High-performance cast-rolled magnesium alloy and preparation method thereof

Abstract

The invention belongs to the field of metal materials, and provides a high-performance cast-rolled magnesium alloy and a preparation method thereof. The alloy is prepared from the following components in percentage by mass: 5.25 to 7.55 percent of zinc, 0.13 to 0.55 percent of calcium, 0.25 to 0.72 percent of manganese, less than or equal to 0.05 percent of inevitable impurities and the balance of magnesium. The preparation method of the alloy comprises the steps of smelting, cast rolling forming and solid solution, single-pass asymmetrical rolling and annealing. The invention provides the cast-rolled magnesium alloy with a short-process preparation method and good mechanical properties, the magnesium alloy with weak texture, uniform fine grain structure and higher room temperature strength and plasticity is obtained, and the yield strength is gt; the tensile strength is 220 MPa, and the elongation is gt; and 20%. The method is simple in process, low in cost and suitable for industrial production.

Description

Technical field:

[0001] The invention belongs to the field of metal materials, and in particular relates to a high-performance cast-rolled magnesium alloy and a preparation method thereof. Background technology:

[0002] As the problem of global warming becomes increasingly serious, the demand for lightweight and environmentally friendly materials for automobiles is growing. As the lightest structural material currently available, magnesium alloy has the advantages of low density, high specific strength, and good recyclability. It has broad application potential in the fields of automobiles, aerospace, 3C electronic products, etc. However, compared with traditional aluminum alloys and steels, the absolute strength and room temperature plasticity of magnesium alloys are relatively poor, which limits their industrial application. For example, due to the strong basal texture and anisotropy, the yield strength of commercial AZ31 magnesium alloy is usually less than 200MPa, and the elongation is only 8-14%. The poor strength, plasticity and formability limit its application development. In the prior art, the grain refinement and texture weakening of magnesium alloys are usually achieved by adding rare earth elements (such as Y, Gd) and adopting complex processing techniques (such as multi-pass cross rolling), thereby improving their strength, plasticity and formability. However, these methods have the following problems: the forming of magnesium alloy sheets generally requires multiple continuous hot rolling and warm rolling, which has a long process flow, high energy consumption, and low yield, resulting in extremely low output and high prices, which seriously restricts the downstream market development and promotion and application of magnesium alloy sheets; in addition, rare earth elements are expensive, which will further increase production costs; for example, the rolled annealed Mg-6.75Zn-0.57Zr-0.4Y-0.18Gd alloy reported by Lin et al. has a total solute element content of 8wt.%, a rare earth content of nearly 0.6wt.%, and is cross-rolled for 12 times at 425°C. The rolling process is complicated, and the obtained alloy texture strength is 11.74, and the yield strength and elongation are 211MPa and 14.7%, respectively. Although the strength and plasticity of the commercial AZ31 alloy are improved, the improvement effect is not significant. In addition, it is difficult to achieve the simultaneous improvement of the strength and plasticity of magnesium alloys and industrial production with the existing technology. Therefore, how to prepare a magnesium alloy sheet with a short process, low cost, simplified technology and simultaneously improved strength and plasticity, as well as industrial production, is a technical problem that needs to be solved urgently. Summary of the invention:

[0003] In order to solve the above technical problems, the present invention provides a high-performance cast-rolled magnesium alloy, which is composed of the following components by mass percentage: zinc: 5.25-7.55%, calcium: 0.13-0.55%, manganese: 0.25-0.72%, unavoidable impurities ≤ 0.05%, and the balance is magnesium. Its preparation method comprises the following steps:

[0004] S1. Magnesium alloy smelting: under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 1:99-22:78, pure magnesium is kept at 250-400°C for 60-100 minutes, then heated to 680-720°C for melting, impurities and oxide layer on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy, and magnesium-manganese master alloy preheated at 100-250°C for 30-80 minutes are added. After fully melting, the mixture is stirred at 690-720°C for 2-10 minutes, and after standing for 2-8 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt;

