Preparation method of high-strength and high-toughness magnesium alloy with refined hard phase and uniform distribution regulation

Abstract

The invention belongs to the technical field of alloy materials, and provides a preparation method of a hard-phase-refined and uniform-distribution-regulated high-toughness magnesium alloy, which comprises the following steps: weighing pure magnesium, pure aluminum, an Mg-30Y intermediate alloy and a refining agent according to the element composition of the hard-phase-refined and uniform-distribution-regulated high-toughness magnesium alloy, and carrying out preheating treatment; under the protection of mixed gas, pure magnesium is molten to obtain molten magnesium, the furnace temperature is increased to the preset temperature, the Mg-30Y intermediate alloy is added, heat preservation treatment is conducted, and a melt is mixed; a refining agent and pure aluminum are added, the refining agent is pressed into the bottom of the melt, oxide inclusions are pulled out, stirring treatment is conducted, oxide inclusions are pulled out again, heat preservation treatment is conducted, and a metal melt is obtained; and the metal melt is cast into a die casting machine for die casting, and the high-toughness magnesium alloy is obtained after cooling. The beneficial effects of collaborative optimization of high strength and good plasticity, controllable microstructure, effective inhibition of crack initiation and expansion and improvement of material service stability are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy materials, and particularly to a method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases. Background Art

[0002] As the lightest structural metal material, magnesium alloys are widely used in the aerospace, automotive, and 3C industries due to their low density, high specific strength, excellent castability, and low recycling cost.

[0003] In the prior art, the two major limitations of magnesium alloys are their low strength and elongation, which greatly limit the popularization and application of magnesium alloys. The addition of rare-earth alloys provides a practical solution for this, mainly because rare-earth magnesium alloys can produce precipitation strengthening. Precipitation strengthening, as one of the most important metal strengthening methods, greatly affects the strength and plasticity of magnesium alloys. Among many rare-earth magnesium alloys, Mg-Y-Al alloy has become one of the most popular magnesium alloys due to its corrosion resistance and good strength and plasticity. In Mg-Y-Al alloy, Al 2 Y has a great influence on its grain size and strength and plasticity. Al 2 Y can be pinned at the grain boundaries to inhibit grain growth, thereby improving the strength of magnesium alloys. However, Al 2 Y, as a hard phase, has an elastic modulus of 147 GPa, while the elastic modulus of α-Mg is only 40 GPa. Therefore, if there are coarse Al 2 Y in α-Mg, it will cause cracks in the magnesium alloy to easily propagate along the Al 2 Y hard phase during the tensile process, thereby reducing the plasticity of the magnesium alloy.

[0004] Therefore, making the Al 2 Y particles in the magnesium alloy finer and more dispersedly distributed can improve the plasticity of the Mg-Y-Al alloy without damaging the strength of Mg-Y-Al. To achieve this goal, the present invention introduces a die-casting process. Different from traditional casting, die-casting can effectively inhibit the growth of precipitates due to its high cooling rate, so the effect of fine and dispersed distribution of Al 2 Y particles can be achieved. Summary of the Invention

[0005] The present invention provides a method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases, so as to solve the technical problem that the coarse Al 2 Y particles in the Mg-Y-Al alloy in the prior art are prone to become the initiation and propagation areas of cracks during the stress service process, thereby reducing the strength-plasticity matching of the Mg-Y-Al magnesium alloy.

[0006] The present invention provides a method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases, comprising the following steps: (1) Weigh pure magnesium, pure aluminum, Mg-30Y master alloy and a refining agent according to the element composition of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases, and perform preheating treatment; (2) Under the protection of a mixed gas, melt pure magnesium to obtain molten magnesium, raise the furnace temperature to a preset temperature, add the Mg-30Y master alloy and perform heat preservation treatment to obtain a mixed melt; (3) Add the refining agent and pure aluminum, press the refining agent to the bottom of the melt, remove oxide inclusions, perform stirring treatment, remove oxide inclusions again, and perform heat preservation treatment to obtain a metal melt; (4) Cast the metal melt into a die-casting machine for die-casting, and after cooling, obtain a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases; The element composition of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases is as follows: yttrium 2-10 wt%, aluminum 0.5-1.5 wt%, and the balance is magnesium and inevitable impurities; In step (2), when adding the Mg-30Y master alloy, first suspend the Mg-30Y master alloy on the surface of the molten magnesium, and then sink the Mg-30Y master alloy into the molten magnesium; In step (3), the refining agent is wrapped with magnesium foil, and the stirring treatment is carried out in an orderly manner from top to bottom.

