A treatment method for improving the microstructure and properties of hypoeutectic Al-Mg 2 Si alloy

Abstract

The present invention provides a treatment method for improving the microstructure and properties of hypoeutectic Al-Mg2Si alloy, belonging to the technical field of metal material treatment. The treatment method provided by the present invention is to perform electro-pulse treatment on the hypoeutectic Al-Mg2Si alloy melt; the process parameters of the electro-pulse treatment are: the pulse voltage is 300V to 700V, the pulse frequency is 22Hz, and the pulse treatment time is 30s. The present invention introduces electro-pulse treatment into the hypoeutectic Al-Mg2Si alloy melt to prepare high-quality ingots. On the one hand, due to the electromagnetic force and pulse oscillation generated by the pulsed electromagnetic field, the clusters of different atoms in the liquid metal are reduced, and the clusters of the same atoms are increased, so as to achieve the purpose of refining the solidification structure of the alloy. On the other hand, the action of the electro-pulse promotes the diffusion of solute atoms, significantly improves the segregation degree of the second phase, and thus improves the properties of the alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material treatment, and particularly relates to a treatment method for improving the microstructure and properties of hypoeutectic Al-Mg 2 Si alloy. Background Art

[0002] Mg 2 Si, as an intermetallic compound, has many excellent properties such as high strength, high hardness, high wear resistance, high melting point, and high elastic modulus. In Al-Mg 2 Si alloy, Mg 2 Si, as the strengthening phase of the alloy, has an important influence on the mechanical properties of the alloy. At present, there are great potential advantages in new structural materials, and this advantage allows it to be applied in many fields, such as power generation, refrigeration, and even military, aerospace, and automotive. However, the conventional casting of Al-Mg 2 Si alloy will cause the size of the intermetallic Mg 2 Si to increase, forming an undesirable coarse skeleton shape. At this time, the formation of large and irregularly shaped particles will cut the matrix and generate crack sources, seriously reducing the mechanical properties of the alloy. Therefore, the key to preparing Al-Mg 2 Si alloy is to control the shape and size of the Mg 2 Si particles formed in the Al matrix, and improve the dendritic segregation in the solidification structure, which directly affects the mechanical properties of the alloy. Therefore, controlling the material microstructure and properties from the metallurgical source has important functions and practical significance. Summary of the Invention

[0003] Based on the above, the object of the present invention is to provide a treatment method for improving the microstructure and properties of hypoeutectic Al-Mg2Si alloy. By performing electro-pulse melt treatment on the hypoeutectic Al-Mg 2 Si alloy and adjusting the electro-pulse treatment parameters, the present invention can improve the microstructure of the hypoeutectic Al-Mg 2 Si alloy, refine the grain size of α-Al, reduce the size of the α-Al+Mg 2 Si eutectic structure, and make its distribution uniform, improve the dendritic segregation in the solidification structure, and thereby improve the properties of the hypoeutectic Al-Mg 2 Si alloy.

[0004] To achieve the above object, the present invention provides the following technical solution: A treatment method for improving the microstructure and properties of hypoeutectic Al-Mg 2 Si alloy, which performs electro-pulse treatment on the hypoeutectic Al-Mg 2 Si alloy melt; the process parameters of the electro-pulse treatment are: the pulse voltage is 300V to 700V, the pulse frequency is 22Hz, and the pulse treatment time is 30s.

[0005] In some embodiments of the present invention, the pulsed voltage is 300V, the pulse frequency is 22Hz, and the pulse time is 30s.

[0006] In some embodiments of the present invention, by mass percentage, the composition in the hypoeutectic Al-Mg 2 Si alloy melt is 93% Al, 5% Mg and 2% Si.

