Preparation method of high-stress-resistance and corrosion-resistance magnesium alloy for unmanned underwater vehicle

Abstract

The invention belongs to the technical field of underwater vehicle structural materials, and particularly relates to a preparation method of a high-stress-resistance corrosion-resistant magnesium alloy for an unmanned underwater vehicle, which comprises the following steps: heating and smelting pure magnesium with the purity of 99.99 wt%, pure zirconium with the purity of 99.99 wt%, a first intermediate alloy and a second intermediate alloy by using a resistance furnace, and removing impurities by using a refining agent; casting is conducted after impurities are removed, homogenizing treatment and hot extrusion are conducted on an alloy material after casting is completed, and the magnesium alloy is obtained by rolling the alloy subjected to hot extrusion; wherein the first intermediate alloy contains 30wt% of gadolinium and 70wt% of magnesium, and the second intermediate alloy contains 30wt% of yttrium and 70wt% of magnesium; by means of the preparation method, the technical defect that in the prior art, impurities are likely to be mixed in the magnesium alloy preparation process, and consequently the performance of the magnesium alloy is unstable under the extreme condition is overcome.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater vehicle structural materials, and in particular relates to a method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle. Background Art

[0002] In the field of modern marine engineering technology, unmanned underwater vehicles (UUVs) have become an indispensable research and application tool. They are widely active in frontier positions such as resource exploration, environmental monitoring and military reconnaissance, and their importance is self-evident. The performance, efficiency and life of the vehicle are all directly affected by the material selection.

[0003] Magnesium alloys, with their ultra-low density (about 1.8 g / cm³) and excellent specific strength, stand out in many fields, especially in the design of unmanned underwater vehicles that pursue extreme lightweight. However, facing the complex and harsh challenges of the marine environment, the limitations of existing magnesium alloys are gradually emerging. Specifically, magnesium alloys are highly susceptible to corrosion in seawater environments due to their high chemical activity.

[0004] At present, the research on magnesium alloys is mainly focused on improving their corrosion resistance and mechanical properties. Although some alloy systems such as the AZ series (aluminum-zinc-magnesium alloy) and the AM series (aluminum-manganese-magnesium alloy) have been developed for specific applications, their corrosion resistance in deep-sea environments is still insufficient. These traditional magnesium alloys are prone to stress corrosion cracking (SCC) when subjected to the combined effects of stress and corrosive media, resulting in a significant decrease in material strength and ductility. This problem is particularly evident in deep-sea applications, because material failure in high pressure and corrosive environments directly affects the safety and reliability of the equipment. In particular, magnesium alloys can be used to manufacture the shells of deep-sea detectors to reduce weight and increase buoyancy. Existing solutions often enhance their corrosion resistance in seawater through surface treatment techniques (such as anodizing and coating), rather than designing new magnesium alloy components to fundamentally achieve material modification. Design lightweight and pressure-resistant submersible structures to reduce the overall weight of the submersible. In addition, Mg-Ni-based ablation magnesium alloys are often used in deep-sea oil and gas extraction equipment. However, in the field of manufacturing deep-sea detectors, it is necessary to consider the stable service life of structural components. At this time, it is necessary to consider stress-corrosion-resistant magnesium alloys that are resistant to stress and corrosion.

[0005] In the scope of the prior art, the main focus is on the technical shortcomings of magnesium alloys in stress corrosion cracking, and attempts to solve them are made by optimizing the selection of raw materials or adding coatings. Among them, the Chinese application with publication number CN108187994B came into being in this context. It improves the stress resistance and corrosion resistance of magnesium alloys by constructing an epoxy coating on the surface of magnesium alloys. However, the introduction of this coating controlled by the content of its application documents also correspondingly increases the production complexity and manufacturing cost of magnesium alloy devices. In addition, the above technical solutions are all aimed at solving the technical defects of magnesium alloys in stress corrosion cracking, and do not solve the technical problem that the magnesium alloy mentioned in this application document is extremely susceptible to corrosion in seawater environments and under load conditions due to its high chemical activity. The preparation method of the magnesium alloy still has the technical defect of easy mixing of impurities, resulting in the magnesium alloy prepared by the preparation method being unable to be used in the environment of underwater vehicles.

[0006] Based on this, there is an urgent need for a method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for unmanned underwater vehicles to solve the technical defects of the above-mentioned prior art. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for unmanned underwater vehicles in response to the shortcomings of the prior art, so as to solve the technical defects of the prior art in that impurities are easily mixed into the traditional magnesium alloy during the preparation process, resulting in unstable performance under extreme conditions, thereby limiting its application potential in underwater vehicles under harsh environments such as deep sea high pressure.

[0008] In order to achieve the above technical objectives, this application implements the following technical solutions: A method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle, comprising the following steps: Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent for impurity removal; After impurities are removed, casting is performed, and after casting, the alloy material is homogenized and hot extruded, and the hot extruded alloy is rolled to obtain a magnesium alloy; The first master alloy contains 30 wt % of gadolinium and 70 wt % of magnesium, and the second master alloy contains 30 wt % of yttrium and 70 wt % of magnesium.

