Micro-alloyed high corrosion resistant Mg-Sn-Ge alloy material and preparation method thereof

Abstract

The application discloses a kind of microalloying high corrosion-resistant Mg-Sn-Ge alloy material and preparation method thereof, belong to the technical field of microalloy material, and its chemical composition mass percentage is as follows: tin 0.01%-0.40%, germanium 0.01%-0.50%, impurity element: iron <0.005%, copper <0.0015%, nickel <0.002%, total impurity <0.025%, and the balance is magnesium.Method includes the following steps: S1, pure magnesium ingot, pure tin, pure germanium are proportioned, and preheated in preheating furnace;S2, crucible and smelting tool are cleaned, and preheated and dried;S3, crucible is heated to 400 DEG C, and SF6 / CO2 mixed protective gas is introduced, after 10 min, preheated charge is added, and the temperature is raised to 720 DEG C to melt charge;S4, under the protection of gas, after melting, charge is stirred for 5 min, and after standing for 15 min, slag is removed, and after slag removal, stand for 5 min;S5, casting, cooling, to obtain microalloying high corrosion-resistant Mg-Sn-Ge alloy material.The alloy material long-term corrosion test shows that the corrosion rate in 3.5 wt.%NaCl solution is as low as 0.1 mm / year, indicating that the alloy material has application potential in harsh environments such as ocean.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of micro-alloyed materials, and particularly relates to a preparation method of a micro-alloyed high-corrosion-resistant Mg-Sn-Ge alloy material. BACKGROUND

[0002] Magnesium alloy has high specific strength, high specific stiffness and good vibration absorption performance, and is thus considered as a material with great application potential in the field of lightweight structural materials. However, magnesium has a high chemical activity, and in some service environments, the corrosion rate is too fast, which easily causes premature failure of the material. Therefore, improving the corrosion resistance of magnesium alloy has been a research hotspot in the field for a long time.

[0003] Introducing alloying elements is an important method to improve the corrosion resistance of magnesium alloy. Some researchers have improved the corrosion resistance of magnesium alloy to some extent by introducing Al, Sc, rare earth elements and the like, but there are still some deficiencies in the related research. First, the addition of alloying elements may increase the number of second phases, which has the potential to cause local corrosion during long-term service. Second, some alloying elements are relatively expensive, and large amounts of addition will increase the cost of the alloy. How to improve the corrosion resistance of magnesium alloy by adding a small amount of alloying elements still needs further research. SUMMARY

[0004] The present application provides a micro-alloyed high-corrosion-resistant Mg-Sn-Ge alloy and a preparation method thereof, which inhibits the anodic and cathodic reactions in the corrosion process, reduces the local corrosion tendency, improves the corrosion resistance of the alloy, and significantly reduces the corrosion rate of the magnesium alloy.

[0005] The technical scheme adopted by the present application to achieve the purpose is as follows:

[0006] A micro-alloyed high-corrosion-resistant Mg-Sn-Ge alloy material, which has the following chemical composition by mass percentage: 0.01%-0.40% of tin, 0.01%-0.50% of germanium, impurity elements: less than 0.005% of iron, less than 0.0015% of copper, less than 0.002% of nickel, and less than 0.025% of total impurities, and the balance being magnesium.

[0007] The preparation method of the micro-alloyed high-corrosion-resistant Mg-Sn-Ge alloy material comprises the following steps:

[0008] S1, the purity of the raw material after cleaning 99.9 wt.% or more than magnesium ingot, purity 99.9 wt.% or more than tin, purity 99.9 wt.% or more than germanium according to the above chemical composition mass percentage, when batching, increase 10% of each raw material, punch the magnesium ingot, put tin and germanium in the hole of magnesium ingot, then add to the preheating furnace at 200 DEG C for 1h, standby;Punch the magnesium ingot, put tin and germanium in the hole of magnesium ingot, the purpose is to prevent tin and germanium from precipitating when smelting;

[0009] S2, the crucible and smelting tools (for example, stirring rod, skimmer, metal mold, etc.) are cleaned and preheated to 200 DEG C, and dried for standby;

[0010] S3, the crucible is heated to 400 DEG C, SF6 / CO2 mixed protective gas is introduced, 10 min later, the preheated charge in step S1 is added, the temperature is raised to 720 DEG C, the charge is melted, and the charge is heated to completely melt;

[0011] S4, under the protection of SF6 / CO2 mixed protective gas, the molten charge in step S3 is stirred for 5 min, and after standing for 15 min, the slag is removed, and after removing the slag, it is standing for 5 min;

[0012] S5, the charge treated in step S4 is added to the casting mold for casting, and the micro alloyed high corrosion resistant Mg-Sn-Ge alloy material is obtained by cooling.

[0013] The volume ratio of SF6 / CO2 mixed protective gas in step S3 is 1:99.

