High-strength plasticity nano-particle reinforced Mg-Al-Ca-RE alloy and preparation method

Abstract

The application provides a high-strength and high-plasticity nano-particle reinforced Mg-Al-Ca-RE alloy and a preparation method thereof, and the preparation method comprises the following steps: uniformly mixing titanium niobium aluminum alloy powder, C powder and BN powder to obtain powder 1; rolling the powder 1 with a stainless steel belt, drawing to obtain a composite wire A, heating and crushing to obtain a mixture 2, and then performing magnetic separation and impurity removal to obtain a mixture 3; uniformly mixing the mixture 3, aluminum calcium particles and lanthanum cerium mixed powder to obtain a mixture 4, coating the mixture 4 with a pure aluminum strip, and drawing to obtain a wire B; adding the wire B into a pure magnesium melt, and performing mechanical stirring and ultrasonic stirring under a protective atmosphere, and then performing slagging, pouring, cooling, solid solution and aging treatment to obtain the high-strength and high-plasticity nano-particle reinforced Mg-Al-Ca-RE alloy, wherein the tensile strength of the alloy is greater than or equal to 170 MPa, the ignition point is greater than or equal to 956 DEG C, the elongation is greater than or equal to 7.0%, the strength and plasticity are higher than those of the magnesium alloy obtained by the prior art, the raw material addition is reduced, the process is simplified, the cost is reduced, and the alloy is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of high-performance magnesium alloys, specifically to a high-strength, high-plasticity nanoparticle-reinforced Mg-Al-Ca-RE alloy and its preparation method. Background Technology

[0002] Magnesium alloys possess low density, high specific strength, and good biocompatibility, making them valuable for applications in automotive lightweighting, aerospace structural components, and biomedical materials. With increasing engineering demands, related components require higher strength, plasticity, and service safety. However, traditional magnesium alloy ingots exhibit low room temperature plasticity. When strength is improved through solid solution strengthening or precipitation strengthening, plasticity often decreases further, making it difficult to achieve synergistic optimization of strength and plasticity. In existing technologies, the tensile strength of magnesium alloy ingots is typically 120-150 MPa, and the elongation is generally 3%-5%, sometimes even lower, failing to meet the application requirements of high-performance structural materials. To address these issues, large plastic deformation processes such as hot extrusion or multi-directional forging are commonly used to improve overall mechanical properties. However, these processes are complex, requiring strict control of temperature and deformation rate, and the extrusion speed is slow, hindering industrial production. Furthermore, the ingots themselves have limited plasticity, making them prone to cracking, edge cracking, and local instability during deformation, resulting in low yield. Multiple deformation processes and subsequent heat treatments further increase the preparation cycle and energy consumption costs, hindering large-scale production. Furthermore, the ignition point of cast magnesium alloys is ≤600℃, posing certain safety risks during smelting and processing, and placing higher demands on process stability. In summary, existing technologies can only address one or two of the issues related to strength, plasticity, and flame retardancy, making it difficult to simultaneously solve all three. Therefore, how to reduce costs, simplify processes, introduce new strengthening mechanisms, and optimize particle dispersion and microstructure control to avoid cracking, thereby achieving a synergistic improvement in the strength, plasticity, and flame retardancy of cast magnesium alloys, is a pressing technical challenge. Summary of the Invention