[0007] The content of Mg in the Al-based alloy is generally 0.8% - 1.2%, and the content of Si is generally 0.4% - 0.8%. The obtained Al-based alloy has relatively low strength and hardness and poor corrosion resistance. In the present invention, in the Al-Mg 2 Si alloy, higher contents of Mg and Si elements are added. The Mg element can lower the eutectic point of the alloy and improve the corrosion resistance. The addition of the Si element can improve the fluidity of the alloy and enhance the mechanical properties. If the contents of Mg and Si elements are too much, it will reach the eutectic alloy level, deviating from the purpose of improving the hypoeutectic alloy in the present invention, and too much Mg and Si elements will play an opposite role.

[0008] In some embodiments of the present invention, when the temperature of the hypoeutectic Al-Mg 2 Si alloy melt is 720 - 750 °C, electro-pulse treatment is carried out.

[0009] In some embodiments of the present invention, after the electro-pulse treatment result, it further includes a heat preservation step.

[0010] In some embodiments of the present invention, the temperature of the heat preservation is 740 °C and the time is 5 min.

[0011] In some embodiments of the present invention, after the heat preservation ends, it further includes a casting and forming step.

[0012] The casting temperature will affect the properties of the alloy. When the casting temperature is high, the cooling rate is slower, the degree of supercooling is small, and during solidification, the atomic clusters grow, resulting in a coarse structure and lower properties of the alloy after forming. When the casting temperature is low, the cooling rate is faster, the degree of supercooling is larger, and during solidification, the growth of atomic clusters will be inhibited, resulting in a relatively fine structure after solidification, which can improve the properties of the alloy. Therefore, the present invention preferably selects the temperature of the alloy melt during casting to be 740 °C (casting is carried out after heat preservation at 740 °C for 5 min, that is, the temperature of the alloy melt during casting is 740 °C).

[0013] The present invention discloses the following technical effects:

[0014] The present invention introduces electro-pulse treatment into the hypoeutectic Al-Mg 2In the Si alloy melt, high-quality ingots are prepared. On the one hand, due to the electromagnetic force and pulse oscillation generated by the pulsed electromagnetic field, the heterogeneous atomic clusters in the liquid metal are reduced, and the homogeneous atomic clusters are increased, thus achieving the purpose of refining the alloy solidification structure. On the other hand, the action of the electric pulse promotes the diffusion of solute atoms, significantly improving the segregation degree of the second phase, thereby improving the properties of the alloy.

[0015] The method of the present invention for processing electric pulses when the hypoeutectic Al-Mg 2 Si alloy is in the melt stage is applicable to the processing of large-scale alloys and is more conducive to industrial production. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 Schematic diagrams of the microstructures of the Al-Mg 2 Si alloys prepared in Comparative Example 1 and Embodiments 1-5 of the present invention, where (a) is Comparative Example 1, (b) is Embodiment 1, (c) is Embodiment 2, (d) is Embodiment 3, (e) is Embodiment 4, and (f) is Embodiment 5.

[0018] Figure 2 Average grain size diagrams of the Al-Mg 2 Si alloys prepared in Comparative Example 1 and Embodiments 1-5 of the present invention.

[0019] Figure 3 Second-phase area fraction diagrams of the Al-Mg 2 Si alloys prepared in Comparative Example 1 and Embodiments 1-5 of the present invention.

[0020] Figure 4 XRD diagrams of the Al-Mg 2 Si alloys prepared in Comparative Example 1 and Embodiments 1-5 of the present invention.

[0021] Figure 5 SEM surface scan diagrams of the Al-Mg 2 Si alloys prepared in Comparative Example 1 and Embodiments 1-5, where (a) is Comparative Example 1, (b) is Embodiment 1, (c) is Embodiment 2, (d) is Embodiment 3, (e) is Embodiment 4, and (f) is Embodiment 5.

[0022] Figure 6 SEM surface scan diagrams of the Al-Mg 2Scanning electron microscope spot scan images of Si alloys, where (a) is Comparative Example 1, (b) is Example 1, (c) is Example 2, (d) is Example 3, (e) is Example 4, and (f) is Example 5.

[0023] Figure 7 For the Al-Mg prepared in Comparative Example 1 and Examples 1-5 2 Hardness change diagram of Si alloy.

