A high fatigue resistance low content nanoparticle reinforced magnesium alloy and a preparation method thereof

Abstract

The application provides a high fatigue resistance low-content nanoparticle reinforced magnesium alloy and a preparation method. The preparation method comprises the following steps: uniformly mixing Ti powder, Nb powder and BN powder, uniformly mixing the Ti powder, the Nb powder and the BN powder with aluminum powder according to different proportions to obtain different kinds of powder mixtures, placing the different kinds of powder mixtures in an aluminum pipe according to a certain mass ratio and sealing the aluminum pipe to obtain a gradient wire, adding the gradient wire in a magnesium alloy smelting process, and finally obtaining the high fatigue resistance low-content nanoparticle reinforced magnesium alloy after homogenization, hot extrusion and annealing treatment. The high fatigue resistance low-content nanoparticle reinforced magnesium alloy obtained by the application has a fatigue limit strength greater than or equal to 126 MPa, and compared with a commercial magnesium alloy, the fatigue limit strength is increased by more than 20%, and the fatigue life is increased by more than 2 times.

Description

Technical Field

[0001] This invention relates to the field of high-performance magnesium alloy technology, specifically to a high-fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy and its preparation method. Background Technology

[0002] Currently, the application of magnesium alloys as structural components is mainly focused on non-load-bearing components. This is primarily because structural components typically need to withstand long-term cyclic alternating loads, while magnesium alloys suffer from rapid fatigue damage and insufficient fatigue service performance, making them prone to fatigue failure. Consequently, magnesium alloy load-bearing structural components are not suitable for applications in fields with high safety requirements, such as automobiles, rail transportation, and aerospace.

[0003] The fatigue performance of magnesium alloys is positively correlated with the strength-ductility product. Existing research often improves the fatigue performance of magnesium alloys through complex deformation processes such as large plastic deformation or the addition of rare earth elements. However, large plastic deformation of magnesium alloys is often accompanied by a sharp decrease in texture and plasticity. For example, while the equal channel angular compression molding (ECAP) process can improve the fatigue performance of magnesium alloys to some extent, if the ECAP parameters cannot be effectively controlled, the fatigue performance of magnesium alloys will decrease. Moreover, the size of magnesium alloys produced by the above techniques is limited, making them unsuitable for large-scale industrial applications. In addition, existing technologies improve fatigue performance by adding precious rare earth elements such as Ga to weaken the texture, but this will significantly increase the production cost of magnesium alloys. In summary, existing technologies for improving the fatigue resistance of magnesium alloys make it difficult to simultaneously improve strength and ductility. For example, excessive strength increases lead to a significant decrease in ductility, or vice versa. In short, it is difficult to simultaneously improve the fatigue performance, strength, and ductility of magnesium alloys. Therefore, current technologies struggle to ensure that magnesium alloys meet all application requirements in terms of fatigue performance, strength, and ductility. Thus, reducing raw material costs, simplifying processes, and simultaneously improving the fatigue, strength, and ductility properties of magnesium alloys, along with achieving industrial-scale production, are pressing technical challenges that need to be addressed. Summary of the Invention

[0004] To address the aforementioned technical challenges, this invention provides a high-fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy, the preparation method of which includes the following steps:

[0005] Step 1: At room temperature, mix Ti powder, Nb powder, and BN powder in a ball mill at a speed of 80-120 rpm for 5-18 hours at a mass ratio of 20-80:10-50:5-30 to obtain powder mixture 1; wherein the particle sizes of Ti powder, Nb powder, and BN powder are 50-150 micrometers, 20-100 micrometers, and 40-220 micrometers, respectively.

[0006] Step 2: Mix the powder mixture 1 obtained in Step 1 with Al powder at mass ratios of 90-70:10-30, 60-40:40-60, and 30-10:70-90 in a ball mill at a speed of 40-80 rpm for 3-6 hours to obtain powder mixture 2, powder mixture 3, and powder mixture 4; wherein the particle size of Al powder is 230-500 micrometers.

