A high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance and its preparation method

Abstract

This invention discloses a high-corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance and its preparation method. The chemical composition of the Mg-Sn-Ge-Mn alloy material, by mass percentage, is: Sn: 0.05–0.30%, Ge: 0.05–0.20%, Mn: 0.05–0.30%, with the balance being Mg. The preparation method includes the following steps: S1, calculating the required weight of each raw material based on the nominal composition of the Mg-Sn-Ge-Mn alloy, and selecting the raw materials Mg, Sn, Ge, and Mn; S2, placing the raw materials Mg, Sn, Ge, and Mn in a crucible and heating to a preset temperature under the protection of an SF6 / CO2 mixed gas for melting; S3, casting the molten alloy raw materials; S4, subjecting the cast Mg-Sn-Ge-Mn alloy ingot to reciprocating extrusion hot processing to obtain the high-corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance.

Description

Technical Field

[0001] This invention belongs to the field of microalloyed materials technology, specifically relating to a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance and its preparation method. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials currently used in engineering, possess characteristics such as high specific strength, thermal conductivity, and good biocompatibility. However, magnesium has a low standard electrode potential, making it susceptible to galvanic corrosion, which leads to premature failure in practical applications. Microalloying can improve corrosion resistance while controlling costs, and can effectively reduce the impact of galvanic corrosion on the alloy's corrosion resistance. However, current research has confirmed that the precipitation of Fe / Si impurity particles during heat treatment and hot working of microalloyed magnesium alloys can cause a sharp decline in corrosion resistance. Summary of the Invention

[0003] In view of this, embodiments of the present invention disclose a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance and its preparation method. By using Mn to coat the Fe / Si impurity particles precipitated during heat treatment, the tendency of local corrosion is suppressed. After repeated extrusion hot working, not only is the high corrosion resistance of the alloy maintained, but the mechanical properties of the alloy are also improved, effectively solving the problem of the sharp decline in corrosion resistance of microalloyed magnesium alloys after heat treatment.

[0004] On the one hand, some embodiments disclose a highly corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance, the chemical composition of which, by mass percentage, is: Sn: 0.05-0.30%, Ge: 0.05-0.20%, Mn: 0.05-0.30%, with the balance being Mg.

[0005] On the other hand, some embodiments disclose a method for preparing a highly corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance, including the following steps:

[0006] S1. Calculate the required weight of each raw material based on the nominal composition of the Mg-Sn-Ge-Mn alloy, and select the raw materials Mg, Sn, Ge, and Mn;

[0007] S2. Raw materials Mg, Sn, Ge and Mn are placed in a crucible and heated to a preset temperature under the protection of SF6 / CO2 mixed gas for melting;

[0008] S3. The molten alloy raw material is cast into shape;

[0009] S4. The cast Mg-Sn-Ge-Mn alloy ingot is subjected to reciprocating extrusion hot processing to obtain a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance.

[0010] Furthermore, in some embodiments, the method for preparing highly corrosion-resistant Mg-Sn-Ge-Mn alloy materials with heat resistance disclosed includes step S1 further comprising:

[0011] The raw materials Mg, Sn, Ge, and Mn are cut and polished to remove the oxide scale;

[0012] The smelting raw materials Mg, Sn, Ge, and Mn are placed in a preheating furnace and heated and dried at 200°C for later use.

[0013] The method for preparing a highly corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance disclosed in some embodiments further includes step S2:

[0014] Before smelting, the casting molds and smelting tools are cleaned and coated with zinc oxide paint.

[0015] Place the casting mold and smelting tools in a preheating furnace and dry them at 200°C for later use.

[0016] Some embodiments disclose a method for preparing highly corrosion-resistant Mg-Sn-Ge-Mn alloy materials with heat resistance. Step S2 specifically includes:

[0017] Spray boron nitride release agent on the inner wall of the crucible, place the crucible in the resistance furnace, introduce SF6 / CO2 mixed protective gas in advance, and heat at 450℃ for 10 minutes.

[0018] After the boron nitride is completely dry, add the preheated raw materials in sequence, raise the temperature to the preset temperature of 750°C to melt, and after reaching the preset temperature of 750°C, adjust the temperature to 720°C and continue heating for 1 hour to completely melt the alloy.