[0024] Figure 8 For the Al-Mg prepared in Comparative Example 1 and Examples 1-5 2 Tensile property change diagram of Si alloy.

[0025] Figure 9 For Al-Mg under different pulse voltages 2 Polarization curves (a) and Nyquist diagrams (b) of Si alloy specimens.

[0026] Figure 10 For the Al-Mg prepared in Comparative Example 1 and Examples 1-5 2 Three-dimensional morphology diagrams of the corroded Al-Mg Si alloy, where (a) is Comparative Example 1, (b) is Example 1, (c) is Example 2, (d) is Example 3, (e) is Example 4, and (f) is Example 5. Detailed implementation manners

[0027] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0028] It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0029] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0030] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the specification of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are merely exemplary.

[0031] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0032] The present invention provides a treatment method for improving the microstructure and properties of hypoeutectic Al-Mg 2 Si alloy. The hypoeutectic Al-Mg 2 Si alloy melt is subjected to electro-pulse treatment; the process parameters of the electro-pulse treatment are: the pulse voltage is 300V - 700V, the pulse frequency is 22Hz, and the pulse treatment time is 30s.

[0033] By subjecting the hypoeutectic Al-Mg 2 Si alloy to electro-pulse melt treatment and adjusting the electro-pulse treatment parameters, the present invention can improve the microstructure of the hypoeutectic Al-Mg 2 Si alloy, refine the grain size of α-Al, reduce the size of the α-Al + Mg 2 Si eutectic structure, and make its distribution uniform, improve the dendritic segregation in the solidification structure, and further improve the properties of the hypoeutectic Al-Mg 2 Si alloy. The specific steps are as follows:

[0034] Step 1. Melting the Al-Mg 2 Si alloy: Weigh the raw materials Al, master alloy Al-22Si and Mg according to the mass ratio. After heating Al and master alloy Al-22Si to 750°C until completely melted, wrap the metallic Mg with aluminum foil paper, and press the metallic Mg into the metal melt using a bell jar. After all the metallic Mg is melted, put it into the furnace and keep it warm for 5 min (the holding temperature is 750°C). Then, bury the refining agent (the dosage of the refining agent is 0.5 wt% of the Al-Mg 2 Si alloy ingot) into the metal melt using a bell jar for about 2 - 3 min, then remove the slag on the surface of the melt, and put it back into the resistance furnace and keep it warm for 5 min (the holding temperature is 750°C) to obtain the Al-Mg 2 Si alloy melt;

[0035] Step 2. Electro-pulse treatment: Perform electro-pulse treatment on the Al-Mg 2 Si alloy melt obtained in Step 1. After the treatment is completed, put it into the furnace and keep it warm at 740°C for 5 min; among them, the pulse voltage is 300V - 700V, the pulse frequency is 22Hz, and the pulse treatment time is 30s;

[0036] Step 3. Casting and molding: Cast the sample obtained in Step 2 into a mold to make the alloy melt cast and molded, obtaining the treated Al-Mg 2 Si alloy specimen.

[0037] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0038] The refining agent used in the embodiments is a commonly used refining agent in the art and is obtained through commercial channels.

[0039] In the embodiments and comparative examples, each component in the alloy melt was weighed according to the mass ratio (Table 1);

[0040] Among them, the content ratio of each element is: Al: 93%, Mg: 5%, Si: 2%;

[0041] The burning loss rate of each element is: Al: 2%, Mg: 25%, Al-22Si: 1%;

[0042] Table 1 Alloy chemical composition table (wt.%)

[0043]

[0044] Example 1

[0045] Step 1. Melting Al-Mg 2 Si alloy: Put the weighed Al and the intermediate alloy Al-22Si into a graphite crucible, put the graphite crucible into an electric resistance furnace and heat it to 750 °C until completely melted. Wrap the metallic Mg with aluminum foil paper, use a bell jar to press the metallic Mg into the metal melt. After all the metallic Mg is melted, put it into the furnace and keep it warm at 750 °C for 5 min. Then, put the refining agent (the dosage of the refining agent is 0.5 wt% of the Al-Mg 2 Si alloy ingot) into the metal melt with a bell jar and bury it for about 3 min, then remove the slag on the surface of the melt, and put it back into the electric resistance furnace and keep it warm at 750 °C for 5 min to obtain the Al-Mg 2 Si alloy melt;