[0007] Step 3: Place powder mixture 2, powder mixture 3, and powder mixture 4 from Step 2 into the aluminum tube in the following order (bottom, middle, top) according to a mass ratio of 5-20:5-30:50-80, and then seal the aluminum tube to obtain gradient wire.

[0008] Step 4: Under argon protection, heat the magnesium alloy to 670-720℃ and hold for 30-60 min to obtain a magnesium alloy melt. Insert the gradient wire obtained in Step 3 into the magnesium alloy melt at a speed of 5-100 m / min until the gradient wire is completely reacted and melted in the magnesium alloy melt to obtain a magnesium alloy melt containing nanoparticles. The mass ratio of the gradient wire to the magnesium alloy melt is 0.01-0.05%:1. The chemical composition of the magnesium alloy by mass percentage is: Al: 8.5-9.5%, Zn: 0.6-1%, Mn≤0.3%, Si≤0.03%, Fe≤0.003%, Cu≤0.002%, Ni≤0.001%, with the balance being Mg.

[0009] Step 5: Cast the magnesium alloy melt containing nanoparticles obtained in Step 4 into magnesium alloy ingots under vacuum conditions. After removing the riser from the magnesium alloy ingots, homogenize, hot extrude and anneal them to obtain a high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy.

[0010] The homogenization process involves maintaining the temperature at 300-450℃ for 2-24 hours.

[0011] The hot extrusion is described as follows: extrusion temperature is 150-400℃, extrusion ratio is 10-30:1, and extrusion speed is 1-5 m / min.

[0012] The annealing process involves holding the temperature at 100-300℃ for 0.1-2 hours.

[0013] The high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy has a fatigue limit strength ≥126 MPa, which is more than 20% higher than that of commercial magnesium alloys, and its fatigue life is increased by more than 2 times.

[0014] Further, in step one, Ti powder, Nb powder, and BN powder are mixed in a ball mill at a speed of 90-110 rpm for 8-12 hours at room temperature according to a mass ratio of 35-60:20-40:10-25 to obtain powder mixture 1; wherein the particle sizes of Ti powder, Nb powder, and BN powder are 60-100 micrometers, 30-80 micrometers, and 90-150 micrometers, respectively.

[0015] Further, in step two, powder mixture 1 and Al powder are mixed in a ball mill at a speed of 50-70 rpm for 4-5 hours at mass ratios of 85-75:15-25, 55-45:45-55 and 25-15:75-85 respectively to obtain powder mixture 2, powder mixture 3 and powder mixture 4; wherein the particle size of Al powder is 260-400 micrometers.

[0016] Further, in step four: under argon protection, the magnesium alloy is heated to 680-710℃ and held for 40-50 min to obtain a magnesium alloy melt. Gradient wire is inserted into the magnesium alloy melt at a speed of 20-80 m / min until the gradient wire is completely reacted and melted in the magnesium alloy melt to obtain a magnesium alloy melt containing nanoparticles. The mass ratio of the gradient wire to the magnesium alloy melt is 0.02-0.04%:1. The chemical composition of the magnesium alloy, by mass percentage, is: Al: 8.5-9.5%, Zn: 0.6-1%, Mn≤0.3%, Si≤0.03%, Fe≤0.003%, Cu≤0.002%, Ni≤0.001%, with the balance being Mg.

[0017] Further, the homogenization treatment in step five involves holding the material at 330-400℃ for 3-10 hours; the hot extrusion involves an extrusion temperature of 200-350℃, an extrusion ratio of 15-28:1, and an extrusion speed of 1.5-3.5 m / min; and the annealing treatment involves holding the material at 150-250℃ for 0.5-1.5 hours.

