Preparation method of high-strength and high-plasticity magnesium-aluminum alloy

Abstract

The application discloses a preparation method of high-strength and high-plasticity magnesium-aluminum alloy, relates to the technical field of concrete, and is prepared by adopting sub-rapid solidification and deep cooling cooperation technology. The alloy is composed of Mg, Al, Ag, Ho and Bi, the grain size of the alloy is small, the alloy has very high strength and plasticity, the compressive strength can reach 536 MPa, and the plasticity (delta) can reach 41.7%.

Description

Technical Field

[0001] This invention relates to the field of metal alloys, specifically a method for preparing a high-strength ductile magnesium-aluminum alloy. Background Technology

[0002] Cast Mg-Al alloys are currently the most widely used and mature magnesium alloy system, holding a very important position in the field of magnesium alloy production and research. As a typical representative of the Mg-Al system, the AZ91D alloy has a coarse solidification structure, with the main strengthening phase β-Mg17Al12 distributed in a network at grain boundaries or between α-Mg dendrites, resulting in poor plasticity and low absolute strength. Therefore, developing high-strength and high-plasticity magnesium alloys is of great significance.

[0003] CN105908039A discloses a novel yttrium-cerium-magnesium alloy and its preparation method. The alloy is composed of the following components by weight percentage: rare earth element Y: 2.5%–3.5%, rare earth element Ce: 0.7%–2.0%, Ca: 0.5%–1.0%, Zr: 0.3%–0.8%, with the balance being magnesium and trace impurities, and the sum of the component percentages is 100%. The preparation method involves smelting under CO2+SF6 mixed gas protection followed by a specific heat treatment process. The alloy exhibits excellent mechanical properties such as room temperature tensile strength, yield strength, and elongation. Its room temperature tensile strength, yield strength, and elongation are 195.35 MPa, 117.49 MPa, and 21%, respectively.

[0004] This invention obtains uniform and fine grains through processes such as melting, sub-rapid solidification, and water-cooled copper mold cooling. The resulting magnesium alloy has high strength and plasticity, with a room temperature elongation of ≥30%. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-strength ductile magnesium-aluminum alloy, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a high-strength ductile-magnesium-aluminum alloy specifically includes the following steps:

[0008] S1: Weigh a certain amount of Mg, Al, Ag, Bi, and Ho, add them to the crucible in sequence, and then place it in a vacuum induction melting furnace;

[0009] S2: Turn on the mechanical pump and molecular pump to evacuate the melting chamber to a vacuum of 2.4 × 10⁻⁶. -2 Argon gas is then introduced after Pa.

[0010] S3: Heat to 760℃, and after the furnace charge melts, gently move the control handle and shake it appropriately to mix the molten metal evenly.

[0011] S4: Pour the molten metal into a graphite crucible containing the Ga-In alloy and cool it at a rate ≥10. 3 K / s;

[0012] S5: Immerse it in liquid nitrogen at -196℃ for 24-96 hours, then remove it and immerse it in water at 0-20℃ to warm it up, and the material can be prepared.

[0013] Furthermore, the substances added to the crucible, by mass fraction, are: 6-21% aluminum, 0.2-2.0% silver, 0.2-2.0% holmium, 0.2-1% bismuth, and the remainder is magnesium.

[0014] Furthermore, the silver is nano-silver with an average particle size of 10-30 nm.

[0015] Furthermore, by directly pouring molten metal into graphite crucibles of different diameters placed in the liquid Gd-In alloy, a high cooling rate of 1.0 × 10⁻⁶ was achieved. 3 -6.0×10 3 K / s; then the alloy sample prepared by sub-rapid solidification was subjected to deep cryogenic treatment.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. This invention obtains uniform and fine grains through processes such as melting, sub-rapid solidification, and water-cooled copper mold cooling. The resulting magnesium-aluminum alloy has high strength and plasticity, with a room temperature elongation of ≥30%. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] In this embodiment of the invention, a magnesium-aluminum alloy is prepared through the following steps:

[0020] (1) Weigh a certain amount of Mg, Al, Ag, Bi and Ho, add them to the crucible in sequence, and then place it in a vacuum induction melting furnace.

