Treatment method for improving performance of magnesium alloy
Through friction stir processing and sol-gel coating technology, the microstructure and surface protective film of magnesium alloy are improved, and the problems of rapid degradation and unstable mechanical properties of magnesium alloy materials are solved, which significantly improves its hardness and corrosion resistance.
Patent Information
- Application Number
- CN202510300498.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-14
- Publication Date
- 2025-06-10
AI Technical Summary
Magnesium alloy materials have a rapid degradation process due to low electronegativity and high chemical activity, and their mechanical properties are difficult to stabilize for a long time, which limits their application.
The surface of the magnesium alloy was treated with friction stir processing technology to form dense and refined microstructure, and a chromate conversion film was prepared by Na2Cr2O7 and KF aqueous solution. Then a sol-gel coating was grown on the surface of the magnesium alloy, and the modified sol micelles were cured by cross-linking using 2-methylimidazole.
It significantly improves the hardness and corrosion resistance of magnesium alloys, extends its service life, and shows excellent cavitation resistance in seawater.
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Figure CN120119237A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of magnesium alloy manufacturing, and particularly relates to a treatment method for improving the performance of magnesium alloys. Background Art
[0002] Magnesium, as the most abundant light metal element on earth, accounts for about 2.3% of the total element content. The density of magnesium (1.74 g / cm3) is only about 2 / 3 of that of aluminum and about 1 / 4 of that of steel. It is the latest generation of engineering structural materials to replace aluminum and steel. Its alloys are known as the lightest metal structural materials due to their high specific strength, specific stiffness, low density, high recovery rate, excellent damping performance, etc. However, due to the low electronegativity and high chemical activity of magnesium, the degradation process of magnesium alloy materials is too fast, which further leads to the mechanical properties being difficult to be stable for a long time, restricting its application.
[0003] Magnesium alloys often exhibit problems such as relatively large grains, chemical composition segregation, β-Mg17Al12 network precipitates, and pore defects during casting in the as-cast state. These disadvantages significantly reduce their mechanical properties and corrosion resistance, restricting their application in a wider range of fields.
[0004] Cavitation refers to the process in which when the pressure of the liquid around the flow components fluctuates during the operation of fluid machinery, the local pressure in the liquid drops suddenly below the critical vapor pressure at the corresponding temperature, and cavitation bubbles will form, develop, collapse, and implode inside the liquid or at the solid-liquid interface. When the cavitation bubbles collapse, high-speed and high-pressure shock waves and microjets act on the flow components, and there is an instantaneous high temperature above several hundred degrees Celsius, which will cause serious fatigue fracture and failure of the material surface, and it is a special form of mechanical wear. Cavitation generally exists in various flow components, such as hydraulic turbines, ship propellers, pipelines, pumps, diesel engine cylinder liners, and components of the aerospace engine fuel supply system, etc. Cavitation damage will reduce the efficiency of fluid machinery, and in severe cases, it will cause component damage and malfunction, not only causing huge economic losses but also major safety accidents. Summary of the Invention
[0005] The purpose of the present invention is to provide a treatment method for improving the performance of magnesium alloys to solve the technical problems proposed in the background art.
[0006] To achieve the above purpose, the specific technical solution of the present invention is as follows: A treatment method for improving the performance of magnesium alloys, including the following steps:
[0007] S1. Cut out the high-purity magnesium alloy from the ingot, and perform friction stir processing on the surface of the magnesium alloy using friction stir processing technology to obtain a magnesium alloy test block. Ultrasonically clean the magnesium alloy test block with acetone and absolute ethanol for 30 min respectively, and dry it with a high-pressure nitrogen stream. Immerse the magnesium alloy test block in an aqueous NaOH solution to obtain a Mg(OH) 2 thin layer; after the immersion is completed, wash it successively with deionized water and absolute ethanol, and dry it with a high-pressure nitrogen stream;
[0008] S2. Prepare an aqueous solution of Na 2 Cr 2 O 7 and KF. Immerse the magnesium alloy test block in the above-mentioned boiling solution for 30 s, then rinse it with hot water, and air-dry it at room temperature to obtain a sample;
[0009] S3. After dropping 4.73 mL of TEOS into a mixed solvent composed of 2.5 mL of ethanol and 2.5 mL of isopropanol, add 335.3 mg of ZrOCl 2 . After all the solid substances are dissolved, 375 μL of HCl solution and 3.96 mL of GPTMS are successively added dropwise to the system. Finally, 20 mg of Hmim is added to the solution. The resulting solution is allowed to stand and age at room temperature for 1 h. Immerse the sample obtained in step S2 completely into the sol for 10 s, then vertically lift and lower it at a speed of 1 cm / min through a robotic arm twice. Finally, place the sample in an oven at 80 °C for curing for 4 h to obtain the finished product.