[0014] In step S3, the charge is heated for 1h to completely melt.

[0015] In step S3, the charge is added in the following order: the magnesium ingot containing tin and germanium is first put into the crucible, and then the remaining magnesium ingot is covered on it to cover the hole, so as to prevent the overburning of tin during heating.

[0016] In step S5, the casting mold is a steel mold, a copper mold or a water-cooled copper mold.

[0017] In step S5, the alloy melt cooling rate is 10-600 K / s.

[0018] In step S5, the casting temperature is 690-720 DEG C.

[0019] The principle of the application is:

[0020] (1) Sn element generates SnO2 in the corrosion process of magnesium alloy, enhances the protective property of corrosion product layer, and effectively controls the anodic reaction of corrosion;Ge element inhibits the cathodic reaction of magnesium alloy corrosion.

[0021] (2) The alloy solidification mold used in the present application is a steel mold, a copper mold or a water-cooled copper mold, which has a high cooling speed and can effectively prevent the supersaturation and precipitation of alloy elements during solidification, thereby solidifying Sn and Ge elements with low solid solubility at room temperature in the alloy matrix, improving the overall potential of the matrix, and inhibiting the precipitation of second phases such as Mg2Sn and Mg2Ge and impurity particles in the alloy, thereby reducing the local corrosion tendency of the alloy.

[0022] Compared with the prior art, the main features of the alloy of the present application are: (1) Sn element generates SnO2 during alloy corrosion, which enhances the protective property of the corrosion product layer and effectively controls the anodic reaction of magnesium alloy corrosion; (2) Ge element inhibits the cathodic reaction of magnesium alloy corrosion; (3) steel mold, copper mold or water-cooled copper mold is used to increase the cooling speed and solidify Sn, Ge and other difficult-to-solid-solution elements in the alloy matrix; (4) through the combination of solidification condition control and micro-alloying method, the precipitation of second phases such as Mg2Sn and Mg2Ge and impurity particles in the alloy is inhibited, thereby reducing the local corrosion tendency of the alloy; (5) the addition amount of alloy elements is small, which will not significantly increase the cost of the alloy. Through the design of alloy composition and the regulation of solidification and cooling speed, the anodic and cathodic reactions during alloy corrosion are synergistically inhibited, the local corrosion tendency of the alloy is weakened, and finally the Mg-Sn-Ge alloy with high corrosion resistance is obtained. The corrosion rate of the optimized Mg-Sn-Ge alloy in 3.5 wt.% NaCl solution is as low as 0.1 mm / year, which is lower than that of high-purity magnesium (0.3-0.5 mm / year) and the "stainless" Mg-11Y-1Al alloy (0.2 mm / year, Nature communications 13.1 (2022): 1-8) reported in the literature. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Scanning electron microscope images (a) (b) (c) of the alloy materials obtained in Examples 1-3.

[0024] Figure 2 The alternating current impedance graph (a) and polarization curve graph (b) of the alloy materials obtained in Examples 1-3 in 3.5 wt.% NaCl solution.

[0025] Figure 3 The hydrogen evolution test results of the alloy materials obtained in Examples 1-3 in 3.5 wt.% NaCl solution for 168 h. DETAILED DESCRIPTION

[0026] The present application will be further described below in conjunction with specific examples. I. Specific Examples

[0028] The raw materials used in the examples were all magnesium ingots with a purity of 99.9 wt.% or more, tin with a purity of 99.9 wt.% or more, and germanium with a purity of 99.9 wt.% or more.

[0029] The volume ratio of the SF6 / CO2 mixed protective gas used in S3 and S4 was 1:99.

[0030] Example 1

[0031] Preparation of the Mg-0.4Sn-0.5Ge alloy material included the following steps:

[0032] S1, ingredients were prepared according to the following mass percentages: tin 0.40%, germanium 0.50%, and the balance being Mg;

[0033] The above raw materials were polished and cleaned with acetone alcohol to remove surface corrosion, solvents, sand, oxide scales, etc. to prevent them from reacting with the magnesium melt and silicon, iron, hydrogen, and oxide inclusions from entering the melt;

[0034] When the ingredients were prepared, each raw material was added by 10% to the magnesium ingot, the magnesium ingot was punched, the tin and germanium were placed in the hole of the magnesium ingot, and then added to the preheating furnace at 200°C for 1 h for standby;

[0035] S2, the melting tools such as the crucible, stirring rod, skimmer, and metal mold were cleaned and preheated to 200°C for standby;

[0036] S3, the crucible was heated to 400°C, SF6 / CO2 mixed protective gas was introduced, and after 10 min, the preheated furnace charge of step S1 was added. The addition sequence was as follows: the magnesium ingot containing tin and germanium was first placed in the crucible, and then the remaining magnesium ingot was placed on top to cover the hole. The temperature was raised to 720°C to melt the furnace charge, and heated for 1 h until the furnace charge was completely melted;

[0037] S4, under the protection of SF6 / CO2 mixed gas, the furnace charge after melting in step S3 was uniformly stirred for 5 min using a mechanical stirring rod. After 15 min of standing, the slag was removed, and after the slag was removed, the material was allowed to stand for 5 min.