[0003] To address the aforementioned technical challenges, this invention provides a high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy, the preparation method of which includes the following steps: (1) Titanium-niobium-aluminum alloy powder, C powder and BN powder were ball-milled in a mass ratio of 82-93:4-10:3-8 to obtain powder mixture 1; The ball milling process is as follows: rotation speed: 20-50 r / min; time: 11-21 hours; The particle size range of the titanium-niobium-aluminum alloy powder is 13-95 micrometers, the particle size range of the C powder is 11-35 micrometers, and the particle size range of the BN powder is 8-70 micrometers. (2) The powder mixture 1 obtained in step (1) is packaged with stainless steel strip, rolled and drawn in multiple passes to obtain composite wire A. Composite wire A is kept at 900-1300℃ for 60-120s and crushed to obtain mixture 2. Then, mixture 2 is subjected to two magnetic separations to remove impurities to obtain mixture 3. The mass ratio of the powder mixture 1 to the stainless steel strip is 45-60:40-55; The multi-pass drawing process consists of 6-15 passes, with a drawing speed of 0.5-1 mm / s per pass and a surface area reduction rate of 12-41% per pass. The stainless steel is austenitic stainless steel, and its composition by mass percentage is: C≤0.08%, Si≤1.0%, Mn≤2.0%, Cr 18.0-20.0%, Ni 8.0-10.5%, P≤0.045%, S≤0.03%, with the remainder being Fe and unavoidable impurities ≤0.05%. The two magnetic separation processes are as follows: the magnetic field strength for the first separation is 0.2-0.4T, and the separation time is 2-5 minutes; the magnetic field strength for the second separation is 0.4-0.8T, and the separation time is 3-8 minutes. (3) Mix the mixture 3 obtained in step (2), aluminum-calcium particles and lanthanum-cerium mixed rare earth powder in a mass ratio of 80-88:8-15:2-5 to obtain mixture 4. Then, the mixture 4 is coated with pure aluminum strip and then drawn through multiple passes to obtain wire B. By mass percentage: the main components of aluminum-calcium granules are: aluminum: 70.6-80.7%, calcium: 19.3-29.4%; The multi-pass drawing process consists of 8-16 passes, with a drawing speed of 0.6-0.9 mm / s per pass and a reduction in surface area of ​​16-42% per pass. The mass ratio of the mixture 4 to the pure aluminum strip is 35-50:50-65; (4) Under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 8-9:1, pure magnesium is heated to 680-700℃ and held for 60-90 minutes to obtain pure magnesium melt. Then, wire B obtained in step (3) is added, and after mechanical stirring and ultrasonic stirring, it is held at 700-730℃ for 3-5 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy is obtained. The high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy contains nanoparticles. The mass ratio of wire B to pure magnesium is 0.2-0.5wt.%:1. The mechanical stirring is described as follows: stirring speed 65-125 r / min, stirring time 1-5 min; The ultrasonic stirring is characterized by an ultrasonic power of 1.2-2.8kW, an ultrasonic frequency of 20.40-22.15kHz, and a stirring time of 4-10min. The composition of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy, by mass percentage, is: Al: 5.5-6.5%, Ca: 1.0-2.0%, La: 0.1-0.3%, Ce: 0.1-0.3%, nanoparticles: 0.02-0.4 wt.%, with the balance being Mg and unavoidable impurities ≤0.05%. The nanoparticles have a particle size of 30-250 nm and are composed of: TiCN+TiB2+NbCN+NbB2. The solution treatment involves holding the solution at 430℃-480℃ for 16-22 hours. The aforementioned aging treatment involves maintaining the temperature at 180℃-220℃ for 14-20 hours. The high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy has a tensile strength of ≥170MPa, an elongation of ≥7%, an ignition point of ≥956℃, and a grain size of ≤116.6μm, which are superior to magnesium alloys obtained by existing technologies.

[0004] Further, the ball milling process in step (1) is as follows: rotation speed: 21-48 r / min; time: 12-20 hours; the particle size range of the titanium-niobium-aluminum alloy powder is 15-90 micrometers, the particle size of C powder is 13-25 micrometers, and the particle size of BN powder is 10-60 micrometers.

[0005] Further, the multi-pass drawing process in step (2) consists of 7-14 passes, with a drawing speed of 0.6-0.9 mm / s and a surface reduction rate of 13-39% per pass; the two magnetic separations are as follows: the magnetic field strength of the first magnetic separation is 0.25-0.38 T, and the magnetic separation time is 2.5-4.5 min; the magnetic field strength of the second magnetic separation is 0.45-0.78 T, and the magnetic separation time is 3.5-7.5 min.