[0019] Some embodiments disclose a method for preparing highly corrosion-resistant Mg-Sn-Ge-Mn alloy materials with heat resistance. Step S3 specifically includes:

[0020] The molten alloy raw material is stirred evenly with a mechanical stirring rod for 5 minutes under the protection of SF6 / CO2 mixed gas. After standing for 15 minutes, the slag is removed. After removing the slag, the slag removal is repeated once the furnace temperature rises to 720℃. Then, the casting is immediately carried out.

[0021] Some embodiments disclose a method for preparing highly corrosion-resistant Mg-Sn-Ge-Mn alloy materials with heat resistance. Step S4 specifically includes:

[0022] The Mg-Sn-Ge-Mn alloy ingot was processed into an extrusion billet by wire cutting. The oxide products on the surface of the extrusion billet were removed by grinding. Graphite emulsion was used as a lubricant. The extrusion billet was placed in a mold preheated to the set temperature and held for 20 minutes to allow it to be fully heated. Then, heating was stopped and reciprocating extrusion was performed immediately. After processing, the billet was demolded and the Mg-Sn-Ge-Mn alloy sample was rapidly water-cooled.

[0023] Some embodiments disclose a method for preparing a highly corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance, wherein the volume ratio of SF6 to CO2 in the SF6 / CO2 mixed gas is 1:99. 。

[0024] In some embodiments, a method for preparing a highly corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance is disclosed. In step S4, the extrusion pressure of the reciprocating extrusion process is 120t, the upward and downward extrusion speeds are both 6mm / s, and the processing temperature is 280~360℃.

[0025] In some embodiments, a method for preparing a highly corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance is disclosed. In step S4, the reciprocating extrusion process consists of 3, 5, or 7 passes.

[0026] The high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance and its preparation method disclosed in the embodiments of the present invention have at least the following beneficial technical effects:

[0027] (1) Trace element Mn can improve the corrosion uniformity of alloys and reduce the occurrence of galvanic corrosion;

[0028] (2) Trace element Mn can coat Fe / Si impurity particles to a certain extent, improve the resistance of Mg-Sn-Ge-Mn alloy to heat input, and improve the local corrosion behavior of the alloy.

[0029] (3) Reciprocating extrusion processing can break the second phase particles in Mg-Sn-Ge-Mn alloy and promote uniform corrosion of the alloy;

[0030] (4) This large plastic deformation process significantly refines the grain size of the alloy and improves the mechanical properties of the alloy;

[0031] (5) Through the synergistic design of alloy composition and processing technology, the precipitation of Fe / Si impurity particles in the alloy during heat treatment was effectively controlled, and the tendency of local corrosion caused by impurity particles was weakened. Ultimately, while maintaining the high corrosion resistance of the alloy, the mechanical properties of the Mg-Sn-Ge-Mn alloy were also improved. After reciprocating extrusion processing, the corrosion rate of the Mg-Sn-Ge-Mn alloy in 3.5wt.% NaCl solution was still only 0.055mm / year. Compared with the Mg-0.15Ca alloy, the Mg-Sn-Ge-Mn alloy has a significant resistance to heat input during hot working. Attached Figure Description

[0032] Figure 1 SEM images of alloy materials disclosed in some embodiments after heat treatment;

[0033] Figure 2 SEM images of impurity particles in alloy materials disclosed in some embodiments after heat treatment;

[0034] Figure 3 The image shows the surface elemental distribution of the alloy material disclosed in some embodiments after heat treatment and corrosion in a 3.5 wt.% NaCl solution for 10 min.

[0035] Figure 4 The test curves of the alloy materials obtained in Examples 1 to 3 in 3.5 wt.% NaCl solution are shown, where (a) is the polarization curve and (b) is the AC impedance diagram.

[0036] Figure 5 The hydrogen evolution test curves of the alloy materials obtained in Examples 1-3 after a cumulative 7 days in 3.5 wt.% NaCl solution are shown.

[0037] Figure 6 The corrosion morphology of the alloy materials obtained in Examples 1-3 after 7 days of corrosion in 3.5 wt.% NaCl solution. Detailed Implementation

[0038] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in these embodiments is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0039] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain; other experimental methods and technical means not specifically noted in the embodiments of this invention refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0040] The terms “basic” and “approximately” as used herein are used to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format herein are used for convenience and brevity only, and should therefore be interpreted flexibly to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0041] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0042] To better illustrate the content of this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the invention can be practiced even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail, in order to highlight the main points of the invention.

