A high-strength alloy material and a method for manufacturing the same

Abstract

The application belongs to the technical field of alloy, and particularly relates to a high-strength alloy material and a preparation method thereof. The alloy material is composed of the following components in percentage by mass: Al: 6-7%, Ca: 4.5-5.5%, Mn: 0.3-0.6%, Sr: 0.8-1.3%, rare earth elements 0.8-1.3%, the rare earth elements are composed of Gd and Nd, and the balance is Mg and inevitable impurities. A small amount of Mn and Sr provides fine-grain strengthening and a good plasticity basis for the alloy, and Gd / Nd provides strong precipitation strengthening effect through solid solution strengthening and precipitation of a large number of nanophases in the grain and grain boundary. At the same time, the composite addition of them will form a multielement, multilayer and high-density composite oxide film composed of multiple oxides on the surface of the alloy, which can serve as an extremely effective barrier to raise the ignition point of the alloy to a very high level and achieve excellent flame retardant effect.

Description

Technical Field

[0001] This invention belongs to the field of alloy technology, specifically relating to a high-strength alloy material and its preparation method. Background Technology

[0002] Lightweighting of materials is an important direction in the development of new materials. Magnesium alloys, as green and environmentally friendly metallic structural materials, possess advantages such as high specific strength, specific stiffness, good damping, and thermal conductivity, and have gradually become a substitute for structural materials such as steel, iron, aluminum, and plastics, attracting widespread attention from the materials science community worldwide. For over a century, the materials science community has been dedicated to developing new industrial magnesium alloys through alloying and heat treatment technologies, achieving significant progress. By the 1970s, several relatively mature magnesium alloy series, including Mg-Al, Mg-Al-Zn, Mg-Zn-Zr, and Mg-RE-Zr, had been formed, possessing valuable applications and broad prospects in aerospace, automotive, and aviation industries. The rapid development of the current communications industry places extremely high demands on the thin-walled and lightweight nature of electronic devices, and the low density and high strength of magnesium alloys have provided a favorable opportunity for their development. However, the widespread attention and application of magnesium alloys has also encountered bottlenecks. Magnesium is chemically reactive, and magnesium alloys are extremely prone to oxidation and combustion during preparation and processing, making magnesium alloy production and preparation quite difficult. At present, the production technology of magnesium alloys is not mature and perfect, especially the forming technology of magnesium alloys, which still has a lot of room for development. The poor heat resistance of magnesium alloys has also become an obstacle to their widespread application.

[0003] Pure magnesium has low hardness and strength, which limits its widespread application in engineering. However, by adding some metallic elements such as aluminum, zinc, alkaline earth elements, and rare earth elements to magnesium, lightweight and high-performance magnesium alloys can be obtained through alloying, which can then be widely used in engineering processes, aerospace and other fields.

[0004] The basic principle of magnesium alloying is the interaction between the added alloying elements and the magnesium matrix or other alloying elements, resulting in solid solution strengthening and second-phase strengthening, thereby improving the room temperature mechanical properties, corrosion resistance, and high-temperature properties of magnesium alloys. Magnesium alloys are widely used in many industries due to their low density, high specific strength, and good electromagnetic shielding properties. Previously, magnesium was mainly used as an alloying element added to aluminum alloys. Currently, the successful application of die-cast magnesium alloys has brought more attention to magnesium alloys, making them a hot topic for research and development. The electronics industry is one of the fastest-growing industries in the world today and a new emerging field for magnesium alloy applications. The demand for magnesium alloys in the electronics industry mainly stems from their advantages such as lightweight, high specific stiffness, and good thin-wall casting performance; in addition, their good thermal conductivity, damping properties, electromagnetic shielding characteristics, and ease of recycling are also important reasons why the electronics industry favors magnesium alloys.

