High-strength extruded magnesium alloy and preparation method thereof

Abstract

The high-strength extruded magnesium alloy comprises the following components in percentage by weight: 0.25 to 1.45 percent of Ce element, 0.5 to 2.5 percent of Yb element, 1 to 2 percent of Sn element, 1.35 to 1.95 percent of Al element and the balance of metal Mg and some inevitable impurity elements. After the high-strength extruded magnesium alloy is subjected to extrusion and aging treatment, the tensile strength and the elongation of the magnesium alloy at the temperature of 275 DEG C are 373 MPa and 15.6% respectively, and the tensile strength and the elongation of the magnesium alloy at the temperature of 300 DEG C are 321 MPa and 18.3% respectively. The high-strength extruded magnesium alloy has excellent tensile strength, high heat resistance and good formability, and the technical problems that an existing magnesium alloy is not high in strength, poor in heat resistance and not prone to forming machining are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of material alloys, and in particular relates to a high-strength extruded magnesium alloy and a preparation method thereof. Background Art

[0002] Magnesium alloy is a green and lightweight metal structural material. It has a wide range of application potential and development space in the fields of transportation, national defense, satellite communications and other fields with lightweight requirements. However, the current commercial magnesium alloys have low heat resistance, low plasticity and poor formability, which seriously limits the further application space of magnesium alloys. Therefore, it is urgent to develop new magnesium alloys with high strength, heat resistance and easy formability.

[0003] The related technology discloses a method for preparing a magnesium alloy, including: a solution process, a hot extrusion process, an aging process, and a three-pass rolling process. Although a high-strength magnesium alloy is obtained, the alloy preparation process is relatively more and the plasticity is relatively low. The related technology discloses a high-strength and high-modulus extrusion casting magnesium alloy and a preparation method thereof. The invented alloy composition design is complex, and although the plasticity is improved, the strength is low. The related technology discloses a high-plasticity, heat-resistant soluble magnesium alloy and a preparation method thereof. The invented alloy is composed of nine components, the alloy composition is complex, and the precious metal element Ag is added, which seriously increases the alloy preparation cost. The existing technology can no longer meet the demand for high-strength, heat-resistant, and easy-to-form and process magnesium alloys in a lightweight environment. Summary of the invention

[0004] In order to overcome the above disadvantages, the present invention provides a high-strength extruded magnesium alloy and a preparation method thereof.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A high-strength extruded magnesium alloy, comprising the following components by weight: 0.25% to 1.45% of Ce element, 0.5% to 2.5% of Yb element, 1% to 2% of Sn element, 1.35% to 1.95% of Al element, and the remainder being metallic Mg and some inevitable impurity elements; The tensile strength and elongation of the magnesium alloy at 275° C. are 373 MPa and 15.6% respectively, and the tensile strength and elongation at 300° C. are 321 MPa and 18.3% respectively.

[0006] Further optimization, the content of the unavoidable impurity elements does not exceed 0.03%.

[0007] A method for preparing a high-strength extruded magnesium alloy comprises the following steps: (1) Put the raw materials industrial pure Mg, Mg-15Yb, and Mg-15Ce master alloy into the crucible in sequence. A mixed gas of CO2 and SF6 is used for protection to melt and obtain alloy liquid A; (2) Raise the temperature of alloy liquid A to 740~760℃, add pure tin and pure aluminum ingots, and keep warm for 15~25 Minutes, alloy liquid B is obtained; (3) Cooling alloy liquid B to 700-730°C to obtain alloy liquid C; pouring alloy liquid C onto the metal In the mold, an alloy ingot is obtained; (4) The alloy ingot obtained in step (3) is subjected to homogenization treatment, hot extrusion and aging treatment. The prepared alloy is obtained.

[0008] Further optimization is that the pure magnesium, pure aluminum, pure tin, magnesium ytterbium, and magnesium cerium master alloy in step (1) and step (2) are descaled and dried before use.

[0009] For further optimization, in step (3), the mold is preheated at 180-200°C before pouring.

[0010] Further optimization, in step (4), the homogenization treatment temperature is 480-500° C., and the homogenization time is 8-16 h.

[0011] Further optimization, in step (4), the hot extrusion temperature is 420-470°C, the extrusion ratio is 9.4-16.7, and the extrusion rate is 1.5-2.5 m / min.