[0010] Preferably, in step S1, the rotational speed of the friction stir tool is 1000 r / min, the processing speed is 30 mm / min, the number of processing passes is one pass, and the root diameter of the friction stir tool is 5 mm.
[0011] Preferably, in step S1, the magnesium alloy test block is immersed in a 1 M aqueous NaOH solution at 80 °C for 4 h.
[0012] Preferably, in step S2, the concentrations of Na 2 Cr 2 O 7 and KF are 125 g / L and 2.5 g / L respectively.
[0013] Preferably, in step S3, TEOS, GPTMS, and Hmim are 19.76 mmol, 15.7 mmol, and 0.244 mmol respectively, and ZrOCl 2 in step S3 is 1.04 mmol, and n(Si):n(Zr) = 5:95.
[0014] Preferably, the pH value of the HCl solution in step S3 is adjusted under the monitoring of a Sartorius pH meter, and its pH is 2.0.
[0015] Preferably, magnetic stirring is used throughout the entire process of step S3.
[0016] A treatment method for improving the properties of magnesium alloys according to the present invention has the following advantages:
[0017] In the present invention, by adopting the friction stir technology, a dense and refined microstructure is formed in the magnesium alloy, the quality of the material is improved, the hardness is greatly increased, a corrosion product film with better protective performance is more easily formed on the surface of the magnesium alloy, and the corrosion resistance of the sample is improved. At the same time, in the present invention, 3-glycidoxypropyltrimethoxysilane is used to introduce epoxy groups into the SiO 2 -based sol-gel, and then 2-methylimidazole is used to crosslink and cure the modified sol micelles. Since no high molecular polymer is introduced, the good adhesion of the sol-gel coating is not affected. On the other hand, the entire preparation process is very simple and no highly toxic chemicals are used. This cross-linking polymerization method is an important way to improve the corrosion resistance of the sol-gel coating, and it has a wide range of operable cross-linking polymerization methods, not limited to the cycloaddition reaction between epoxy groups and amino groups (or amine groups, hydroxyl groups, etc.). Other forms of polymer curing processes can also be used as alternative preparation ideas and should be considered when designing and preparing corrosion-resistant sol-gel coatings in the future. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.
[0019] Figure 1 It is a macroscopic structure diagram of the magnesium alloy specimen after friction stir processing in the present invention;
[0020] Figure 2 It is a sample diagram of the magnesium alloy specimen after friction stir processing in the present invention;
[0021] Figure 3 It is a comparison diagram of the hardness values of the as-cast and friction stir processed magnesium alloys in the present invention;
[0022] Figure 4 It is a potentiodynamic polarization curve diagram of the as-cast and friction stir processed magnesium alloys in the present invention;
[0023] Figure 5 It is a graph showing the relationship between the cavitation mass loss and time of the as-cast and friction stir processed magnesium alloys in the present invention in artificial seawater;
[0024] Figure 6 It is a diagram showing the surface microstructure change of the finished product in the present invention after being exposed in 0.6M neutral NaCl solution for a period of time. Detailed implementation manners
[0025] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.
[0026] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the embodiments of the present invention.
[0027] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.
[0028] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the internal connection of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.
[0029] The following disclosure provides many different embodiments or examples for implementing different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the embodiments of the present invention. In addition, the embodiments of the present invention may repeat reference numerals and / or reference letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.