[0018] Furthermore, the annealing treatment described in step five involves holding the temperature at 180-220℃ for 0.8-1.2 hours. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the gradient wire prepared in Example 1 of the present invention;

[0020] Figure 2 The stress-life of the high fatigue resistance, low content nanoparticle-reinforced magnesium alloy 1 prepared in Example 2 of this invention is shown to be... S - N (Line graph)

[0021] Figure 3The stress-life of the high fatigue resistance, low content nanoparticle-reinforced magnesium alloy 2 prepared in Example 3 of this invention is shown to be... S - N (Line graph)

[0022] Figure 4 The stress-life of the high fatigue resistance, low content nanoparticle-reinforced magnesium alloy 3 prepared in Example 4 of this invention is shown to be... S - N (Curve graph) Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0024] Example 1

[0025] The fabrication method for gradient wires includes the following steps:

[0026] Step 1: At room temperature, Ti powder, Nb powder and BN powder are mixed in a ball mill at 100 rpm for 10 hours at a mass ratio of 4:3:2 to obtain powder mixture 1; wherein, the particle sizes of Ti powder, Nb powder and BN powder are 80 micrometers, 40 micrometers and 120 micrometers respectively.

[0027] Step 2: Mix the powder mixture 1 obtained in Step 1 with Al powder at mass ratios of 5:1, 1:1 and 1:5 in a ball mill at a speed of 60 rpm for 4 hours to obtain powder mixture 2, powder mixture 3 and powder mixture 4; wherein the particle size of Al powder is 280 micrometers.

[0028] Step 3: Place powder mixture 2, powder mixture 3, and powder mixture 4 from Step 2 into an aluminum tube in a bottom-middle-top order according to a mass ratio of 2:3:15, and then seal the aluminum tube to obtain a gradient wire. Figure 1 As shown.

[0029] Example 2

[0030] The preparation method of a high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy 1 includes the following steps:

[0031] Step 1: Under argon protection, the magnesium alloy is heated to 670℃ and held for 60 minutes to obtain a magnesium alloy melt. The gradient wire obtained in Example 1 is inserted into the magnesium alloy melt at a speed of 10 m / min until the gradient wire is completely reacted and melted in the magnesium alloy melt to obtain a magnesium alloy melt containing nanoparticles. The mass ratio of the gradient wire to the magnesium alloy melt is 0.01%:1. The chemical composition of the magnesium alloy by mass percentage is: Al: 8.6%, Zn: 0.6%, Mn: 0.1%, Si: 0.01%, Fe: 0.001%, Cu: 0.001%, Ni: 0.001%, with the balance being Mg.

[0032] Step 2: The magnesium alloy melt containing nanoparticles obtained in Step 1 is cast into magnesium alloy ingots under vacuum conditions. After removing the riser, the magnesium alloy ingots are homogenized, hot extruded and annealed to obtain a high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy 1.

[0033] The homogenization process involves holding the sample at 300℃ for 12 hours.

[0034] The hot extrusion is described as follows: extrusion temperature is 200℃, extrusion ratio is 15:1, and extrusion speed is 1 m / min.

[0035] The annealing process involves holding the temperature at 100°C for 2 hours.

[0036] In this embodiment, the high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy 1 was subjected to mechanical tensile-compressive fatigue testing at room temperature, with a stress ratio of... R = -1, frequency of 60 Hz, fatigue limit strength of 126 MPa. Compared with magnesium alloy without nanoparticles, its fatigue limit strength is increased by 23%, fatigue life at stress amplitude of 180 MPa is increased by 2.2 times, and fatigue life at stress amplitude of 136 MPa is increased by 10.8 times, while maintaining good strength and plasticity, making it suitable for industrial production. Stress-life of high fatigue-resistant, low-nanoparticle-content reinforced magnesium alloy 1 ( S - N (The curve is as follows) Figure 2 As shown.

[0037] Example 3

[0038] The preparation method of a high-fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy 2 includes the following steps:

[0039] Step 1: Under argon protection, the magnesium alloy is heated to 720℃ and held for 30 minutes to obtain a magnesium alloy melt. The gradient wire obtained in Example 1 is inserted into the magnesium alloy melt at a speed of 100 m / min until the gradient wire is completely reacted and melted in the magnesium alloy melt to obtain a magnesium alloy melt containing nanoparticles. The mass ratio of the gradient wire to the magnesium alloy melt is 0.05%:1. The chemical composition of the magnesium alloy by mass percentage is: Al: 9.3%, Zn: 1%, Mn: 0.05%, Si: 0.02%, Fe: 0.002%, Cu: 0.002%, Ni: 0.001%, with the balance being Mg.