[0009] The above technical solution produces the following technical effects: During the preparation process, firstly, high-purity pure magnesium and pure zirconium are used as the base material, which not only reduces the introduction of impurity elements, but also improves the purity of the alloy. At the same time, the introduction of the first master alloy and the second master alloy realizes the stable addition of key elements such as gadolinium and yttrium, avoiding the unevenness problem that may be caused by direct addition. Secondly, in the smelting stage, the precise temperature control capability of the resistance furnace can ensure that the alloy melt is evenly mixed at a suitable temperature, and the addition of refining agents effectively removes the gas and inclusions in the melt, further improving the purity and quality of the alloy. Subsequently, the melt is solidified and formed through a casting process to obtain a preliminary alloy material.

[0010] Meanwhile, based on the above technical solution, the present invention proposes a new alloy system VW-UUV, the design of which is based on the superior properties of magnesium-rare earth metal (Mg-RE) alloys, especially the ability to resist stress corrosion.

[0011] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, the magnesium alloy contains gadolinium, yttrium, zirconium, and magnesium; The gadolinium content is: 7wt%-10wt%, the yttrium content is: 2.5wt%-4wt%, the zirconium content is: 0.25wt%-1wt%; and the magnesium content is: 80wt%-90wt%.

[0012] Furthermore, by introducing elements such as gadolinium (Gd), yttrium (Y) and zirconium (Zr), the present application creates a magnesium alloy that performs well in high stress and corrosion environments, and the addition of gadolinium and yttrium to the magnesium alloy can not only significantly improve the strength and toughness of the alloy, but also improve its corrosion resistance. These improvements are intended to enable the VW-UUV alloy to maintain good mechanical properties under the extreme working conditions of unmanned underwater vehicles, ensuring its long-term stable operation.

[0013] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, any one of neodymium, cerium and erbium is added to the magnesium alloy during the preparation process.

[0014] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, neodymium is added to the magnesium alloy in an amount of 2.5wt%-4wt% during the preparation process. As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, the gadolinium content in the magnesium alloy is: 8wt%-9wt%, the yttrium content is: 3wt%-4wt%, the zirconium content is: 0.25wt%-0.5wt%, the magnesium content is: 80wt%-90wt%, and the neodymium content is: 3wt%-4wt%.

[0015] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, the hot extrusion process includes the following steps: Extruding the homogenized alloy material at a temperature of 380-430° C. with an extrusion ratio of 14:1 to 20:1; During the hot extrusion process, the extrusion equipment extrudes the alloy material at a head speed of 1 mm / s.

[0016] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, the furnace in the smelting process is a medium carbon steel crucible, the carbon steel crucible is heated to 700-750° C. during the smelting process, and the alloy material in the carbon steel crucible during the smelting process is stirred at a stirring rate of 200RPM-400RPM by a stirring device; A mixture of SF6 and CO2 is used as the protective gas during the smelting process; The mass fraction of SF6 in the mixed gas is 0.5wt%, and the mass fraction of CO2 is 99.5wt%.

[0017] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle in the present application, the carbon steel crucible is heated to 720°C during the smelting process, and after the refining agent is added, the stirring equipment starts to stir the alloy material in the carbon steel crucible during the smelting process at a stirring rate of 300RPM for 10 minutes to 15 minutes after the refining agent is added.

[0018] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, the refining agent is a mixture of chloride or fluoride, and the temperature of the alloy material is maintained at 700° C.-750° C. during the refining process; During the rolling process, the temperature of the alloy material is maintained at 250℃-400℃, the rolling speed is maintained at 0.5m / s-2m / s, and the deformation per pass is 10%-50%.

[0019] As a further improvement to the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application, a third master alloy is added during the process of heating and melting in a resistance furnace and removing impurities through a refining agent; the third master alloy contains 30wt% neodymium and 70wt% magnesium. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1The sample size diagram for the slow strain rate tensile test (SSRT) in the present invention; Figure 2 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in the present invention was heated to 5×10 -6 Metal morphology after strain rate tensile fracture - surface macroscopic image under electron microscope (low magnification); Figure 3 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in the present invention was heated to 5×10 -6 Metal morphology after strain rate tensile fracture - surface image under electron microscope (high magnification); Figure 4 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in the present invention was heated to 5×10 -6 Metal morphology after strain rate tensile fracture - fracture image under electron microscope (low magnification); Figure 5 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in the present invention was heated to 5×10 -6 Metal morphology after strain rate tensile fracture - fracture image under electron microscope (high magnification); Figure 6 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in the present invention was subjected to 5×10 -6 strain rate stretching; Figure 7 The VW-UUV high stress corrosion resistant magnesium alloy prepared for unmanned underwater vehicle was heated in 3.5% NaCl solution (simulated seawater solution) at 5×10 -6 Metal morphology after strain rate tensile fracture - surface macroscopic image under electron microscope (low magnification); Figure 8 The VW-UUV high stress corrosion resistant magnesium alloy prepared for unmanned underwater vehicle was heated in 3.5% NaCl solution (simulated seawater solution) at 5×10 -6 Metal morphology after strain rate tensile fracture - fracture image under electron microscope (low magnification); Fig. 9 The prepared VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle was heated to 5×10 -6 Metal morphology after strain rate tensile fracture - fracture image under electron microscope (high magnification); Fig.10 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle was prepared in 3.5 wt% NaCl simulated seawater solution with a rolling speed of 1×10 -5 Stress-strain diagram for strain rate tension; Fig.11 The VW-UUV high stress corrosion resistant magnesium alloy prepared for unmanned underwater vehicle was heated in 3.5% NaCl solution (simulated seawater solution) at 1×10 -5 Metal morphology after strain rate tensile fracture - surface macroscopic image under electron microscope (low magnification); Fig.12 The VW-UUV high stress corrosion resistant magnesium alloy prepared for unmanned underwater vehicle was heated in 3.5% NaCl solution (simulated seawater solution) at 1×10 -5 Metal morphology after strain rate tensile fracture - surface image under electron microscope (high magnification); Fig.13 The VW-UUV high stress corrosion resistant magnesium alloy prepared for unmanned underwater vehicle was heated in 3.5% NaCl solution (simulated seawater solution) at 1×10 -5 Metal morphology after strain rate tensile fracture - fracture image under electron microscope (low magnification); Fig.14 The prepared VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle was heated to 1×10 -5 Metal morphology after strain rate tensile fracture - fracture image under electron microscope (high magnification). DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0022] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any technical personnel in this field may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