[0030] To better understand the purpose, structure and function of the present invention, the following further describes in detail a method for treating magnesium alloy to improve its performance in conjunction with the accompanying drawings.
[0031] A method for treating magnesium alloy to improve its performance according to the present invention includes the following steps:
[0032] S1. Cut out the high-purity magnesium alloy from the ingot, and perform friction stir processing on the surface of the magnesium alloy by friction stir processing technology to obtain a magnesium alloy test block. The rotational speed of the friction stir tool is 1000 r / min, the processing speed is 30 mm / min, the number of processing passes is one pass, and the root diameter of the friction stir tool is 5 mm. Ultrasonically clean the magnesium alloy test block with acetone and absolute ethanol for 30 min respectively, and dry it with a high-pressure nitrogen stream. Immerse the magnesium alloy test block in a 1M NaOH aqueous solution at 80 °C for 4 h to obtain a Mg(OH) 2 thin layer; after the immersion is completed, wash it successively with deionized water and absolute ethanol, and dry it with a high-pressure nitrogen stream;
[0033] S2. Prepare an aqueous solution of 125 g / L Na 2 Cr 2 O 7 and 2.5 g / L KF, and use it to prepare a chromate conversion film on the magnesium alloy test block. Immerse the magnesium alloy test block in the above solution at boiling for 30 s, then rinse it with hot water, and air-dry it at room temperature to obtain a sample;
[0034] S3. After dropping 4.73 mL of TEOS (19.76 mmol) into a mixed solvent composed of 2.5 mL of ethanol and 2.5 mL of isopropanol, then add 335.3 mg of ZrOCl 2(1.04 mmol, n(Si):n(Zr) = 5:95). After all the solid substances were dissolved, 375 μL of HCl solution (pH = 2.0) and 3.96 mL of GPTMS (15.7 mmol) were successively added dropwise into the system. Among them, the pH value of the HCl solution was adjusted under the monitoring of a Sartorius pH meter (PB - 10). Finally, 20 mg of Hmim (0.244 mmol) was added to the solution, and the resulting solution was allowed to stand and age at room temperature for 1 h. The whole process was carried out with magnetic stirring. A sol - gel coating was grown on the surface of the magnesium alloy sample by the dip - coating method, that is, the sample obtained in step S2 was completely immersed in the sol for 10 s, and then vertically lifted and lowered at a speed of 1 cm / min by an electric arm, twice. Finally, the sample was placed in an oven at 80 °C and cured for 4 h to obtain the finished product.
[0035] Figure 2 In it, after friction stir processing, the magnesium alloy becomes fine and uniform, and the coarse second phase disappears. Figure 3 In it, the microhardness values of the as - cast and friction stir processed magnesium alloys are 71.5 HV and 86.5 HV respectively. After friction stir processing, the hardness of the sample is increased by 21%. Figure 4 In it are the potentiodynamic polarization curves of the as - cast sample and the friction stir processed magnesium alloy measured in a 3.5% NaCl solution by mass fraction. According to the Tafel extrapolation method, the corrosion potential Ecorr and the corrosion current density Icorr are obtained. The corrosion current density of the as - cast sample is 7.460×10 -6 A·cm -2 , the corrosion potential is - 1.505 V. The corrosion current density of the friction stir processed magnesium alloy is 1.694×10 -6 A·cm -2 , the corrosion potential is - 1.427 V. The corrosion current density represents the rate of metal dissolution per unit area. The smaller the value, the slower the corrosion reaction of the material and the stronger the corrosion resistance. A more positive corrosion potential indicates that the material is more difficult to corrode in the environment and has better corrosion resistance. The corrosion current density of the friction stir processed magnesium alloy is less than that of the as - cast sample, indicating that friction stir processing improves the corrosion resistance; the corrosion potential is more positive than that of the as - cast sample, indicating that it is more difficult to corrode in the corrosive medium. It shows that by improving the problems of uneven distribution of the substrate tissue and defects existing during casting through friction stir processing, after obtaining a sample with refined grains and uniform distribution of the second phase, a corrosion product film with better protective performance is more easily formed on the surface, improving the corrosion resistance of the sample. Figure 5The curves show the relationship between the cavitation mass loss and time of as-cast and friction stir processed magnesium alloys in artificial seawater. It can be seen from the figure that the cavitation weight losses of both the as-cast and friction stir processed magnesium alloys increase linearly with time, and the weight loss gap gradually widens. At 90 minutes of cavitation, the as-cast sample has the largest weight loss, reaching 16.2 mg, indicating that the as-cast sample has the worst resistance to cavitation damage in seawater and suffers the most serious cavitation damage. The cavitation weight loss of the friction stir processed magnesium alloy is the least, 7.5 mg, only accounting for 46% of the weight loss of the as-cast sample, showing excellent corrosion resistance in seawater. From Figure 6 It can be seen that there are slight changes on the surface of the finished coating of the present invention, and only a small amount of corrosion products are generated, indicating its good corrosion resistance and a very significant improvement in its corrosion resistance.
