High performance, fatigue resistant, nanoparticle strengthened magnesium alloy and method of making

Abstract

The application provides a high-performance, fatigue-resistant nano-particle reinforced magnesium alloy and a preparation method thereof, and comprises the following steps: uniformly mixing Ti powder and B4C powder to obtain mixed powder 1; uniformly mixing the mixed powder 1 with Al powder according to three different molar ratios to obtain mixed powders 2, 3 and 4; sequentially placing the three kinds of powders in a pure aluminum thin cylinder according to a certain mass ratio, and sealing the opening by using a packaging machine and laser welding to finally obtain an aluminum-coated mixed powder material; adding the aluminum-coated mixed powder material in a magnesium alloy melting process, and performing mechanical stirring and ultrasonic stirring under a protective atmosphere; and finally obtaining the high-performance, fatigue-resistant nano-particle reinforced magnesium alloy after slagging, pouring, cooling, solid solution and aging heat treatment, wherein the tensile strength of the magnesium alloy is greater than or equal to 332 MPa, the elongation rate is greater than or equal to 8.5%, the cycle number is greater than or equal to 3117614 times when the fatigue load is 90 MPa, and the fatigue limit is greater than or equal to 86 MPa, which is much higher than that of the existing commercial magnesium alloy, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of high-performance magnesium alloys, specifically to high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloys and their preparation methods. Background Technology

[0002] Sustainable development has gradually become a national development strategy, and improving energy efficiency is a reliable solution to support this strategy. Therefore, the manufacturing industry's demand for advanced, high-performance, lightweight materials is constantly increasing. Among metallic materials, magnesium alloys have a low density (1.738 g·cm³). -3 Magnesium alloys, with their high specific strength and stiffness, strong thermal conductivity, excellent damping capacity, and electromagnetic shielding performance, show great application potential and broad prospects in the energy and transportation fields. Currently, when magnesium alloys are used in engine parts, seats, and steering wheels, they need to withstand cyclic loads. Long-term cyclic loads will lead to the accumulation of microscopic plastic deformation inside the parts, causing cracking, deformation, and fatigue failure on the mold surface, seriously damaging the service life of the parts. Fatigue damage is the main cause of damage to automotive parts. Currently, there are solutions to improve fatigue service performance, such as rare earth element regulation and hot deformation treatment. For example, in the article "Study on High Cycle Fatigue Behavior of Gravity Casting Mg-3Nd-0.2Zn-Zr Magnesium Alloy" published by Li Zhifeng et al. in Volume 41, Issue 9 of Rare Metals Materials and Engineering in 2012, the composition of magnesium alloys was regulated by rare earth Nd to improve the fatigue resistance of magnesium alloys. However, its strength can only reach 290 MPa and its elongation is 8.0%, which undoubtedly limits its practical application. Moreover, the excessively high rare earth element content increases the cost of industrialization.

[0003] Furthermore, improving the fatigue resistance of alloys often negatively impacts their strength and plasticity. These key mechanical properties often exhibit a trade-off relationship, making it difficult for the overall performance of the material to meet engineering application requirements and hindering its industrial production. Therefore, how to simultaneously improve the fatigue resistance, strength, and plasticity of magnesium alloys to achieve industrialized production while reducing costs and simplifying processes has become an urgent technical challenge. Summary of the Invention

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

[0005] (1) At room temperature, Ti: 60-80% and B4C: 20-40% were put into a ball mill with a speed of 45-55 rpm and mixed evenly for 4-6 hours to obtain mixed powder 1. The particle size range of Ti powder is 5-20 micrometers and the particle size range of B4C powder is 8-25 micrometers.

[0006] (2) Al powder and mixed powder 1 obtained in step (1) are mixed in three mass percentages: mixed powder 1: Al: 65-75%: 25-35%, mixed powder 1: Al: 45-55%: 45-55%, mixed powder 1: Al: 15-25%: 75-85%, respectively. After mixing for 10-12 hours in a ball mill with a speed of 35-45 rpm, three mixed powders with high, medium and low contents are obtained, which are defined as mixed powder 2, mixed powder 3 and mixed powder 4, respectively. The particle size range of Al powder is 30-100 micrometers.

[0007] (3) The mixed powder 2, mixed powder 3 and mixed powder 4 obtained in step (2) are placed in the pure aluminum strip in order of mass ratio 5-10:5-10:80-90; the aluminum-coated mixed powder material is finally prepared by using a packaging machine and laser welding to seal the powder.

[0008] (4) Under the protection of a CO2:SF6 mixed gas with a volume ratio of 4-9:1, the magnesium alloy is heated to 680-700℃ and held for 60-90 minutes to obtain a magnesium alloy melt. Then, the aluminum-coated mixed powder material obtained in step (3) is added, and then mechanically stirred for 1-2 minutes. Ultrasonic stirring is performed at 750-780℃ and 20.20-20.40MHz for 3-9 minutes. Then, it is held at 700-720℃ for 3-5 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy is obtained. The mass ratio of the aluminum-coated mixed powder material to the magnesium alloy is 0.05-0.5wt.%:1.