[0007] According to the method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, the refining agent is a JDMJ refining agent, and the dosage is 1-2% of the total mass of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases.

[0008] According to the method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, the temperature of the preheating treatment is 150-200 °C, and the time of the preheating treatment is 40-80 min.

[0009] According to the method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, the mixed gas is a mixed gas of SF 6 and CO 2 The ratio of SF 6 and CO 2 is 40-60:1.

[0010] According to the method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, the temperature of the heat preservation treatment in step (2) is 750 °C, and the time of the heat preservation treatment is 10-20 min.

[0011] According to a preparation method of a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, in the step (3), the stirring treatment time is 1 - 5 min, the heat preservation treatment temperature is 700 - 750 °C, and the heat preservation treatment time is 1 - 10 min.

[0012] According to a preparation method of a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, before adding the refining agent and pure aluminum in the step (3), the temperature of the mixed melt is 710 - 740 °C.

[0013] According to a preparation method of a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, in the step (4), the casting temperature is 700 - 750 °C, and the initial temperature of the die-casting mold is 200 - 250 °C.

[0014] According to a preparation method of a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, in the step (4), the casting speed is 0.25 - 4 m / s, the boosting pressure of die-casting is 80 - 110 MPa, and the cooling time is 1 - 10 s.

[0015] The preparation method of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention precisely regulates the precipitation behavior of the Al 2 Y hard phase through the die-casting process, enabling it to be dispersed along the grain boundaries in a sub-micron scale and forming a duplex structure of α-Mg matrix and Al 2 Y, which solves the technical problems in the prior art such as the coarsening and segregation of the Al 2 Y phase, easy crack propagation leading to the imbalance between strength and plasticity, achieves the synergistic optimization of high strength and good plasticity, and the microstructural controllable Al 2 Y phase is refined to the sub-micron scale and uniformly distributed, effectively inhibiting the initiation and propagation of cracks, and enhancing the beneficial effect of the service stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0017] Figure 1 It is a SEM comparison diagram of the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention and the traditional casting magnesium alloy provided in Comparative Example 1; Figure 2 It is a comparison diagram of the precipitated phase particle size distribution of the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention and the traditional casting magnesium alloy provided in Comparative Example 1; Figure 3 It is a comparison chart of the grain sizes of the high-strength and high-toughness magnesium alloy provided in Example 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1; Figure 4 It is the Al 2 Y size comparison chart of the high-strength and high-toughness magnesium alloy provided in Example 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1. Detailed implementation manners

[0018] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0019] Below in conjunction with Figures 1 to 4 Describe the preparation method of the high-strength and high-toughness magnesium alloy with refined and uniformly distributed hard phases of the present invention.

[0020] Figure 1 It is a SEM comparison chart of the high-strength and high-toughness magnesium alloy provided in Example 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1.

[0021] As Figure 1 shown, in the SEM comparison chart of the high-strength and high-toughness magnesium alloy provided in Example 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1, Figure 1 (a) is the SEM image of the high-strength and high-toughness magnesium alloy provided in Example 1, Figure 1 (b) is the SEM image of the traditional cast magnesium alloy provided in Comparative Example 1. By comparing Figure 1 (a) and Figure 1 (b), it can be seen that for the high-strength and high-toughness magnesium alloy prepared by the preparation method of the high-strength and high-toughness magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, the size of the precipitated phases on the surface of the high-strength and high-toughness magnesium alloy is much smaller than that of the precipitated phases on the surface of the traditional cast magnesium alloy provided in Comparative Example 1, and the distribution of the precipitated phases of the high-strength and high-toughness magnesium alloy provided in Example 1 is more uniform than that of the precipitated phases of the traditional cast magnesium alloy provided in Comparative Example 1. It proves that the preparation method of the high-strength and high-toughness magnesium alloy with refined and uniformly distributed hard phases provided by the present invention achieves the technical effects of refining and uniformly distributing the hard phases.

[0022] Figure 2 It is a comparison chart of the precipitated phase particle size distributions of the high-strength and high-toughness magnesium alloy provided in Example 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1.