[0006] Further, in step (4), the mass ratio of wire B to pure magnesium is 0.25-0.4wt.%:1; the mechanical stirring is carried out at a stirring speed of 70-120r / min for 2-4min; the ultrasonic stirring is carried out at an ultrasonic power of 1.4-2.2kW, an ultrasonic frequency of 20.50-22.10kHz for 5-8min; the composition of the high-strength plastic nanoparticle-reinforced Mg-Al-Ca-RE alloy is as follows: Al: 5.6-6.4%, Ca: 1.1-1.9%, La: 0.11-0.29%, Ce: 0.12-0.28%, nanoparticles: 0.04-0.35wt.%, with the balance being Mg and unavoidable impurities ≤0.05%; the solution treatment is carried out at 450℃-470℃ for 18-20h; the aging treatment is carried out at 190℃-200℃ for 15-19h.

[0007] Furthermore, the high-strength plastic nanoparticle-reinforced Mg-Al-Ca-RE alloy described in step (4) has a tensile strength of 175-210 MPa, an elongation of 8-10%, an ignition point of 960-1000℃, and a grain size of 95-115 μm.

[0008] Compared with existing technologies, the advantages of this invention lie in the optimization and simplification of the preparation process and the simultaneous improvement of strong plasticity and ignition point. Compared to existing methods that rely on high-temperature slow extrusion or forging and other large plastic deformation processes to achieve microstructure refinement and performance improvement, this invention controls the nanoparticle content to below 0.4 wt.%, and does not use high-cost metal elements such as rare earth elements in the nanoparticles. By constructing a composite intermediate carrier, nanoparticles and alloying elements are introduced into the magnesium alloy melt in a pre-dispersed form, achieving uniform distribution and microstructure control of the reinforcing phase during the ingot casting stage, thereby avoiding reliance on complex subsequent deformation processes. This method integrates powder preparation, particle dispersion, and microstructure control processes into the melt processing stage, and combines the synergistic control of component interactions, proportions, processes, and process parameters to improve the uniform dispersion and interfacial bonding quality of nanoparticles in the melt, enabling the material to obtain superior refined microstructure, high mechanical properties, and high flame retardancy under as-cast conditions. In terms of microstructure, the grain size of existing cast magnesium alloys is typically 150-300 μm, while the grain size of the alloy obtained by this invention can be refined to ≤116.6 μm, significantly improving microstructure uniformity. Regarding mechanical properties, the material's room temperature tensile strength can reach ≥170 MPa, an increase of 20%-40% compared to traditional cast alloys; its elongation can reach ≥7%, an improvement of 40%-80% compared to existing technologies; and its ignition point can reach ≥956℃, an improvement of 30%-40% compared to existing technologies. This achieves a synergistic improvement in strength, plasticity, and high flame retardancy. Compared to traditional processes, this invention does not use large amounts of high-cost rare earth elements, avoids complex heat treatment processes involving large deformations, simplifies the process flow, reduces requirements on equipment and process windows, avoids cracking, and employs a slow extrusion process, which is beneficial for improving the stability and yield of industrial production, achieving a simultaneous improvement in the high strength, high plasticity, and high flame retardancy of magnesium alloy materials. Attached Figure Description

[0009] Figure 1 This is a SEM microstructure of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 1 in Example 1 of the present invention.

[0010] Figure 2 This is a stress-strain tensile curve of the high-strength, plastic nanoparticle-reinforced Mg-Al-Ca-RE alloy 1 in Example 1 of the present invention.

[0011] Figure 3 This is a SEM image of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 2 in Example 2 of the present invention.

[0012] Figure 4 This is a stress-strain tensile curve of the high-strength, plastic nanoparticle-reinforced Mg-Al-Ca-RE alloy 2 in Example 2 of the present invention.

[0013] Figure 5 This is a SEM image of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 3 in Example 3 of the present invention.

[0014] Figure 6 This is a stress-strain tensile curve of the high-strength, plastic nanoparticle-reinforced Mg-Al-Ca-RE alloy in Example 3 of the present invention. Detailed Implementation