[0046] Step 2. Electric pulse treatment: Insert the metal electrode into the crucible, and perform electric pulse treatment on the Al-Mg 2 Si alloy melt obtained in Step 1. After the treatment is completed, put it into the furnace and keep it warm at 740 for 5 min; among them, the pulse voltage is 300 V, the pulse frequency is 22 Hz, and the pulse treatment time is 30 s;

[0047] Step 3. Casting and molding: Cast the sample obtained in Step 2 into a mold to make the alloy melt cast and molded, obtaining Al-Mg 2Si alloy sample.

[0048] Example 2

[0049] In this example, Al-Mg 2 The preparation method of the Si alloy sample is the same as that of Example 1, except that the pulse voltage is 400V.

[0050] Example 3

[0051] In this example, Al-Mg 2 The preparation method of the Si alloy sample is the same as that of Example 1, except that the pulse voltage is 500V.

[0052] Example 4

[0053] In this example, Al-Mg 2 The preparation method of the Si alloy sample is the same as that of Example 1, except that the pulse voltage is 600V.

[0054] Example 5

[0055] In this example, Al-Mg 2 The preparation method of the Si alloy sample is the same as that of Example 1, except that the pulse voltage is 700V.

[0056] Comparative Example 1

[0057] In this comparative example, Al-Mg 2 The preparation method of the Si alloy sample is the same as that of Example 1, except that the step of electro-pulse treatment is omitted.

[0058] Figure 1 Schematic diagrams of the microstructures of the Al-Mg 2 Si alloys prepared in Examples 1-5 and Comparative Example 1. Figure 1 In (a), it is the alloy solidification structure of the untreated original sample (Comparative Example 1). It can be seen that the eutectic α-Al+Mg 2 Si structure presents a coarse lamellar structure, and the primary α-Al presents a coarse dendritic structure; Figure 1 In (b), it is the alloy solidification structure when the pulse voltage is 300V (Example 1). It can be seen that when the pulse voltage is 300V, α-Al and α-Al+Mg 2 Si structures are significantly refined and the grain distribution is uniform; Figure 1 In (c), it is the alloy solidification structure when the pulse voltage is 400V (Example 2). Compared with the alloy solidification structure of the untreated alloy (Comparative Example 1), α-Al is significantly refined, and α-Al+Mg 2 Si structure is slightly refined; Figure 1Figure (d) shows the solidification structure of the alloy at a pulse voltage of 500 V (Example 3). Compared with the solidification structure of the original specimen (Comparative Example 1), the α-Al + Mg 2 Si structure is significantly refined, and α-Al is slightly coarser than that at a pulse voltage of 300 V (Example 1); Figure 1 Figure (e) shows the solidification structure of the alloy at a pulse voltage of 600 V (Example 4). Compared with the original specimen (Comparative Example 1), α-Al is significantly refined, and the α-Al + Mg 2 Si structure is somewhat refined; Figure 1 Figure (f) shows the solidification structure of the alloy at a pulse voltage of 700 V (Example 5). Compared with the original specimen (Comparative Example 1), both the α-Al and α-Al + Mg 2 Si structures are refined. Therefore, when the pulse voltage is 300 V, the refinement effect of the alloy solidification structure is the most significant. When the pulse voltages are 500 V, 600 V, and 700 V, the tissue differences are not significant.