[0023] As Figure 2As shown in the figure, in the comparison chart of the precipitation phase particle size distribution between the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1, Figure 2 (a) is the precipitation phase particle size distribution diagram of the high-strength and tough magnesium alloy provided in Embodiment 1, Figure 2 (b) is the precipitation phase particle size distribution diagram of the traditional cast magnesium alloy provided in Comparative Example 1. By comparing Figure 2 (a) and Figure 2 (b), it can be seen that for the high-strength and tough magnesium alloy prepared by the method for regulating the refinement and uniform distribution of hard phases provided by the present invention, the average particle size of the precipitation phase (Al 2 Y) of the prepared high-strength and tough magnesium alloy is 0.18 μm, while the average particle size of the precipitation phase (Al 2 Y) of the traditional cast magnesium alloy provided in Comparative Example 1 is 18 μm, which proves that the method for preparing a high-strength and tough magnesium alloy by regulating the refinement and uniform distribution of hard phases provided by the present invention achieves the technical effect of fine grains.

[0024] Figure 3 is the comparison chart of the grain sizes between the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1.

[0025] As Figure 3 shown, in the comparison chart of the grain sizes between the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1, Figure 3 (a) is the grain size diagram of the high-strength and tough magnesium alloy provided in Embodiment 1, Figure 3 (b) is the grain size diagram of the traditional cast magnesium alloy provided in Comparative Example 1. By comparing Figure 3 (a) and Figure 3 (b), it can be seen that the grain size of the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention is much smaller than that of the traditional cast magnesium alloy provided in Comparative Example 1, and the grain distribution is more uniform, which once again proves that the method for preparing a high-strength and tough magnesium alloy by regulating the refinement and uniform distribution of hard phases provided by the present invention achieves the technical effect of fine grains.

[0026] Figure 4 is the comparison chart of the Al 2 Y sizes between the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1.

[0027] As Figure 4 shown, in the comparison chart of the Al 2 Y sizes between the high-strength and tough magnesium alloy provided in Embodiment 1 of the present invention and the traditional cast magnesium alloy provided in Comparative Example 1, Figure 4 (a) is the Al 2 Y size diagram of the high-strength and tough magnesium alloy provided in Embodiment 1, Figure 4 (b) is the Al 2Y Dimension Diagram. By comparison Figure 4 (a) and Figure 4 (b), it can be seen that the size of the precipitated phase (Al 2 Y) of the high-strength and tough magnesium alloy provided in Example 1 of the present invention is much smaller than that of the precipitated phase (Al 2 Y) of the conventional cast magnesium alloy provided in Comparative Example 1. Moreover, from Figure 4 (a), it can be seen that the precipitated phase (Al 2 Y) is dispersed along the grain boundary at the sub-micron level and forms a duplex structure of α-Mg matrix and Al 2 Y.

[0028] In the present invention, a method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases includes the following steps: (1) Weigh pure magnesium, pure aluminum, Mg-30Y master alloy and refining agent according to the elemental composition of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases, and perform preheating treatment; (2) Under the protection of a mixed gas, melt pure magnesium to obtain molten magnesium, raise the furnace temperature to a preset temperature, add the Mg-30Y master alloy and perform heat preservation treatment to obtain a mixed melt; (3) Add the refining agent and pure aluminum, press the refining agent to the bottom of the melt, remove the oxide inclusions, perform stirring treatment, remove the oxide inclusions again, and perform heat preservation treatment to obtain a metal melt; (4) Pour the metal melt into a die-casting machine for die-casting, and obtain a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases after cooling; In step (2), when adding the Mg-30Y master alloy, first suspend the Mg-30Y master alloy on the surface of the molten magnesium, and then sink the Mg-30Y master alloy into the molten magnesium; In step (3), the refining agent is wrapped with magnesium foil, and the stirring treatment is carried out in an orderly manner from top to bottom.

[0029] The elemental composition of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases is as follows: yttrium 2-10 wt%, preferably 3-5 wt%, aluminum 0.5-1.5 wt%, preferably 0.8-1.2 wt%, and the balance is magnesium and inevitable impurities.

[0030] In the present invention, the refining agent is JDMJ refining agent, and the dosage is 1-2% of the total mass of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases, preferably 1.2-1.8%.

[0031] In the present invention, the temperature of the preheating treatment is 150-200 °C, preferably 160-190 °C, and more preferably 170-180 °C; the time of the preheating treatment is 40-80 min, preferably 50-70 min.

