Magnesium alloy with low cost and high service performance and preparation method

Abstract

The invention provides a magnesium alloy with low cost and high service performance and a preparation method. The preparation method comprises the following steps: uniformly mixing Ti powder and BN powder as well as Nb powder and B4C powder in different proportions to obtain two types of mixtures, and uniformly mixing the two types of mixtures with Al powder in different proportions to obtain a nano precursor; placing the nano precursor in an aluminum tube and a stainless steel tube layer by layer according to a certain mass ratio, and sealing to obtain an aluminum-coated wire and a stainless steel-coated wire; the stainless steel wrapped wire is subjected to induction heating reaction and then the stainless steel skin is stripped to obtain the nano reinforcing agent wire; in the smelting process of the magnesium alloy, an aluminum-coated wire and a nano reinforcing agent wire are added at the same time according to a certain mass ratio, then homogenization, hot extrusion and annealing treatment are conducted, and finally the magnesium alloy with the low cost and the high service performance is obtained. The ultimate fatigue strength of the magnesium alloy is larger than or equal to 130 MPa and is improved by 25% or above compared with that of commercial magnesium alloy, and the fatigue life is prolonged by 12 times or above.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance magnesium alloys, and particularly to low-cost magnesium alloys with high service performance and a preparation method thereof. Background Art

[0002] Magnesium alloys are the lightest metal structural materials (ρ = 1.4 - 1.9 g·cm -3 )), having high specific strength and specific stiffness, showing broad development and application prospects in the fields of automobiles, aerospace, national defense, and military industries, and playing an irreplaceable role in the process of structural lightweighting. However, the low strength, low ignition point, and insufficient service performance of magnesium alloys are still important factors restricting their applications. Magnesium alloy structural components in practical applications have to bear both monotonic loads and cyclic loads. Premature fatigue failure, especially at low stress levels, can lead to catastrophic consequences. Therefore, it is crucial to improve the service performance (mainly referring to fatigue performance) of magnesium alloys.

[0003] Alloys prepared by conventional processing methods (such as extrusion and rolling), without adding texture-modifying rare-earth alloy elements (such as Gd), usually have a strong basal texture, resulting in poor fatigue performance and plasticity of magnesium alloys. Therefore, at present, improving the fatigue performance of magnesium alloys mainly relies on complex deformation processes (such as multi-pass ultrasonic rolling, repeated upsetting and extrusion, etc.) or adding precious rare-earth elements. However, the prior art cannot achieve the simultaneous improvement of strength, plasticity, flame retardancy, and fatigue performance. Pursuing high strength inevitably sacrifices the plasticity of magnesium alloys, leading to a sharp decline in fatigue performance. On the other hand, improving fatigue performance by improving plasticity will reduce strength, and improving flame retardancy cannot take into account both strength and plasticity and fatigue performance. In addition, complex treatment processes and adding precious rare-earth elements will increase the cost of magnesium alloys and significantly increase the difficulty of industrialization. Therefore, how to reduce raw material costs, simplify the process to improve the service performance of magnesium alloys, and simultaneously improve strength, plasticity, and flame retardancy, and be suitable for industrial production is a technical problem that urgently needs to be solved in the current magnesium alloy field. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a low-cost magnesium alloy with high service performance, and its preparation method includes the following steps:

[0005] A low-cost magnesium alloy with high service performance, characterized in that its preparation method includes the following steps:

[0006] Step 1: At room temperature, mix Ti powder and BN powder according to a mass ratio of 80 - 95:5 - 20, and mix Nb powder and B according to a mass ratio of 60 - 80:20 - 40 4The C powders are respectively put into a ball mill with a rotation speed of 150 - 300 rpm and mixed for 3 - 6 hours to obtain powder mixture 1 and powder mixture 2; among them, the particle size dimensions of the Ti powder and the BN powder are respectively: 80 - 200 microns, 100 - 300 microns, and the particle size dimensions of the Nb powder and the B 4 C powders are respectively: 60 - 160 microns, 160 - 360 microns;