[0043] Without conflict, the technical features disclosed in the embodiments of the present invention can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of the present invention.

[0044] In some embodiments, the high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance has the following chemical composition by mass percentage: Sn: 0.05-0.30%, Ge: 0.05-0.20%, Mn: 0.05-0.30%, with the balance being Mg.

[0045] In some embodiments, the preparation method of a highly corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance includes the following steps:

[0046] S1. Calculate the required weight of each raw material based on the nominal composition of the Mg-Sn-Ge-Mn alloy, and select the raw materials Mg, Sn, Ge, and Mn. Usually, the raw materials Mg, Sn, Ge, and Mn also need to be cut and polished to remove the oxide scale. Place the smelting raw materials Mg, Sn, Ge, and Mn in a preheating furnace and heat them at 200℃ to dry them for later use.

[0047] S2. Raw materials Mg, Sn, Ge, and Mn are placed in a crucible and heated to a preset temperature under the protection of SF6 / CO2 mixed gas for melting. Usually, before melting, the casting mold and melting tools need to be cleaned and coated with zinc oxide paint. The casting mold and melting tools are then dried in a preheating furnace at 200°C for later use.

[0048] In some embodiments, a boron nitride release agent is sprayed onto the inner wall of the crucible, the crucible is placed in a resistance furnace, and a SF6 / CO2 mixed protective gas is introduced in advance. The crucible is heated at 450°C for 10 minutes. After the boron nitride is completely dry, the preheated raw materials are added in sequence, and the temperature is raised to the preset temperature of 750°C to melt. After reaching the preset temperature of 750°C, the temperature is adjusted to 720°C and the heating continues for 1 hour to completely melt the alloy.

[0049] In some embodiments, the volume ratio of SF6 to CO2 in the SF6 / CO2 mixture is 1:99. 。

[0050] S3. The molten alloy raw material is cast into shape; in some embodiments, the molten alloy raw material is uniformly stirred for 5 minutes with a mechanical stirring rod under the protection of SF6 / CO2 mixed gas, and after standing for 15 minutes, the slag is removed. After removing the slag, the slag removal is repeated once the furnace temperature rises to 720°C, and then casting is performed immediately.

[0051] S4. The cast Mg-Sn-Ge-Mn alloy ingot is subjected to reciprocating extrusion hot processing to obtain a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance. In some embodiments, the Mg-Sn-Ge-Mn alloy ingot is processed into an extrusion billet using wire cutting. The oxide products on the surface of the extrusion billet are removed by grinding. Graphite emulsion is used as a lubricant. The extrusion billet is placed in a mold preheated to a set temperature and held for 20 minutes to allow it to be fully heated. Then, heating is stopped and reciprocating extrusion processing is performed immediately. After processing, the sample is demolded and the Mg-Sn-Ge-Mn alloy sample is rapidly water-cooled.

[0052] In some embodiments, the extrusion pressure of the reciprocating extrusion process is 120t, the upward and downward extrusion speeds are both 6mm / s, and the processing temperature is 280~360℃.

[0053] In some embodiments, the reciprocating extrusion process consists of 3, 5, or 7 passes.

[0054] Typically, heat input during heat treatment and processing leads to the precipitation of a large number of Fe / Si particles in the alloy. These impurities cause rapid corrosion of magnesium alloys. Mn can coat these impurities, suppressing galvanic corrosion, improving localized corrosion behavior, and enhancing corrosion resistance. Reciprocating extrusion is a high-plasticity deformation process that can significantly refine grains, break down second-phase particles, and change the alloy's corrosion mode. Reciprocating extrusion results in finer, more dispersed second-phase particles in the Mg-Sn-Ge-Mn alloy matrix, suppressing galvanic corrosion and giving the alloy uniform corrosion characteristics. Simultaneously, the finer grains produced by reciprocating extrusion improve the alloy's mechanical properties. These finer grains also have higher energy, providing more active sites during corrosion, promoting the rapid formation of a dense corrosion product film on the alloy surface, and reducing the corrosion depth.