[0023] In order to avoid ambiguity or ambiguity in the description of this application, this application explains the following technical terms as follows: Unmanned underwater vehicles (UUVs) are usually mobile devices driven by remote control or automation technology that can perform various tasks in underwater environments. These devices do not require human piloting and are usually used in the following main applications: 1) Scientific research and exploration: used for marine biological research, seabed topography mapping, deep-sea detection, geological exploration and archaeological excavation, etc.

[0024] 2) Industrial application: Used in the oil and gas industry for submarine pipeline inspection, oil field exploration and maintenance.

[0025] 3) Environmental monitoring: used to observe and monitor changes in the marine environment, pollution assessment, data collection, etc.

[0026] 4) Commercial use: including detection of submarine cables, wind power infrastructure inspection, etc. From the above application environment, it can be seen that magnesium alloy materials used as structural materials for unmanned underwater vehicles will be in various harsh underwater environments.

[0027] Inductively coupled plasma atomic emission spectroscopy (ICP-AES) is a highly sensitive chemical analysis technology that is widely used in the quantitative detection of metal elements and their compounds. This technology generates plasma through high-frequency induction heating, so that the atoms or ions in the sample emit light of a specific wavelength in an excited state, and then analyzes the intensity of these lights through a spectrometer to achieve accurate measurement of the element concentration in the sample. In the preparation and detection process of the high stress-resistant and corrosion-resistant magnesium alloy involved in this application, ICP-AES technology can play an important role. For example, in the alloy composition optimization stage, ICP-AES can be used to accurately determine the content of various metal elements in the alloy to ensure the accuracy and stability of the alloy formula. At the same time, in the alloy performance evaluation stage, ICP-AES can also be used to analyze the element precipitation of the alloy in a corrosive environment, providing a scientific basis for the corrosion resistance of the alloy.

[0028] A lattice is a regular, repeating arrangement of atoms, ions or molecules in three-dimensional space. They define the atomic structure and physical properties of a material.

[0029] The present invention is further described in detail below in conjunction with specific implementation methods, but the embodiments of the present invention are not limited thereto.

[0030] It is known that the existing magnesium alloys, whether adjusted in alloy composition or improved in structural treatment, have not been able to overcome the potential corrosion resistance and high strength requirements of the internal structural materials in the application of unmanned underwater vehicles. It is urgent to develop an innovative magnesium alloy material. The material should not only have excellent mechanical properties, but also show corrosion resistance that exceeds that of traditional commercial magnesium alloys in underwater operations, so as to achieve the purpose of lightweighting under the premise of ensuring the safe and reliable operation of unmanned underwater vehicles. In recent years, magnesium alloys have been widely used in aerospace, automobiles, digital electronics and other fields due to their light weight, high strength and good processing properties. When considering the extreme environment faced by the outside of unmanned underwater vehicles (UUVs), even the performance requirements of the materials inside the unmanned underwater vehicles are becoming more and more stringent. Traditional metal materials often face significant challenges when dealing with high pressure and corrosive environments.

[0031] Therefore, the method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle of the present application comprises the following steps: Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent for impurity removal; After impurities are removed, casting is performed, and after casting, the alloy material is homogenized and hot extruded, and the hot extruded alloy is rolled to obtain a magnesium alloy; The first master alloy contains 30 wt % of gadolinium and 70 wt % of magnesium, and the second master alloy contains 30 wt % of yttrium and 70 wt % of magnesium.

[0032] Further, regarding the preparation of raw materials, as the preparation raw materials of the magnesium alloy of the present application, high-purity magnesium (Mg): 99.99% purity, mainly as the base metal, comes from high-purity magnesium ingots supplied on the market. Mg-30Gd as the first master alloy: contains 30% gadolinium (Gd) and 70% magnesium, as additive elements, comes from a standard master alloy supplier. Mg-30Y as the second master alloy: contains 30% yttrium (Y) and 70% magnesium, as additive elements, comes from a standard master alloy supplier. High-purity zirconium (Zr): 99.99% purity, as a grain refining element, comes from a high-purity metal supplier.

[0033] Furthermore, a third master alloy is added during the process of heating and melting in a resistance furnace and removing impurities through a refining agent to prepare a magnesium alloy based on the mass fraction of each element in "Mg-9Gd-3Nd-3Y-0.5Zr". The third master alloy contains 30wt% neodymium and 70wt% magnesium. As an added element, the third master alloy is sourced from a standard master alloy supplier.