[0005] Defense and aerospace products have extremely high requirements for lightweight materials and their performance, and magnesium alloys are widely used due to their light weight. Alloying to improve the properties of magnesium alloys has been widely applied in aerospace, for example, in helicopter horizontal rotor accessories, aircraft gearbox covers, and landing wheels. With the continuous improvement of magnesium and its alloy manufacturing technology, the application of magnesium alloys in armor structural components, tanks, missile tail fins, and casings will greatly increase. Furthermore, magnesium alloys are widely used in radio communications due to their good anti-interference properties for electrical signals. Among these, Mg-Al-Ca magnesium alloys are the most widely used. However, existing Mg-Al-Ca magnesium alloys have relatively low mechanical properties and poor flame retardancy, limiting their further application. Summary of the Invention

[0006] To address the problems existing in the aforementioned Mg-Al-Ca magnesium alloys, the purpose of this invention is to provide a high-strength alloy material and its preparation method. This alloy material, while improving the mechanical properties of magnesium alloys, further enhances their flame-retardant properties, showing broad application prospects.

[0007] This objective of the present invention is achieved through the following technical solution:

[0008] A high-strength alloy material is composed of the following components by mass percentage:

[0009] Al: 6-7%, Ca: 4.5-5.5%, Mn: 0.3-0.6%, Sr: 0.8-1.3%, rare earth elements 0.8-1.3%, rare earth elements are composed of Gd and Nd in a mass ratio of 1:(0.2-0.4), with the balance being Mg and unavoidable impurities.

[0010] The basic principle of magnesium alloying is the interaction between the added alloying elements and the magnesium matrix or alloying elements, resulting in solid solution strengthening and second-phase strengthening. Aluminum is a commonly used alloying element and also the most effective strengthening element, significantly improving the casting performance of magnesium alloys. The maximum solid solubility of aluminum in magnesium can reach 12%. As the temperature decreases, the solid solubility of alloying elements in magnesium decreases significantly. Adding aluminum can effectively improve the strength and deformation capacity of magnesium alloys. However, aluminum has an adverse effect on the heat resistance of magnesium alloys. This is because a low-melting-point phase forms in aluminum-containing magnesium alloys, which softens and coarsens as the service temperature increases, negatively impacting the alloy's performance. While it is difficult for calcium (Ca) to form intermetallic compounds with Mg or Al in magnesium-aluminum based alloys, Ca atoms diffuse very slowly during metal solidification, hindering grain growth at the interface and achieving a good grain refinement effect. Adding Ca can also improve the flame retardancy of the alloy; however, excessive Ca content can lead to hot cracking, so generally only trace amounts of Ca are added. Therefore, the performance improvement of Mg-Al-Ca magnesium alloys is limited.

[0011] To address the problems existing in Mg-Al-Ca magnesium alloys, this invention first adds a trace amount of Mn. Fine grains are key to simultaneously improving strength and ductility. According to the theory of grain refinement strengthening, the more grain boundaries there are, the more effectively dislocation movement is hindered. The addition of Mn helps refine the alloy's microstructure, thus positively impacting strength. A small amount of Mn can improve alloy strength while maintaining good ductility, producing wrought magnesium alloys with both strength and ductility. However, when the amount of Mn is excessive, the excessive coarse Al-Mn particles within the alloy consume a large amount of Al. Because Al is preempted by excessive Mn, the number of strengthening phases that can form within the grains is significantly reduced, and the effective number of nano-precipitates decreases, meaning their ability to pin grain boundaries and refine grains is weakened. As a result, the average recrystallized grain size of the alloy actually increases. According to the theory of grain refinement strengthening, grain coarsening directly leads to a decrease in alloy strength. This also means that simply adding Mn has very limited effect on improving the mechanical properties and flame retardant effect of Mg-Al-Ca magnesium alloys.

[0012] To this end, this invention specifically adds Sr and rare earth elements composed of Gd and Nd in a mass ratio of 1:(0.2-0.4). Sr itself has surface activity and can accumulate at the solid-liquid interface during solidification, hindering grain growth and playing a role in refining grains. At high temperatures, Sr participates in the formation of the surface oxide film. It not only promotes the formation of a denser composite oxide film but also forms Sr-containing oxides, filling voids in the oxide film, improving the film's density and integrity, thereby more effectively preventing oxygen diffusion and increasing the alloy's ignition point. Gd and Nd have a high maximum solid solubility in magnesium, which changes significantly with temperature. During solidification and heat treatment, they can dissolve into the magnesium matrix, causing lattice distortion, hindering dislocation movement, and bringing a direct strengthening effect. Moreover, the introduction of rare earth elements composed of Gd and Nd not only solves the problem of reduced alloy plasticity and strength caused by excessive Sr content but also further densifies the surface oxide film, improving its barrier properties and resistance to spalling.