[0005] S2. Casting and rolling: After the magnesium alloy melt obtained in step S1 is kept at a temperature of 5-20 minutes, it is cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 2-10 mm, the rolling speed is 4-10 m / min, the casting and rolling temperature is set to 540-700 ° C, the pouring is as follows: the pouring speed is 420-620 g / s, the pouring temperature is 650-710 ° C, and the water cooling is as follows: the cooling rate is 30-150 ° C / s;

[0006] S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 300-400℃ for 6-10h; the single-pass asynchronous rolling is: the linear speed of the upper roller is 8-15m / min, the linear speed of the lower roller is 4-10m / min, the roller temperature is 80-200℃, preheating at 250-350℃ for 5-15min before rolling, and the rolling reduction is 65-80%; the annealing treatment is: keeping warm at 230-350℃ for 10-30min.

[0007] Furthermore, in S3, the linear speed of the upper roller is 9-12 m / min, and the linear speed of the lower roller is 5-8 m / min.

[0008] Furthermore, the temperature of the roller in S3 is 100-150°C.

[0009] Compared with the prior art, the advantages of the present invention are:

[0010] The present invention achieves the following advantages through the coordinated regulation of components, ratios, processes and industrial parameters:

[0011] The present invention realizes a short process, good mechanical properties, and a cast-rolled magnesium alloy with a uniform fine-grained structure with weak texture under the condition of large reduction and reduced cracking. The cast-rolled magnesium alloy obtained has high room temperature strength and plasticity, a yield strength of >220MPa, and an elongation of >20%;

[0012] The specific advantages of the present invention include: first, it can greatly refine the grains, so that the grain size of the magnesium alloy is 3-5.5μm, achieving significant refinement. Grain refinement doubles the grain boundary density, effectively hinders dislocation movement, and achieves improved yield strength. At the same time, grain refinement can also promote the opening of more slip systems, significantly improve room temperature plasticity, and the co-segregation of elements on the grain boundary can reduce the grain boundary energy and inhibit the migration of the basal plane grain boundary; second, texture weakening is achieved, and the texture strength of the obtained alloy is 3-4.5. Texture weakening can reduce the anisotropy of the alloy, thereby improving the plasticity and formability of the alloy; third, the raw material cost obtained by the present invention is low, the process is simple, and the manufacturing cost is low, realizing the low-cost preparation of lightweight, high-performance magnesium alloy sheets; fourth, the entire time cost of preparing the alloy by the present invention is lower than the prior art, breaking the problem that the prior art is difficult to achieve the industrial production of high-strength and plastic magnesium alloys and the strength and plasticity are difficult to improve simultaneously, and can stably achieve the industrial production of high-strength and plastic magnesium alloys and the simultaneous improvement of performance. Specific implementation method:

[0013] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] Example 1

[0015] Cast-rolled Mg-6Zn-0.3Ca-0.5Mn magnesium alloy (composed of the following components by mass percentage: zinc: 6%, calcium: 0.3%, manganese: 0.5%, unavoidable impurities ≤ 0.05%, and the balance is magnesium), the preparation method of which comprises the following steps:

[0016] S1. Magnesium alloy smelting: according to the designed alloy composition, pure magnesium, pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy are selected; under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 10:90, pure magnesium is kept at 300°C for 60 minutes, and then heated to 710°C for melting, and impurities and oxide layer on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy preheated at 200°C for 50 minutes are added, and after fully melting, they are stirred at 700°C for 3 minutes, and after standing for 3 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt;

[0017] S2. Casting and rolling: the magnesium alloy melt obtained in step S1 is kept at a temperature for 10 minutes, and then cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 4 mm, the rolling speed is 5 m / min, the casting and rolling temperature is set to 540°C, the pouring is as follows: the pouring speed is 420 g / s, the pouring temperature is 710°C, and the water cooling is as follows: the cooling rate is 30°C / s;

[0018] S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 400°C for 10 hours; the single-pass asynchronous rolling is: the linear speed of the upper roller is 15m / min, the linear speed of the lower roller is 7m / min, the roller temperature is 100°C, preheating at 250°C for 10 minutes before rolling, and the rolling reduction is 70%; the annealing heat treatment is: keeping warm at 350°C for 15 minutes.