[0055] Generally, as the Mn content increases, the content of impurity elements precipitated during the heat treatment of the alloy decreases significantly. Figure 1 SEM images of three alloy materials disclosed in some embodiments are listed, where (a) is alloy Mg-0.1Sn-0.1Ge; (b) is alloy Mg-0.1Sn-0.1Ge-0.05Mn; and (c) is alloy Mg-0.1Sn-0.1Ge-0.3Mn. From the SEM images, it can be seen that the Mg-0.1Sn-0.1Ge alloy has large impurity particles precipitated. With the addition of Mn element, it transforms into strip-shaped symbiotic phase, and finally is completely covered and transforms into spherical symbiotic phase. Table 1 lists the EDS results of the three alloys. Combining the EDS results in Table 1, it can also be found that the impurity content is significantly reduced. Figure 2 SEM images of impurity particles for two alloys are shown, where (a) is alloy Mg-0.1Sn-0.1Ge-0.05Mn and (b) is alloy Mg-0.1Sn-0.1Ge-0.3Mn; see [link to SEM image]. Figure 2 The morphology of the impurity particles, combined with the elemental distribution map, provides a more intuitive understanding of this coating effect. The distribution of Mn and other impurity elements such as Fe / Si shows that their distributions overlap, and with increasing Mn content, the symbiotic structure changes from strip-like to spherical coating. Figure 3 The surface elemental distributions of two heat-treated alloys after corrosion in 3.5 wt.% NaCl solution for 10 min are shown. (a) is alloy Mg-0.1Sn-0.1Ge-0.05Mn, and (b) is alloy Mg-0.1Sn-0.1Ge-0.3Mn. (See also...) Figure 3This can better illustrate the impact of this transformation on the corrosion resistance of the alloy. Figure 3 (a) shows, in conjunction with the O element distribution diagram, that the sites where Fe impurity particles precipitate are preferentially corroded; while... Figure 3 In (b), the Mn element coats the impurity particles, inhibiting the tendency of the alloy to undergo galvanic corrosion. During the alloy corrosion process, these impurity particles do not serve as sites for corrosion initiation.

[0056] Table 1. EDS results of alloy materials after homogenization treatment

[0057]

[0058] The technical details are further illustrated below with reference to the embodiments.

[0059] Example 1

[0060] Example 1 discloses the preparation of Mg-0.1Sn-0.1Ge-0.05Mn alloy material. The equipment used is model (YX32-200D), the extrusion pressure is 120t, the upward and downward extrusion speeds are both 6mm / s, and the volume ratio of SF6 / CO2 mixed protective gas is 1:99.

[0061] The preparation method of Mg-0.1Sn-0.1Ge-0.05Mn alloy material includes the following steps:

[0062] S1. Calculate the required weight of each raw material based on the nominal composition of the alloy, then cut and grind the raw materials to remove the oxide scale for later use; after the raw materials are prepared, place all the smelting raw materials in a preheating furnace and heat them at 200℃ to dry them for later use; by mass content, Mg: 99.3%, Sn: 0.1%, Ge: 0.1%, Mn: 0.05%;

[0063] S2. Before smelting, clean the casting mold and smelting tools, then spray zinc oxide coating on their surfaces and dry them in a preheating furnace at 200°C for later use.

[0064] S3. After cleaning the crucible, spray boron nitride release agent on its inner wall, put the crucible into the resistance furnace, introduce SF6 / CO2 mixed protective gas in advance, heat at 450℃ for 10 minutes, and after the boron nitride is completely dry, add the preheated raw materials in sequence, heat to the preset temperature of 750℃ to melt, and after reaching the preset temperature, adjust the temperature to 720℃ and continue heating for one hour to completely melt the alloy.

[0065] S4. After melting, stir evenly with a mechanical stirring rod for 5 minutes under gas protection, let stand for 15 minutes, remove the slag, and repeat the slag removal process once the furnace temperature rises to 720℃. Then immediately cast.

[0066] S5. The ingot is processed into an extrusion billet of Ф36 mm×60 mm using wire cutting. The oxide products on the surface of the extrusion billet are removed by polishing with 200# sandpaper. Graphite emulsion is used as a lubricant. The extrusion billet is placed in a mold preheated to 320℃ and kept at the temperature for 20 minutes to allow it to be fully heated. Then, heating is stopped and reciprocating extrusion is performed immediately. After reciprocating extrusion for 5 passes, the matching demolding ejector pin is used to demold the billet. The sample is then rapidly water-cooled to obtain a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance.

