a tensile strength greater than 300 MPa. Attached Figure Description

[0023] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the textual description, serve to explain the principles of the invention.

[0024] Figure 1 This is a schematic flowchart illustrating the preparation method of a high-strength and tough soluble magnesium alloy according to the present invention.

[0025] Figure 2 This is a photograph illustrating the metallographic structure of a soluble magnesium alloy according to a first embodiment of the present invention.

[0026] Figure 3 This is a photograph illustrating the metallographic structure of a soluble magnesium alloy according to a second embodiment of the present invention.

[0027] Figure 4This is a photograph illustrating the metallographic structure of a soluble magnesium alloy according to a third embodiment of the present invention. Detailed Implementation

[0028] The composition and manufacturing process of the high-strength and tough soluble magnesium alloy of the present invention will be described below with reference to specific embodiments.

[0029] Below, refer to Figure 1 The preparation process of the soluble magnesium alloy of the present invention is described, wherein the soluble magnesium alloy comprises the following components by weight percentage: Al 3-9%, Mn 0.1-1%, Zn 1-3%, Zr 0.1-1.0%, Ni 0.1-3%, and the remainder is Mg.

[0030] First, in step S1, magnesium ingots and a first flux are placed in a container (e.g., a crucible) and heated to 650°C to 750°C to melt the magnesium ingots. The magnesium ingots can be pure magnesium ingots with a purity of 99%-99.99%. The first flux serves to prevent the magnesium ingots from burning during the melting process. In this invention, the first flux can be, for example, a mixture of magnesium chloride, calcium chloride, and potassium chloride.

[0031] Next, after the magnesium ingot is melted, in step S2, the other required components, except for Zr, are added to the container sequentially. These components can be added as pure metals, master alloys, or compounds. The method of adding each component is such that the previously added component melts before the next component is added to ensure sufficient alloying. In this invention, the components are added in the following weight percentages: pure zinc, pure aluminum, pure manganese (or anhydrous manganese chloride), and pure nickel (or Mg-Ni master alloy) for alloying. Note that the order in which the metals are added is not limited in this step; the order can be arbitrary, as long as the next component is added after the previous one has melted. This ensures sufficient alloying.

[0032] After alloying, in step S3, a second flux is added to the container for refining for a certain period of time (e.g., 20 to 30 minutes) at a temperature of 720 to 740°C. This second flux combines with impurities such as oxides in the melt, causing them to settle to the bottom of the crucible, thus achieving a refining effect. In this invention, the second flux can be, for example, a mixture of magnesium chloride, calcium chloride, potassium chloride, and barium chloride.

[0033] After refining with a second flux, the refined product is held still for 2 to 4 hours.

[0034] Furthermore, in this invention, preferably, after refining with the second flux, argon gas is introduced for argon refining for 10 to 30 minutes before static holding. Argon is an inert gas and does not react with magnesium itself. However, the introduction of argon gas can generate small bubbles, resulting in a relatively low gas pressure. This allows it to adsorb tiny impurities such as oxygen, water vapor, and hydrogen in the melt, carrying these impurities out of the melt and thus degassing. This reduces defects such as porosity and shrinkage cavities during the solidification of magnesium alloy casting.

[0035] Furthermore, in this invention, preferably, argon gas can be introduced during the refining process with the addition of the second flux. In this case, the above-mentioned argon refining process can be omitted.

[0036] Next, after refining, in step S4, the molten alloy is transferred from the container to the tundish and a Mg-Zr master alloy is added for casting to obtain a high-temperature resistant, high-strength, and tough soluble magnesium alloy billet. During the transfer of the molten alloy from the container to the tundish, argon gas can be introduced into the container at a pressure of 1 to 2 atmospheres, thereby using this pressure to transfer the molten alloy from the container to the tundish. This low-pressure transfer method ensures a stable injection of the molten alloy.

[0037] In this invention, the tundish serves as a buffer and distribution container for the molten alloy, and is equipped with a stirring device inside. While transferring the molten alloy into the tundish, a Mg-Zr master alloy is added, allowing it to melt into the molten alloy in the tundish. Simultaneously, the stirring device is activated to agitate the molten alloy. This agitation ensures faster and more uniform melting of the Mg-Zr master alloy and prevents the formation of Al3Zr intermediate compounds, thereby achieving grain refinement. In this invention, to achieve better grain refinement, the stirring speed is preferably 100-200 rpm.