[0012] Further optimization, in step (4), the aging treatment temperature is 180-220° C., and the aging time is 16-24 h.

[0013] The beneficial effects of the present invention are: 1. The high-strength extruded magnesium alloy of the present invention adds a trace amount of rare earth elements Ce and Yb and a small amount of non-rare earth elements Sn and Al to the magnesium alloy, fully exerts the role of the alloy elements and the synergistic effect between them, reasonably regulates the alloy structure, and improves the mechanical properties of the alloy; 2. The solubility of rare earth element Ce in pure Mg is small. At 590℃, the maximum solubility is 0.74 wt.%, and when the temperature drops to 200℃, it decreases to 0.04 wt.%. Trace Ce can refine the grains of magnesium alloy and weaken the basal texture. When the addition amount of Ce is greater than a certain content, rare earth texture will be formed. In addition, Ce has a large atomic radius and is easily concentrated at the grain boundary. During extrusion deformation, Ce atoms interact with dislocations and grain boundaries, and promote dynamic recrystallization to form recrystallized grains with weak texture, weakening and changing the alloy texture. The addition of Ce can activate the non-basal slip of magnesium alloy, especially<c+a> Slip, and inhibit twinning, making deformation more uniform and inhibiting the formation of local deformation bands, thus improving the plasticity of the alloy; 3. The maximum solid solubility of rare earth element Yb in pure Mg is 3.3 wt.%, which has good solid solution strengthening and aging strengthening effects; at the same time, Yb element has a large atomic radius and is easily concentrated at the grain boundary, hindering the growth of grains and having the effect of refining grains; the difference in radius between Yb and Mg atoms is large, which will reduce the generalized stacking fault energy of magnesium alloy and improve the plasticity of the alloy; Yb dissolving into the magnesium matrix will cause large lattice distortion, which is beneficial to improve the strength of the alloy; 4. The maximum solid solubility of Sn in Mg is 14.48 wt.% (561.2℃). As the temperature decreases, the solid solubility drops sharply, reaching 4.4 wt.% and 0.45 wt.% at 400℃ and 200℃, respectively. Sn has typical aging strengthening ability. Sn can generate Mg2Sn phase with face-centered crystal structure in magnesium. This phase has a high melting point (776℃) and can significantly improve the high-temperature mechanical properties of magnesium alloys. At the same time, Sn is prone to segregation and enrichment at the grain boundaries, causing atomic dragging, which weakens the texture by hindering grain boundary migration and grain rotation. The composite addition of Al and Sn can significantly improve plasticity. 5. The high-strength extruded magnesium alloy of the present invention, by reasonably regulating the proportion of added elements, combined with extrusion and aging processes, gives full play to the role of each element, refines the grains, promotes alloy aging precipitation and non-basal slip, and weakens the basal texture, thereby improving the strength of the alloy, improving the alloy forming performance, and broadening the application field of magnesium alloys. The tensile strength and elongation of the magnesium alloy of the present invention at 275°C are 373MPa and 15.6%, respectively, and the tensile strength and elongation at 300°C are 321MPa and 18.3%, respectively. The magnesium alloy of the present invention has excellent tensile strength, high heat resistance and good formability, solving the technical problems of low strength, poor heat resistance and difficult forming and processing of existing magnesium alloys; In summary, compared with the prior art, the preparation method of the high-strength extruded magnesium alloy of the present invention has a simple alloy composition design, low preparation cost, and easy preparation process. The obtained alloy has excellent high-temperature mechanical properties and plasticity and is suitable for large-scale promotion and application. DETAILED DESCRIPTION

[0014] In order to more clearly understand the above-mentioned purposes, features and advantages of the present invention, the present invention is described in detail below in conjunction with specific embodiments. The following embodiments are implemented based on the technical solutions of the present invention, and detailed implementation methods and specific operating procedures are given. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the following embodiments.

[0015] Example 1 The high-strength extruded magnesium alloy of this embodiment is composed of the following components in percentage by mass: 0.25% Ce, 0.5% Yb, 1% Sn, 1.35% Al, and the rest are Mg and some inevitable impurity elements, and the content of impurity elements does not exceed 0.03%.