[0036] It should be understood that the present invention is described by way of some embodiments. Those skilled in the art will know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Additionally, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.
Claims
1. A method for improving the performance of magnesium alloy, characterized in that: The steps include: S1. Cut a high-purity magnesium alloy from an ingot, perform friction stir processing on the surface of the magnesium alloy using a friction stir processing technique to obtain a magnesium alloy test block, ultrasonically clean the magnesium alloy test block with acetone and anhydrous ethanol for 30 minutes, respectively, and blow dry with a high-pressure nitrogen flow, and soak the magnesium alloy test block in a NaOH aqueous solution to obtain a Mg(OH)2 thin layer; after the soaking, wash with deionized water and anhydrous ethanol in turn, and blow dry with a high-pressure nitrogen flow; S2. Prepare Na2Cr2O7 and KF aqueous solutions, soak the magnesium alloy test block in the boiled solution for 30 seconds, then rinse with hot water, and air-dry at room temperature to obtain a sample; S3, after adding 4.73mL of TEOS dropwise into a mixed solvent consisting of 2.5mL of ethanol and 2.5mL of isopropanol, 335.3mg of ZrOCl2 was added, and after all the solid substances were dissolved, 375μL of HCl solution and 3.96mL of GPTMS were added dropwise to the system in sequence, and finally, 20mg of Hmim was added to the solution, and the resulting solution was aged at room temperature for 1h, the sample obtained in step S2 was completely immersed in the sol for 10s, and then vertically lifted and lowered at a speed of 1cm / min by an electric arm, and repeated twice, and finally, the sample was placed in an oven at 80°C for curing for 4h to obtain a finished product.
2. A method for improving the performance of magnesium alloy according to claim 1, characterized in that: In step S1, the rotation speed of the friction stir tool is 1000 r / min, the processing speed is 30 mm / min, the processing pass is one pass, and the root diameter of the friction stir tool is 5 mm.
3. A method for improving the performance of magnesium alloy according to claim 1, characterized in that: In step S1, the magnesium alloy test block is immersed in a 1M NaOH aqueous solution at 80° C. for 4 hours.
4. A method for improving the performance of magnesium alloy according to claim 1, characterized in that: The concentrations of Na2Cr2O7 and KF in step S2 are 125 g / L and 2.5 g / L respectively.
5. The method for improving the performance of magnesium alloy according to claim 1, characterized in that: The TEOS, GPTMS and Hmim in the step S3 are 19.76 mmol, 15.7 mmol and 0.244 mmol respectively, the ZrOCl2 in the step S3 is 1.04 mmol, and n(Si):n(Zr)=5:
95.
6. A method for improving the performance of magnesium alloy according to claim 1, characterized in that: The pH value of the HCl solution in step S3 is adjusted under the monitoring of a Sartorius pH meter, and the pH value is 2.
0.
7. The method for improving the performance of magnesium alloy according to claim 1, characterized in that: The entire process of step S3 adopts magnetic stirring.