[0032] In the present invention, the mixed gas is SF 6 and CO 2 mixed gas, and the ratio of SF 6 and CO 2 is 40 - 60:1, preferably 45 - 55:1.

[0033] In the present invention, in the step (2), the temperature of the heat preservation treatment is 750 °C, and the time of the heat preservation treatment is 10 - 20 min, preferably 12 - 18 min.

[0034] In the present invention, according to a method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, in the step (3), the stirring treatment time is 1 - 5 min, preferably 2 - 4 min; the temperature of the heat preservation treatment is 700 - 750 °C, preferably 710 - 740 °C; more preferably 720 - 730 °C; the time of the heat preservation treatment is 1 - 10 min, preferably 2 - 8 min, and more preferably 4 - 6 min.

[0035] In the present invention, according to a method for preparing a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided by the present invention, before adding the refining agent and pure aluminum in the step (3), the temperature of the mixed melt is 710 - 740 °C, preferably 720 - 730 °C.

[0036] In the present invention, in the step (4), the casting temperature is 700 - 750 °C, preferably 710 - 740 °C, more preferably 720 - 730 °C; the initial temperature of the die-casting mold is 200 - 250 °C, preferably 210 - 240 °C, more preferably 220 - 230 °C.

[0037] In the present invention, in the step (4), the casting speed is 0.25 - 4 m / s, preferably 1 - 3 m / s, more preferably 1.5 - 2.5 m / s; the boosting pressure of die-casting is 80 - 110 MPa, preferably 85 - 105 MPa, more preferably 90 - 100 MPa; the cooling time is 1 - 10 s, preferably 2 - 8 s, more preferably 4 - 6 s.

[0038] Example 1 With the ratio of Mg - 3.5Y - 1Al, considering alloy burning loss, pure magnesium, pure aluminum, and Mg - 30Y master alloy were weighed according to the element composition, and a refining agent accounting for 1.5% of the total mass of the high-strength and tough magnesium alloy was weighed. The above raw materials were preheated at 175 °C for 60 min; In SF 6 and CO 2Under the protection of a mixed gas with a ratio of 50:1, pure magnesium was melted to obtain molten magnesium. The furnace temperature was raised to 750 °C, and the Mg-30Y master alloy was clamped with pliers and suspended on the surface of the melt. After the Mg-30Y master alloy was fully heated, the pliers were released to let the Mg-30Y master alloy sink into the melt, and heat preservation treatment was carried out for 15 minutes to obtain a mixed melt; The temperature of the mixed melt was maintained at 740 °C, and the JDMJ refining agent and pure aluminum wrapped with magnesium foil were added. The refining agent was pressed to the bottom of the melt with a bell jar. After the oxide inclusions fully floated up, the oxide inclusions were removed with a refining spoon, and the molten metal was stirred orderly from top to bottom for 3 minutes. The remaining oxide inclusions were removed again, and heat preservation treatment was carried out at 725 °C for 5 minutes to obtain a molten metal; Under the condition that the casting temperature was 740 °C, the molten metal was cast into the chamber of a TOYO-BD350V5 cold chamber die casting machine preheated to 230 °C at a casting speed of 2 m / s. The boosting pressure was set at 95 Mpa for die casting, and after cooling for 6 s, a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases was obtained.

[0039] After testing, the yield strength of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided in this example was 150 Mpa, the tensile strength was 206 Mpa, and the elongation was 9%.

[0040] Example 2 With a ratio of Mg-3.5Y-1Al, considering alloy burning loss, pure magnesium, pure aluminum, and Mg-30Y master alloy were weighed according to the elemental composition, and a refining agent accounting for 1.5% of the total mass of the high-strength and tough magnesium alloy was also weighed. The above raw materials were preheated at 175 °C for 60 minutes; In SF 6 and CO 2 Under the protection of a mixed gas with a ratio of 50:1, pure magnesium was melted to obtain molten magnesium. The furnace temperature was raised to 750 °C, and the Mg-30Y master alloy was clamped with pliers and suspended on the surface of the melt. After the Mg-30Y master alloy was fully heated, the pliers were released to let the Mg-30Y master alloy sink into the melt, and heat preservation treatment was carried out for 15 minutes to obtain a mixed melt; The temperature of the mixed melt was maintained at 730 °C, and the JDMJ refining agent and pure aluminum wrapped with magnesium foil were added. The refining agent was pressed to the bottom of the melt with a bell jar. After the oxide inclusions fully floated up, the oxide inclusions were removed with a refining spoon, and the molten metal was stirred orderly from top to bottom for 3 minutes. The remaining oxide inclusions were removed again, and heat preservation treatment was carried out at 725 °C for 5 minutes to obtain a molten metal; Under the condition that the casting temperature is 730 °C, the metal melt is cast into the chamber of the TOYO-BD350V5 cold chamber die-casting machine preheated to 230 °C at a casting speed of 2 m / s. The boosting pressure is set to 95 Mpa for die-casting. After cooling for 6 s, a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases is obtained.