[0007] Step 2: The powder mixture 1 obtained in Step 1 and the Al powder are respectively mixed in a ball mill with a rotation speed of 60 - 150 rpm for 1 - 4 hours according to the mass ratios of 95 - 75:5 - 25, 65 - 45:55 - 35, 35 - 15:65 - 85 to obtain nano - precursor 1, nano - precursor 2, and nano - precursor 3; among them, the particle size dimension of the Al powder is 310 - 510 microns;

[0008] Step 3: The powder mixture 2 obtained in Step 1 and the Al powder are respectively mixed in a ball mill with a rotation speed of 200 - 400 rpm for 2 - 5 hours according to the mass ratios of 85 - 65:15 - 35, 55 - 35:45 - 65, 25 - 5:75 - 95 to obtain nano - precursor 4, nano - precursor 5, and nano - precursor 6; among them, the particle size dimension of the Al powder is 370 - 570 microns;

[0009] Step 4: The nano - precursor 1, nano - precursor 2, and nano - precursor 3 in Step 2 are placed layer by layer in the lower - middle - upper order in an aluminum tube according to the mass ratio of 5 - 25:10 - 30:50 - 85, and the aluminum tube is sealed to obtain an aluminum - wrapped wire;

[0010] Step 5: The nano - precursor 4, nano - precursor 5, and nano - precursor 6 in Step 3 are placed layer by layer in the lower - middle - upper order in a stainless - steel thin tube according to the mass ratio of 5 - 30:5 - 40:30 - 90, and the stainless - steel tube is sealed to obtain a stainless - steel - wrapped wire; the stainless - steel - wrapped wire is heated to 700 - 1000 °C by electromagnetic induction to achieve complete reaction, and then the stainless - steel skin is peeled off to finally prepare a nano - enhanced wire;

[0011] Step 6: Under the protection of argon, heat the magnesium alloy to 680 - 730 °C and hold for 20 - 50 min to obtain a magnesium alloy melt. Insert the aluminum-coated wire obtained in Step 4 and the nano-reinforcement wire obtained in Step 5 into the magnesium alloy melt simultaneously at a speed of 20 - 120 m / min according to the mass ratio of 20 - 80:80 - 20 for melting. Finally, obtain a magnesium alloy melt containing nano-particles. Among them, the mass ratio of the aluminum-coated wire and the nano-reinforcement wire to the magnesium alloy melt is 0.05 - 0.1%:1. By mass percentage, the chemical composition of the magnesium alloy is: Al: 7.5 - 8.5%, Zn: 0.6 - 1%, Ca: 0.2 - 1%, Mn ≤ 0.2%, Si ≤ 0.03%, Fe ≤ 0.005%, Cu ≤ 0.002%, Ni ≤ 0.001%, and the balance is Mg.

[0012] Step 7: Cast the magnesium alloy melt containing nano-particles obtained in Step 6 into a magnesium alloy ingot under vacuum conditions. Then, remove the riser from the magnesium alloy ingot and perform homogenization, hot extrusion, and annealing treatments to obtain a low-cost magnesium alloy with high service performance.

[0013] The homogenization treatment: Hold at 320 - 480 °C for 2 - 18 h.

[0014] The hot extrusion: The extrusion temperature is 220 - 420 °C, the extrusion ratio is 12 - 32:1, and the extrusion speed is 0.5 - 3 m / min.

[0015] The annealing treatment: Hold at 150 - 320 °C for 0.3 - 2.5 hours.

[0016] The low-cost magnesium alloy with high service performance has fine nano-particles uniformly distributed inside, simultaneously improving the anti-fatigue performance and the strength and plasticity. Among them, the fatigue limit strength ≥ 130 MPa. Compared with the magnesium alloy without nano-particles, the fatigue limit strength is increased by ≥ 25%, the fatigue life is increased by > 12 times, the room-temperature yield strength is increased by ≥ 3%, and the elongation is increased by ≥ 20%.

[0017] Further, at room temperature, mix Ti powder and BN powder according to the mass ratio of 85 - 90:10 - 15, and mix Nb powder and B 4 C powder according to the mass ratio of 65 - 75:25 - 35 in a ball mill with a rotation speed of 200 - 250 rpm for 4 - 5 hours to obtain powder mixture 1 and powder mixture 2. Among them, the particle size of Ti powder and BN powder is 100 - 180 microns and 150 - 250 microns respectively, and the particle size of Nb powder and B 4 C powder is 80 - 160 microns and 180 - 300 microns respectively.