[0013] Although Nd is used in small amounts, it is a surface-active element that tends to agglomerate at grain boundaries. Combined with Gd, it can significantly affect alloy properties. Appropriate amounts of Nd can refine grains and precipitates. However, when there is too much Nd and the Gd content decreases, excessive and oversized second phases will precipitate at grain boundaries. These coarse phases have weak interfacial bonding with the matrix and are prone to cracking under stress, leading to intergranular fracture of the alloy and a sharp decrease in plasticity and strength. Nd itself can effectively improve the density of the oxide film and increase the ignition temperature. When Nd increases and Gd decreases, the composition and structure of the oxide film will change, reducing its overall stability and protective effect.

[0014] In one embodiment, the high-strength alloy material is composed of the following components by mass percentage: Al: 6.2-6.8%, Ca: 4.6-5.3%, Mn: 0.3-0.5%, Sr: 0.9-1.2%, and rare earth elements: 0.9-1.2%. The rare earth elements consist of Gd and Nd in a mass ratio of 1:(0.2-0.4), with the balance being Mg and unavoidable impurities. By adjusting the amounts of Ca, Mn, Sr, and rare earth components, especially those with both reinforcing and flame-retardant effects, it is possible to avoid increasing the alloy cost due to excessive component amounts, while also balancing the mechanical properties and flame-retardant effect of the alloy. This avoids the negative impact of excessive rare earth component content, achieving superior technical results with minimal additions. Furthermore, the Ca content is 4.7-5.2%, the Mn content is 0.4-0.5%, the Sr content is 0.9-1.1%, and the rare earth element content is 0.9-1.1%.

[0015] Specifically, the unavoidable impurity content described in this invention Furthermore, the unavoidable content of impurities... Or ≤0.01%.

[0016] In one embodiment, the rare earth elements consist of Gd and Nd in a mass ratio of 1:0.3.

[0017] In summary, Sr provides the alloy with fine-grained strengthening and a good plasticity foundation. Gd / Nd, through solid solution strengthening and the precipitation of numerous nanophases within the grains / grain boundaries, offers powerful precipitation strengthening. The combination of the two achieves a better strength-plasticity balance than adding either element alone. Sr optimizes the grain boundary structure, delaying grain boundary weakening at high temperatures. The thermally stable nanophases formed by Gd / Nd effectively pin dislocations and grain boundaries even at high temperatures. Together, they significantly improve the alloy's high-temperature strength and creep resistance. Simultaneously, their combined addition forms a multi-element, multi-layered, highly dense composite oxide film on the alloy surface. This composite film's density, stability, and adhesion to the matrix far exceed those of a single oxide film, serving as an extremely effective barrier to raise the alloy's ignition point to a very high level, achieving excellent flame-retardant properties.

[0018] On the other hand, the present invention also provides a method for preparing the aforementioned high-strength alloy material, comprising the following steps:

[0019] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them.

[0020] S2. Preheated pure Mg and pure Al are placed in a container, then placed in an apparatus heated to 700-750℃, and heated and held at that temperature under a protective atmosphere until they melt to obtain a melt.

[0021] S3 is added to preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and kept at a constant temperature. After the master alloys melt, they are stirred, slag is removed, and the temperature is kept higher.

[0022] S4 is removed from the container and cooled to room temperature under a protective atmosphere to form an alloy ingot, which is then heat-treated and quenched.

[0023] S5 extrusion deformation yields high-strength alloy materials.

[0024] In one embodiment, the preheating temperature in step S1 is 200-300℃, and the preheating time is 15-25 min. Preheating can increase the initial temperature of raw materials such as pure Mg, pure Al, Mg-30Ca master alloy (wt%), Mg-20Sr master alloy (wt%), Mg-6Mn master alloy (wt%), Mg-20Gd master alloy (wt%), and Mg-30Nd master alloy (wt%), reducing the impact on the molten pool temperature when they are added to the melt, helping to maintain the stability of the melt temperature, thereby better controlling the alloying process and the uniformity of the final composition.