[0038] Furthermore, in this step, the alloy liquid is injected simultaneously, magnesium-zirconium master alloy is added according to the alloy composition, and casting is carried out concurrently. This simultaneous process prevents the formation of Al3Zr intermediate compounds and significantly improves production efficiency. Specifically, the alloy liquid and magnesium-zirconium master alloy are injected through the solution injection port at the top of the tundish, and the stirred alloy solution flows into the crystallizer through the outlet at the bottom of the tundish. In the crystallizer, it is then cast into bars of the required size, yielding a high-temperature resistant, high-strength, and tough soluble magnesium alloy billet.

[0039] In this invention, in order to improve casting efficiency, preferably, multiple outlets can be provided in the tundish, and the number of outlets is the same as the number of crystallizers.

[0040] Furthermore, in this invention, the composition of the Mg-Zr master alloy can be 25-30% zirconium by weight, with the remainder being magnesium.

[0041] Furthermore, in this invention, preferably, the Mg-Zr master alloy added in step S4 is preheated to a temperature of 400 to 600°C, thereby enabling the Mg-Zr master alloy to melt into the alloy liquid more quickly and uniformly. Additionally, preferably, the preheating of the Mg-Zr master alloy can be performed during the refining operation in step S3, thereby saving time and improving production efficiency.

[0042] Furthermore, in this invention, the amount of each component added is controlled according to the desired percentage (by weight) of the magnesium alloy composition to be prepared.

[0043] The soluble magnesium alloy prepared according to the present invention has low manufacturing cost and its mechanical properties decrease by less than 10% after extrusion processing in an environment of 120-200℃. It maintains high plasticity while having high strength, that is, the elongation after fracture is still greater than 10% when the tensile strength is greater than 300MPa.

[0044] The following describes specific embodiments of the soluble magnesium alloy and its preparation process of the present invention.

[0045] Example 1

[0046] In this embodiment, the composition of the high-temperature resistant, high-strength, and tough soluble magnesium alloy is as follows by weight percentage: Al 7%, Zr 0.8%, Mn 0.5%, Zn 1%, Ni 2%, and the remainder is Mg.

[0047] The preparation process of this magnesium alloy is described below.

[0048] 884.95 kg of pure magnesium ingot and 30 kg of the first flux were added to a crucible, and the temperature was raised to 650°C to fully melt the magnesium ingot. Then, pure zinc, pure aluminum, pure manganese, and pure nickel in the above proportions were added. The other metals were added sequentially after the first metal had melted.

[0049] After all the alloy has melted, slowly add 3% of the second flux by mass of the melt and refine at 720°C for 30 minutes, followed by argon refining for 10 minutes. After refining, maintain the mixture at rest for 4 hours.

[0050] After refining, the refined molten alloy is transferred to a tundish using a low-pressure transfer method. Simultaneously, a preheated Mg-Zr master alloy (preheated to, for example, 500°C) according to the above-mentioned proportions is added to the tundish, melting into the molten alloy. At the same time, a stirring device is activated to agitate the molten alloy at a speed of 150 rpm. The molten alloy is injected, the magnesium-zirconium master alloy is added, and casting is performed simultaneously. In this embodiment, the stirred molten alloy flows into a corresponding crystallizer through an outlet at the bottom of the tundish, where it is cast into bars of the required size, yielding a high-temperature resistant, high-strength, and tough soluble magnesium alloy billet.

[0051] After the soluble magnesium alloy billet is prepared, it is sawn into bars of a certain length. These bars are then heated to 380℃ in an induction heating furnace and extruded into smaller round bars at an extrusion ratio of 20. The mechanical properties of the extruded bars are tested; the tensile strength is 320 MPa, the specified non-proportional elongation strength is 220 MPa, and the elongation is 16%. The microstructure is measured using a metallographic microscope, and the microstructure is as follows: Figure 2 As shown, the grain size is approximately 20 μm.

[0052] The magnesium alloy billet prepared according to this embodiment has a low cost, and its mechanical properties decrease by less than 10% after extrusion processing at 200°C. It maintains high plasticity under high strength conditions, that is, the elongation after fracture is still greater than 12% under a tensile strength greater than 300MPa.