[0009] The magnesium alloy composition, by mass percentage, is: Al: 8.52-9.43%; Mn: 0.18-0.40%; Zn: 0.45-0.76%; balance Mg.

[0010] The solution treatment involves holding the solution at 400℃-420℃ for 7 hours under argon protection, followed by water quenching.

[0011] The aforementioned aging treatment involves maintaining the temperature at 180-220℃ for 10 hours.

[0012] The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy contains uniformly distributed nanoparticles with a particle size of 50-200 nm. Under stress ratio R = -1, frequency f = 80 Hz, and loads of 100 MPa, 95 MPa, and 90 MPa, the high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy exhibits room temperature fatigue cycle counts of ≥100994, 698212, and 3117614, respectively, fatigue limit ≥86 MPa, tensile strength ≥332 MPa, and elongation ≥8.5%.

[0013] Furthermore, the Ti powder in step (1) has a particle size of 10-15 micrometers, and the B4C powder has a particle size of 13-18 micrometers.

[0014] Furthermore, the particle size of the Al powder described in step (2) is 50-80 micrometers.

[0015] Further, the mass ratio of the aluminum-coated mixed powder material to the magnesium alloy in step (4) is 0.1-0.3 wt.%:1. Detailed Implementation

[0016] 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.

[0017] Example 1

[0018] The preparation method of aluminum-coated mixed powder material includes the following steps:

[0019] (1) At room temperature, Ti powder and B4C powder are mixed at a molar ratio of 3:1 and then mixed evenly in a ball mill at a speed of 50 rpm for 6 hours to obtain mixed powder 1: the particle size of the Ti powder is 9-14 micrometers and the particle size of the B4C powder is 15-17 micrometers.

[0020] (2) Al powder and mixed powder 1 obtained in step (1) are mixed in a ball mill at a speed of 40 rpm for 12 hours at molar ratios of 3:7, 5:5 and 8:2 respectively to obtain mixed powder 2, mixed powder 3 and mixed powder 4.

[0021] The particle size of the Al powder is 50 micrometers;

[0022] (3) The mixed powder 2, mixed powder 3 and mixed powder 4 obtained in step (2) are placed in the pure aluminum strip in order of mass ratio 1:1:8, and sealed by packaging machine and laser welding to finally prepare aluminum-coated mixed powder material.

[0023] Example 2

[0024] A high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 1 is prepared by the following steps:

[0025] Magnesium alloy was heated to 700°C and held for 1 hour under the protection of a CO2:SF6 mixed gas with a volume ratio of 9:1 to obtain magnesium alloy melt 1. Then, aluminum-coated mixed powder material obtained in Example 1 was added, mechanically stirred for 2 minutes, and ultrasonically stirred for 9 minutes at 780°C and 20.40MHz. After holding at 720°C for 5 minutes, slag removal, casting, cooling, solution treatment and aging treatment were performed to obtain high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 1.

[0026] The mass ratio of the aluminum-coated mixed powder material to the magnesium alloy is 0.3%:1;

[0027] The magnesium alloy composition, by mass percentage, is: Al: 9.43%; Mn: 0.18%; Zn: 0.76%; balance Mg;

[0028] The solution treatment involved holding the solution at 405°C for 7 hours under argon protection, followed by water quenching.

[0029] The aforementioned aging treatment involves maintaining the temperature at 190℃ for 10 hours.

[0030] The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 1 contains uniformly distributed nanoparticles with a particle size of 50-200 nm.

[0031] The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 1 prepared in Example 2 has the following room temperature fatigue cycle counts at stress ratio R = -1, frequency f = 80 Hz, and loads of 100 MPa, 95 MPa, and 90 MPa: 100,994, 698,212, and 3,117,614, respectively. The fatigue limit is 86 MPa, the tensile strength is 332 MPa, and the elongation is 8.5%.

[0032] Compared with the magnesium alloy treated according to the method of Example 2, the fatigue cycle count of the high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 1 of the present invention increased by 87,309, 677,358 and 3,076,545 cycles at 100 MPa, 95 MPa and 90 MPa, respectively. The tensile strength and elongation increased by 39.5% and 110.3%, respectively. Moreover, while improving the service performance, the present invention also simultaneously improved the strength and plasticity of the material. That is, the magnesium alloy 1 obtained in Example 2 of the present invention has high strength, high plasticity and toughness, and is suitable for industrial production.