[0067] See Figure 4 The polarization curve (a) and AC impedance diagram (b) of the Mg-0.1Sn-0.1Ge-0.05Mn alloy obtained in Example 1, tested in a 3.5 wt.% NaCl solution, show that the low-frequency impedance film value of the alloy is approximately 7000 Ω·cm. 2 The alloy has excellent corrosion resistance.

[0068] See Figure 5 The hydrogen evolution test curve of the Mg-0.1Sn-0.1Ge-0.05Mn alloy material obtained in Example 1 after 7 days in 3.5 wt.% NaCl solution showed that the corrosion rate of the material was only 0.055 mm / year.

[0069] See Figure 6 In Example (a), the corrosion morphology of the Mg-0.1Sn-0.1Ge-0.05Mn alloy obtained in Example 1 after 7 days of corrosion in 3.5wt.%NaCl solution showed that the corrosion morphology of the material surface was relatively smooth, and the refinement of alloy grains and second phase particles effectively improved the corrosion uniformity of the alloy.

[0070] Example 2

[0071] Example 2 discloses the preparation of Mg-0.05Sn-0.05Ge-0.05Mn alloy material. The equipment used is model (YX32-200D), the extrusion pressure is 120t, the upward and downward extrusion speeds are both 6mm / s, and the volume ratio of SF6 / CO2 mixed protective gas is 1:99.

[0072] The preparation method of Mg-0.05Sn-0.05Ge-0.05Mn alloy material includes the following steps:

[0073] S1. Calculate the required weight of each raw material based on the nominal composition of the alloy, then cut and grind the raw materials to remove the oxide scale for later use; after the raw materials are prepared, place all the smelting raw materials in a preheating furnace and heat them at 200℃ to dry them for later use; by mass content, Mg: 99.85%, Sn: 0.05%, Ge: 0.05%, Mn: 0.05%;

[0074] S2. Before smelting, clean the casting mold and smelting tools, then spray zinc oxide coating on their surfaces and dry them in a preheating furnace at 200°C for later use.

[0075] S3. After cleaning the crucible, spray boron nitride release agent on its inner wall, put the crucible into the resistance furnace, introduce SF6 / CO2 mixed protective gas in advance, heat at 450℃ for 10 minutes, and after the boron nitride is completely dry, add the preheated raw materials in sequence, heat to the preset temperature of 750℃ to melt, and after reaching the preset temperature, adjust the temperature to 720℃ and continue heating for one hour to completely melt the alloy.

[0076] S4. After melting, stir evenly with a mechanical stirring rod for 5 minutes under gas protection, let stand for 15 minutes, remove the slag, and repeat the slag removal process once the furnace temperature rises to 720℃. Then immediately cast.

[0077] S5. The ingot is processed into an extrusion billet of Ф36 mm×60 mm using wire cutting. The oxide products on the surface of the extrusion billet are removed by polishing with 200# sandpaper. Graphite emulsion is used as a lubricant. The extrusion billet is placed in a mold preheated to 360℃ and kept at the temperature for 20 minutes to allow it to be fully heated. Then, heating is stopped and reciprocating extrusion is performed immediately. After reciprocating extrusion for 5 passes, the matching demolding ejector pin is used to demold the billet. The sample is then rapidly water-cooled to obtain a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance.

[0078] See Figure 4 The polarization curve (a) and AC impedance diagram (b) of the Mg-0.05Sn-0.05Ge-0.05Mn alloy obtained in Example 2, tested in a 3.5 wt.% NaCl solution, show that the low-frequency impedance film value of the alloy is approximately 7000 Ω·cm. 2 The alloy has excellent corrosion resistance.

[0079] See Figure 5 The hydrogen evolution test curve of the Mg-0.05Sn-0.05Ge-0.05Mn alloy material obtained in Example 2 after 7 days in 3.5 wt.% NaCl solution showed that the corrosion rate of the material was only 0.06 mm / year.

[0080] See Figure 6In Example (b), the corrosion morphology of the Mg-0.05Sn-0.05Ge-0.05Mn alloy obtained in Example 2 after 7 days of corrosion in 3.5wt.%NaCl solution showed that the corrosion morphology of the material surface was relatively smooth, and the refinement of alloy grains and second phase particles effectively improved the corrosion uniformity of the alloy.