[0019] The cast-rolled magnesium alloy obtained in this embodiment has a yield strength of 225 MPa, an elongation of 22.5%, a grain size of 3.6 μm, and a texture strength of 3.5.

[0020] Example 2

[0021] Cast-rolled Mg-5.5Zn-0.5Ca-0.6Mn magnesium alloy (composed of the following components by mass percentage: zinc: 5.5%, calcium: 0.5%, manganese: 0.6%, unavoidable impurities ≤ 0.05%, and the balance is magnesium), the preparation method of which comprises the following steps:

[0022] S1. Magnesium alloy smelting: according to the designed alloy composition, pure magnesium, pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy are selected; under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 5:95, pure magnesium is kept at 350°C for 70 minutes, and then the temperature is raised to 710°C for melting, and impurities and oxide layers on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy preheated at 190°C for 60 minutes are added, and after fully melting, the mixture is stirred at 710°C for 4 minutes, and after standing for 3 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt;

[0023] S2. Casting and rolling: the magnesium alloy melt obtained in step S1 is kept at a temperature for 12 minutes, and then cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 2 mm, the rolling speed is 6 m / min, the casting and rolling temperature is set to 700°C, the pouring is as follows: the pouring speed is 620 g / s, the pouring temperature is 650°C, and the water cooling is as follows: the cooling rate is 150°C / s;

[0024] S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 400°C for 8 hours; the single-pass asynchronous rolling is: the linear speed of the upper roller is 8m / min, the linear speed of the lower roller is 4m / min, the roller temperature is 110°C, preheating at 250°C for 10 minutes before rolling, and the rolling reduction is 75%; the annealing heat treatment is: keeping warm at 350°C for 10 minutes.

[0025] The cast-rolled magnesium alloy obtained in this embodiment has a yield strength of 230 MPa, an elongation of 20.2%, a grain size of 3 μm, and a texture strength of 4.2.

[0026] Example 3

[0027] Cast-rolled Mg-6.2Zn-0.13Ca-0.25Mn magnesium alloy (composed of the following components by mass percentage: zinc: 6.2%, calcium: 0.13%, manganese: 0.25%, unavoidable impurities ≤ 0.05%, and the balance is magnesium), the preparation method of which comprises the following steps:

[0028] S1. Magnesium alloy smelting: According to the designed alloy composition, pure magnesium, pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy are selected; under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 11:89, pure magnesium is kept at 300°C for 90 minutes, and then the temperature is raised to 710°C for melting, and impurities and oxide layers on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy preheated at 180°C for 50 minutes are added. After fully melting, the mixture is stirred at 700°C for 8 minutes, and after standing for 5 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt;

[0029] S2. Casting and rolling: the magnesium alloy melt obtained in step S1 is kept at a temperature for 20 minutes, and then cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 4.8 mm, the rolling speed is 10 m / min, the casting and rolling temperature is set to 690°C, the pouring is as follows: the pouring speed is 500 g / s, the pouring temperature is 680°C, and the water cooling is as follows: the cooling rate is 80°C / s;

[0030] S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 390°C for 10 hours; the single-pass asynchronous rolling is: the linear speed of the upper roller is 12m / min, the linear speed of the lower roller is 10m / min, the roller temperature is 115°C, preheating at 300°C for 15min before rolling, and the rolling reduction is 65%; the annealing heat treatment is: keeping warm at 275°C for 30min.

[0031] The cast-rolled magnesium alloy obtained in this embodiment has a yield strength of 223 MPa, an elongation of 23.5%, a grain size of 5.1 μm, and a texture strength of 3.