[0034] Furthermore, the present application has made improvements to the above-mentioned high stress-resistant and corrosion-resistant magnesium alloy for unmanned underwater vehicles, wherein the magnesium alloy contains gadolinium, yttrium, zirconium, and magnesium; the gadolinium content is: 7wt%-10wt%, the yttrium content is: 2.5wt%-4wt%, the zirconium content is: 0.25wt%-1wt%; and the magnesium content is: 80wt%-90wt%. Specifically, the chemical composition of the magnesium alloy in the present application is confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis after smelting.

[0035] Specifically, gadolinium is a rare earth element. In the technical solution of this application, the content of gadolinium is controlled at 7wt%-10wt%. In the specific implementation process, the content of gadolinium is preferably 8wt%-9wt%. As the element with the highest content other than magnesium (substrate), its higher content can significantly improve the strength and hardness of the alloy. It also has good corrosion resistance, which helps to improve the durability of the alloy in the marine environment.

[0036] Specifically, the addition of yttrium can improve the strength and oxidation resistance of magnesium alloys and enhance their stability in extreme service environments. At the same time, Al2Y helps to refine the grains of the alloy and improve the toughness and impact resistance of the material. In the technical solution of the present application, the yttrium content is: 2.5wt%-4wt%. In the specific implementation process, the yttrium content is preferably: 2.5wt%-4wt%.

[0037] Specifically, zirconium is a transition metal, which is commonly used in high temperature materials, corrosion resistant alloys and nuclear industry because it has good corrosion resistance and high temperature stability. In the technical solution of the present application, the zirconium content is: 0.25wt%-1wt%. In the specific implementation process, the zirconium content is preferably: 0.25wt%-0.5wt%.

[0038] Furthermore, any one of neodymium, cerium and erbium will be added to the magnesium alloy during the preparation process. In the specific implementation process, the present application further improves the magnesium alloy based on the mass fraction of each element in "Mg-9Gd-3Nd-3Y-0.5Zr", and specifically selects neodymium as an additive. Specifically, in the preparation process of the magnesium alloy, the content of the added neodymium accounts for 2.5wt%-4wt% of the total mass of the magnesium alloy. In the specific implementation process, for the magnesium alloy based on the mass fraction of each element in "Mg-9Gd-3Nd-3Y-0.5Zr", the content of each element is: 8wt%-9wt% of gadolinium, 3wt%-4wt% of yttrium, 0.25wt%-0.5wt% of zirconium, 80wt%-90wt% of magnesium, and 3wt%-4wt% of neodymium. Such a ratio helps to improve the performance of the magnesium alloy or meet specific application requirements.

[0039] Specifically, magnesium is used as the base material of magnesium alloy, and other elements are usually the remainder of other elements. However, the elements of the magnesium alloy of the present application are not limited to the above elements. Among them, the rare earth element neodymium added in the present application is often used as a refiner in the alloy to improve the grain structure of the metal material and enhance the material performance.

[0040] In summary, the present application can significantly improve the grain refinement effect of materials such as magnesium alloys by adding appropriate rare earth elements and optimizing the ratio, thereby improving the overall performance of the material. Rare earth elements can achieve grain refinement by affecting the solidification and microstructural process of the alloy, thereby improving the overall performance of the material. In this process, rare earth elements may change the formation and growth path of grains, resulting in a more uniform and fine grain structure.

[0041] Further, regarding the smelting process in the present application, the smelting equipment: uses a resistance furnace for heating and smelting, and the furnace is a medium carbon steel crucible. To prevent oxidation, a mixed gas of SF6 and CO2 is used as a protective gas during the smelting process, and the mass fraction of SF6 in the mixed gas is 0.5wt%, and the mass fraction of CO2 is 99.5wt%. Among them, the carbon steel crucible is heated to 700-750℃ during the smelting process, and the alloy material in the carbon steel crucible during the smelting process is stirred at a stirring rate of 200-400 RPM after adding the refining agent through the stirring equipment; wherein, as the preferred value of the heating temperature of the raw materials in the crucible during the smelting process, -720℃ can ensure that all alloy elements are fully dissolved and evenly mixed. At the same time, the preferred stirring rate and stirring time of the stirring equipment are preferably stirred at 300 RPM for 10 minutes, which further ensures that the alloy components are evenly distributed.

[0042] Further, regarding the refining process in the present application, the refining agent selected in the present application is a specific refining agent for impurity removal treatment to remove oxides, nitrides and inclusions in the melt. Specifically, the refining agent is a chloride or fluoride mixture, and the working principle of the specific chloride or fluoride mixture as a refining agent is: through the chemical action of the refining agent, impurities in the melt, including oxides, nitrides and various inclusions, can be effectively removed, thereby improving the purity and performance of the alloy. During the refining process, the refining agent is added to the melt in an appropriate proportion, and the refining agent and the melt are fully mixed by a stirring device. The chloride or fluoride in the refining agent reacts chemically with the impurities in the melt to form a compound that is easy to float and separate, and then the impurities are removed from the melt by standing and skimming operations. This step is crucial to improving the uniformity and quality of the alloy. Further, the temperature of the alloy material during the refining process is maintained at 700°C-750°C, wherein the temperature value is preferably 720°C.