[0025] In one embodiment, the container in step S2 is a crucible.

[0026] In one embodiment, the process in step S2 is carried out in a pit-type resistance furnace, which can ensure uniform alloy composition and allow elements such as Sr, Gd / Nd to react fully.

[0027] In one embodiment, the protective atmosphere in step S2 is . and There is a powerful synergistic effect between them, and their protective effect far exceeds that of using any one gas alone.

[0028] In one embodiment, the heat preservation time in step S3 is 10-25 minutes.

[0029] In one embodiment, the holding time in step S3 is 10-15 minutes. After all raw materials have melted in the pit-type resistance furnace and reached the predetermined temperature, a holding period is required to allow the alloy composition to achieve macroscopic homogeneity through diffusion. A longer holding time is not necessarily better; prolonged holding may cause a small amount of oxidation and burn-off, leading to a deviation of the final composition from the target. Furthermore, if the holding temperature is too high and the time is too long, it may adversely affect the subsequent solidification structure.

[0030] In one embodiment, the cooling in step S4 is water cooling.

[0031] In one embodiment, the specific heat treatment process in step S4 is as follows: treatment at 380-430℃ for 10-15 hours. Specifically, graphite powder is applied to the surface of the ingot during the heat treatment process. Through heat treatment, component segregation generated during the smelting process can be eliminated, resulting in a more uniform alloy structure and properties.

[0032] In one embodiment, the specific process of extrusion deformation in step S5 is as follows: the ingot is preheated to 350-400°C, and the extrusion cylinder temperature is 350-400°C, with an extrusion speed of... Extrusion deformation under an extrusion ratio of 20-28:1.

[0033] Beneficial effects:

[0034] To address the problems associated with Mg-Al-Ca magnesium alloys, this invention first adds trace amounts of Mn. A small amount of Mn improves the alloy's strength while maintaining good plasticity, resulting in wrought magnesium alloys with both strength and ductility. Sr itself has surface activity and can accumulate at the solid-liquid interface during solidification, hindering grain growth and aiding in grain refinement. At high temperatures, Sr participates in the formation of the surface oxide film. It not only promotes the formation of a denser composite oxide film but also forms Sr-containing oxides (such as SrO), filling voids in the oxide film, improving its density and integrity, and thus more effectively preventing oxygen diffusion and increasing the alloy's ignition point. Gd and Nd have relatively high maximum solid solubility in magnesium, which varies significantly with temperature. During solidification and heat treatment, they can dissolve into the magnesium matrix, causing lattice distortion, hindering dislocation movement, and resulting in a direct strengthening effect.

[0035] In summary, Sr provides the alloy with fine-grained strengthening and a good plasticity foundation. Gd / Nd, through solid solution strengthening and the precipitation of a large number of nanophases within the grains / grain boundaries, provides a strong precipitation strengthening effect. The combination of the two achieves a better strength and plasticity match than adding either element alone. Sr optimizes the grain boundary structure and delays the weakening of grain boundaries at high temperatures. The thermally stable nanophases formed by Gd / Nd can still effectively pin dislocations and grain boundaries at high temperatures. Together, they can significantly improve the high-temperature strength and creep resistance of the alloy. At the same time, their composite addition forms a multi-element, multi-layer, highly dense composite oxide film composed of various oxides on the alloy surface. The density, stability, and adhesion to the matrix of this composite film are far superior to those of a single oxide film, serving as an extremely effective barrier to raise the alloy's ignition point to a very high level, achieving excellent flame retardant effects. The Mg-Al-Ca magnesium alloy prepared by this invention simultaneously possesses excellent tensile strength, plasticity, and flame retardant properties, showing broad application prospects. Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0037] Performance testing: Tensile properties were tested in accordance with GB / T228.1-2021; and the ignition point was tested using a continuous heating method.

[0038] Example 1

[0039] A high-strength alloy material is composed of the following components by mass percentage:

[0040] Al: 6%, Ca: 4.5%, Mn: 0.3%, Sr: 0.8%, rare earth elements: 1.2%, the rare earth elements are composed of Gd and Nd in a mass ratio of 1:0.2, with the balance being Mg and unavoidable impurities.