[0021] (2) Turn on the mechanical pump and molecular pump to evacuate the melting chamber to 2.4 × 10⁻⁶. -2 Argon gas is then introduced after Pa.

[0022] (3) Heat to 760°C. After the furnace charge melts, gently move the control handle and shake it appropriately to mix the molten metal evenly.

[0023] (4) The molten metal is poured into graphite crucibles (of different diameters) placed in the liquid Ga-In alloy and cooled by kinetic supercooling of the molten metal (cooling rate of 1.0 × 10⁻⁶). 3 -6.0×10 3 While achieving deep undercooling (K / s), alloy test bars with a diameter of 8~20mm and a length of 160mm were finally obtained.

[0024] The solidification structure of this alloy is characterized by being a supersaturated solid solution with an average grain size of <20 μm and no grain boundary segregation.

[0025] (5) The alloy test bar is machined into a Φ6×10mm sample, and then immersed in liquid nitrogen at -150~-196℃ for 24~96h. After removal, it is immersed in water at 0-20℃ for rewarming. During the cryogenic process, a large number of twins can be stimulated to produce structural refinement. Solute atoms agglomerate at twin boundaries and pin twin boundaries to cause strengthening, promote the precipitation of nano-phase and produce dispersion strengthening. Therefore, it can improve the strength and plasticity of the alloy at the same time. Example 1:

[0026] (1) Weigh 6g of aluminum, 93.09g of magnesium, 0.1g of nano silver, 0.8g of holmium and 0.01g of bismuth, add them to the crucible in sequence, and then place it in a vacuum induction melting furnace.

[0027] (2) Turn on the mechanical pump and molecular pump to evacuate the melting chamber to 2.4 × 10⁻⁶. -2 Argon gas is then introduced after Pa.

[0028] (3) Heat to 760°C. After the furnace charge melts, gently move the control handle and shake it appropriately to mix the molten metal evenly.

[0029] (4) Pour the molten metal into a 20 mm diameter graphite crucible placed in the liquid Ga-In alloy for cooling at a rate of 1.0 × 10⁻⁶. 3 K / s.

[0030] (5) Cut the alloy test bar into Φ8×10mm samples, then immerse them in liquid nitrogen at -196℃ for 24h, take them out and then immerse them in water at 0℃ to warm them up, and the material can be prepared.

[0031] The resulting material has a small grain size of about 25 μm, and exhibits high strength and plasticity, with a compressive strength of up to 536 MPa and a maximum elongation δ of 41.7%. Example 2:

[0032] (1) Weigh 10g aluminum, 86.95g magnesium, 1g nano silver, 2g holmium and 0.05g bismuth, add them to the crucible in sequence, and then put it into the vacuum induction melting furnace.

[0033] (2) Turn on the mechanical pump and molecular pump to evacuate the melting chamber to 2.4 × 10⁻⁶. -2 Argon gas is then introduced after Pa.

[0034] (3) Heat to 760°C. After the furnace charge melts, gently move the control handle and shake it appropriately to mix the molten metal evenly.

[0035] (4) The molten metal is poured into a 16 mm diameter graphite crucible placed in the Ga-In alloy and cooled at a rate of 3.0 × 10⁻⁶ mm. 3 K / s.

[0036] (5) Cut the alloy test bar into Φ8×10mm samples, then immerse them in liquid nitrogen at -180℃ for 48h, take them out and then immerse them in water at 20℃ to warm them up, and the material can be prepared.

[0037] The resulting material has a small grain size of about 20 μm, and has high strength and plasticity, with a compressive strength of up to 539 MPa and a maximum elongation δ of 43.6%. Example 3:

[0038] (1) Weigh 15g of aluminum, 81.5g of magnesium, 2g of nano-Ag, 1g of holmium and 0.5g of bismuth, add them to the crucible in sequence, and then place it in a vacuum induction melting furnace.