[0053] In this embodiment, although the above-described addition of metals is based on pure metals, the present invention is not limited thereto, and intermediate alloys in the same proportion may also be added.

[0054] Although the soluble magnesium alloy billet is extruded into a round bar in this embodiment, the present invention is not limited thereto and can also be extruded into other shapes.

[0055] Example 2

[0056] In this embodiment, the composition of the high-temperature resistant, high-strength, and tough soluble magnesium alloy is as follows by weight percentage: Al 8%, Zr 0.5%, Mn 1%, Zn 3%, Ni 2%, with the remainder being Mg.

[0057] The preparation process of this magnesium alloy is described below.

[0058] 862.95 kg of pure magnesium ingot and 30 kg of the first flux were placed in a crucible and heated to 720 °C to fully melt the magnesium ingot. Then, pure zinc, pure aluminum, anhydrous manganese chloride, and pure nickel, in the proportions described above, were added. After the first component melted, the other components were added sequentially. After all the alloy had melted, 3% (by weight) of the second flux was slowly added, and the mixture was refined at 720 °C for 20 minutes, followed by argon refining for 10 minutes. After refining, the mixture was left to stand for 3 hours.

[0059] After refining, the refined molten alloy is transferred to a tundish. Simultaneously, a preheated Mg-Zr master alloy (preheated to, for example, 600°C) according to the above-mentioned proportions is added to the tundish, melting into the molten alloy. At the same time, a stirring device is activated to agitate the molten alloy at a speed of 100 rpm. The molten alloy is injected, the magnesium-zirconium master alloy is added, and casting is performed simultaneously. In this embodiment, the stirred molten alloy flows through two outlets at the bottom of the tundish into two corresponding crystallizers, where it is cast into bars of the required size, yielding a high-temperature resistant, high-strength, and tough soluble magnesium alloy billet.

[0060] After the billet is prepared, it is sawn into bars of a certain length. These bars are then heated to 380℃ in an induction heating furnace and forged into round bars using a forging machine. The forged bars undergo mechanical property testing, showing a tensile strength of 300 MPa, a specified non-proportional elongation strength of 230 MPa, and an elongation of 17%. The microstructure is measured using a metallographic microscope, and its microstructure is as follows: Figure 3 As shown, the grain size is around 25 μm.

[0061] Although the above-described forging is into a round bar, the present invention is not limited thereto and can also be forged into other shapes. The magnesium alloy billet prepared according to this embodiment has a low cost, and its mechanical properties decrease by less than 10% after subsequent forging processing in an environment with a temperature of 120-200°C; it maintains high plasticity under high strength, that is, the elongation after fracture is still greater than 10% under a tensile strength greater than 260MPa.

[0062] Example 3

[0063] In this embodiment, the composition of the high-temperature resistant, high-strength, and tough soluble magnesium alloy is as follows by weight percentage: Al 9%, Zr 1%, Mn 0.7%, Zn 2%, Ni 0.8%, and the remainder is Mg.

[0064] The preparation process of this magnesium alloy is described below.

[0065] 847.95 kg of pure magnesium ingot and 30 kg of the first flux were placed in a crucible and heated to 750 °C to fully melt the magnesium ingot. Then, pure zinc, pure aluminum, anhydrous manganese chloride, and a Mg-Ni master alloy were added. After the first component melted, the other components were added in sequence. After all the alloys had melted, 3% (by mass) of the second flux was slowly added, and the mixture was refined at 740 °C for 40 minutes, followed by argon refining for 10 minutes. After refining, the mixture was left to stand for 2 hours.

[0066] After refining, the refined molten alloy is transferred to a tundish. Simultaneously, a preheated Mg-Zr master alloy (preheated to, for example, 400°C) according to the above-mentioned proportions is added to the tundish, melting into the molten alloy. At the same time, a stirring device is activated to agitate the molten alloy at a speed of 200 rpm. The molten alloy is injected, the magnesium-zirconium master alloy is added, and casting is performed simultaneously. In this embodiment, the stirred molten alloy flows through three outlets at the bottom of the tundish into three corresponding crystallizers, where it is cast into bars of the required size, yielding a high-temperature resistant, high-strength, and tough soluble magnesium alloy billet.