[0018] Further, the powder mixture 1 and Al powder are mixed in a ball mill at a rotation speed of 80 - 130 rpm for 1.5 - 3.5 hours according to the mass ratios of 95 - 80:5 - 20, 65 - 50:50 - 35, and 30 - 20:70 - 80 respectively to obtain nano-precursor 1, nano-precursor 2, and nano-precursor 3; wherein, the particle size of the Al powder is 360 - 460 microns.

[0019] Further, the powder mixture 2 and Al powder are mixed in a ball mill at a rotation speed of 230 - 370 rpm for 2.5 - 4.5 hours according to the mass ratios of 80 - 70:20 - 35, 55 - 40:45 - 60, and 25 - 10:75 - 90 respectively to obtain nano-precursor 4, nano-precursor 5, and nano-precursor 6; wherein, the particle size of the Al powder is 400 - 520 microns.

[0020] Further, nano-precursor 1, nano-precursor 2, and nano-precursor 3 are placed layer by layer in the lower, middle, and upper order in an aluminum tube according to the mass ratio of 10 - 20:15 - 25:55 - 80, and the aluminum tube is sealed to obtain an aluminum-coated wire.

[0021] Further, nano-precursor 4, nano-precursor 5, and nano-precursor 6 are placed layer by layer in the lower, middle, and upper order in a stainless-steel thin tube according to the mass ratio of 10 - 25:10 - 35:35 - 85, and the stainless-steel tube is sealed to obtain a stainless-steel-coated wire; after the stainless-steel-coated wire is heated to 800 - 900 °C by electromagnetic induction heating to complete the reaction, the stainless-steel skin is peeled off, and finally a nano-enhanced wire is prepared.

[0022] Further, under the condition of argon protection, the magnesium alloy is heated to 680 - 730 °C and held for 25 - 55 min to obtain a magnesium alloy melt. The aluminum-coated wire and the nano-enhanced wire are inserted into the magnesium alloy melt simultaneously at a speed of 40 - 120 m / min according to the mass ratio of 30 - 80:70 - 20 to be melted, and finally a magnesium alloy melt containing nano-particles is obtained; wherein, the mass ratio of the aluminum-coated wire and the nano-enhanced wire to the magnesium alloy melt is 0.06 - 0.09%:1; by mass percentage, the chemical composition of the magnesium alloy is: Al: 7.5 - 8.5%, Zn: 0.6 - 1%, Ca: 0.2 - 1%, Mn ≤ 0.2%, Si ≤ 0.03%, Fe ≤ 0.005%, Cu ≤ 0.002%, Ni ≤ 0.001%, and the balance is Mg.

[0023] Further, the homogenization treatment in step seven: hold at 350 - 460 °C for 5 - 12 h; the hot extrusion: the extrusion temperature is 260 - 380 °C, the extrusion ratio is 15 - 30:1, and the extrusion speed is 1.5 - 2.5 m / min; the annealing treatment: hold at 180 - 290 °C for 0.8 - 2 hours.

[0024] Further, the annealing treatment described in Step 7: Keep the temperature at 200 - 250 °C for 1 - 1.8 hours. Description of the Drawings

[0025] Figure 1 Schematic diagram of the aluminum - wrapped wire prepared in Example 1 of the present invention;

[0026] Figure 2 Schematic diagram of the nano - enhancer wire prepared in Example 2 of the present invention;

[0027] Figure 3 S - N curve of the low - cost high - fatigue - damage - resistant deformed magnesium alloy 1 prepared in Example 3 of the present invention;

[0028] Figure 4 S - N curve of the low - cost high - fatigue - damage - resistant deformed magnesium alloy 2 prepared in Example 4 of the present invention;

[0029] Figure 5 S - N curve of the low - cost high - fatigue - damage - resistant deformed magnesium alloy 3 prepared in Example 5 of the present invention. Detailed Embodiments

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Example 1

[0032] For the aluminum - wrapped wire, its preparation method steps are as follows:

[0033] Step 1: At room temperature, put Ti powder and BN powder into a ball mill with a rotation speed of 225 rpm according to a mass ratio of 17:3 and mix for 4 hours to obtain powder mixture 1; among them, the particle size of Ti powder and BN powder are 140 microns and 200 microns respectively;