[0059] Figure 2 This is the average grain size diagram of the Al-Mg 2 Si alloys prepared in Comparative Example 1 and Examples 1-5 of the present invention. It can be Figure 2 seen that when the pulse voltage increases from 0 V to 300 V, the average grain sizes of α-Al and Mg 2 Si decrease rapidly. When the pulse voltage increases from 300 V to 700 V, the average grain sizes of α-Al and Mg 2 Si first increase and then tend to be stable. The average grain sizes of α-Al and eutectic α-Al + Mg 2 Si structures of the untreated specimen are 150.39 μm and 155.74 μm respectively. When the pulse voltage is 300 V, the average grain sizes of α-Al and eutectic α-Al + Mg 2 Si are 110.89 μm and 93.35 μm respectively; when the pulse voltage is 400 V, the average grain sizes of α-Al and eutectic α-Al + Mg 2 Si are 127.98 μm and 110.11 μm respectively; when the pulse voltage is 500 V, the average grain sizes of α-Al and eutectic α-Al + Mg 2 Si are 132.31 μm and 125.96 μm respectively; when the pulse voltage is 600 V, the average grain sizes of α-Al and eutectic α-Al + Mg 2 Si are 131.29 μm and 122.37 μm respectively; when the pulse voltage is 700 V, the average grain sizes of α-Al and eutectic α-Al + Mg 2 Si are 133.65 μm and 126.27 μm respectively. The α-Al and Mg 2The average grain size of Si is 1.36 times and 1.67 times that at a pulsed voltage of 300 V. Therefore, when the pulsed voltage is 300 V, the grains are the finest.

[0060] Figure 3 For the Al-Mg 2 Si alloys prepared in Comparative Example 1 and Examples 1-5 of the present invention. Figure 3 It can be seen that as the pulsed voltage continuously increases, the area fraction (Acre) of the second phase in the solidified structure of the alloy first increases, then decreases, and then increases again. When the pulsed voltage is 300 V, the area fraction of the second phase is 40.47%; when the pulsed voltage is 400 V, the area fraction of the second phase is 43.53%; when the pulsed voltage is 500 V, the area fraction of the second phase is 44.71%; when the pulsed voltage is 600 V, the area fraction of the second phase is 44.33%; when the pulsed voltage is 700 V, the area fraction of the second phase is 45.18%. The area fraction of the second phase of the specimens with pulsed voltage applied is better than that of the untreated specimens. The area fraction of the second phase of the untreated specimen is 46.58%, which is 1.15 times that at a pulsed voltage of 300 V. Therefore, when the pulsed voltage is 300 V, the area fraction of the second phase is the smallest.

[0061] Figure 4 For the Al-Mg 2 XRD patterns of the Si alloys prepared in Comparative Example 1 and Examples 1-5 of the present invention. Before and after the electro-pulse treatment, 2 the positions of the diffraction peaks of the XRD curves of the Al-Mg 2 Si alloys did not change, and they were both composed of α-Al and Mg 2 Si two phases. It can be determined from this that only α(Al) and Mg 2 Si two phases exist in the alloy structure, and no new diffraction peaks appear, that is, there is no increase or decrease in other elements. However, after the electro-pulse treatment, the diffraction peak intensities and diffraction angles 2θ of the α(Al) and η(Mg

[0062] Figure 5 For the Al-Mg 2 SEM surface scan images of the Si alloys prepared in Comparative Example 1 and Examples 1-5 of the present invention. Figure 5 In (a) is the surface scan of the untreated specimen (Comparative Example 1), Figure 5 (b) is the surface scan of the specimen at a pulsed voltage of 300 V (Example 1), Figure 5 (c) is the surface scan of the specimen at a pulsed voltage of 400 V (Example 2), Figure 5 (d) is the surface scan of the specimen at a pulsed voltage of 500 V (Example 3). Figure 5(e) is a surface scan of a sample with a pulse voltage of 600 V (Example 4), Figure 5 (f) is a surface scan of the sample with a pulse voltage of 700 V (Example 5). Overall, Al, Mg, and Si elements are evenly distributed, with most of Mg and Si distributed on the grain boundaries and only a small amount of Mg and Si elements distributed on the Al matrix.