[0081] Example 3

[0082] Example 3 discloses the preparation of Mg-0.3Sn-0.2Ge-0.3Mn alloy material. The equipment used is model (YX32-200D), the extrusion pressure is 120t, the upward and downward extrusion speeds are both 6mm / s, and the volume ratio of SF6 / CO2 mixed protective gas is 1:99.

[0083] The preparation method of Mg-0.3Sn-0.2Ge-0.3Mn alloy material includes the following steps:

[0084] S1. Calculate the required weight of each raw material based on the nominal composition of the alloy, then cut and grind the raw materials to remove the oxide scale for later use; after the raw materials are prepared, place all the smelting raw materials in a preheating furnace and heat them at 200℃ to dry them for later use; by mass content, Mg: 99.2%, Sn: 0.3%, Ge: 0.2%, Mn: 0.3%;

[0085] S2. Before smelting, clean the casting mold and smelting tools, then spray zinc oxide coating on their surfaces and dry them in a preheating furnace at 200°C for later use.

[0086] S3. After cleaning the crucible, spray boron nitride release agent on its inner wall, put the crucible into the resistance furnace, introduce SF6 / CO2 mixed protective gas in advance, heat at 450℃ for 10 minutes, and after the boron nitride is completely dry, add the preheated raw materials in sequence, heat to the preset temperature of 750℃ to melt, and after reaching the preset temperature, adjust the temperature to 720℃ and continue heating for one hour to completely melt the alloy.

[0087] S4. After melting, stir evenly with a mechanical stirring rod for 5 minutes under gas protection, let stand for 15 minutes, remove the slag, and repeat the slag removal process once the furnace temperature rises to 720℃. Then immediately cast.

[0088] S5. The ingot is processed into an extrusion billet of Ф36 mm×60 mm using wire cutting. The oxide products on the surface of the extrusion billet are removed by polishing with 200# sandpaper. Graphite emulsion is used as a lubricant. The extrusion billet is placed in a mold preheated to 320℃ and kept at the temperature for 20 minutes to allow it to be fully heated. Then, heating is stopped and reciprocating extrusion is performed immediately. After 7 reciprocating extrusions, the matching demolding ejector pin is used to demold the billet. The sample is then rapidly water-cooled to obtain a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance.

[0089] See Figure 4 The polarization curve (a) and AC impedance diagram (b) of the Mg-0.3Sn-0.2Ge-0.3Mn alloy obtained in Example 3, tested in a 3.5 wt.% NaCl solution, show that the low-frequency impedance film value of the alloy is approximately 11000 Ω·cm. 2 The alloy has excellent corrosion resistance.

[0090] See Figure 5 The hydrogen evolution test curve of the Mg-0.3Sn-0.2Ge-0.3Mn alloy material obtained in Example 3 after 7 days in 3.5wt.% NaCl solution showed that the corrosion rate of the material was only 0.10 mm / year.

[0091] See Figure 6 In Example (c), the corrosion morphology of the Mg-0.3Sn-0.2Ge-0.3Mn alloy obtained in Example 3 after 7 days of corrosion in 3.5wt.%NaCl solution showed that the corrosion morphology of the material surface was relatively smooth, and the refinement of alloy grains and second phase particles effectively improved the corrosion uniformity of the alloy.

[0092] Combination Figure 4 , Figure 5 , Figure 6 The test results of the various embodiments demonstrate that the Mg-Sn-Ge-Mn alloy material exhibits good resistance to heat input. Different levels of heat input and reciprocating extrusion passes (deformation) during processing have little impact on the corrosion resistance of the alloy material. The Mg-Sn-Ge-Mn alloy materials processed using several different processes maintained high corrosion resistance, with corrosion rates all below 0.1 mm / year. The preparation method disclosed in this invention, through alloy design, controls the precipitation of impurity elements in the microalloyed magnesium alloy during heat treatment, thus solving the problem of a sharp decline in corrosion resistance of microalloyed magnesium alloys after heat treatment.

[0093] The high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance and its preparation method disclosed in the embodiments of the present invention have at least the following beneficial technical effects:

[0094] (1) Trace element Mn can improve the corrosion uniformity of alloys and reduce the occurrence of galvanic corrosion;

[0095] (2) Trace element Mn can coat Fe / Si impurity particles to a certain extent, improve the resistance of Mg-Sn-Ge-Mn alloy to heat input, and improve the local corrosion behavior of the alloy.