[0015] 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. Example 1

[0016] The high-strength, high-plasticity nanoparticle-reinforced Mg-Al-Ca-RE alloy 1 is prepared by the following steps: (1) Titanium niobium aluminum alloy powder, C powder and BN powder were ball-milled in a mass ratio of 84:8:8 to obtain powder mixture 1; The ball milling process was performed with the following parameters: rotation speed: 25 r / min; time: 12 hours. The particle size range of the titanium-niobium-aluminum alloy powder is 20-80 micrometers, the particle size range of the C powder is 15-30 micrometers, and the particle size range of the BN powder is 25-65 micrometers. (2) The powder mixture 1 obtained in step (1) is packaged with stainless steel strip, rolled and drawn in multiple passes to obtain composite wire A. Composite wire A is kept at 950℃ for 90s and crushed to obtain mixture 2. Then, mixture 2 is subjected to two magnetic separations to remove impurities to obtain mixture 3. The mass ratio of the powder mixture 1 to the stainless steel strip is 47:53; The multi-pass drawing process consists of 8 passes, with a drawing speed of 0.7 mm / s per pass and a surface area reduction rate of 18% per pass. The stainless steel is austenitic stainless steel, and its composition by mass percentage is: C: 0.08%, Si: 1.0%, Mn: 2.0%, Cr: 18.6%, Ni: 8.8%, P: 0.038%, S: 0.02%, with the remainder being Fe and unavoidable impurities ≤0.05%. The two magnetic separation processes are as follows: the first magnetic separation has a magnetic field strength of 0.3T and a separation time of 3 minutes; the second magnetic separation has a magnetic field strength of 0.6T and a separation time of 4 minutes. (3) Mix the mixture 3 obtained in step (2), aluminum-calcium particles and lanthanum-cerium mixed rare earth powder in a mass ratio of 86:11:3 to obtain mixture 4. Then, the mixture 4 is coated with pure aluminum strip and then drawn through multiple passes to obtain wire B. By mass percentage: the main components of aluminum-calcium granules are: aluminum: 72.6%, calcium: 27.4%; The multi-pass drawing process consists of 9 passes, with a drawing speed of 0.7 mm / s per pass and a surface area reduction rate of 21% per pass. The mass ratio of the mixture 4 to the pure aluminum strip is 39:61; (4) Under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 9:1, pure magnesium is heated to 690℃ and held for 70 minutes to obtain pure magnesium melt. Then, wire B obtained in step (3) is added. After mechanical stirring and ultrasonic stirring, it is held at 720℃ for 3 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy is obtained. The high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy contains nanoparticles. The mass ratio of wire B to pure magnesium is 0.3wt.%:1. The mechanical stirring is described as follows: stirring speed 75 r / min, stirring time 2 min; The ultrasonic stirring was performed with an ultrasonic power of 1.8 kW, an ultrasonic frequency of 21.12 kHz, and a stirring time of 7 min. The composition of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy, by mass percentage, is: Al: 6.4%, Ca: 1.3%, La: 0.2%, Ce: 0.25%, nanoparticles: 0.06 wt.%, with the balance being Mg and unavoidable impurities ≤0.05%. The solution treatment involves holding the solution at 435°C for 16 hours. The aforementioned aging treatment involves maintaining the temperature at 185℃ for 15 hours. Scanning electron microscopy microstructure of high-strength and ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 1 is shown below. Figure 1 As shown, its average grain size is 95.8 μm, and alloy 1 contains uniformly distributed nanoparticles with an average particle size of 95 nm. Figure 2 The results show that the tensile strength of alloy 1 at room temperature is 202.7 MPa and the elongation is 9.0%. Compared with the magnesium alloy without nanoparticles in step (4), the high-strength and ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 1 obtained in the example has 34.3% and 95.6% higher tensile strength and ductility, respectively, and a grain refinement degree of 30%. At the same time, the ignition point is also improved to 983℃. Example 2