[0041] A method for preparing a high-strength alloy material includes the following steps:

[0042] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 200℃ for 25 minutes.

[0043] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0044] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 13 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 14 minutes.

[0045] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 13 hours and then remove it for quenching.

[0046] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 371.3 MPa, elongation is 4.7%, and ignition point is 1106.2℃.

[0047] Example 2

[0048] A high-strength alloy material is composed of the following components by mass percentage:

[0049] Al: 7%, Ca: 5.3%, Mn: 0.6%, Sr: 1.2%, rare earth elements: 0.8%, the rare earth elements consist of Gd and Nd in a mass ratio of 1:0.4, with the balance being Mg and unavoidable impurities.

[0050] A method for preparing a high-strength alloy material includes the following steps:

[0051] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 300℃ for 15 minutes.

[0052] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0053] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 19 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 10 minutes.

[0054] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 420℃ for 11 hours and then remove it for quenching.

[0055] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 377.5 MPa, elongation is 5.2%, and ignition point is 1110.3℃.

[0056] Example 3

[0057] A high-strength alloy material is composed of the following components by mass percentage:

[0058] Al: 6.5%, Ca: 5.5%, Mn: 0.5%, Sr: 1.1%, rare earth elements: 1.1%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.3, with the balance being Mg and unavoidable impurities.

[0059] A method for preparing a high-strength alloy material includes the following steps:

[0060] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 20 minutes.

[0061] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0062] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 13 minutes.

[0063] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0064] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 375.1 MPa, elongation is 5.0%, and ignition point is 1107.3℃.

[0065] Example 4

[0066] A high-strength alloy material is composed of the following components by mass percentage:

[0067] Al: 6.1%, Ca: 5.2%, Mn: 0.6%, Sr: 1.0%, rare earth elements: 1.1%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.2, with the balance being Mg and unavoidable impurities.

[0068] A method for preparing a high-strength alloy material includes the following steps:

[0069] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 200℃ for 15 minutes.

[0070] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0071] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 14 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 11 minutes.

[0072] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 420℃ for 13 hours, then remove and quench it.

[0073] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 372.2 MPa, elongation is 5.1%, and ignition point is 1108.8℃.

[0074] Example 5

[0075] A high-strength alloy material is composed of the following components by mass percentage:

[0076] Al: 6.5%, Ca: 5%, Mn: 0.5%, Sr: 1.3%, rare earth elements: 1.1%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.3, with the balance being Mg and unavoidable impurities.

[0077] A method for preparing a high-strength alloy material includes the following steps:

[0078] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 20 minutes.

[0079] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a temperature under a protective atmosphere until melting is obtained;

[0080] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 13 minutes.

[0081] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0082] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 375.6 MPa, elongation is 4.9%, and ignition point is 1107.4℃.

[0083] Example 6

[0084] A high-strength alloy material is composed of the following components by mass percentage:

[0085] Al: 6.3%, Ca: 4.7%, Mn: 0.4%, Sr: 0.9%, rare earth elements: 1%, the rare earth elements consist of Gd and Nd in a mass ratio of 1:0.25, with the balance being Mg and unavoidable impurities.

[0086] A method for preparing a high-strength alloy material includes the following steps:

[0087] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 15 minutes.

[0088] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a temperature under a protective atmosphere until melting is obtained;

[0089] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 12 minutes.

[0090] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0091] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 369.7 MPa, elongation is 4.8%, and ignition point is 1105.7℃.

[0092] Example 7

[0093] A high-strength alloy material is composed of the following components by mass percentage:

[0094] Al: 6.5%, Ca: 5%, Mn: 0.5%, Sr: 1.1%, rare earth elements: 1.3%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.3, with the balance being Mg and unavoidable impurities.

[0095] A method for preparing a high-strength alloy material includes the following steps:

[0096] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 20 minutes.

[0097] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a temperature under a protective atmosphere until melting is obtained;

[0098] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 13 minutes.

[0099] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0100] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 373.1 MPa, elongation is 4.8%, and ignition point is 1108.4℃.