[0043] Furthermore, during the rolling process, the temperature of the alloy material is maintained at 250°C-400°C, the rolling speed is maintained at 0.5m / s-2m / s, and the deformation per pass is 10%-50%. During the rolling process of this magnesium rare earth alloy, we carefully selected the following rolling parameters to ensure that the material can meet the predetermined performance and dimensional requirements. The rolling temperature is set to 300°C. This optimal temperature range can not only maintain the plasticity of the alloy, but also effectively control the growth of grains, thereby ensuring the stability of the material during the rolling process and the final mechanical properties.

[0044] Furthermore, the rolling speed is controlled at 2 m / s. This optimal speed can not only ensure production efficiency, but also ensure good surface quality of materials during the rolling process and reduce surface defects. A moderate rolling speed can also help reduce equipment load and extend the service life of the mold.

[0045] In addition, the pass deformation is preferably set to 20%, which can ensure that the material is fully plastically deformed during each rolling process, but will not cause cracks or breaks inside the material due to excessive deformation. Through reasonable distribution of pass deformation, we can achieve uniform deformation of the material during the rolling process, thereby obtaining good dimensional accuracy and surface finish.

[0046] Specifically, during the entire rolling process, we will also pay close attention to the temperature changes, lubrication conditions and rolling force distribution of the material to ensure that each step of the operation is within the controllable range. By precisely controlling these rolling parameters, we expect the final magnesium rare earth alloy sheet to have good mechanical properties, dimensional accuracy and surface quality to meet the requirements of high-end application fields.

[0047] Furthermore, the hot extrusion process in the present application includes the following steps: The homogenized alloy material is extruded at a temperature of 380-430°C with an extrusion ratio of 14:1 to 20:1. During the hot extrusion process, the extrusion equipment extrude the alloy material at a head speed of 1 mm / s, thereby ensuring that the extruded material has good mechanical properties and surface quality.

[0048] Furthermore, the refined melt is quickly poured into the mold to avoid excessive cooling and ensure the molding quality of the casting. The heat treatment process is homogenized annealing at 400℃ for 12 hours to eliminate the component segregation that may occur during the casting process and ensure the uniformity of the internal microstructure of the material.

[0049] Further, through X-ray diffraction (XRD) analysis, the crystal form of the high stress corrosion resistance magnesium alloy of the present application is hexagonal close packing (HCP). Specifically, the HCP structure has two coordination layers, and the atoms of each layer are arranged above the pores of the other layer. Usually one out of every six atoms is covered by another layer. This arrangement makes each atom in the unit cell have 12 nearest neighbor atoms, that is, the coordination number is 12. Physically, the HCP structure has higher density and strength in metals.

[0050] In order to further reflect the technical effect of the present application, the present application respectively conducts slow strain rate tensile tests (SSRT) through Examples 1-5 and Comparative Examples 1-3 to evaluate the mechanical properties of magnesium alloys under SCC. The tests are conducted using a YYF-50 testing machine equipped with a glass chamber specially designed to contain corrosive solutions. The tensile specimens used in these tests are processed according to the design shown in FIG1 . Specifically, the parameters of Examples 1-5 and Comparative Examples 1-3 are as follows: Example 1 Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent to remove impurities; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentages of each element in the magnesium alloy are: gadolinium (Gd): 9.2 wt%, yttrium (Y): 2.8 wt%, zirconium (Zr): 0.4 wt%, and magnesium (Mg): 87.6.

[0051] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 14:1.

[0052] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0053] During the rolling process, the temperature of the alloy material was maintained at 300°C, the rolling speed was maintained at 2m / s, and the deformation per pass was 20%.

[0054] Example 2 Using a resistance furnace to heat and melt pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy, a second master alloy and a third alloy, and performing a de-impurity treatment with a refining agent; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentages of each element in the magnesium alloy are: gadolinium (Gd): 8.2wt%, yttrium (Y): 2.8 wt%, zirconium (Zr): 0.4 wt%, neodymium (Nd): 3%, and magnesium (Mg): 85.6.

[0055] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 14:1.

[0056] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0057] During the rolling process, the temperature of the alloy material was maintained at 300°C, the rolling speed was maintained at 2m / s, and the deformation per pass was 20%.

[0058] Example 3 Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent to remove impurities; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentage of each element in the magnesium alloy is: gadolinium (Gd): 9.1 wt%, yttrium (Y): 3.4wt%, zirconium (Zr): 0.4 wt%, and magnesium (Mg): 87.1wt%.

[0059] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 14:1.

[0060] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0061] During the rolling process, the temperature of the alloy material was maintained at 300°C, the rolling speed was maintained at 2m / s, and the deformation per pass was 20%.

[0062] Example 4 Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent to remove impurities; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentages of each element in the magnesium alloy are: gadolinium (Gd): 9.2 wt%, yttrium (Y): 2.8 wt%, zirconium (Zr): 0.4 wt%, and magnesium (Mg): 87.6.

[0063] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 20:1.

[0064] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0065] During the rolling process, the temperature of the alloy material was maintained at 300°C, the rolling speed was maintained at 2m / s, and the deformation per pass was 20%.

[0066] Example 5 Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent to remove impurities; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentages of each element in the magnesium alloy are: gadolinium (Gd): 9.2 wt%, yttrium (Y): 2.8 wt%, zirconium (Zr): 0.4 wt%, and magnesium (Mg): 87.6.