[0038] S5, the steel mold was cleaned and preheated to 200°C for standby. The furnace charge treated in step S4 was added to the steel mold for casting, and the casting temperature was 690°C. The material after casting was cooled together with the mold, and the cooling rate was controlled at 10-600 K / s. A micro-alloyed high corrosion-resistant Mg-0.4Sn-0.5Ge alloy material was obtained.

[0039] Reference Figure 1The SEM image of the Mg-0.4Sn-0.5Ge alloy material after the steel mold is cooled is shown in Fig. 2(a), and the results show that the alloy has fine grains and low second phase content, which can effectively reduce the local corrosion tendency of the alloy.

[0040] Referring to Fig. 3, Figure 2 The AC impedance graph (a) and the polarization curve graph (b) of the obtained Mg-0.4Sn-0.5Ge alloy material in a 3.5 wt.% NaCl solution are shown in Fig. 3, and the results show that the alloy has good corrosion resistance.

[0041] Referring to Fig. 4, Figure 3 The hydrogen evolution test results of the obtained Mg-0.4Sn-0.5Ge alloy material in a 3.5 wt.% NaCl solution for 168 h are shown in Fig. 4. After unit conversion, the corrosion rate is about 0.15 mm / year.

[0042] Example 2

[0043] Preparation of Mg-0.05Sn-0.01Ge alloy material, including the following steps:

[0044] S1, ingredients are prepared according to the following mass percentages: tin 0.05%, germanium 0.01%, and the balance is Mg;

[0045] The above raw materials are polished and cleaned with acetone alcohol to remove corrosion on the surface, solvents, sand, oxide scales, etc., so as to prevent them from reacting with the magnesium melt and silicon, iron, hydrogen, and oxide inclusions from entering the melt;

[0046] When ingredients are prepared, each raw material is added by 10%, the magnesium ingot is punched, tin and germanium are placed in the hole of the magnesium ingot, and then added to the preheating furnace at 200°C for 1 h for standby;

[0047] S2, the crucible, stirring rod, skimmer, and other smelting tools are cleaned and preheated to 200°C for standby;

[0048] S3, the crucible is heated to 400°C, SF6 / CO2 mixed protective gas is introduced, after 10 min, the preheated furnace charge of step S1 is added, the addition sequence is: the magnesium ingot containing tin and germanium is first placed in the crucible, then the remaining magnesium ingot is covered on it to cover the hole, the temperature is raised to 720°C to melt the furnace charge, and heated for 1 h until the furnace charge is completely melted;

[0049] S4, under the protection of SF6 / CO2 mixed gas, the mechanically stirred rod is used to uniformly stir the melted furnace charge in step S3 for 5 min, and after 15 min of standing, the slag is removed, and after the slag is removed, it is stood for 5 min;

[0050] S5, the copper mold is cleaned and preheated to 200℃, the furnace charge treated in step S4 is added to the mold for casting, the casting temperature is 720℃, the material after casting is cooled with the mold, the cooling rate is controlled to be 10-600 K / s, and a micro-alloyed high-corrosion-resistant Mg-0.05Sn-0.01Ge alloy material is obtained.

[0051] Referring to Figure 1 , the SEM image of the Mg-0.05Sn-0.01Ge alloy material after cooling with the copper mold is shown in (b), and the results show that the grains in the alloy are relatively small, the content of the second phase in the structure is low, and the local corrosion tendency of the alloy can be effectively reduced.

[0052] Referring to Figure 2 , the AC impedance graph (a) and the polarization curve graph (b) of the obtained Mg-0.05Sn-0.01Ge alloy material in a 3.5 wt.% NaCl solution are shown, and the results show that the alloy has good corrosion resistance.

[0053] Referring to Figure 3 , the hydrogen evolution test results of the obtained Mg-0.05Sn-0.01Ge alloy material in a 3.5 wt.% NaCl solution for 168h are shown. After unit conversion, the corrosion rate is about 0.13mm / year.