[0101] Example 8

[0102] A high-strength alloy material is composed of the following components by mass percentage:

[0103] Al: 6.7%, Ca: 5.1%, Mn: 0.5%, Sr: 1%, rare earth elements: 0.9%, the rare earth elements are composed of Gd and Nd in a mass ratio of 1:0.35, with the balance being Mg and unavoidable impurities.

[0104] A method for preparing a high-strength alloy material includes the following steps:

[0105] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 300℃ for 20 minutes.

[0106] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a temperature under a protective atmosphere until melting is obtained;

[0107] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 17 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 11 minutes.

[0108] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 420℃ for 12 hours and then remove it for quenching.

[0109] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 373.7 MPa, elongation is 5.3%, and ignition point is 1107.5℃.

[0110] Example 9

[0111] A high-strength alloy material is composed of the following components by mass percentage:

[0112] Al: 6.8%, Ca: 4.8%, Mn: 0.3%, Sr: 1.3%, rare earth elements: 1.2%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.4, with the balance being Mg and unavoidable impurities.

[0113] A method for preparing a high-strength alloy material includes the following steps:

[0114] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 25 minutes.

[0115] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a temperature under a protective atmosphere until melting is obtained;

[0116] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 18 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 12 minutes.

[0117] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 13 hours and then remove it for quenching.

[0118] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 377.2 MPa, elongation is 4.9%, and ignition point is 1109.6℃.

[0119] Example 10

[0120] A high-strength alloy material is composed of the following components by mass percentage:

[0121] Al: 6.5%, Ca: 5%, Mn: 0.5%, Sr: 1.1%, rare earth elements: 1.1%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.3, with the balance being Mg and unavoidable impurities.

[0122] A method for preparing a high-strength alloy material includes the following steps:

[0123] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 20 minutes.

[0124] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0125] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 13 minutes.

[0126] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0127] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 375.5 MPa, elongation is 5.5%, and ignition point is 1111.6℃.

[0128] Comparative Example 1

[0129] A high-strength alloy material is composed of the following components by mass percentage:

[0130] Al: 6.5%, Ca: 5%, Mn: 0.5%, rare earth elements: 2.2%, the rare earth elements are composed of Gd and Nd in a mass ratio of 1:0.3, with the balance being Mg and unavoidable impurities.

[0131] A method for preparing a high-strength alloy material includes the following steps:

[0132] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 20 minutes.

[0133] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0134] Add preheated Mg-30Ca master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy and Mg-30Nd master alloy to S3, hold for 15 min, stir after the master alloy melts, remove the slag, and continue to hold for 13 min.

[0135] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0136] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 347.6 MPa, elongation is 3.9%, and ignition point is 1078.6℃.

[0137] Comparative Example 2

[0138] A high-strength alloy material is composed of the following components by mass percentage:

[0139] Al: 6.5%, Ca: 5%, Mn: 0.5%, Sr: 2.2%, balance Mg and unavoidable impurities.

[0140] A method for preparing a high-strength alloy material includes the following steps:

[0141] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, and Mg-6Mn master alloy, and preheats them at 250℃ for 20 minutes.

[0142] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0143] Add S3 to the preheated Mg-30Ca master alloy, Mg-20Sr master alloy, and Mg-6Mn master alloy, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 13 minutes.

[0144] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0145] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 355.2 MPa, elongation is 3.7%, and ignition point is 1088.3℃.

[0146] Comparative Example 3

[0147] A high-strength alloy material is composed of the following components by mass percentage:

[0148] Al: 6.5%, Ca: 5%, Mn: 0.5%, Sr: 1.1%, rare earth elements: 1.1%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.7, with the balance being Mg and unavoidable impurities.

[0149] A method for preparing a high-strength alloy material includes the following steps:

[0150] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 20 minutes.

[0151] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0152] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 13 minutes.

[0153] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0154] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 359.2 MPa, elongation is 4.2%, and ignition point is 1094.2℃.

[0155] Comparative Example 4

[0156] A high-strength alloy material is composed of the following components by mass percentage:

[0157] Al: 6.5%, Ca: 5%, Mn: 0.9%, Sr: 1.1%, rare earth elements: 1.1%, rare earth elements consist of Gd and Nd in a mass ratio of 1:0.3, with the balance being Mg and unavoidable impurities.

