Magnesium alloy preparation process with optimized rare earth elements Y and Sm

Abstract

The invention provides a forming and preparation method of a high-performance magnesium alloy. The magnesium alloy comprises the following components: 7% of Al, 1% of Ca, more than or equal to 0.4% and less than or equal to 1.0% of Y, more than or equal to 0.2% and less than or equal to 0.5% of Sm, and main metals of Mg and corresponding compounds of Mg elements. The preparation method comprises the following steps: putting pretreated pure magnesium, pure aluminum, an Mg-Ca intermediate alloy, an Mg-Y intermediate alloy and an Mg-Sm intermediate alloy into a smelting crucible, carrying out vacuum smelting for at least four times, pouring the melt into a preheated and dried mold at a constant speed, taking out a casting after the mold is completely cooled, and carrying out heat treatment on the casting to obtain the magnesium alloy. And carrying out heat treatment and electromagnetic extrusion on the as-cast alloy. Rare earth elements Y and Sm (Y: Sm = 2: 1) are added into the Mg-7Al-1Ca alloy in an equal proportion, the Mg-7Al-1Ca-xY-ySm (x = 0.4, 0.7 and 1.0 wt.%) alloys in different states are prepared through a large number of experiments, it is obtained that when the total content of Y and Sm reaches 1.05 wt.%, the room-temperature tensile property and hardness of the alloy reach the optimal, and the optimal technological parameters are that the tensile strength is 285 MPa, the ductility is 8.3%, and the microhardness is 78.03 HV.

Description

Technical Field

[0001] The invention relates to the field of lightweight metal materials, in particular to a method for preparing a high-performance magnesium alloy. Background Art

[0002] As the lightest structural metal material, magnesium alloy has shown broad application prospects in aerospace, automobile manufacturing, electronic products, biomedicine and other fields due to its excellent specific strength, good rigidity and low density.

[0003] Although magnesium alloys have many advantages, they have poor plastic deformation ability at room temperature and are prone to brittle fracture, which limits their further application. The hexagonal close-packed (HCP) crystal structure of magnesium alloys results in fewer slip systems and mainly relies on the basal plane. Slip, only two independent slip systems are provided, which is far less than the requirement of five independent slip systems. Therefore, non-basal slip modes, such as prismatic and cone<c + a> Slip becomes crucial in plastic deformation.

[0004] In order to improve the mechanical properties and processability of magnesium alloys, researchers have explored a variety of methods, including grain refinement, addition of rare earth elements, use of twins and phase transformation, etc. These methods have improved the performance of magnesium alloys to a certain extent, but there are still problems such as complex processing, high cost and limited effect.

[0005] In the prior art, optimizing the properties of magnesium alloys by adjusting the alloy composition is an effective method. For example, by precisely controlling the content of aluminum, zinc, rare earth and other elements in the alloy, the strength, toughness and corrosion resistance of magnesium alloys can be significantly affected. However, the optimal content and ratio of these elements have not yet been fully clarified, and the interaction between different elements on the properties of the alloy also needs further study.

[0006] In addition, the preparation process of magnesium alloys, such as melting, casting, heat treatment and deformation processing, has an important influence on their final properties. Traditional preparation methods often make it difficult to achieve precise control of alloy composition and optimization of microstructure. Therefore, developing new preparation technologies to achieve low-cost and high-efficiency production of high-performance magnesium alloys has become a research hotspot in this field. Summary of the invention

[0007] The purpose of the present invention is to provide a forming and preparation method of a high-performance magnesium alloy, which can significantly improve the strength and toughness of the magnesium alloy by precisely controlling the alloy composition and microstructure, while reducing the processing complexity and cost.

[0008] The present invention provides a method for preparing a high-performance magnesium alloy, comprising the following steps: 1. Pretreatment: mechanically grinding and ultrasonically cleaning pure magnesium, pure aluminum, Mg-Ca master alloy, Mg-Y master alloy and Mg-Sm master alloy to remove surface oxide layer and impurities. 2. Melting: under the protection of inert gas, the pretreated raw materials are placed in a melting crucible and vacuum melted at least 4 times to ensure uniform distribution of alloy components. 3. Pouring: pouring the molten alloy into a metal mold preheated to an appropriate temperature at a uniform rate. 4. Cooling and molding: after the mold is cooled to room temperature, the molded magnesium alloy casting is taken out. 5. Heat treatment: heat treatment of the cast alloy, including solution treatment at 420 ° C + 12 h, to optimize the microstructure of the alloy. 6. Electromagnetic extrusion: electromagnetic extrusion of the alloy to further improve the microstructure and mechanical properties of the alloy.

[0009] The invention has the advantage that by adding rare earth elements Y and Sm (Y: Sm=2:1) ​​to the Mg-7Al-1Ca alloy in a moderate proportion, when the total content of Y and Sm reaches 1.05 wt.%, the room temperature tensile properties and hardness of the alloy are optimal. The optimal process parameters are: tensile strength 285 MPa, elongation 8.3%, and microhardness 78.03HV. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 : Vickers hardness of alloys with different Y and Sm contents

[0011] Figure 2 :Mechanical properties of toughened wrought magnesium alloys prepared with different Y and Sm contents after electromagnetic extrusion DETAILED DESCRIPTION

[0012] The following examples describe the specific embodiments of the present invention in detail, but the protection scope of the present invention is not limited to these examples.