[0017] The high-strength, high-plasticity nanoparticle-reinforced Mg-Al-Ca-RE alloy 2 is prepared by the following steps: (1) Titanium niobium aluminum alloy powder, C powder and BN powder were ball-milled in a mass ratio of 86:8:6 to obtain powder mixture 1; The ball milling process was performed with the following parameters: rotation speed: 30 r / min; time: 14 hours. The particle size range of the titanium-niobium-aluminum alloy powder is 20-85 micrometers, the particle size range of the C powder is 26-35 micrometers, and the particle size range of the BN powder is 32-65 micrometers. (2) The powder mixture 1 obtained in step (1) is packaged with stainless steel strip, rolled and drawn in multiple passes to obtain composite wire A. Composite wire A is kept at 1000℃ for 100s and crushed to obtain mixture 2. Then, mixture 2 is subjected to two magnetic separations to remove impurities to obtain mixture 3. The mass ratio of the powder mixture 1 to the stainless steel strip is 48:52; The multi-pass drawing process consists of 10 passes, with a drawing speed of 0.6 mm / s and a surface area reduction of 24% per pass. The stainless steel is austenitic stainless steel, and its composition by mass percentage is: C: 0.06%, Si: 1.0%, Mn: 1.6%, Cr: 18.6%, Ni: 8.7%, P: 0.035%, S: 0.02%, with the remainder being Fe and unavoidable impurities ≤0.05%. The two magnetic separation processes are as follows: the first magnetic separation has a magnetic field strength of 0.35T and a separation time of 3.5min; the second magnetic separation has a magnetic field strength of 0.65T and a separation time of 5min. (3) Mix the mixture 3 obtained in step (2), aluminum-calcium particles and lanthanum-cerium mixed rare earth powder in a mass ratio of 84:12:4 to obtain mixture 4. Then, the mixture 4 is coated with pure aluminum strip and then drawn through multiple passes to obtain wire B. By mass percentage: the main components of aluminum-calcium granules are: aluminum: 76.2%, calcium: 23.8%; The multi-pass drawing process consists of 11 passes, with a drawing speed of 0.6 mm / s and a surface area reduction rate of 31% per pass. The mass ratio of the mixture 4 to the pure aluminum strip is 40:60; (4) Under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 9:1, pure magnesium is heated to 690℃ and held for 75 minutes to obtain pure magnesium melt. Then, wire B obtained in step (3) is added, and after mechanical stirring and ultrasonic stirring, it is held at 720℃ for 4 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy is obtained. The high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy contains nanoparticles. The mass ratio of wire B to pure magnesium is 0.35wt.%:1. The mechanical stirring is described as follows: stirring speed 85 r / min, stirring time 3 min; The ultrasonic stirring was performed with an ultrasonic power of 1.6 kW, an ultrasonic frequency of 21.32 kHz, and a stirring time of 5 min. The composition of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy, by mass percentage, is: Al: 5.9%, Ca: 1.4%, La: 0.25%, Ce: 0.19%, nanoparticles: 0.25 wt.%, with the balance being Mg and unavoidable impurities ≤0.05%. The solution treatment involves holding the solution at 445℃ for 18 hours. The aforementioned aging treatment involves maintaining the temperature at 195℃ for 19 hours. Scanning electron microscopy microstructure of high-strength and ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 2 is shown below. Figure 3 As shown, its average grain size is 116.6 μm, and alloy 2 contains uniformly distributed nanoparticles with an average particle size of 97 nm. Figure 4 The results show that the alloy 2 has a tensile strength of 170 MPa and an elongation of 7% at room temperature. Compared with the magnesium alloy without nanoparticles in step (4), the high-strength and ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 2 obtained in this example has 15.8% and 41.9% higher tensile strength and ductility, respectively, and a grain refinement of 14.8%. At the same time, the ignition point is also improved to 956°C. Example 3