[0041] After testing, the yield strength of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided in this example is 131 Mpa, the tensile strength is 173 Mpa, and the elongation is 8.8%.

[0042] Example 3 With the ratio of Mg-3.5Y-1Al, considering alloy burn-off, pure magnesium, pure aluminum, and Mg-30Y master alloy are weighed according to the elemental composition, and a refining agent accounting for 1.5% of the total mass of the high-strength and tough magnesium alloy is also weighed. The above raw materials are preheated at 175 °C for 60 min. In SF 6 and CO 2 Under the protection of a mixed gas with a ratio of 50:1, pure magnesium is melted to obtain molten magnesium. The furnace temperature is raised to 750 °C, and the Mg-30Y master alloy is clamped with pliers and suspended on the surface of the melt. After the Mg-30Y master alloy is fully heated, the pliers are released to let the Mg-30Y master alloy sink into the melt, and heat preservation treatment is carried out for 15 minutes to obtain a mixed melt. The temperature of the mixed melt is maintained at 720 °C, and the JDMJ refining agent and pure aluminum wrapped with magnesium foil are added. The refining agent is pressed to the bottom of the melt with a bell jar. After the oxide inclusions fully float up, the oxide inclusions are removed with a refining spoon. The metal melt is stirred orderly from top to bottom for 3 min, and the remaining oxide inclusions are removed again. Heat preservation treatment is carried out at 725 °C for 5 min to obtain a metal melt. Under the condition that the casting temperature is 720 °C, the metal melt is cast into the chamber of the TOYO-BD350V5 cold chamber die-casting machine preheated to 230 °C at a casting speed of 2 m / s. The boosting pressure is set to 95 Mpa for die-casting. After cooling for 6 s, a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases is obtained.

[0043] After testing, the yield strength of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided in this example is 127 Mpa, the tensile strength is 170 Mpa, and the elongation is 8.5%.

[0044] Example 4 With the ratio of Mg-3.5Y-1Al, considering alloy burn-off, pure magnesium, pure aluminum, and Mg-30Y master alloy are weighed according to the elemental composition, and a refining agent accounting for 1.5% of the total mass of the high-strength and tough magnesium alloy is also weighed. The above raw materials are preheated at 175 °C for 60 min. In SF6 and CO 2 Under the protection of a mixed gas with a ratio of 50:1 of and CO , pure magnesium was melted to obtain molten magnesium. The furnace temperature was raised to 750 °C, and the Mg-30Y master alloy was clamped with pliers and suspended on the surface of the melt. After the Mg-30Y master alloy was fully heated, the pliers were released to allow the Mg-30Y master alloy to sink into the melt, and heat preservation treatment was carried out for 15 minutes to obtain a mixed melt; The temperature of the mixed melt was maintained at 715 °C, and a JDMJ refining agent wrapped with magnesium foil and pure aluminum were added. The refining agent was pressed to the bottom of the melt with a bell jar. After the oxide inclusions fully floated up, the oxide inclusions were removed with a refining spoon, and the molten metal was stirred orderly from top to bottom for 3 minutes. The remaining oxide inclusions were removed again, and heat preservation treatment was carried out at 725 °C for 5 minutes to obtain a molten metal; Under the condition that the casting temperature was 715 °C, the molten metal was cast into the chamber of a TOYO-BD350V5 cold chamber die casting machine preheated to 230 °C at a casting speed of 2 m / s. The boosting pressure was set at 95 Mpa for die casting, and a high-strength and tough magnesium alloy with refined and uniformly distributed hard phases was obtained after cooling for 6 s.