[0033] Example 3

[0034] High-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 2, its preparation method includes the following steps:

[0035] Under the protection of a CO2:SF6 mixed gas with a volume ratio of 8:2, the magnesium alloy was heated to 680°C and held for 1.5 hours to obtain magnesium alloy melt 2. Then, the aluminum-coated mixed powder material obtained in Example 1 was added, and the mixture was mechanically stirred for 1 minute. The melt was then ultrasonically stirred at 750°C and 20.20MHz for 3 minutes, and then held at 700°C for 3 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 2 was obtained. The mass ratio of the aluminum-coated mixed powder material to the magnesium alloy was 0.1%:1.

[0036] The magnesium alloy composition, by mass percentage, is: Al: 8.52%; Mn: 0.40%; Zn: 0.45%; balance Mg;

[0037] The solution treatment described above involves holding at 410℃ for 7 hours under argon protection, followed by water quenching.

[0038] The aforementioned aging treatment involves maintaining the temperature at 195℃ for 10 hours.

[0039] The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 2 contains uniformly distributed nanoparticles with a particle size of 50-200 nm.

[0040] Compared with the magnesium alloy treated according to the method of Example 2, the fatigue performance, tensile strength and elongation of the high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 2 of the present invention are improved. That is, the magnesium alloy 2 obtained in Example 3 of the present invention has high strength, high plasticity and toughness, and is suitable for industrial production.

[0041] Comparative Example

[0042] In their 2012 article "Study on High-Cycle Fatigue Behavior of Gravity Casting Mg-3Nd-0.2Zn-Zr Magnesium Alloy," published in Volume 41, Issue 9 of Rare Metals Materials and Engineering, Li Zhifeng et al. utilized rare earth Nd to regulate the composition of magnesium alloys, thereby improving their fatigue resistance. The magnesium alloy described in Comparative Example 2 underwent casting, solution treatment, and aging. The prepared magnesium alloy, under a stress ratio R of -1, a frequency f of 60 Hz, and applied loads of 100 MPa, 95 MPa, and 90 MPa, achieved room temperature fatigue cycles of 46429, 66901, and 91736, respectively, with a fatigue limit of 76 MPa, tensile strength of 290 MPa, and elongation of 8.0%.

[0043] The magnesium alloy composition, by mass percentage, is: Zr: 0.46%; Nd: 2.87%; Zn: 0.19%; balance Mg;

[0044] The solution treatment involved holding the solution at 540°C for 10 hours under argon protection, followed by water quenching.

[0045] The aging process involves maintaining the temperature at 200℃ for 14 hours.

[0046] Table 1 Comparison of magnesium alloy composition and cost in the examples and comparative examples.

[0047]

[0048] The magnesium alloy used in this invention has the following composition: Al: 8.52-9.43%; Mn: 0.18-0.40%; Zn: 0.45-0.76%; balance Mg. The magnesium alloy used in the comparative example has the following composition: Zr: 0.46%; Nd: 2.87%; Zn: 0.19%; balance Mg. Compared to the comparative example, this invention does not require the addition of Zr and the rare earth element Nd. The rare earth element Nd is expensive, costing 645 yuan per kilogram, while Zr costs 190 yuan per kilogram. The price of Al and Mn used in this invention is equivalent to 10.2% of Zr and 3.1% of Nd per kilogram. The highest magnesium alloy cost of this invention is 145.3 yuan / kg, equivalent to 11.5% of the cost of the magnesium alloy used in the comparative example, which is significantly lower than the cost of the magnesium alloy used in the comparative example, as shown in Table 1. Furthermore, the solution and aging temperatures and times used in the comparative example were 540℃×10h and 200℃×14h, respectively, while the highest solution and aging temperatures and times used in this invention were 405℃×7h and 190℃×10h, respectively. The solution and aging temperatures and times used in this invention are all lower than those in the comparative example, which reduces costs while improving utilization efficiency and facilitates industrial application.

[0049] The magnesium alloy 1 obtained in Example 2 exhibited room temperature fatigue cycle counts of ≥100994, 698212, and 3117614 at stress ratio R = -1, frequency f = 80 Hz, and loads of 100 MPa, 95 MPa, and 90 MPa, respectively. Its fatigue limit was ≥86 MPa, tensile strength ≥332 MPa, and elongation ≥8.5%. Compared to the magnesium alloy treated according to the method in Example 2, the fatigue cycle counts of the high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 1 of this invention were increased by 873 at 100 MPa, 95 MPa, and 90 MPa, respectively. The fatigue limit increased from 75 MPa to 86 MPa after 9, 677,358, and 3,076,545 cycles, an increase of 14.67%, with tensile strength and elongation increasing by 39.5% and 110.3%, respectively. Compared with the magnesium alloy in the control example without nanoparticles, magnesium alloy 1 showed an increase of 54,565, 631,311, and 3,025,878 cycles at stress amplitudes of 100, 95, and 90 MPa, respectively, with the fatigue limit increasing from 76 MPa to 86 MPa, an increase of 13.16%, with tensile strength and elongation increasing by 14.48% and 6.25%, respectively. This indicates that the high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy 1 prepared according to the method provided in this paper not only improves service performance but also simultaneously enhances strength and ductility, achieving a simultaneous improvement in all three properties.