[0032] Example 4

[0033] Cast-rolled Mg-5.25Zn-0.55Ca-0.5Mn magnesium alloy (composed of the following components by mass percentage: zinc: 5.25%, calcium: 0.55%, manganese: 0.5%, unavoidable impurities ≤ 0.05%, and the balance is magnesium), the preparation method of which comprises the following steps:

[0034] S1. Magnesium alloy smelting: according to the designed alloy composition, pure magnesium, pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy are selected; under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 22:78, pure magnesium is kept at 400°C for 80 minutes, and then heated to 710°C for melting, and impurities and oxide layer on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy preheated at 180°C for 50 minutes are added, and after fully melting, they are stirred at 720°C for 4 minutes, and after standing for 5 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt;

[0035] S2. Casting and rolling: the magnesium alloy melt obtained in step S1 is kept at a temperature for 15 minutes, and then cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 10 mm, the rolling speed is 5 m / min, the casting and rolling temperature is set to 550°C, the pouring is as follows: the pouring speed is 500 g / s, the pouring temperature is 685°C, and the water cooling is as follows: the cooling rate is 90°C / s;

[0036] S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 400°C for 6 hours; the single-pass asynchronous rolling is: the linear speed of the upper roller is 10m / min, the linear speed of the lower roller is 5m / min, the roller temperature is 130°C, preheating at 350°C for 5min before rolling, and the rolling reduction is 65%; the annealing heat treatment is: keeping warm at 350°C for 10min.

[0037] The cast-rolled magnesium alloy obtained in this embodiment has a yield strength of 221 MPa, an elongation of 20.5%, a grain size of 5.5 μm, and a texture strength of 4.5.

[0038] Example 5

[0039] Cast-rolled Mg-7.55Zn-0.2Ca-0.72Mn magnesium alloy (composed of the following components by mass percentage: zinc: 7.55%, calcium: 0.2%, manganese: 0.72%, unavoidable impurities ≤ 0.05%, and the balance is magnesium), the preparation method of which comprises the following steps:

[0040] S1. Magnesium alloy smelting: according to the designed alloy composition, pure magnesium, pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy are selected; under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 20:80, pure magnesium is kept at 400°C for 60 minutes, and then the temperature is raised to 700°C for melting, and impurities and oxide layers on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy preheated at 150°C for 60 minutes are added. After fully melting, the mixture is stirred at 720°C for 6 minutes, and after standing for 5 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt;

[0041] S2. Casting and rolling: the magnesium alloy melt obtained in step S1 is kept at a temperature for 5 minutes, and then cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 5 mm, the rolling speed is 7 m / min, the casting and rolling temperature is set to 600°C, the pouring is as follows: the pouring speed is 450 g / s, the pouring temperature is 670°C, and the water cooling is as follows: the cooling rate is 70°C / s;

[0042] S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 380°C for 10 hours; the single-pass asynchronous rolling is: the linear speed of the upper roller is 15m / min, the linear speed of the lower roller is 8m / min, the roller temperature is 100°C, preheating at 300°C for 10 minutes before rolling, and the rolling reduction is 70%; the annealing heat treatment is: keeping warm at 300°C for 20 minutes.

[0043] The cast-rolled magnesium alloy obtained in this embodiment has a yield strength of 228 MPa, an elongation of 21.3%, a grain size of 4.3 μm, and a texture strength of 3.9.

[0044] Example 6

[0045] Cast-rolled Mg-6.5Zn-0.45Ca-0.25Mn magnesium alloy (composed of the following components by mass percentage: zinc: 6.5%, calcium: 0.45%, manganese: 0.25%, unavoidable impurities ≤ 0.05%, and the balance is magnesium), the preparation method of which comprises the following steps:

[0046] S1. Magnesium alloy smelting: according to the designed alloy composition, pure magnesium, pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy are selected; under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 10:90, pure magnesium is kept at 380°C for 70 minutes, and then the temperature is raised to 690°C for melting, and impurities and oxide layers on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy and magnesium-manganese master alloy preheated at 200°C for 30 minutes are added, and after fully melting, the mixture is stirred at 710°C for 7 minutes, and after standing for 4 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt;

[0047] S2. Casting and rolling: the magnesium alloy melt obtained in step S1 is kept at a temperature for 15 minutes, and then cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 4.6 mm, the rolling speed is 10 m / min, the casting and rolling temperature is set to 550°C, the pouring is as follows: the pouring speed is 420 g / s, the pouring temperature is 650°C, and the water cooling is as follows: the cooling rate is 60°C / s;

[0048] S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 370°C for 9 hours; the single-pass asynchronous rolling is: the linear speed of the upper roller is 10m / min, the linear speed of the lower roller is 8m / min, the roller temperature is 110°C, preheating at 250°C for 15min before rolling, and the rolling reduction is 75%; the annealing heat treatment is: keeping warm at 350°C for 10min.