[0067] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 20:1.

[0068] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0069] During the rolling process, the temperature of the alloy material was maintained at 250°C, the rolling speed was maintained at 1m / s, and the deformation per pass was 10%.

[0070] Comparative Example 1 Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent to remove impurities; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentages of each element in the magnesium alloy are: aluminum (Al): 9.8wt%; zirconium (Zr): 0.4 wt%; magnesium (Mg): 89.8%.

[0071] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 14:1.

[0072] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0073] Comparative Example 2 Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent to remove impurities; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentages of each element in the magnesium alloy are: aluminum (Al): 12.5wt%; zirconium (Zr): 0.4 wt%; magnesium (Mg): 87.1%.

[0074] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 14:1.

[0075] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0076] Comparative Example 3 Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent to remove impurities; After impurities are removed, casting is performed, and after casting is completed, the alloy material is homogenized and hot extruded to obtain a magnesium alloy; The mass percentages of each element in the magnesium alloy are: aluminum (Al): 9.8wt%, yttrium (Y): 3 wt%, zirconium (Zr): 0.4wt%, and magnesium (Mg): 86.8%.

[0077] Among them, the homogenized alloy material is extruded at a temperature of 380°C and an extrusion ratio of 5:1.

[0078] During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

[0079] For the magnesium alloy samples prepared in the above Examples 1-5 and Comparative Examples 1-3, the present application tests the following standards: 1. The Ultimate Tensile Strength (UTS) test usually uses different standards depending on the material type. This application is based on the Chinese national standard GB / T 228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method".

[0080] 2. Yield strength refers to the maximum stress that a material can withstand before plastic deformation begins. Exceeding this stress level will cause the material to undergo irreversible deformation and be unable to return to its original shape. This application is based on the Chinese national standard GB / T228.1-2010 "Metallic Material Tensile Test Part 1: Room Temperature Test Method".

[0081] 3. Maximum elongation refers to the maximum plastic deformation experienced by a material before fracture, usually expressed as the percentage of the elongated length of the gauge length of the specimen at fracture to the original gauge length. Maximum elongation is an important indicator of material plasticity, reflecting the toughness and ductility of the material. This application is based on the Chinese national standard GB / T 228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method".

[0082] In view of the above-mentioned test objects and test methods, the test environment of this application is as follows: In order to evaluate the influence of corrosive media on cracking behavior, slow strain rate tests (SSRT) were carried out in two different environments: dry laboratory air and 3.5 wt% NaCl solution. Among them, the tensile test in dry air was used as the first test, and the tensile test in 3.5 wt% NaCl simulated seawater solution was carried out with a vertical rolling direction as the Y direction of 5×10 -6 Strain rate tensile testing was performed as the second test in a 3.5 wt% NaCl simulated seawater solution with the vertical rolling direction as the Y direction 5×10 -6 Strain rate stretching is used as the third test to observe the stress-strain curves under different embodiments to obtain data such as tensile strength, yield strength, and elongation. At the same time, data such as fracture morphology and surface morphology under different stretching rates and corrosion environments are obtained. The experimental data are as follows: Examples 1-4 are all not in air at 1×10 -6 Tensile test, Example 5 and Comparative Example 3: In air at 1×10 -5 Tensile test (higher strain rate, considering its extreme service conditions), the experimental data are as follows:

[0083] Table 1 Among them, Examples 1-4 and Comparative Examples 1-2 are prepared by mixing 1×10 -6 Tensile test, Example 5 and Example 3 are carried out in 3.5% NaCl simulated seawater solution at 1×10 -5 Tensile test (higher strain rate, considering its extreme service conditions):

[0084] Table 2 It can be seen from the contents of Table 1 and Table 2 that the magnesium alloys shown in Examples 1-5 of the present application are superior to the magnesium alloys in the comparative examples in terms of tensile strength, yield strength and elongation.

[0085] Specifically, in an air environment, the magnesium alloy samples of Examples 1 to 5 exhibited relatively high yield strength and tensile strength, and the relatively low elongation reflects that the material can still maintain good strength performance when subjected to high stress. However, the yield strength and tensile strength of the magnesium alloys in the comparative examples 1, 2, and 3 were significantly lower than those in the examples, showing the insufficiency of the material performance under the same conditions.

[0086] When the test environment was changed to a 3.5% NaCl simulated seawater solution, the magnesium alloy of the embodiment still maintained good yield strength and tensile strength. This shows that the magnesium alloy prepared in the present application not only performs well in a conventional environment, but also has good mechanical properties in a seawater environment containing a corrosive medium, which is higher than that of the comparative example. Although the performance of the magnesium alloy in the comparative example in a seawater environment is improved, it is still inferior to that of the embodiment as a whole.

[0087] In summary, the high stress-resistant and corrosion-resistant magnesium alloy for unmanned underwater vehicles prepared in the present application exhibits excellent mechanical properties in both air and simulated seawater environments, and can maintain good performance stability at different tensile rates, which is of great significance for improving the reliability and durability of unmanned underwater vehicles.

[0088] Furthermore, Figure 1 The sample dimensions for slow strain rate testing (SSRT) are shown in Figure 1. Figure 2 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 5×10 -6 Metal morphology after strain rate tensile fracture (optical image).