[0050] In summary, under the same cyclic load, the fatigue specimens of this invention exhibit a higher number of cycles than the comparative example, and both tensile strength and elongation are superior. This results in a high-performance magnesium alloy with superior fatigue resistance, strength, and ductility. This significant performance improvement means a substantial increase in the service life of the magnesium alloy under normal operating conditions, facilitating industrial application. Furthermore, the high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy prepared in this invention not only improves service performance but also simultaneously and significantly enhances the material's strength and ductility, demonstrating that this invention achieves superior results compared to existing technologies. Moreover, the nanoparticle content added in this invention is controlled at ≤0.5 wt.%, and the process parameters and component ratios used are different from those in the comparative example, resulting in different alloy properties. This indicates that this invention simplifies the process, reduces costs, and minimizes the amount of raw materials added, ultimately achieving a simultaneous improvement in fatigue resistance, strength, and ductility, making it suitable for industrial production. The superior performance of this invention is not determined by a single ratio or process parameter, but rather by the combined effect of the interaction of components, the ratio, and the process parameters. This superior performance and industrial production are only achievable within the scope of the claims of this invention. This invention has achieved significantly improved technical results, providing new ideas and development directions for the manufacturing and application of magnesium alloys in the industry.

Claims

1. A high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy, characterized in that: Its preparation method includes the following steps: (1) At room temperature, Ti: 60-80% and B4C: 20-40% were put into a ball mill with a speed of 45-55 rpm and mixed evenly for 4-6 hours to obtain mixed powder 1. The particle size range of Ti powder is 5-20 micrometers and the particle size range of B4C powder is 8-25 micrometers. (2) Al powder and mixed powder 1 obtained in step (1) are mixed in three mass percentages: mixed powder 1: Al: 65-75%: 25-35%, mixed powder 1: Al: 45-55%: 45-55%, mixed powder 1: Al: 15-25%: 75-85%, respectively. After mixing for 10-12 hours in a ball mill with a speed of 35-45 rpm, three mixed powders with high, medium and low contents are obtained, which are defined as mixed powder 2, mixed powder 3 and mixed powder 4, respectively. The particle size range of Al powder is 30-100 micrometers. (3) The mixed powder 2, mixed powder 3 and mixed powder 4 obtained in step (2) are placed in the pure aluminum strip in order of mass ratio 5-10:5-10:80-90; the aluminum-coated mixed powder material is finally prepared by using a packaging machine and laser welding to seal the powder. (4) Under the protection of a CO2:SF6 mixed gas with a volume ratio of 4-9:1, the magnesium alloy is heated to 680-700℃ and held for 60-90 minutes to obtain a magnesium alloy melt. Then, the aluminum-coated mixed powder material obtained in step (3) is added, and then mechanically stirred for 1-2 minutes. Ultrasonic stirring is performed at 750-780℃ and 20.20-20.40MHz for 3-9 minutes. Then, it is held at 700-720℃ for 3-5 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy is obtained. The mass ratio of the aluminum-coated mixed powder material to the magnesium alloy is 0.05-0.5wt.%:

1. The magnesium alloy composition, by mass percentage, is: Al: 8.52-9.43%; Mn: 0.18-0.40%; Zn: 0.45-0.76%; balance Mg. The solution treatment involves holding the solution at 400℃-420℃ for 7 hours under argon protection, followed by water quenching. The aforementioned aging treatment involves maintaining a temperature of 180-220℃ for 10 hours. The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy contains uniformly distributed nanoparticles with a particle size of 50-200 nm. Under stress ratio R = -1, frequency f = 80 Hz, and loads of 100 MPa, 95 MPa, and 90 MPa, the high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy exhibits room temperature fatigue cycle counts of ≥100994, 698212, and 3117614, respectively, fatigue limit ≥86 MPa, tensile strength ≥332 MPa, and elongation ≥8.5%.

2. The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy according to claim 1, characterized in that: The Ti powder in step (1) has a particle size of 10-15 micrometers, and the B4C powder has a particle size of 13-18 micrometers.

3. The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy according to claim 1, characterized in that, The particle size of the Al powder mentioned in step (2) is 50-80 micrometers.

4. The high-performance, fatigue-resistant nanoparticle-reinforced magnesium alloy according to claim 1, characterized in that, The mass ratio of the aluminum-coated mixed powder material to the magnesium alloy in step (4) is 0.1-0.3 wt.%:1.

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