[0034] Step 2: Mix the powder mixture 1 obtained in Step 1 with Al powder according to three mass ratios of 19:1, 13:7, and 7:15 respectively in a ball mill with a rotation speed of 105 rpm for 3 hours to obtain nano - precursor 1, nano - precursor 2, and nano - precursor 3; among them, the particle size of Al powder is 410 microns;

[0035] Step 3: Place the nano-precursor 1, nano-precursor 2, and nano-precursor 3 obtained in Step 2 layer by layer in the order of bottom, middle, and top in an aluminum tube according to a mass ratio of 3:4:13, and seal the aluminum tube to obtain an aluminum-wrapped wire; as Figure 1 shown.

[0036] Example 2

[0037] The nano-enhanced wire, and its preparation method steps include the following:

[0038] Step 1: At room temperature, put Nb powder and B 4 C powder into a ball mill with a rotation speed of 230 rpm and mix for 5 hours to obtain a powder mixture 2; among them, the particle sizes of Nb powder and B 4 C powder are 110 microns and 260 microns respectively;

[0039] Step 2: Mix the powder mixture 2 obtained in Step 1 with Al powder at three mass ratios of 15:7, 11:9, and 1:3 respectively in a ball mill with a rotation speed of 300 rpm for 3 hours to obtain nano-precursor 4, nano-precursor 5, and nano-precursor 6; among them, the particle size of Al powder is 470 microns;

[0040] Step 3: Place the nano-precursor 4, nano-precursor 5, and nano-precursor 6 obtained in Step 2 layer by layer in the order of bottom, middle, and top in a stainless-steel thin tube according to a mass ratio of 3:5:12, and seal the stainless-steel tube to obtain a stainless-steel-wrapped wire; heat the stainless-steel-wrapped wire to 850 °C by electromagnetic induction to achieve complete reaction, and then strip the stainless-steel skin to finally prepare the nano-enhanced wire; as Figure 2 shown.

[0041] Example 3

[0042] Low-cost and high-service-performance magnesium alloy 1, and its preparation method steps include the following:

[0043] Step 1: Under the condition of argon protection, heat the magnesium alloy to 680 °C and keep it warm for 50 min to obtain a magnesium alloy melt. Insert the aluminum-wrapped wire obtained in Example 1 and the nano-enhanced wire obtained in Example 2 into the magnesium alloy melt at a speed of 30 m / min according to a mass ratio of 1:4 for melting, and finally obtain a magnesium alloy melt containing nano-particles; among them, the mass ratio of the aluminum-wrapped wire and the nano-enhanced wire to the magnesium alloy melt is 0.06%:1; by mass percentage, the chemical composition of the magnesium alloy is: Al: 7.6%, Zn: 0.7%, Ca: 0.2%, Mn: 0.06%, Si: 0.01%, Fe: 0.001%, Cu: 0.0005%, Ni: 0.0005%, and the balance is Mg;

[0044] Step 2: Cast the magnesium alloy melt containing nanoparticles obtained in Step 1 into a magnesium alloy ingot under vacuum conditions. After removing the riser from the magnesium alloy ingot, perform homogenization, hot extrusion, and annealing treatments to obtain a low-cost high-serviceability magnesium alloy 1;

[0045] The homogenization treatment: Keep it at 320 °C for 15 h;

[0046] The hot extrusion: The extrusion temperature is 220 °C, the extrusion ratio is 16:1, and the extrusion speed is 0.6 m / min;

[0047] The annealing treatment: Keep it at 150 °C for 2.5 hours.

[0048] The low-cost high-serviceability magnesium alloy 1 prepared in this example has uniformly distributed fine nanoparticles inside. A mechanical tensile-compressive fatigue test is carried out at room temperature, the stress ratio R = -1, the fatigue limit strength is 130 MPa. Compared with the magnesium alloy without nanoparticles, the fatigue limit strength is increased by 25%. Under the stress amplitude of 140 MPa, the fatigue life of this example is increased by 12.2 times, the room temperature yield strength is increased by 3%, and the elongation is increased by 20%. The stress-life (S-N) curve of the low-cost high-serviceability magnesium alloy 1 is as Figure 3 shown. It can be seen from the figure that the low-cost high-serviceability magnesium alloy 1 can maintain good high-serviceability (fatigue performance) whether under high or low stress.