[0018] The high-strength, high-plasticity nanoparticle-reinforced Mg-Al-Ca-RE alloy 3 is prepared by the following steps: (1) Titanium niobium aluminum alloy powder, C powder and BN powder were ball-milled in a mass ratio of 89:6:5 to obtain powder mixture 1; The ball milling process was performed with the following parameters: rotation speed: 35 r / min; time: 17 hours. The particle size range of the titanium-niobium-aluminum alloy powder is 36-85 micrometers, the particle size range of the C powder is 18-32 micrometers, and the particle size range of the BN powder is 26-43 micrometers. (2) The powder mixture 1 obtained in step (1) is packaged with stainless steel strip, rolled and drawn in multiple passes to obtain composite wire A. Composite wire A is kept at 1200℃ for 70s and crushed to obtain mixture 2. Then, mixture 2 is subjected to two magnetic separations to remove impurities to obtain mixture 3. The mass ratio of the powder mixture 1 to the stainless steel strip is 49:51; The multi-pass drawing process consists of 8 passes, with a drawing speed of 0.8 mm / s per pass and a surface area reduction of 35% per pass. The stainless steel is austenitic stainless steel, and its composition by mass percentage is: C: 0.07%, Si: 0.9%, Mn: 1.5%, Cr: 18.6%, Ni: 9.5%, P: 0.042%, S: 0.03%, with the remainder being Fe and unavoidable impurities ≤0.05%. The two magnetic separation processes are as follows: the first magnetic separation has a magnetic field strength of 0.35T and a separation time of 4 minutes; the second magnetic separation has a magnetic field strength of 0.55T and a separation time of 6 minutes. (3) Mix the mixture 3 obtained in step (2), aluminum-calcium particles and lanthanum-cerium mixed rare earth powder in a mass ratio of 86:12:2 to obtain mixture 4. Then, the mixture 4 is coated with pure aluminum strip and then drawn through multiple passes to obtain wire B. By mass percentage: the main components of aluminum-calcium granules are: aluminum: 79.6%, calcium: 20.4%; The multi-pass drawing process consists of 9 passes, with a drawing speed of 0.7 mm / s per pass and a surface area reduction rate of 39% per pass. The mass ratio of the mixture 4 to the pure aluminum strip is 42:58; (4) Under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 9:1, pure magnesium is heated to 695℃ and held for 75 minutes to obtain pure magnesium melt. Then, wire B obtained in step (3) is added, and after mechanical stirring and ultrasonic stirring, it is held at 710℃ for 5 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy is obtained. The high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy contains nanoparticles. The mass ratio of wire B to pure magnesium is 0.45wt.%:1. The mechanical stirring is described as follows: stirring speed 105 r / min, stirring time 4 min; The ultrasonic stirring was performed with an ultrasonic power of 2.0 kW, an ultrasonic frequency of 22.10 kHz, and a stirring time of 6 min. The composition of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy, by mass percentage, is: Al: 6.1%, Ca: 1.5%, La: 0.3%, Ce: 0.15%, nanoparticles: 0.29 wt.%, with the balance being Mg and unavoidable impurities ≤0.05%. The solution treatment involves holding the solution at 460℃ for 17 hours. The aforementioned aging treatment involves maintaining the temperature at 205℃ for 20 hours. Scanning electron microscopy microstructure of high-strength and ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 3 is shown below. Figure 5 As shown, its average grain size is 98.4 μm, and alloy 3 contains uniformly distributed nanoparticles with an average particle size of 120 nm. Figure 6 The results show that the alloy 3 has a tensile strength of 205.4 MPa and an elongation of 8.6% at room temperature. Compared with the magnesium alloy without nanoparticles in step (4), the high-strength and ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy 3 obtained in the example has 36.1% and 86.9% higher tensile strength and ductility, respectively, and a grain refinement degree of 28.1%. At the same time, the ignition point is also improved to 988℃. Comparative Example 1

[0019] Feng (Feng Qiangqiang. Effects of the addition of rare earth elements Y and Nd on the microstructure and properties of Mg-Al-Ca alloys [D]. Xi'an University of Technology, 2020. DOI:10.27391 / d.cnki.gxagu.2020.000264.) prepared magnesium rare earth alloys by metal mold casting followed by solution treatment and aging. The alloy composition with the highest performance in the article was Mg-5Al-5Ca-1Y-1.5Nd, that is, by controlling the content of Y and Nd, the tensile strength and elongation at room temperature reached 162.3 MPa and 5%, respectively. The solution treatment involves maintaining the temperature at 420℃ for 24 hours. The aforementioned aging treatment involves maintaining the temperature at 200℃ for 15 hours. Comparing the comparative examples with Examples 1-3 reveals that the alloy element content of the present invention is ≤9 wt.%, while the comparative examples have an element content of 12.5 wt.%, which is higher than the total alloy content of the present invention. Furthermore, the comparative examples' magnesium alloy contains a large amount of rare earth elements, reaching ≥2.5 wt.%, while the present invention only contains ≤0.6 wt.%. Simultaneously, the comparative examples contain ≥1.5 wt.% heavy rare earth element Nd and ≥1 wt.%, with prices significantly higher than the light rare earth elements La (≤0.3 wt.%) and Ce (≤0.3 wt.%) added in the present invention. Moreover, the comparative examples contain ≥5 wt.%, far exceeding the ≤2 wt.% in the present invention. In summary, the present invention achieves significantly superior strength and ductility compared to the comparative examples at a much lower cost. Compared to the comparative examples, Example 1 shows a 24.9% increase in tensile strength and an 80% increase in elongation; Example 2 shows a 4.7% increase in tensile strength and a 40% increase in elongation; and Example 3 shows a 26.5% increase in tensile strength and a 72% increase in elongation. Therefore, the present invention has superior strength and plasticity. Compared with the comparative example, it not only reduces the cost and the amount of rare earth used, but also improves the strength and plasticity of the alloy. In addition, the comparative example did not disclose the ignition point of the magnesium alloy, while the alloy obtained by the present invention has an ignition point of ≥956℃.