[0049] The cast-rolled magnesium alloy obtained in this embodiment has a yield strength of 222 MPa, an elongation of 23%, a grain size of 5.3 μm, and a texture strength of 4.1.

[0050] Comparative Example 1

[0051] In the prior art, a journal article entitled "Deformation mechanism, orientation evolution and mechanical properties of annealed cross-rolled Mg-Zn-Zr-Y-Gd sheet during tension" (published in Journal of Magnesium and Alloys, Journal Volume: Volume 11, Paper Published in July 2023, Paper Author: Xia Li et al.) mentioned in the experimental materials that the materials selected are calculated by mass percentage: Zn: 6.75%, Zr: 0.57%, Y: 0.4%, Gd: 0.18%, and the balance is Mg. The preparation method is as follows:

[0052] The forged Mg-Zn-Zr-Y-Gd alloy was preheated at 425°C for 30 min, and then rolled at 425°C for 12 passes with a total reduction of 90%. The alloy was kept at 425°C for 15 min between passes. After each rolling pass, the sample was rotated 90° before the next rolling pass. The rolled alloy was annealed at 400°C / 1h and then water quenched to room temperature. The obtained Mg-Zn-Zr-Y-Gd alloy had a yield strength of 211 MPa, an elongation of 14.7%, a grain size of 7 μm, and a texture strength of 11.74.

[0053] Comparative Example 2

[0054] In the prior art, a journal article entitled "Hot Rolling of the Twin-Roll Cast and Homogenized Mg-6.8Y-2.5Zn (WZ73) Magnesium Alloy Containing LPSO Structures" (published in Metals, volume number: Volume 1771, published in November 2021, author: Madlen Ullmann, etc.) mentioned in the experimental materials that the mass percentages of the materials used were Y: 6.8%, Zn: 2.5%, and the balance was Mg. The preparation method is as follows:

[0055] Pure Mg (99.9wt.%), pure Zn (99.99wt.%) and Mg-40Y (wt.%) were melted at 720°C, and the molten metal was poured into a runner preheated to 650°C for casting and rolling under a protective atmosphere. The casting and rolling process was as follows: the roll gap was set to 6mm, the rolling speed was 5m / min, the casting temperature was 700°C, and the cooling rate was 100°C / s; the obtained cast-rolled plate was homogenized at 500°C for 2h and then single-pass rolled. The single-pass rolling was as follows: the roll temperature was 120°C, the rolling speed was 2m / s, the temperature was preheated at 480°C for 10min before rolling, and the rolling reduction was 50%; after rolling, the alloy was quenched to room temperature, and the yield strength of the alloy obtained was 191MPa and the elongation was 12.4%.

[0056] Comparative Example 3

[0057] In the prior art, a journal article entitled "The recrystallization, texture and mechanical behavior of hot rolled and annealed Mg-10Ho binary alloy" (published in Journal of Alloys and Compounds, Journal Volume No. 955, Paper Published in September 2023, Paper Author: Karthik Kumar, etc.) mentioned in the experimental materials that the mass percentage of the selected materials is Ho: 10%, and the balance is Mg. The preparation method is as follows:

[0058] The Mg-10Ho ingot was solutionized at 550°C for 24h under a protective atmosphere and then water quenched. Subsequently, the obtained solution sample was hot rolled at 420°C for 10 times with a total reduction of 50% and a reduction of 5% per pass. The obtained hot-rolled plate was then annealed at 400°C for 3-60min and then water quenched to room temperature. The maximum yield strength of the alloy was 150MPa, the maximum elongation was 10%, the grain size was 14μm, and the texture strength was 5.77.