[0013] Example 1 describes a preparation process of a magnesium alloy. According to the above steps, a high-performance magnesium alloy is prepared, and its composition is: Al 7%, Ca 1%, Y 0.4%, Sm 0.2%. First, the raw material is mechanically polished and ultrasonically cleaned to remove the oxide layer and impurities, and then vacuum melting is performed at least 4 times under the protection of inert gas to ensure that the alloy composition is uniform. The molten alloy is poured into a preheated metal mold, and after cooling and forming, a solid solution treatment is performed. Finally, the microstructure and mechanical properties of the alloy are further improved by electromagnetic extrusion. The mechanical property test results after electromagnetic extrusion are shown in Table 1.

[0014] Example 2 describes a preparation process of a magnesium alloy. According to the above steps, a high-performance magnesium alloy is prepared, and its composition is: Al 7%, Ca 1%, Y 0.7%, Sm 0.35%. First, the raw material is mechanically polished and ultrasonically cleaned to remove the oxide layer and impurities, and then vacuum melting is performed at least 4 times under the protection of inert gas to ensure that the alloy composition is uniform. The molten alloy is poured into a preheated metal mold, and after cooling and forming, a solid solution treatment is performed. Finally, the microstructure and mechanical properties of the alloy are further improved by electromagnetic extrusion. The mechanical property test results after electromagnetic extrusion are shown in Table 1.

[0015] Example 3 describes a preparation process of a magnesium alloy. According to the above steps, a high-performance magnesium alloy is prepared, and its composition is: Al 7%, Ca 1%, Y 1%, Sm 0.5%. First, the raw material is mechanically polished and ultrasonically cleaned to remove the oxide layer and impurities, and then vacuum melting is performed at least 4 times under the protection of inert gas to ensure that the alloy composition is uniform. The molten alloy is poured into a preheated metal mold, and after cooling and forming, a desolventizing treatment is performed. Finally, electromagnetic extrusion is used to further improve the microstructure and mechanical properties of the alloy. The mechanical property test results after electromagnetic extrusion are shown in Table 1.

[0016] Combining the analysis of the three embodiments of the present invention, the optimal process parameters of the magnesium alloy obtained by electromagnetic extrusion after solution treatment at 420°C for 12 h are as follows: tensile strength of 285 MPa, elongation of 8.3%, and microhardness of 78.03 HV.

[0017]

[0018] Table 1.

Claims

1. A high performance magnesium alloy and a method for preparing the same, characterized in that: The magnesium alloy comprises, by weight percentage, 7% Al, 1% Ca, 0.4%≤Y≤1.0%, 0.2%≤Sm≤0.5%, and the main metal is Mg and its corresponding compound of Mg element; The preparation method comprises the following steps: Step S1: putting the pretreated pure magnesium, pure aluminum, Mg-Ca master alloy, Mg-Y master alloy and Mg-Sm master alloy into a smelting furnace; Step S2: performing vacuum melting at least 4 times under inert gas protection to ensure uniform distribution of alloy components; Step S3: pouring the molten alloy into a metal mold preheated to an appropriate temperature at a uniform rate; Step S4: After the mold is cooled to room temperature, the formed magnesium alloy casting is taken out, and the cast alloy is subjected to heat treatment and electromagnetic extrusion.

2. The magnesium alloy and the preparation method thereof according to claim 1, characterized in that: In the step S1, the pretreatment includes ultrasonic cleaning and drying the raw material to remove the surface oxide layer and impurities.

3. The magnesium alloy and the preparation method thereof according to claim 1, characterized in that: During the vacuum melting process in step S2, the vacuum degree in the furnace is maintained at less than 1.0×10 -3 Pa, and the rate of increase of heating power is controlled at 20-40 kW / min.

4. The magnesium alloy and the preparation method thereof according to claim 1, characterized in that: In step S4, the heat treatment is to perform a solution treatment on the alloy at 420°C+12 h.

5. The magnesium alloy and the method for preparing the same according to claim 1, characterized in that: In the electromagnetic extrusion process of step S4, the electromagnetic winding is arranged to be wound helically around the chamber and is configured to carry a direct current to generate a magnetic field with a magnetic flux density of at least 2 Tesla to reduce the rheological stress of the extruded material. Electromagnetic extrusion during plastic processing can further improve the microstructure and mechanical properties of the alloy.

6. The magnesium alloy and the method for preparing the same according to claim 1, characterized in that: The addition ratio of the rare earth elements Y and Sm is Y:Sm=2:1, and when the total content of Y and Sm reaches 1.05 wt.%, the room temperature tensile properties and hardness of the alloy reach the optimum.

7. The magnesium alloy and the preparation method thereof according to claim 1, characterized in that: The magnesium alloy has excellent radiation resistance and is suitable for preparing shielding materials for deep space detectors.

8. The magnesium alloy and the method for preparing the same according to claim 1, characterized in that: The microstructure of the magnesium alloy consists of fine and evenly distributed grains, the grain size is less than 4µ, and there are dispersedly distributed second phase particles at the grain boundaries.

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