[0039] (2) Turn on the mechanical pump and molecular pump to evacuate the melting chamber to 2.4 × 10⁻⁶. -2 Argon gas is then introduced after Pa.

[0040] (3) Heat to 760°C. After the furnace charge melts, gently move the control handle and shake it appropriately to mix the molten metal evenly.

[0041] (4) The molten metal was poured into a 12 mm diameter graphite crucible placed in the Ga-In alloy and cooled at a rate of 4.0 × 10⁻⁶. 3 K / s.

[0042] (5) Cut the alloy test bar into Φ8×10mm samples, then immerse them in liquid nitrogen at -186℃ for 72h, take them out and then immerse them in water at 12℃ to warm them up, and the material can be prepared.

[0043] The resulting material has a small grain size of about 18 μm, and exhibits high strength and plasticity, with a compressive strength of up to 536 MPa and a deformation rate of δ of 44.1%. Example 4:

[0044] (1) Weigh 21g of aluminum, 75.9g of magnesium, 1.6g of nano silver, 1.4g of holmium and 0.1g of bismuth, add them to the crucible in sequence, and then place it in a vacuum induction melting furnace.

[0045] (2) Turn on the mechanical pump and molecular pump to evacuate the melting chamber to 2.4 × 10⁻⁶. -2 Argon gas is then introduced after Pa.

[0046] (3) Heat to 760°C. After the furnace charge melts, gently move the control handle and shake it appropriately to mix the molten metal evenly.

[0047] (4) The molten metal was poured into an 8 mm diameter graphite crucible placed in the Ga-In alloy and cooled at a rate of 5.4 × 10⁻⁶. 3 K / s.

[0048] (5) Cut the alloy test bar into Φ8×10mm samples, then immerse them in liquid nitrogen at -160℃ for 96h, take them out and then immerse them in water at 8℃ to warm them up, and the material can be prepared.

[0049] The resulting material has a small grain size of about 15 μm, and has high strength and plasticity, with a compressive strength of up to 547 MPa and a maximum elongation δ of 40.3%.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a high strength to ductility magnesium-aluminum alloy, characterized in that, Specifically comprising the following steps: S1: weighing a certain amount of Mg, Al, Ag, Bi, Ho, and sequentially adding them into a crucible, and then putting them into a vacuum induction melting furnace; wherein the aluminum is added in an amount of 6-21% by mass, the silver is added in an amount of 0.2-2.0% by mass, the holmium is added in an amount of 0.2-2.0% by mass, the bismuth is added in an amount of 0.2-1% by mass, and the balance is magnesium; S2: Turn on the mechanical pump and the molecular pump, and vacuumize the smelting chamber to 2.4x10 -2 After 20 Pa, fill in argon gas; S3: heating to 760℃, and after the charge is melted, slightly pulling the control handle and appropriately shaking to make the metal liquid uniformly mixed; S4: The metal liquid is poured into a graphite crucible placed in liquid Ga-In alloy for cooling, cooling speed ≥ 10 3 K / s, to obtain an alloy test bar; S5: machining the alloy test bar into a Φ8x10mm alloy test sample, and then putting it into liquid nitrogen at-196℃ for soaking for 24-96h, and after taking it out, immersing it into water at 0-20℃ for rewarming, so that a high-strength and high-plasticity magnesium-aluminum alloy can be prepared.

2. The method for preparing a high-strength ductile-magnesium-aluminum alloy according to claim 1, characterized in that, In the step S1, the silver is nano silver, and the average particle size is 10-30nm.

3. The method for preparing a high-strength ductile-magnesium-aluminum alloy according to claim 1, characterized in that, The cooling rate in the step S4 is 1.0 x 10 3 -6.0 x 10 3 K / s.