[0049] Example 4

[0050] A low-cost high-serviceability magnesium alloy 2, and its preparation method steps are as follows:

[0051] Step 1: Under argon protection, heat the magnesium alloy to 730 °C and keep it for 20 min to obtain a magnesium alloy melt. Insert the aluminum-coated wire obtained in Example 1 and the nano-reinforcement wire obtained in Example 2 into the magnesium alloy melt at the same time at a speed of 120 m / min according to the mass ratio of 1:1 for melting. Finally, obtain a magnesium alloy melt containing nanoparticles; among them, the mass ratio of the aluminum-coated wire and the nano-reinforcement wire to the magnesium alloy melt is 0.1%:1; by mass percentage, the chemical composition of the magnesium alloy is: Al: 8.5%, Zn: 1%, Ca: 0.8%, Mn: 0.2%, Si: 0.03%, Fe: 0.005%, Cu: 0.002%, Ni: 0.001%, and the balance is Mg;

[0052] Step 2: Cast the magnesium alloy melt containing nanoparticles obtained in Step 1 into a magnesium alloy ingot under vacuum conditions. After removing the riser from the magnesium alloy ingot, perform homogenization, hot extrusion, and annealing treatments to obtain a low-cost high-serviceability magnesium alloy 2;

[0053] The homogenization treatment: keep the temperature at 480 °C for 3 h;

[0054] The hot extrusion: the extrusion temperature is 420 °C, the extrusion ratio is 32:1, and the extrusion speed is 1 m / min;

[0055] The annealing treatment: keep the temperature at 320 °C for 0.3 h.

[0056] In the low-cost high-serviceability magnesium alloy 2 prepared in this example, fine nano-particles are evenly distributed inside. A mechanical tensile-compressive fatigue test is carried out at room temperature, the stress ratio R = -1, the fatigue limit strength is 136 MPa. Compared with the magnesium alloy without nano-particles, the fatigue limit strength is increased by 30%. Under the stress amplitude of 145 MPa, the fatigue life in this example is increased by 12.6 times, the room-temperature yield strength is increased by 4%, and the elongation is increased by 40%. The stress-life (S-N) curve of the low-cost high-serviceability magnesium alloy 2 is as Figure 4 shown. It can be seen from the figure that the low-cost high-serviceability magnesium alloy 2 can maintain good high-serviceability (fatigue performance) whether under high or low stress.

[0057] Example 5

[0058] The low-cost high-serviceability magnesium alloy 3, and its preparation method steps are as follows:

[0059] Step 1: Under the condition of argon protection, heat the magnesium alloy to 700 °C and keep it for 35 min to obtain a magnesium alloy melt. Insert the aluminum-coated wire obtained in Example 1 and the nano-reinforcement wire obtained in Example 2 into the magnesium alloy melt at the same time at a speed of 70 m / min according to the mass ratio of 4:1 for melting, and finally obtain a magnesium alloy melt containing nano-particles; among them, the mass ratio of the aluminum-coated wire and the nano-reinforcement wire to the magnesium alloy melt is 0.08%:1; by mass percentage, the chemical composition of the magnesium alloy is: Al: 8.0%, Zn: 0.8%, Ca: 0.6%, Mn: 0.1%, Si: 0.015%, Fe: 0.0025%, Cu: 0.001%, Ni ≤ 0.0005%, and the balance is Mg;

[0060] Step 2: Cast the magnesium alloy melt containing nano-particles obtained in Step 1 into a magnesium alloy ingot under vacuum conditions, and then obtain the low-cost high-serviceability magnesium alloy 3 after removing the riser of the magnesium alloy ingot and performing homogenization, hot extrusion and annealing treatments;

[0061] The homogenization treatment: keep the temperature at 400 °C for 9 h;

[0062] The hot extrusion: the extrusion temperature is 320 °C, the extrusion ratio is 18:1, and the extrusion speed is 2 m / min;

[0063] The annealing treatment: Keep the temperature at 230°C for 1.5 hours.