[0059] In Comparative Example 1, the total solute element content reaches 8wt.%, the rare earth content is 0.58wt.%, the raw material cost is high (the present invention only contains low-cost Zn, Ca and Mn elements, and does not use any rare earth elements), and the alloy in Comparative Example 1 needs to be rolled 12 times at 425°C, and the rolling process is complicated (the present invention only needs single-pass rolling). In Comparative Example 2, the rare earth content reaches 6.8wt.%, the total solute element content reaches 9.3wt.%, and the raw material cost is high. In Comparative Example 3, the rare earth content reaches 10wt.%, and the sample needs to be hot-rolled at 420°C for 10 times. The components, proportions and process parameters used in each embodiment of the present invention are different, and the obtained strong plasticity, grain size and texture strength are all different. This shows that the excellent effect obtained by the present invention is not determined by a single component or process or parameter. In addition, the performance effect obtained by the present invention is significantly better than the material performance obtained by the prior art or the comparative example. Compared with comparative examples 1-3, the present invention reduces the cost of raw material addition, does not use rare earth elements, omits high-temperature multi-pass insulation rolling, realizes a short process, simplifies the process, and effectively refines the grains and weakens the texture. The co-segregation of the added elements on the grain boundary can reduce the grain boundary energy, inhibit grain boundary migration, promote grain refinement (size is about 3-5.5μm) and texture weakening (texture strength is 3-4.5). In addition, even at a large reduction, the present invention avoids the occurrence of cracking, simultaneously refines the grains, weakens the texture, and simultaneously improves the strong plasticity and formability of the alloy, with a yield strength>220MPa and an elongation>20%; the production of low-cost, high-performance, and lightweight magnesium alloys is realized. In summary: The excellent effects obtained by the present invention are achieved by the coordinated regulation of components, ratios, processes and process parameters.

Claims

1. A high performance cast-rolled magnesium alloy, characterized in that: According to mass percentage, it consists of the following ingredients composition: Zinc: 5.25-7.55%, calcium: 0.13-0.55%, manganese: 0.25-0.72%, inevitable impurities ≤ 0.05%, the balance is magnesium; its preparation method comprises the following steps: S1. Magnesium alloy smelting: under the protection of a mixed gas of sulfur hexafluoride and carbon dioxide in a volume ratio of 1:99-22:78, pure magnesium is kept at 250-400°C for 60-100 minutes, then heated to 680-720°C for melting, impurities and oxide layer on the surface of the melt are removed to obtain a pure magnesium melt, and then pure zinc, magnesium-calcium master alloy, and magnesium-manganese master alloy preheated at 100-250°C for 30-80 minutes are added. After fully melting, the mixture is stirred at 690-720°C for 2-10 minutes, and after standing for 2-8 minutes, high-purity argon is blown in for refining and slag removal to obtain a magnesium alloy melt; S2. Casting and rolling: After the magnesium alloy melt obtained in step S1 is kept at a temperature of 5-20 minutes, it is cast-rolled, poured and water-cooled to obtain a magnesium alloy sheet, wherein the casting and rolling is as follows: the roll gap is set to 2-10 mm, the rolling speed is 4-10 m / min, the casting and rolling temperature is set to 540-700 ° C, the pouring is as follows: the pouring speed is 420-620 g / s, the pouring temperature is 650-710 ° C, and the water cooling is as follows: the cooling rate is 30-150 ° C / s; S3. Post-casting and rolling treatment: The magnesium alloy sheet obtained in step S2 is subjected to solid solution treatment, single-pass asynchronous rolling and annealing treatment to obtain a high-performance cast-rolled magnesium alloy, wherein the solid solution treatment is: keeping warm at 300-400℃ for 6-10h; the single-pass asynchronous rolling is: the linear speed of the upper roller is 8-15m / min, the linear speed of the lower roller is 4-10m / min, the roller temperature is 80-200℃, preheating at 250-350℃ for 5-15min before rolling, and the rolling reduction is 65-80%; the annealing treatment is: keeping warm at 230-350℃ for 10-30min.

2. A high performance cast-rolled magnesium alloy according to claim 1, characterized in that: In the S3, the linear speed of the upper roller is 9-12 m / min, and the linear speed of the lower roller is 5-8 m / min.

3. The high performance cast-rolled magnesium alloy according to claim 1, characterized in that: The temperature of the roller in S3 is 100-150°C.