[0020] Table 1 Comparison of grain size with tensile strength, elongation and ignition point in comparative examples and various embodiments.

[0021] In summary, compared with existing technologies, this invention reduces the total amount of alloy or rare earth added, significantly reducing raw material costs and simplifying the process. The resulting alloy exhibits higher strength and plasticity than existing technologies, meeting the demands of industrial production. It solves the technical problems of low strength or plasticity, difficulty in industrialization, and the inability to simultaneously improve strength and plasticity in existing technologies. Furthermore, while the comparative examples do not disclose the ignition point of magnesium alloys, this invention, while improving strength and plasticity, also achieves a significant increase in ignition point, solving the problem of simultaneously improving strength, plasticity, and ignition point in existing technologies. As seen in the various embodiments of this invention, the component ratios and process parameters differ in each embodiment, resulting in variations in the strength, plasticity, and ignition point of the final alloy. Therefore, the superior effects of this invention are not determined by a single component, ratio, process, or process parameter, but rather by the interaction between components, the synergistic regulation of the ratio, process, and process parameters. Moreover, the significantly improved technical effects can only be achieved within the scope of protection of the claims of this invention.

Claims

1. A high-strength, high-plasticity nanoparticle-reinforced Mg-Al-Ca-RE alloy, characterized in that: Its preparation method includes the following steps: (1) Titanium-niobium-aluminum alloy powder, C powder and BN powder were ball-milled in a mass ratio of 82-93:4-10:3-8 to obtain powder mixture 1; The ball milling process is performed at a rotation speed of 20-50 r / min. Time: 11-21 hours; The particle size range of the titanium-niobium-aluminum alloy powder is 13-95 micrometers, the particle size range of the C powder is 11-35 micrometers, and the particle size range of the BN powder is 8-70 micrometers. (2) The powder mixture 1 obtained in step (1) is packaged with stainless steel strip, rolled and drawn in multiple passes to obtain composite wire A. Composite wire A is kept at 900-1300℃ for 60-120s and crushed to obtain mixture 2. Then, mixture 2 is subjected to two magnetic separations to remove impurities to obtain mixture 3. The mass ratio of the powder mixture 1 to the stainless steel strip is 45-60:40-55; The multi-pass drawing process consists of 6-15 passes, with a drawing speed of 0.5-1 mm / s per pass and a surface area reduction rate of 12-41% per pass. The stainless steel is austenitic stainless steel, and its composition by mass percentage is: C≤0.08%, Si≤1.0%, Mn≤2.0%, Cr 18.0-20.0%, Ni 8.0-10.5%, P≤0.045%, S≤0.03%, with the remainder being Fe and unavoidable impurities ≤0.05%. The two magnetic separation processes are as follows: the magnetic field strength for the first separation is 0.2-0.4T, and the separation time is 2-5 minutes; the magnetic field strength for the second separation is 0.4-0.8T, and the separation time is 3-8 minutes. (3) Mix the mixture 3 obtained in step (2), aluminum-calcium particles and lanthanum-cerium mixed rare earth powder in a mass ratio of 80-88:8-15:2-5 to obtain mixture 4. Then, the mixture 4 is coated with pure aluminum strip and then drawn through multiple passes to obtain wire B. By mass percentage: the main components of aluminum-calcium granules are: aluminum: 70.6-80.7%, calcium: 19.3-29.4%; The multi-pass drawing process consists of 8-16 passes, with a drawing speed of 0.6-0.9 mm / s per pass and a reduction in surface area of ​​16-42% per pass. The mass ratio of the mixture 4 to the pure aluminum strip is 35-50:50-65; (4) Under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 8-9:1, pure magnesium is heated to 680-700℃ and held for 60-90 minutes to obtain pure magnesium melt. Then, wire B obtained in step (3) is added, and after mechanical stirring and ultrasonic stirring, it is held at 700-730℃ for 3-5 minutes. After slag removal, casting, cooling, solution treatment and aging treatment, a high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy is obtained. The high-strength plastic nanoparticle reinforced Mg-Al-Ca-RE alloy contains nanoparticles. The mass ratio of wire B to pure magnesium is 0.2-0.5wt.%:

1. The mechanical stirring is described as follows: stirring speed 65-125 r / min, stirring time 1-5 min; The ultrasonic stirring is characterized by an ultrasonic power of 1.2-2.8kW, an ultrasonic frequency of 20.40-22.15kHz, and a stirring time of 4-10min. The composition of the high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy, by mass percentage, is: Al: 5.5-6.5%, Ca: 1.0-2.0%, La: 0.1-0.3%, Ce: 0.1-0.3%, nanoparticles: 0.02-0.4 wt.%, with the balance being Mg and unavoidable impurities ≤0.05%. The nanoparticles have a particle size of 30-250 nm and are composed of: TiCN+TiB2+NbCN+NbB2. The solution treatment involves holding the solution at 430℃-480℃ for 16-22 hours. The aforementioned aging treatment involves maintaining the temperature at 180℃-220℃ for 14-20 hours. The high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy has a tensile strength of ≥170MPa, an elongation of ≥7%, an ignition point of ≥956℃, and a grain size of ≤116.6μm, which are superior to magnesium alloys obtained by existing technologies.

2. The high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy according to claim 1, characterized in that: The ball milling process described in step (1) is as follows: rotation speed: 21-48 r / min; Time: 12-20 hours; the particle size range of the titanium-niobium-aluminum alloy powder is 15-90 micrometers, the particle size of C powder is 13-25 micrometers, and the particle size of BN powder is 10-60 micrometers.

3. The high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy according to claim 1, characterized in that, The multi-pass drawing process in step (2) consists of 7-14 passes, with a drawing speed of 0.6-0.9 mm / s and a surface reduction rate of 13-39% per pass. The two magnetic separations are as follows: the magnetic field strength of the first magnetic separation is 0.25-0.38 T, and the magnetic separation time is 2.5-4.5 min; the magnetic field strength of the second magnetic separation is 0.45-0.78 T, and the magnetic separation time is 3.5-7.5 min.

4. The high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy according to claim 1, characterized in that, The mass ratio of wire B to pure magnesium in step (4) is 0.25-0.4wt.%:1; the mechanical stirring is carried out at a stirring speed of 70-120r / min for 2-4min; the ultrasonic stirring is carried out at an ultrasonic power of 1.4-2.2kW, an ultrasonic frequency of 20.50-22.10kHz for 5-8min; the composition of the high-strength plastic nanoparticle-reinforced Mg-Al-Ca-RE alloy is as follows: Al: 5.6-6.4%, Ca: 1.1-1.9%, La: 0.11-0.29%, Ce: 0.12-0.28%, nanoparticles: 0.04-0.35wt.%, with the balance being Mg and unavoidable impurities ≤0.05%; the solution treatment is carried out at 450℃-470℃ for 18-20h; the aging treatment is carried out at 190℃-200℃ for 15-19h.

5. The high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy according to claim 1, characterized in that, The high-strength, ductile nanoparticle-reinforced Mg-Al-Ca-RE alloy has a tensile strength of 175-210 MPa, an elongation of 8-10%, an ignition point of 960-1000℃, and a grain size of 95-115 μm.

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