[0158] A method for preparing a high-strength alloy material includes the following steps:

[0159] S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them at 250℃ for 20 minutes.

[0160] S2 places preheated pure Mg and pure Al into a crucible, then places it in a pit-type resistance furnace heated to 720℃, and... Heating and holding at a protective atmosphere until melting is achieved, yielding a melt.

[0161] Add preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy to S3, hold for 15 minutes, stir after the master alloy melts, remove the slag, and continue to hold for 13 minutes.

[0162] S4 Remove the crucible and water-cool it to room temperature under a protective atmosphere to form an alloy ingot. Heat treat it at 410℃ for 12 hours and then remove it for quenching.

[0163] S5 preheats the ingot to 380℃, and the extrusion cylinder temperature is 380℃, with an extrusion speed of [missing information]. High-strength alloy material is obtained by extrusion deformation under an extrusion ratio of 25:1. Tests show that its tensile strength is 372.8 MPa, elongation is 4.1%, and ignition point is 1091.5℃.

[0164] As can be seen from the above examples and comparative examples, a small amount of Mn can improve the strength of the alloy while maintaining its good plasticity, thus producing a wrought magnesium alloy with both strength and plasticity. Sr itself has surface activity and can accumulate at the solid-liquid interface during solidification, hindering grain growth and playing a role in refining grains. At high temperatures, Sr participates in the formation of the surface oxide film. It can not only promote the formation of a denser composite oxide film, but also form Sr-containing oxides to fill the voids in the oxide film, improve the film's density and integrity, and thus more effectively prevent oxygen from diffusing inward, increasing the alloy's ignition point. Gd and Nd have a large maximum solid solubility in magnesium, which changes significantly with temperature. During solidification and heat treatment, they can dissolve into the magnesium matrix, causing lattice distortion, hindering dislocation movement, and bringing a direct strengthening effect.

[0165] Specifically, compared to Example 10, Comparative Examples 1-2 lacked Sr and rare earth elements, resulting in varying degrees of reduction in mechanical strength and flame retardant effect. This is because Sr itself has surface activity and can accumulate at the solid-liquid interface during solidification, hindering grain growth and playing a role in refining grains. However, increasing Sr content easily leads to a decrease in alloy plasticity. The introduction of rare earth elements composed of Gd and Nd not only solves the problem of reduced alloy plasticity caused by excessive Sr content, but also further densifies the surface oxide film, improving its barrier ability and spalling resistance. Comparative Example 3 shows that in the reinforced system formed by the combination of Sr and rare earth elements, when the proportion of Gd and Nd is too small, the decrease in ignition point is not significant, but the decrease in mechanical strength is substantial. This is because Nd is a surface-active element and tends to agglomerate at grain boundaries. An appropriate amount of Nd can refine grains and precipitates. However, when Nd is excessive, too many and too large second phases will precipitate at the grain boundaries. These coarse phases have weak interfacial bonding with the matrix, making them prone to cracking under stress, leading to intergranular fracture and a sharp decrease in plasticity and strength. Ignition point data also show that Nd effectively improves oxide film density and increases ignition temperature. However, due to the reduction of Gd, the composition and structure of the oxide film change, reducing its overall stability and protective effect. Meanwhile, Comparative Example 4 shows that a small amount of Mn can improve alloy strength while maintaining good plasticity, producing wrought magnesium alloys with both strength and plasticity. However, when Mn content is excessive, the excessive coarse Al-Mn particles consume a large amount of Al. Because Al is preempted by excessive Mn, the number of strengthening phases that can form within the grains is significantly reduced, and the effective number of nano-precipitates decreases, meaning their ability to pin grain boundaries and refine grains is weakened. As a result, the average recrystallized grain size of the alloy actually increases. According to the theory of grain refinement strengthening, grain coarsening directly leads to a decrease in alloy strength.