[0054] Example 3

[0055] Preparation of Mg-0.3Sn-0.2Ge alloy material, including the following steps:

[0056] S1, the following mass percentages are prepared: tin 0.30%, germanium 0.20%, and the balance is Mg;

[0057] The above raw materials are polished and cleaned with acetone alcohol to remove surface corrosion, solvents, sand, oxide scales, etc. to prevent them from reacting with the magnesium melt and silicon, iron, hydrogen, and oxide inclusions from entering the melt;

[0058] When batching, add 10% of each raw material, punch the magnesium ingot, place tin and germanium in the hole of the magnesium ingot, and then add to the preheating furnace at 200℃ for 1h preheating;

[0059] S2, the crucible, stirring rod, skimmer, metal mold and other smelting tools are cleaned and preheated to 200℃, and dried for standby use;

[0060] S3, the crucible is heated to 400℃, SF6 / CO2 mixed protective gas is introduced, after 10 min, the furnace charge preheated in step S1 is added, the adding sequence is: the magnesium ingot containing tin and germanium is first put into the smelting furnace, then the remaining magnesium ingot is covered on it to cover the hole, the temperature is raised to 720℃ to melt the furnace charge, heating for 1 h until the furnace charge is completely melted;

[0061] S4, under the protection of SF6 / CO2 mixed gas, the furnace charge melted in step S3 is uniformly stirred for 5 min using a mechanical stirring rod, and after standing for 15 min, the slag is removed, and after the slag is removed, it is stood for 5 min;

[0062] S5, the water-cooled copper mold is cleaned and preheated to 200℃ for use, the furnace charge treated in step S4 is added to the water-cooled copper mold for casting, the casting temperature is 700℃, the material after casting is cooled with the mold, and the cooling rate is controlled to be 10-600 K / s, to obtain a micro-alloyed high corrosion-resistant Mg-0.3Sn-0.2Ge alloy material.

[0063] Referring to Figure 1 , the SEM image (c) under the secondary electron mode of the Mg-0.3Sn-0.2Ge alloy material after cooling with the water-cooled copper mold is shown, and the results show that the grains in the alloy are finer, the content of the second phase in the structure is the lowest, and the local corrosion tendency of the alloy can be effectively reduced.

[0064] Referring to Figure 2 , the alternating current impedance graph (a) and the polarization curve graph (b) of the obtained Mg-0.3Sn-0.2Ge alloy material in a 3.5 wt.% NaCl solution are shown, and the results show that the alloy has good corrosion resistance.

[0065] Referring to Figure 3 , the hydrogen evolution test results of the obtained Mg-0.3Sn-0.2Ge alloy material in a 3.5 wt.% NaCl solution for 168 h are shown. After unit conversion, the corrosion rate is about 0.10 mm / year.

[0066] The above describes the present application in an exemplary manner, and it is obvious that the specific implementation of the present application is not limited by the above manner, as long as various non-essential improvements are made by adopting the method concept and technical scheme of the present application, or the concept and technical scheme of the present application is applied to other occasions without improvement, all of which are within the protection scope of the present application.

Claims

1. A microalloyed high corrosion resistant Mg-Sn-Ge alloy material, characterized in that, The chemical composition percentage by mass is: tin 0.01%-0.40%, germanium 0.01%-0.50%, impurity elements: iron <0.005%, copper <0.0015%, nickel <0.002%, total impurities <0.025%, and the balance is magnesium; The micro-alloyed high corrosion-resistant Mg-Sn-Ge alloy material is prepared by the following method comprising the following steps: S1, the cleaned raw material magnesium ingot, tin and germanium are matched according to the mass percentage, 10% of each raw material is added during batching, the magnesium ingot is punched, the tin and germanium are placed in the hole of the magnesium ingot, and then added to the preheating furnace at 200℃ for 1h for standby; S2, the crucible and smelting tools are cleaned and preheated to 200℃, and dried for standby; S3, the crucible is heated to 400℃, SF6 / CO2 mixed protective gas is introduced, after 10min, the preheated furnace charge of step S1 is added, the temperature is raised to 720℃ to melt the furnace charge, and the furnace charge is heated to completely melt; S4, under the protection of SF6 / CO2 mixed gas, the furnace charge after melting in step S3 is stirred for 5min, and after standing for 15min, the slag is removed, and after removing the slag, it is standing for 5min; S5, the furnace charge treated by step S4 is added to the casting mold for casting, and the micro-alloyed high corrosion-resistant Mg-Sn-Ge alloy material is obtained by cooling, the casting mold is a steel mold or a copper mold, the alloy melt cooling rate is 10-600K / s, and the casting temperature is 690-720℃.

2. The microalloyed high corrosion resistant Mg-Sn-Ge alloy material according to claim 1, characterized in that, The volume ratio of the SF6 / CO2 mixed protective gas in step S3 is 1:

99. 3.The micro-alloyed high-corrosion-resistant Mg-Sn-Ge alloy material according to claim 1, characterized in that, In step S3, the heating is 1h to completely melt the furnace charge.

4. The microalloyed high corrosion resistant Mg-Sn-Ge alloy material according to claim 1, characterized in that, In step S3, the furnace charge is added in the following order: the magnesium ingot containing tin and germanium is first placed in the crucible, and then the remaining magnesium ingot is covered on it.

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