[0063] Figure 6 Al-Mg prepared in Comparative Example 1 and Examples 1-5 of the present invention 2 Scanning electron microscope dot scan images of Si alloy, where (a) is comparative example 1, (b) is example 1, (c) is example 2, (d) is example 3, (e) is example 4, and (f) is example 5. Figure 6 In the figure, the flat black area is the α-Al matrix, and the white and black strips are the Mg 2 Si phase. α-Al and Mg are distributed in (a)-(f) 2 Si phase. (a) Coarse lamellar eutectic α-Al+Mg 2 Si structure, and Mg 2 The Si phase is in the form of coarse blocks. (b) Eutectic α-Al+Mg 2 Si structure is the finest and evenly distributed, Mg 2 The Si phase is obviously refined and presents thin strips. (c)-(d) Eutectic α-Al+Mg 2 Si organization size gradually increases, and Mg 2 Si also increases accordingly.

[0064] right Figure 6 α-Al matrix and Mg 2 The Si phase was scanned and its element content was determined as shown in Tables 2 and 3. The results show that with the increase of pulse voltage, the Al content in the α-Al matrix does not change much, the Mg content gradually increases, and the Si content gradually decreases. 2 The Al content in the Si phase gradually increases, the Mg content decreases first, then increases, and then decreases. The Si content increases first, then decreases, and then increases.

[0065] Table 2 SEM point scanning results of α-Al matrix under different pulse voltages (Wt%)

[0066]

[0067] Table 3 Mg under different pulse voltages 2 SEM point scanning results of Si (Wt%)

[0068]

[0069]

[0070] Figure 7 For Comparative Example 1 and Al-Mg prepared in Examples 1-5 2 Si alloy hardness change diagram. As the pulse voltage increases, the microhardness of the Al-Mg 2 Si alloy first increases, then decreases, and then increases again. When the pulse voltage is 300 V (Example 1), the hardness of the alloy is 82.65 HV 0.2 , when the pulse voltage is 400 V (Example 2), the hardness of the alloy is 84.20 HV 0.2 , when the pulse voltage is 500 V (Example 3), the hardness of the alloy is 87.70 HV 0.2 , when the pulse voltage is 600 V (Example 4), the hardness of the alloy is 86.50 HV 0.2 , when the pulse voltage is 700 V (Example 5), the hardness of the alloy is 87.80 HV 0.2 , the hardness of the alloy of the untreated specimen (Comparative Example 1) is 75.75 HV 0.2 , when the pulse voltage is 700 V, the maximum hardness is 87.80 HV 0.2 , which is 1.16 times that of the untreated specimen. Therefore, the hardness is the largest when the pulse voltage is 700 V.

[0071] Such as Figure 8 For Comparative Example 1 and Al-Mg prepared in Examples 1-5 2 Si alloy tensile property change diagram. The tensile strength rapidly decreases and then levels off as the pulse voltage increases, and the elongation rapidly decreases and then increases as the pulse voltage increases. The tensile strength and elongation of the untreated specimen (Comparative Example 1) are 161.28 MPa and 1.43%, respectively. When the pulse voltage is 300 V (Example 1), the tensile strength of the alloy is 261.01 MPa and the elongation is 5.87%; when the pulse voltage is 400 V (Example 2), the tensile strength of the alloy is 224.23 MPa and the elongation is 3.14%; when the pulse voltage is 500 V (Example 3), the tensile strength of the alloy is 211.15 MPa and the elongation is 2.66%; when the pulse voltage is 600 V (Example 4), the tensile strength of the alloy is 213.01 MPa and the elongation is 2.79%; when the pulse voltage is 700 V (Example 5), the tensile strength of the alloy is 212.12 MPa and the elongation is 3.52%. When the pulse voltage is 300 V, the tensile strength of the alloy is the largest, which is 1.22 times and 3.06 times the tensile strength and elongation of the untreated alloy specimen, respectively. Thus, when the pulse voltage is 300 V, the tensile strength and elongation are the best.