[0089] Furthermore, Figure 2 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 1×10 -6 Metal morphology after strain rate tensile fracture - surface macroscopic image under electron microscope (low magnification); it can be seen that the fracture surface presents a relatively smooth and dense morphology, without obvious crack extension paths or corrosion pits, which further confirms the high stress resistance of the magnesium alloy material in a dry environment.

[0090] Furthermore, Figure 3 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 1×10-6 Metal morphology after strain rate tensile fracture - surface image under electron microscope (high magnification); among them, the fine structure of the metal surface after extrusion can be observed, and the grains show a uniform and fine shape without obvious defects or impurities. In addition, it is worth noting that after the magnesium alloy is tensile fractured, its fracture surface does not show obvious brittle fracture characteristics, such as cleavage planes or river patterns, but shows the morphology of ductile fracture, such as dimples and tear edges. These characteristics indicate that when the magnesium alloy is subjected to external force, it can absorb energy through a large amount of plastic deformation, thereby improving its fracture resistance and reliability.

[0091] Furthermore, Figure 4 The prepared VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle was heated to 5×10 -6 Metal morphology after strain rate tensile fracture—fracture image under electron microscope (low magnification) and Figure 6 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 5×10 -6 The metal morphology after strain rate tensile fracture - the fracture image under electron microscope (high magnification). Figure 5 , we can see obvious dimple-shaped fracture surfaces (or ductile pits). These dimples are formed because the dislocation movement leads to local plastic flow during the plastic deformation of the material, and finally a series of pits are formed on the fracture surface. The presence of more dimples actually reflects the excellent tensile properties of the material during the tensile process, which is specifically reflected in the following aspects.

[0092] Plastic deformation capability: The formation of dimples indicates that the material can withstand large plastic deformation without immediate fracture during stretching. This means that the material has good plasticity and can absorb external energy to a certain extent, thus providing better safety and reliability when subjected to external forces. At the same time, the dimples also show that the VW-UUV high stress corrosion resistant magnesium alloy designed for unmanned underwater vehicles has good toughness: the presence of dimples is usually closely related to the toughness of the material. Toughness refers to the energy that a material can absorb before fracture. More toughness means that the material can absorb more energy before fracture and exhibits higher toughness, which is crucial to preventing sudden fractures and improving the safety of the structure. Further, Figure 6 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle was rolled in 3.5 wt% NaCl simulated seawater solution at a rolling speed of 5×10 -6 Strain rate tensile. By analyzing the stress-strain curve, it can be clearly seen that stress corrosion cracking (SSC) is one of the main factors leading to the degradation of material mechanical properties.

[0093] Furthermore, Figure 7 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 5×10 -6 Metal morphology after strain rate tensile fracture - surface macroscopic image under electron microscope (low magnification), among which, although Figure 7 In the low-magnification electron microscope image shown, the surface of the magnesium alloy after fracture in the simulated seawater solution is slightly rougher than that in the dry environment, but overall it still maintains a relatively flat and dense shape.

[0094] Furthermore, Figure 8 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 5×10 -6 The metal morphology after strain rate tensile fracture - the fracture picture under electron microscope (low magnification), among which, Fig.11 Observation under a low-power electron microscope shows that the fracture morphology of the VW-UUV high stress corrosion resistant magnesium alloy after fracture in a 3.5% NaCl simulated seawater solution still presents a complex structure. Despite the presence of slight corrosion marks, the overall fracture still maintains a relatively regular fracture surface, indicating that the alloy still has a high fracture resistance in a corrosive environment.

[0095] Furthermore, Fig. 9 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 5×10 -6 Metal morphology after strain rate tensile fracture - Strain rate tensile fracture under electron microscope (high magnification), in which the VW-UUV high stress corrosion resistant magnesium alloy used for unmanned underwater vehicles was tensile tested in dry laboratory air at 5×10 -6 Metal morphology after strain rate tensile fracture - The fracture image under the electron microscope shows that the fracture section has dimples, tear edges and tear ridges. This microstructural feature shows that the alloy can effectively absorb energy during the stretching process and exhibit good plastic deformation ability. The formation of dimples shows that the material has undergone significant plastic deformation before fracture, while the presence of tear edges and tear ridges further proves the tensile strength and toughness of the material. These features together show that the VW-UUV alloy has excellent mechanical properties under stress, can work reliably under high loads and extreme environments, and ensure the structural safety and stability of unmanned underwater vehicles.

[0096] Furthermore, Fig.10 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was subjected to 1×10-5 The stress-strain diagram of strain rate tension. Fig.14 In the stress-strain diagram, we can observe that the VW-UUV high stress corrosion resistant magnesium alloy has a higher strain rate (1×10 -5 ) and tensile behavior in 3.5wt% NaCl simulated seawater solution. This test further verifies the performance of the alloy under extreme conditions.

[0097] Further, such as Fig.11 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 1×10 -5 Metal morphology after strain rate tensile fracture - surface macroscopic image under electron microscope (low magnification), where Fig.11 In the low-magnification electron microscope image of VW-UUV high stress corrosion resistant magnesium alloy in 3.5% NaCl simulated seawater solution at a higher strain rate (1×10 -5 ) After being stretched and broken, its surface morphology still shows good corrosion resistance. Although the increase in strain rate increases the risk of stress corrosion cracking (SSC) of the alloy during the stretching process, there are no significant deep pits or large areas of corrosion on the alloy surface, but relatively uniform and dense corrosion marks. This shows that the microstructure and chemical composition of the VW-UUV alloy can still maintain stable performance when dealing with high strain rates and corrosive environments.