[0045] After testing, the yield strength of the high-strength and tough magnesium alloy with refined and uniformly distributed hard phases provided in this example was 110 Mpa, the tensile strength was 150 Mpa, and the elongation was 5%.

[0046] Comparative Example 1 With a ratio of Mg-3.5Y-1Al, considering alloy burn-off, pure magnesium, pure aluminum, and Mg-30Y master alloy were weighed according to the elemental composition, and a refining agent accounting for 1.5% of the total mass of the high-strength and tough magnesium alloy was also weighed. The above raw materials were preheated at 175 °C for 60 minutes; In SF 6 and CO 2 Under the protection of a mixed gas with a ratio of 50:1 of and CO , pure magnesium was melted to obtain molten magnesium. The furnace temperature was raised to 750 °C, and the Mg-30Y master alloy was clamped with pliers and suspended on the surface of the melt. After the Mg-30Y master alloy was fully heated, the pliers were released to allow the Mg-30Y master alloy to sink into the melt, and heat preservation treatment was carried out for 15 minutes to obtain a mixed melt; The temperature of the mixed melt was maintained at 715 °C, and a JDMJ refining agent wrapped with magnesium foil and pure aluminum were added. The refining agent was pressed to the bottom of the melt with a bell jar. After the oxide inclusions fully floated up, the oxide inclusions were removed with a refining spoon, and the molten metal was stirred orderly from top to bottom for 3 minutes. The remaining oxide inclusions were removed again, and heat preservation treatment was carried out at 725 °C for 5 minutes to obtain a molten metal; The molten metal was cast into a mold and left to cool statically to obtain a traditional magnesium alloy.

[0047] After testing, the yield strength of the traditional magnesium alloy provided in this comparative example is 80 Mpa, the tensile strength is 125 Mpa, and the elongation is 9%.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control, characterized in that: The following steps are involved: (1) According to the elemental composition of the high-strength and toughness magnesium alloy controlled by hard phase refinement and uniform distribution, pure magnesium, pure aluminum, Mg-30Y master alloy and refining agent are weighed and preheated; (2) Under the protection of the mixed gas, pure magnesium is melted to obtain molten magnesium, the furnace temperature is increased to a preset temperature, Mg-30Y master alloy is added, and heat preservation treatment is performed to obtain a mixed melt; (3) adding a refining agent and pure aluminum, pressing the refining agent into the bottom of the melt, removing the oxide inclusions, stirring, removing the oxide inclusions again, and heat-insulating to obtain a metal melt; (4) The molten metal is poured into a die-casting machine for die-casting, and after cooling, a high-strength and tough magnesium alloy with refined and uniformly distributed hard phase is obtained; The element composition of the high-strength and toughness magnesium alloy with hard phase refinement and uniform distribution control is 2-10wt% yttrium, 0.5-1.5wt% aluminum, and the balance is magnesium and inevitable impurities; In the step (2), when adding the Mg-30Y master alloy, the Mg-30Y master alloy is first suspended on the surface of the molten magnesium, and then the Mg-30Y master alloy is sunk into the molten magnesium; In the step (3), the refining agent is wrapped with magnesium foil, and the stirring process is carried out in an orderly manner from top to bottom.

2. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: The refining agent is JDMJ refining agent, and the amount used is 1-2% of the total mass of the high-strength and tough magnesium alloy for hard phase refinement and uniform distribution control.

3. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: The preheating treatment temperature is 150-200° C., and the preheating treatment time is 40-80 minutes.

4. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: The mixed gas is a mixed gas of SF6 and CO2, and the ratio of SF6 to CO2 is 40-60:

1.

5. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: The temperature of the heat preservation treatment in step (2) is 750° C., and the time of the heat preservation treatment is 10 to 20 minutes.

6. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: In the step (3), the stirring treatment time is 1 to 5 minutes, the insulation treatment temperature is 700 to 750° C., and the insulation treatment time is 1 to 10 minutes.

7. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: Before adding the refining agent and pure aluminum in step (3), the temperature of the mixed melt is 710-740°C.

8. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: The casting temperature in step (4) is 700-750°C, and the initial temperature of the die-casting mold is 200-250°C.

9. The method for preparing a high-strength and tough magnesium alloy with hard phase refinement and uniform distribution control according to claim 1, characterized in that: In step (4), the casting speed is 0.25-4 m / s, the boost pressure of the die casting is 80-110 MPa, and the cooling time is 1-10 s.

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