[0040] Step 2: Cast the magnesium alloy melt containing nanoparticles obtained in Step 1 into magnesium alloy ingots under vacuum conditions. After removing the riser from the magnesium alloy ingots, homogenize, hot extrude and anneal them to obtain high fatigue resistance and low content nanoparticle reinforced magnesium alloy 2.

[0041] The homogenization process involves holding the sample at 450℃ for 2 hours.

[0042] The hot extrusion is described as follows: extrusion temperature is 400℃, extrusion ratio is 20:1, and extrusion speed is 5 m / min.

[0043] The annealing process involves holding the temperature at 300℃ for 0.5 hours.

[0044] In this embodiment, the high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy 2 was subjected to mechanical tensile-compressive fatigue testing at room temperature, with a stress ratio of... R = -1, frequency of 80 Hz, fatigue limit strength of 129 MPa. Compared with magnesium alloy without nanoparticles, its fatigue limit strength is increased by 28%, fatigue life at stress amplitude of 190 MPa is increased by 2.7 times, and fatigue life at stress amplitude of 139 MPa is increased by 11.3 times, while maintaining good strength and plasticity, making it suitable for industrial production. Stress-life of high fatigue-resistant, low-nanoparticle-content reinforced magnesium alloy 2. S - N (The curve is as follows) Figure 3 As shown.

[0045] Example 4

[0046] The preparation method of a high-fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy 3 includes the following steps:

[0047] Step 1: Under argon protection, the magnesium alloy is heated to 690℃ and held for 40 minutes to obtain a magnesium alloy melt. The gradient wire obtained in Example 1 is inserted into the magnesium alloy melt at a speed of 30 m / min until the gradient wire is completely reacted and melted in the magnesium alloy melt to obtain a magnesium alloy melt containing nanoparticles. The mass ratio of the gradient wire to the magnesium alloy melt is 0.03%:1. The chemical composition of the magnesium alloy by mass percentage is: Al: 8.8%, Zn: 0.8%, Mn: 0.1%, Si: 0.01%, Fe: 0.001%, Cu: 0.001%, Ni: 0.001%, with the balance being Mg.

[0048] Step 2: Cast the magnesium alloy melt containing nanoparticles obtained in Step 1 into magnesium alloy ingots under vacuum conditions. After removing the riser from the magnesium alloy ingots, homogenize, hot extrude and anneal them to obtain high fatigue resistance and low content nanoparticle reinforced magnesium alloy 3.

[0049] The homogenization process involves holding the sample at 350°C for 3 hours.

[0050] The hot extrusion is described as follows: extrusion temperature is 300℃, extrusion ratio is 25:1, and extrusion speed is 2 m / min.

[0051] The annealing process involves holding the temperature at 200°C for 1 hour.

[0052] In this embodiment, the high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy 3 was subjected to mechanical tensile-compressive fatigue testing at room temperature. The stress ratio was... R = -1, frequency of 100 Hz, fatigue limit strength of 135 MPa. Compared with magnesium alloy without nanoparticles, its fatigue limit strength is increased by 32%, fatigue life at stress amplitude of 210 MPa is increased by 2.5 times, and fatigue life at stress amplitude of 145 MPa is increased by 11.6 times, while maintaining good strength and plasticity, making it suitable for industrial production. Stress-life of high fatigue-resistant, low-nanoparticle-content reinforced magnesium alloy 3 ( S - N (The curve is as follows) Figure 4 As shown.

[0053] Comparative Example 1

[0054] In their 2015 article "Fatigue properties of magnesium alloy AZ91 processed by severe plastic deformation" published in Volume 42 of the *Journal of the Mechanical Behavior of Biomedical Materials*, Stanislava Fintova et al. prepared AZ91 magnesium alloy and subjected it to large plastic deformation treatment using equal channel angular extrusion (ECAP) at room temperature. R =-1. Mechanical tensile and compressive fatigue tests were conducted under a loading frequency of 60 Hz, showing that the fatigue limit strength of AZ91 was 85 MPa, which is 6.25% higher than that of the magnesium alloy without ECAP treatment. The chemical composition of this magnesium alloy, by mass percentage, is: Al: 8.7%, Zn: 0.65%, Mn: 0.25%, Si: 0.006%, Fe: 0.003%, Be: 0.0008%, Ni: 0.0006%, Cu: 0.0005%, with the balance being Mg.