[0098] Further, such as Fig.12 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 1×10 -5 The metal morphology after strain rate tensile fracture - surface image under electron microscope (high magnification), where Fig.12 The high-power electron microscope image of VW-UUV high stress corrosion resistant magnesium alloy in 3.5% NaCl simulated seawater solution at 1×10 -5 The microstructure after strain rate tensile fracture is further revealed Further, such as Fig.13 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 1×10 -5 The metal morphology after strain rate tensile fracture - the fracture picture under electron microscope (low magnification), among which, Fig.13 Under a low-magnification electron microscope, the fracture morphology of the VW-UUV high stress corrosion resistant magnesium alloy in a simulated seawater environment appears particularly complex and orderly.

[0099] Further, such as Fig.14 The VW-UUV high stress corrosion resistant magnesium alloy for unmanned underwater vehicle prepared in Example 1 was heated to 1×10 -5 Metal morphology after strain rate tensile fracture - SEM fracture image (high magnification), in which the VW-UUV high stress corrosion resistant magnesium alloy prepared for unmanned underwater vehicle was subjected to 1×10 -5 It can be clearly seen from the stress after the strain rate tensile fracture and the characterization diagram of the fracture and cross section that stress corrosion cracking (SSC) is one of the key factors causing the degradation of the mechanical properties of the material. -5 In a slow strain rate tensile test such as the strain rate Fig.14 It is difficult to find dimples in the electron microscope image of the metal morphology after high-multiple tensile fracture. The small number of dimples and the large number of tear edges and tear ridges in the fracture morphology usually indicate that the material has experienced lower ductility and higher brittleness during the fracture process. This phenomenon may be related to the influence of stress corrosion cracking (SSC), indicating that the material fails to effectively absorb energy when subjected to stress, resulting in poor toughness during the fracture process, manifested as more tearing characteristics.

[0100] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle, characterized in that: Here are the steps: Pure magnesium with a purity of 99.99wt%, pure zirconium with a purity of 99.99wt%, a first master alloy and a second master alloy are heated and melted in a resistance furnace and subjected to a refining agent for impurity removal; After impurities are removed, casting is performed, after casting, the alloy material is homogenized and hot extruded, and the hot extruded alloy is rolled to obtain a magnesium alloy; The first master alloy contains 30 wt % of gadolinium and 70 wt % of magnesium, and the second master alloy contains 30 wt % of yttrium and 70 wt % of magnesium.

2. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 1, characterized in that: The magnesium alloy contains gadolinium, yttrium, zirconium and magnesium; The gadolinium content is: 7wt%-10wt%, the yttrium content is: 2.5wt%-4wt%, the zirconium content is: 0.25wt%-1wt%; and the magnesium content is: 80wt%-90wt%.

3. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 2, characterized in that: During the preparation of the magnesium alloy, any one of neodymium, cerium and erbium is added.

4. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 3, characterized in that: During the preparation of the magnesium alloy, neodymium is added in an amount of 2.5wt%-4wt% of the magnesium alloy.

5. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 4, characterized in that: In the magnesium alloy, the gadolinium content is: 8wt%-9wt%, the yttrium content is: 3wt%-4wt%, the zirconium content is: 0.25wt%-0.5wt%, the magnesium content is: 80wt%-90wt%, and the neodymium content is: 3wt%-4wt%.

6. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 1, characterized in that: The hot extrusion process comprises the following steps: Extruding the homogenized alloy material at a temperature of 380-430° C. with an extrusion ratio of 14:1 to 20:1; During the hot extrusion process, the extrusion equipment extrudes the alloy material at a ram speed of 1 mm / s.

7. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 1, characterized in that: The furnace in the smelting process is a medium carbon steel crucible, the carbon steel crucible is heated to 700-750° C. during the smelting process, and the alloy material in the carbon steel crucible during the smelting process is stirred at a stirring rate of 200RPM-400RPM by a stirring device; In the smelting process, a mixed gas of SF6 and CO2 is used as a protective gas; The mass fraction of SF6 in the mixed gas is 0.5wt%, and the mass fraction of CO2 is 99.5wt%.

8. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 7, characterized in that: The carbon steel crucible is heated to 720° C. during the smelting process. After the refining agent is added, the stirring device starts to stir the alloy material in the carbon steel crucible during the smelting process at a stirring rate of 300 RPM for 10 minutes to 15 minutes.

9. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 1, characterized in that: The refining agent is a chloride or fluoride mixture, and the temperature of the alloy material is maintained at 700° C.-750° C. during the refining process; During the rolling process, the temperature of the alloy material is maintained at 250° C.-400° C., the rolling speed is maintained at 0.5 m / s-2 m / s, and the deformation amount per pass is 10%-50%.

10. The method for preparing a high stress-resistant and corrosion-resistant magnesium alloy for an unmanned underwater vehicle according to claim 1, characterized in that: A third master alloy is added during the process of heating and melting in a resistance furnace and removing impurities through a refining agent; the third master alloy contains 30wt% neodymium and 70wt% magnesium.

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