[0072] Al-Mg under different pulse voltages2 The polarization curves of the Si alloy specimens are as Figure 9 shown in (a) below. It can be seen that, under different pulse voltages, the cathodic polarization curves of the Al-Mg 2 Si alloy are relatively smooth, and there is a large passivation region at the anode, indicating that the polarization rate and resistance are poor during the electrode reaction process. The self-corrosion potential Ecorr of the untreated specimen (Comparative Example 1) is -1.4474 V, and the self-corrosion current density Icorr is 1.544×10 -3 A / cm 2 , when the pulse voltage is 300 V (Example 1), the self-corrosion potential Ecorr of the alloy is -1.2056 V, and the self-corrosion current density Icorr is 5.740×10 -6 A / cm 2 ; when the pulse voltage is 400 V (Example 2), the self-corrosion potential Ecorr of the alloy is -1.3430 V, and the self-corrosion current density Icorr is 9.820×10 -5 A / cm 2 ; when the pulse voltage is 500 V (Example 3), the self-corrosion potential Ecorr of the alloy is -1.0052 V, and the self-corrosion current density Icorr is 5.776×10 -4 A / cm 2 ; when the pulse voltage is 600 V (Example 4), the self-corrosion potential Ecorr of the alloy is -1.3525 V, and the self-corrosion current density Icorr is 1.537×10 -4 A / cm 2 ; when the pulse voltage is 700 V (Example 5), the self-corrosion potential Ecorr of the alloy is -1.3544 V, and the self-corrosion current density Icorr is 1.629×10 -4 A / cm 2 .

[0073] In the Nyquist plot, the smaller the diameter of the impedance arc, the greater the corrosion rate. As can be seen from Figure 9 (b) below, when no electric pulse is applied (Comparative Example 1), the diameter of the impedance arc of the Al-Mg 2 Si alloy is the smallest, which is 1074, and when the electric pulse is 300 V (Example 1), the diameter of the impedance arc is the largest, which is 3007.

[0074] The electrochemical parameters of the alloy under different pulse voltages are shown in Table 4.

[0075] Table 4 Electrochemical parameters of the alloy under different casting temperatures

[0076]

[0077] Figure 10The three-dimensional morphology of the alloy after corrosion under different pulsed voltages is mainly pitting corrosion. Among them, (a) shows the average corrosion pit depth of 18.646 μm after electrochemical corrosion without treatment (Comparative Example 1). (b) shows the average corrosion pit depth of 13.686 μm after electrochemical corrosion when the pulsed voltage is 300 V (Example 1). (c) shows the average corrosion pit depth of 14.172 μm after electrochemical corrosion when the pulsed voltage is 400 V (Example 2). (d) shows the average corrosion pit depth of 24.615 μm after electrochemical corrosion when the pulsed voltage is 500 V (Example 3). (e) shows the average corrosion pit depth of 15.722 μm after electrochemical corrosion when the pulsed voltage is 600 V (Example 4). (f) shows the average corrosion pit depth of 26.892 μm after electrochemical corrosion when the pulsed voltage is 300 V (Example 5). The average corrosion pit depth of the untreated specimen after electrochemical corrosion is 18.646 μm, which is 1.36 times that when the pulsed voltage is 300 V. It can be seen that the corrosion resistance is the best when the pulsed voltage is 300 V.

[0078] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for improving the structure and properties of a hypoeutectic Al-Mg2Si alloy, characterized in that: The hypoeutectic Al-Mg2 Si alloy melt is subjected to electric pulse treatment; the process parameters of the electric pulse treatment are: pulse voltage of 300V, pulse frequency of 22Hz, and pulse treatment time of 30s; The hypoeutectic Al-Mg2 Si alloy melt has a composition of 93% Al, 5% Mg and 2% Si; When the temperature of the hypoeutectic Al-Mg2 Si alloy melt is 720-750° C., performing electric pulse treatment; After the electric pulse treatment is completed, a heat preservation step is also included; the heat preservation temperature is 740° C. and the time is 5 minutes.

2. The method for improving the structure and properties of hypoeutectic Al-Mg2Si alloy according to claim 1, characterized in that: After the heat preservation is completed, a casting step is also included.

Images