[0064] In the low-cost high-serviceability magnesium alloy 3 prepared in this embodiment, fine nanoparticles are evenly distributed inside. A mechanical tensile-compressive fatigue test is carried out at room temperature, the stress ratio R = -1, the fatigue limit strength is 140 MPa. Compared with the magnesium alloy without nanoparticles, the fatigue limit strength is increased by 33%. At a stress amplitude of 150 MPa, the fatigue life of this embodiment is increased by 13.1 times, the room-temperature yield strength is increased by 5%, and the elongation is increased by 45%. The stress-life (S-N) curve of the low-cost high-serviceability magnesium alloy 3 is as Figure 5 shown. It can be seen from the figure that the low-cost high-serviceability magnesium alloy 3 can maintain good high-serviceability (fatigue performance) whether under high or low stress.

[0065] Comparative Example 1

[0066] In the article "Very high cycle fatigue resistance improvement of Mg-Gd-Zn-Zr alloy by introducing curved long-period stacking ordered lamellae, https: / / doi.org / 10.1016 / j.jma.2024.04.025" published online by Zhan et al. in the Journal of Magnesium and Alloys in May 2024, an extruded and heat-treated rare earth magnesium alloy (RE-Mg) was obtained. By mass percentage, the chemical composition of the magnesium alloy is: Mg: 86.8 wt.%, Gd: 12 wt.%, Zn: 0.8 wt.%, Zr: 0.4 wt.%. Up to 12 wt.% of the precious Gd element was added to the alloy, and a micron-scale lamellar (LPSO) structure was formed in the magnesium alloy. The tensile-compressive fatigue limit strength of this alloy at room temperature with R = -1 is 123 MPa. The price of the rare earth element Gd in Comparative Example 1 is the highest among rare earth elements, and the addition amount reaches 12 wt.%, which is much higher than the cost of the magnesium alloy prepared in the present invention. Therefore, the cost of the high-service-performance magnesium alloy obtained in the present invention is relatively low. In addition, the internal structures of the alloy of the present invention and Comparative Example 1 are different. Fine nano-particles are uniformly distributed in the internal structure of the alloy obtained in the present invention, while the internal structure of Comparative Example 1 is a micron-scale lamellar (LPSO) structure. Finally, compared with Comparative Example 1, the present invention can still make the fatigue strength greater than the fatigue limit strength in Comparative Example 1 without using any rare earth elements. In addition, the comparative example did not show whether the alloy strength, plasticity, and flame retardancy can be improved simultaneously, while the present invention not only improves the fatigue resistance but also simultaneously improves the strength, plasticity, and flame retardancy of the alloy. Compared with the comparative example, a significant technical improvement effect has been achieved.

[0067] Table 1 Comparison of Fatigue Performance of Magnesium Alloys in Comparative Examples and Each Example

[0068]

[0069] In Examples 3-5 of the present invention, the components, ratios, and process parameters used are all different. Among them, the anti-fatigue performance effect of the magnesium alloy obtained in Example 5 is the best, but the component ratio used in this example is not the highest. This shows that the best performance of the magnesium alloy obtained in the present invention is not determined by a certain component or process parameter, but is achieved through the synergistic regulation of components, component ratios, processes, and process parameters. And only within the scope protected by the claims of the present invention can a significant improvement in technical effects be achieved.

[0070] In summary, compared with the prior art, through the synergistic regulation of components, ratios, processes, and process parameters, the present invention significantly enhances the fatigue performance of magnesium alloys, simultaneously improves the strength, plasticity, and flame retardancy of magnesium alloys without using complex deformation processes or adding precious metals such as rare earths, and only within the scope of protection of the claims of the present invention. This provides a higher safety guarantee for the long-term service of magnesium alloys, thereby expanding the application fields of magnesium alloys and being suitable for industrial production.

[0071] The low-cost magnesium alloy with high service performance obtained by the present invention contains uniformly distributed nanoparticles with a particle size of 20 - 400 nm. The fatigue limit strength of the low-cost magnesium alloy with high service performance obtained by the present invention is ≥130 MPa. Compared with commercial magnesium alloys, the fatigue life of the alloy obtained by the present invention is increased by more than 12 times. At room temperature, the yield strength and elongation are simultaneously improved, with the improvement ranges being 3% - 5% and ≥20% respectively, significantly improving the elongation, and at the same time improving the flame retardancy. Compared with the fatigue performance of existing magnesium alloys, the present invention has achieved a significant improvement effect. More importantly, the magnesium alloy obtained by the present invention has low cost, simple process, and no pollution, and is suitable for large-scale industrial production.