[0096] (3) Reciprocating extrusion processing can break the second phase particles in Mg-Sn-Ge-Mn alloy and promote uniform corrosion of the alloy;

[0097] (4) This large plastic deformation process significantly refines the grain size of the alloy and improves the mechanical properties of the alloy;

[0098] (5) Through the coordinated design of alloy composition and processing technology, the precipitation of Fe / Si impurity particles in the alloy during heat treatment was effectively controlled, and the tendency of local corrosion caused by impurity particles was weakened. In the end, the mechanical properties of Mg-Sn-Ge-Mn alloy were improved while maintaining the high corrosion resistance of the alloy. After reciprocating extrusion processing, the corrosion rate of Mg-Sn-Ge-Mn alloy in 3.5wt.% NaCl solution was still only 0.055mm / year, while the corrosion resistance of cast Mg-0.15Ca (0.13mm / year) decreased sharply after extrusion and rolling (1.7-3.3mm / year) (Journal of Magnesium and Alloys, 2023, 11(4): 1193-1205); compared with Mg-0.15Ca alloy, Mg-Sn-Ge-Mn alloy has obvious resistance to heat input during hot working.

[0099] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of the embodiments of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance, characterized in that, The chemical composition, by mass percentage, is: Sn: 0.05–0.30%, Ge: 0.05–0.20%, Mn: 0.05–0.30%, with the balance being Mg.

2. The method for preparing the high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance as described in claim 1, characterized in that, Including the following steps: S1. Calculate the required weight of each raw material based on the nominal composition of the Mg-Sn-Ge-Mn alloy, and select the raw materials Mg, Sn, Ge, and Mn; S2. Raw materials Mg, Sn, Ge and Mn are placed in a crucible and heated to a preset temperature under the protection of SF6 / CO2 mixed gas for melting; S3. The molten alloy raw material is cast into shape; S4. The cast Mg-Sn-Ge-Mn alloy ingot is subjected to reciprocating extrusion hot processing to obtain a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance.

3. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, Step S1 also includes: The raw materials Mg, Sn, Ge, and Mn are cut and polished to remove the oxide scale; The smelting raw materials Mg, Sn, Ge, and Mn are placed in a preheating furnace and heated and dried at 200°C for later use.

4. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, Step S2 also includes: Before smelting, the casting molds and smelting tools are cleaned and coated with zinc oxide paint. Place the casting mold and smelting tools in a preheating furnace and dry them at 200°C for later use.

5. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, Step S2 specifically includes: Spray boron nitride release agent on the inner wall of the crucible, place the crucible in the resistance furnace, introduce SF6 / CO2 mixed protective gas in advance, and heat at 450℃ for 10 minutes. After the boron nitride is completely dry, add the preheated raw materials in sequence, raise the temperature to the preset temperature of 750°C to melt, and after reaching the preset temperature of 750°C, adjust the temperature to 720°C and continue heating for 1 hour to completely melt the alloy.

6. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, Step S3 specifically includes: The molten alloy raw material is stirred evenly with a mechanical stirring rod for 5 minutes under the protection of SF6 / CO2 mixed gas. After standing for 15 minutes, the slag is removed. After removing the slag, the slag removal is repeated once the furnace temperature rises to 720℃. Then, the casting is immediately carried out.

7. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, Step S4 specifically includes: The Mg-Sn-Ge-Mn alloy ingot was processed into an extrusion billet by wire cutting. The oxide products on the surface of the extrusion billet were removed by grinding. Graphite emulsion was used as a lubricant. The extrusion billet was placed in a mold preheated to the set temperature and held for 20 minutes to allow it to be fully heated. Then, heating was stopped and reciprocating extrusion was performed immediately. After processing, the billet was demolded and the Mg-Sn-Ge-Mn alloy sample was rapidly water-cooled.

8. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, In the SF6 / CO2 mixture, the volume ratio of SF6 to CO2 is 1:

99. 。 9. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, In step S4, the extrusion pressure of the reciprocating extrusion process is 120t, the upward and downward extrusion speeds are both 6mm / s, and the processing temperature is 280~360℃.

10. The method for preparing a high corrosion-resistant Mg-Sn-Ge-Mn alloy material with heat resistance according to claim 2, characterized in that, In step S4, the reciprocating extrusion process consists of 3, 5, and 7 passes.

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