[0166] In general, a small amount of Mn can improve the strength of the alloy while maintaining good plasticity, thus producing wrought magnesium alloys with both strength and plasticity. Sr provides fine-grained strengthening and a good plasticity foundation for the alloy. Gd / Nd provides strong precipitation strengthening through solid solution strengthening and the precipitation of a large number of nanophases within the grains / grain boundaries. The combination of the two can achieve a better balance between strength and plasticity than adding either element alone. Sr optimizes the grain boundary structure and delays the weakening of grain boundaries at high temperatures. The thermally stable nanophases formed by Gd / Nd can still effectively pin dislocations and grain boundaries at high temperatures. Together, the two can significantly improve the high-temperature strength and creep resistance of the alloy. At the same time, their composite addition forms a multi-element, multi-layer, highly dense composite oxide film composed of various oxides on the alloy surface. The density, stability, and adhesion to the matrix of this composite film are far superior to those of a single oxide film, serving as an extremely effective barrier to raise the ignition point of the alloy to a very high level, achieving excellent flame retardant effects.

[0167] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-strength alloy material, characterized in that, It consists of the following components by mass percentage: Al: 6.2-6.8%, Ca: 4.7-5.2%, Mn: 0.4-0.5%, Sr: 0.9-1.1%, rare earth elements 0.9-1.1%, rare earth elements are composed of Gd and Nd in a mass ratio of 1:(0.2-0.4), with the balance being Mg and unavoidable impurities; The method for preparing a high-strength alloy material includes the following steps: S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them. S2. Preheated pure Mg and pure Al are placed in a container, then placed in an apparatus heated to 700-750℃, and heated and held at that temperature under a protective atmosphere until they melt to obtain a melt. S3 is added to preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and kept at a constant temperature. After the master alloys melt, they are stirred, slag is removed, and the temperature is kept higher. S4 is removed from the container and cooled to room temperature under a protective atmosphere to form an alloy ingot, which is then heat-treated and quenched. S5 extrusion deformation yields high-strength alloy materials; The specific process of heat treatment in step S4 is as follows: treatment at 380-430℃ for 10-15 hours; The specific process of extrusion deformation in step S5 is as follows: preheat the ingot to 350-400℃, and extrude at a cylinder temperature of 350-400℃ and an extrusion speed of 1-2 mm·min. -1 Extrusion deformation under an extrusion ratio of 20-28:

1.

2. The high-strength alloy material as described in claim 1, characterized in that, Rare earth elements are composed of Gd and Nd in a mass ratio of 1:0.

3.

3. The method for preparing a high-strength alloy material according to any one of claims 1-2, characterized in that, Includes the following steps: S1 prepares raw materials according to the proportions of each group: pure Mg, pure Al, Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and preheats them. S2. Preheated pure Mg and pure Al are placed in a container, then placed in an apparatus heated to 700-750℃, and heated and held at that temperature under a protective atmosphere until they melt to obtain a melt. S3 is added to preheated Mg-30Ca master alloy, Mg-20Sr master alloy, Mg-6Mn master alloy, Mg-20Gd master alloy, and Mg-30Nd master alloy, and kept at a constant temperature. After the master alloys melt, they are stirred, slag is removed, and the temperature is kept higher. S4 is removed from the container and cooled to room temperature under a protective atmosphere to form an alloy ingot, which is then heat-treated and quenched. S5 extrusion deformation yields high-strength alloy materials; The specific process of heat treatment in step S4 is as follows: treatment at 380-430℃ for 10-15 hours; The specific process of extrusion deformation in step S5 is as follows: preheat the ingot to 350-400℃, and extrude at a cylinder temperature of 350-400℃ and an extrusion speed of 1-2 mm·min. -1 Extrusion deformation under an extrusion ratio of 20-28:

1.

4. The method for preparing a high-strength alloy material as described in claim 3, characterized in that, The preheating temperature in step S1 is 200-300℃.

5. The method for preparing a high-strength alloy material as described in claim 3, characterized in that, The preheating time for step S1 is 15-25 minutes.

6. The method for preparing a high-strength alloy material as described in claim 3, characterized in that, The heat preservation time in step S3 is 10-25 minutes.

7. The method for preparing a high-strength alloy material as described in claim 3, characterized in that, The heat preservation time in step S3 is 10-15 minutes.

8. The method for preparing a high-strength alloy material as described in claim 3, characterized in that, The cooling in step S4 is water cooling.