Claims

1. Low-cost and high-service performance magnesium alloy, characterized by: Its preparation method comprises the following steps: Step 1: at room temperature, Ti powder and BN powder in a mass ratio of 80-95:5-20, and Nb powder and B4C powder in a mass ratio of 60-80:20-40 are respectively put into a ball mill at a rotation speed of 150-300 rpm and mixed for 3-6 hours to obtain powder mixture 1 and powder mixture 2; wherein the particle sizes of Ti powder and BN powder are 80-200 microns and 100-300 microns, respectively, and the particle sizes of Nb powder and B4C powder are 60-160 microns and 160-360 microns, respectively; Step 2: Mix the powder mixture 1 obtained in step 1 with Al powder in a ball mill at a mass ratio of 95-75:5-25, 65-45:55-35, and 35-15:65-85 for 1-4 hours at a rotation speed of 60-150 rpm to obtain nano precursor 1, nano precursor 2, and nano precursor 3; wherein the particle size of the Al powder is 310-510 microns; Step 3: Mix the powder mixture 2 obtained in step 1 with Al powder in a ball mill at a mass ratio of 85-65:15-35, 55-35:45-65, and 25-5:75-95 for 2-5 hours at a rotation speed of 200-400 rpm to obtain nano precursor 4, nano precursor 5, and nano precursor 6; wherein the particle size of Al powder is 370-570 microns; Step 4: placing the nano-precursor 1, nano-precursor 2 and nano-precursor 3 in step 2 layer by layer in the order of bottom, middle and top in a mass ratio of 5-25:10-30:50-85 in an aluminum tube and sealing the aluminum tube to obtain an aluminum-wrapped wire; Step 5: placing the nano-precursor 4, nano-precursor 5, and nano-precursor 6 in step 3 layer by layer in a stainless steel thin tube in the order of bottom, middle, and top according to a mass ratio of 5-30:5-40:30-90, and sealing the stainless steel tube to obtain a stainless steel wrapped wire; heating the stainless steel wrapped wire to 700-1000° C. by electromagnetic induction to achieve complete reaction, and then peeling off the stainless steel skin to finally prepare a nano-enhancer wire; Step 6. Under argon protection conditions, the magnesium alloy is heated to 680-730° C. and kept warm for 20-50 minutes to obtain a magnesium alloy melt. The aluminum-wrapped wire obtained in step 4 and the nano-reinforcement agent wire obtained in step 5 are simultaneously inserted into the magnesium alloy melt at a mass ratio of 20-80:80-20 at a speed of 20-120 m / min for melting, and finally a magnesium alloy melt containing nanoparticles is obtained; wherein the mass ratio of the aluminum-wrapped wire and the nano-reinforcement agent wire to the magnesium alloy melt is 0.05-0.1%:1; in terms of mass percentage, the chemical composition of the magnesium alloy is: Al: 7.5-8.5%, Zn: 0.6-1%, Ca: 0.2-1%, Mn≤0.2%, Si≤0.03%, Fe≤0.005%, Cu≤0.002%, Ni≤0.001%, and the balance is Mg; Step 7: Casting the magnesium alloy melt containing nanoparticles obtained in step 6 into a magnesium alloy ingot under vacuum conditions, and then removing the riser from the magnesium alloy ingot, homogenizing, hot extruding and annealing to obtain a low-cost and high-service performance magnesium alloy; The homogenization treatment: keeping warm at 320-480°C for 2-18h; The hot extrusion: the extrusion temperature is 220-420°C, the extrusion ratio is 12-32:1, and the extrusion speed is 0.5-3m / min; The annealing treatment is carried out at 150-320°C for 0.3-2.5 hours; The low-cost and high-service performance magnesium alloy has fine nanoparticles uniformly distributed inside, which simultaneously improves fatigue resistance and strong plasticity. The fatigue limit strength is ≥130MPa. Compared with the magnesium alloy without nanoparticles, the fatigue limit strength is increased by ≥25%, the fatigue life is increased by >12 times, the room temperature yield strength is increased by ≥3%, and the elongation is increased by ≥20%.