[0067] After the billet is prepared, it is sawn into square billets of a certain length. These are then heated to 380℃ in an induction heating furnace and subsequently rolled in a rolling mill to produce plates of a specific thickness as needed. The rolled plates are then subjected to mechanical property tests, revealing a tensile strength of 310 MPa, a specified non-proportional elongation strength of 230 MPa, and an elongation of 12%. The microstructure is measured using a metallographic microscope, and the microstructure is shown in the attached figure. Figure 4 As shown, the grain size is around 22 μm.

[0068] Although the above-mentioned billet is directly cast into a square billet, and then the square billet is directly rolled into a plate of the required thickness, the present invention is not limited to this. The billet can also be cast into a round bar, then extruded into a thick plate in an extruder, and then the thick plate is placed in a rolling mill and rolled into a thin plate of a certain thickness.

[0069] The beneficial effects of this embodiment are that the magnesium alloy billet prepared above has a low cost, and its mechanical properties decrease by less than 10% after extrusion processing in an environment of 120-200℃; it maintains high plasticity under high strength, that is, the elongation after fracture is still greater than 16% under a tensile strength greater than 260MPa.

[0070] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-aluminum, high-temperature resistant, high-strength, and high-toughness soluble magnesium alloy, wherein the soluble magnesium alloy comprises the following components by weight percentage: Al 3-9%, Mn 0.1-1%, Zn 1-3%, Zr 0.1-1.0%, Ni 0.1-3%, with the remainder being Mg, and the preparation method comprising the following steps: Step 1: Place the magnesium ingot and the first flux into a container and heat to 650°C to 750°C to melt the magnesium ingot; Step 2: After the magnesium ingot is melted, pure metals, intermediate alloys, or compounds other than Zr are added to the container in the above percentages to carry out alloying. Step 3: After alloying, add a second flux to the container and refine for a certain period of time; and Step 4: After refining, the molten alloy is transferred to an intermediate ladle and a Mg-Zr master alloy is added for casting to obtain a high-temperature resistant, high-strength, and tough soluble magnesium alloy billet. in, The tundish is equipped with a stirring device. While the molten alloy is being transferred into the tundish, the Mg-Zr master alloy is added and the stirring device is activated to agitate the molten alloy. In step 3, a second flux is added to the container and refined for 20-30 minutes. After refining, the container is left to stand for 2 to 4 hours.

2. The method for preparing the soluble magnesium alloy according to claim 1, wherein, In step 2, after the magnesium ingot is melted, pure zinc, pure aluminum, pure manganese or anhydrous manganese chloride, pure nickel or Mg-Ni master alloy are added to the container in sequence for alloying. The method of adding each component is to melt the previously added component and then add the next component to fully achieve alloying.

3. The method for preparing the soluble magnesium alloy according to claim 1, wherein, In step 4, the Mg-Zr master alloy added to the intermediate ladle is preheated.

4. The method for preparing the soluble magnesium alloy according to claim 1, wherein, The prepared magnesium alloy billet is heated to 350-450℃ and placed in an extruder for extrusion.

5. A high-aluminum-content, high-temperature-resistant, high-strength, and high-toughness soluble magnesium alloy prepared using the preparation method according to claim 1, wherein, The soluble magnesium alloy comprises the following components by weight percentage: Al 3-9%, Mn 0.1-1%, Zn 1-3%, Zr 0.1-1.0%, Ni 0.1-3%, with the remainder being Mg.

6. The high-aluminum-content, high-temperature-resistant, high-strength, and tough soluble magnesium alloy according to claim 5, wherein, The composition of this soluble magnesium alloy by weight percentage is: Al 7%, Zr 0.8%, Mn 0.5%, Zn 1%, Ni 2%, with the remainder being Mg.

7. The high-aluminum-content, high-temperature-resistant, high-strength, and tough soluble magnesium alloy according to claim 5, wherein, The composition of this soluble magnesium alloy by weight percentage is: Al 8%, Zr 0.5%, Mn 1%, Zn 3%, Ni 2%, with the remainder being Mg.

8. The high-aluminum-content, high-temperature-resistant, high-strength, and tough soluble magnesium alloy according to claim 5, wherein, The composition of this soluble magnesium alloy by weight percentage is: Al 9%, Zr 1%, Mn 0.7%, Zn 2%, Ni 0.8%, with the remainder being Mg.

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