[0055] Table 1 Comparison of fatigue properties of magnesium alloys in comparative examples and various embodiments

[0056] sample Test conditions Fatigue limit strength Example 2 Room temperature mechanical tensile-compressive fatigue, stress ratio = -1, frequency 60 Hz 126 Example 3 Room temperature mechanical tensile-compressive fatigue, stress ratio = -1, frequency 80 Hz 129 Example 4 Room temperature mechanical tensile-compressive fatigue, stress ratio = -1, frequency 100 Hz 135 Comparative Example 1 Room temperature mechanical tensile-compressive fatigue, stress ratio = -1, frequency 60 Hz 85

[0057] Compared with Comparative Example 1, the present invention does not employ a high-cost, large-plastic-deformation process. Its minimum fatigue limit strength is greater than that of Comparative Example 1, and is significantly higher than that of commercial alloys. In addition, the present invention also significantly improves fatigue life, which is a technical effect not disclosed in the comparative example. At the same time, the present invention also enables the alloy to maintain high strength and plasticity. Therefore, the present invention achieves superior high fatigue resistance performance compared with the prior art.

[0058] The components, proportions, and process parameters used in Examples 2-4 of this invention are all different. Among them, the magnesium alloy obtained in Example 4 has the best fatigue resistance, but the component proportion used in this example is not the highest. This shows that the best performance of the magnesium alloy obtained by this invention is not determined by a certain component or process parameter, but is achieved through the synergistic regulation of components, component proportions, processes, and process parameters. Moreover, the significantly improved technical effect can only be achieved within the scope of the claims of this invention.

[0059] In summary, compared with existing technologies, this invention, through the synergistic regulation of components, proportions, processes, and process parameters, simultaneously and significantly enhances the fatigue limit strength and fatigue life of magnesium alloys without employing complex deformation processes, adding rare earth elements or other precious metals, or reducing the strength and plasticity of magnesium alloys. This provides higher safety assurance for the application of magnesium alloys as load-bearing structural components, thereby expanding the application fields and industrial production of magnesium alloys.

[0060] The high fatigue-resistant magnesium alloy obtained by this invention contains uniformly distributed nanoparticles with a particle size of 50-600 nm. The high fatigue-resistant, low-content nanoparticle magnesium alloy obtained by this invention has a fatigue limit strength ≥126 MPa. Compared with existing commercial magnesium alloys, the magnesium alloy obtained by this invention exhibits a fatigue life that is more than twice that under high stress (210-180 MPa) and more than 11 times that under low stress (145-136 MPa), representing a significant improvement in fatigue resistance compared to existing magnesium alloys. More importantly, the magnesium alloy preparation method of this invention is simple, low-cost, and pollution-free, making it suitable for large-scale industrial production.

Claims

1. A high-fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy, characterized in that: Its preparation method includes the following steps: Step 1: At room temperature, mix Ti powder, Nb powder, and BN powder in a ball mill at a speed of 80-120 rpm for 5-18 hours at a mass ratio of 20-80:10-50:5-30 to obtain powder mixture 1; wherein the particle sizes of Ti powder, Nb powder, and BN powder are 50-150 micrometers, 20-100 micrometers, and 40-220 micrometers, respectively. Step 2: Mix the powder mixture 1 obtained in Step 1 with Al powder at mass ratios of 90-70:10-30, 60-40:40-60, and 30-10:70-90 in a ball mill at a speed of 40-80 rpm for 3-6 hours to obtain powder mixture 2, powder mixture 3, and powder mixture 4; wherein the particle size of Al powder is 230-500 micrometers. Step 3: Place powder mixture 2, powder mixture 3, and powder mixture 4 from Step 2 into the aluminum tube in the following order (bottom, middle, top) according to a mass ratio of 5-20:5-30:50-80, and then seal the aluminum tube to obtain gradient wire. Step 4: Under argon protection, heat the magnesium alloy to 670-720℃ and hold for 30-60 min to obtain a magnesium alloy melt. Insert the gradient wire obtained in Step 3 into the magnesium alloy melt at a speed of 5-100 m / min until the gradient wire is completely reacted and melted in the magnesium alloy melt to obtain a magnesium alloy melt containing nanoparticles. The mass ratio of gradient wire to magnesium alloy melt is 0.01-0.05%:

1. The chemical composition of the magnesium alloy by mass percentage is: Al: 8.5-9.5%, Zn: 0.6-1%, Mn≤0.3%, Si≤0.03%, Fe≤0.003%, Cu≤0.002%, Ni≤0.001%, with the balance being Mg. Step 5: Cast the magnesium alloy melt containing nanoparticles obtained in Step 4 into magnesium alloy ingots under vacuum conditions. After removing the riser from the magnesium alloy ingots, homogenize, hot extrude and anneal them to obtain a high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy. The homogenization process involves holding the temperature at 300-450℃ for 2-24 hours. The hot extrusion is described as follows: extrusion temperature is 150-400℃, extrusion ratio is 10-30:1, and extrusion speed is 1-5 m / min. The annealing process involves holding the temperature at 100-300℃ for 0.1-2 hours. The high fatigue-resistant, low-content nanoparticle-reinforced magnesium alloy has a fatigue limit strength ≥126 MPa, which is more than 20% higher than that of commercial magnesium alloys, and its fatigue life is increased by more than 2 times.

2. The high fatigue resistance, low content nanoparticle-reinforced magnesium alloy according to claim 1, characterized in that: In step one, Ti powder, Nb powder, and BN powder are mixed in a ball mill at a speed of 90-110 rpm for 8-12 hours at room temperature according to a mass ratio of 35-60:20-40:10-25 to obtain powder mixture 1; wherein the particle sizes of Ti powder, Nb powder, and BN powder are 60-100 micrometers, 30-80 micrometers, and 90-150 micrometers, respectively.

3. The high fatigue resistance, low content nanoparticle-reinforced magnesium alloy according to claim 1, characterized in that: In step two, powder mixture 1 is mixed with Al powder in a ball mill at a speed of 50-70 rpm for 4-5 hours at mass ratios of 85-75:15-25, 55-45:45-55, and 25-15:75-85 to obtain powder mixture 2, powder mixture 3, and powder mixture 4; wherein the particle size of Al powder is 260-400 micrometers.

4. The high fatigue resistance, low content nanoparticle-reinforced magnesium alloy according to claim 1, characterized in that: Step four describes the process of heating the magnesium alloy to 680-710℃ under argon protection for 40-50 minutes to obtain a magnesium alloy melt. Gradient wire is then inserted into the magnesium alloy melt at a speed of 20-80 m / min until the gradient wire completely reacts and melts into the magnesium alloy melt, resulting in a magnesium alloy melt containing nanoparticles. The mass ratio of the gradient wire to the magnesium alloy melt is 0.02-0.04%:

1. The chemical composition of the magnesium alloy, by mass percentage, is: Al: 8.5-9.5%, Zn: 0.6-1%, Mn≤0.3%, Si≤0.03%, Fe≤0.003%, Cu≤0.002%, Ni≤0.001%, with the balance being Mg.

5. The high fatigue resistance, low content nanoparticle-reinforced magnesium alloy according to claim 1, characterized in that: The homogenization process described in step five involves holding the material at 330-400℃ for 3-10 hours; the hot extrusion process involves extrusion temperature of 200-350℃, extrusion ratio of 15-28:1, and extrusion speed of 1.5-3.5 m / min; and the annealing process involves holding the material at 150-250℃ for 0.5-1.5 hours.

6. The high fatigue resistance, low content nanoparticle-reinforced magnesium alloy according to claim 5, characterized in that: The annealing process described in step five involves holding the temperature at 180-220℃ for 0.8-1.2 hours.

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