2. The low-cost and high-service performance magnesium alloy according to claim 1, characterized in that: As described in step 1: at room temperature, Ti powder and BN powder in a mass ratio of 85-90:10-15, and Nb powder and B4C powder in a mass ratio of 65-75:25-35 are respectively placed in a ball mill with a rotation speed of 200-250 rpm and mixed for 4-5 hours to obtain powder mixture 1 and powder mixture 2; wherein the particle sizes of Ti powder and BN powder are: 100-180 microns and 150-250 microns, respectively, and the particle sizes of Nb powder and B4C powder are: 80-160 microns and 180-300 microns, respectively.

3. The low-cost and high-service performance magnesium alloy according to claim 1, characterized in that: In step 2, the powder mixture 1 and the Al powder are mixed in a ball mill at a rotation speed of 80-130 rpm for 1.5-3.5 hours in a mass ratio of 95-80:5-20, 65-50:50-35, and 30-20:70-80 to obtain nano precursor 1, nano precursor 2, and nano precursor 3; wherein the particle size of the Al powder is 360-460 microns.

4. The low-cost and high-service performance magnesium alloy according to claim 1, characterized in that: As described in step three: the powder mixture 2 and the Al powder are mixed in a ball mill at a rotation speed of 230-370 rpm for 2.5-4.5 hours at a mass ratio of 80-70:20-35, 55-40:45-60, and 25-10:75-90 to obtain nano precursor 4, nano precursor 5, and nano precursor 6; wherein the particle size of the Al powder is 400-520 microns.

5. The low-cost and high-service performance magnesium alloy according to claim 1, characterized in that: As described in step 4: placing nano-precursor 1, nano-precursor 2 and nano-precursor 3 layer by layer in the order of bottom, middle and top in a mass ratio of 10-20:15-25:55-80 in an aluminum tube and sealing the aluminum tube to obtain an aluminum-wrapped wire.

6. The low-cost and high-service performance magnesium alloy according to claim 1, characterized in that: As described in step five: placing nano-precursor 4, nano-precursor 5, and nano-precursor 6 layer by layer in a stainless steel thin tube in the order of bottom, middle, and top according to a mass ratio of 10-25:10-35:35-85, and sealing the stainless steel tube to obtain a stainless steel wrapped wire; heating the stainless steel wrapped wire to 800-900°C by electromagnetic induction to achieve complete reaction, peeling off the stainless steel skin, and finally preparing a nano-reinforcement agent wire.

7. The low-cost and high-service performance magnesium alloy according to claim 1, characterized in that: As described in step six: under argon protection conditions, the magnesium alloy is heated to 680-730° C. and kept warm for 25-55 minutes to obtain a magnesium alloy melt, and the aluminum-wrapped wire and the nano-reinforcement agent wire are simultaneously inserted into the magnesium alloy melt at a mass ratio of 30-80:70-20 at a speed of 40-120 m / min for melting, and finally a magnesium alloy melt containing nanoparticles is obtained; wherein the mass ratio of the aluminum-wrapped wire and the nano-reinforcement agent wire to the magnesium alloy melt is 0.06-0.09%:1; in terms of mass percentage, the chemical composition of the magnesium alloy is: Al: 7.5-8.5%, Zn: 0.6-1%, Ca: 0.2-1%, Mn≤0.2%, Si≤0.03%, Fe≤0.005%, Cu≤0.002%, Ni≤0.001%, and the balance is Mg.

8. The low-cost and high-service performance magnesium alloy according to claim 1, characterized in that: The homogenization treatment described in step 7: keep warm at 350-460℃ for 5-12h; the hot extrusion: the extrusion temperature is 260-380℃, the extrusion ratio is 15-30:1, and the extrusion speed is 1.5-2.5m / min; the annealing treatment: keep warm at 180-290℃ for 0.8-2h.

9. The low-cost and high-service performance magnesium alloy according to claim 8, characterized in that: Annealing treatment in step 7: keep warm at 200-250°C for 1-1.8 hours.

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