[0016] The method for preparing the high-strength extruded magnesium alloy of this embodiment comprises the following steps: (1) Put the raw materials of industrial pure Mg, Mg-15Yb and Mg-15Ce master alloy into a crucible in sequence, use a mixed gas of CO2 and SF6 for protection, and melt to obtain alloy liquid A; (2) Raise the temperature of alloy liquid A to 740°C, add pure tin and pure aluminum ingots, and keep warm for 25 minutes to obtain alloy liquid B; (3) Cooling the alloy liquid B to 700°C to obtain alloy liquid C; pouring the alloy liquid C into a metal mold preheated to 200°C to obtain an alloy ingot; (4) homogenizing the alloy ingot obtained in step (3); the homogenization temperature is 480° C. and the homogenization time is 16 h; (5) hot extruding the alloy after homogenization treatment in step (4) at an extrusion temperature of 420° C., an extrusion ratio of 9.4, and an extrusion rate of 2.5 m / min; (6) The alloy extruded in step (5) is subjected to aging treatment at a temperature of 220° C. for 16 h to obtain the prepared alloy.

[0017] Example 2 The high-strength extruded magnesium alloy of this embodiment is composed of the following components in percentage by mass: 0.85% Ce, 1.5% Yb, 1.5% Sn, 1.65% Al, and the rest is Mg and some inevitable impurity elements, and the content of impurity elements does not exceed 0.03%.

[0018] The method for preparing the high-strength extruded magnesium alloy of this embodiment comprises the following steps: (1) Put the raw materials of industrial pure Mg, Mg-15Yb and Mg-15Ce master alloy into a crucible in sequence, use a mixed gas of CO2 and SF6 for protection, and melt to obtain alloy liquid A; (2) Raise the temperature of alloy liquid A to 750°C, add pure tin and pure aluminum ingots, and keep the temperature for 20 minutes to obtain alloy liquid B; (3) Cooling the alloy liquid B to 715°C to obtain alloy liquid C; pouring the alloy liquid C into a metal mold preheated to 190°C to obtain an alloy ingot; (4) homogenizing the alloy ingot obtained in step (3); the homogenization temperature is 490° C. and the homogenization time is 12 h; (5) hot extruding the alloy after homogenization treatment in step (4) at an extrusion temperature of 450° C., an extrusion ratio of 11.9, and an extrusion rate of 2 m / min; (6) The alloy extruded in step (5) is subjected to aging treatment at a temperature of 200° C. for 20 h. The prepared alloy is obtained.

[0019] Example 3 The high-strength extruded magnesium alloy of this embodiment is composed of the following components in percentage by mass: 1.45% Ce, 2.5% Yb, 2% Sn, 1.95% Al, and the rest are Mg and some inevitable impurity elements, and the content of impurity elements does not exceed 0.03%.

[0020] The method for preparing the high-strength extruded magnesium alloy of this embodiment comprises the following steps: (1) Put the raw materials of industrial pure Mg, Mg-15Yb and Mg-15Ce master alloy into a crucible in sequence, use a mixed gas of CO2 and SF6 for protection, and melt to obtain alloy liquid A; (2) Raise the temperature of alloy liquid A to 760°C, add pure tin and pure aluminum ingots, and keep warm for 15 minutes to obtain alloy liquid B; (3) Cooling the alloy liquid B to 730°C to obtain alloy liquid C; pouring the alloy liquid C into a metal mold preheated to 180°C to obtain an alloy ingot; (4) subjecting the alloy ingot obtained in step (3) to homogenization treatment; the homogenization treatment temperature is 500° C., and the homogenization time is 8 h; (5) hot extruding the alloy after homogenization treatment in step (4) at an extrusion temperature of 470° C., an extrusion ratio of 16.7, and an extrusion rate of 1.5 m / min; (6) The alloy extruded in step (5) is subjected to aging treatment at an aging temperature of 180° C. for 24 h to obtain the prepared alloy.

[0021] The room temperature and high temperature tensile strength and elongation of the high-strength extruded magnesium alloy prepared in Examples 1-3 were tested. The room temperature tensile strength and elongation test method: According to the national standard GB / T228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the Shimadzu precision universal electronic tensile testing machine was used for testing; the high temperature tensile strength and elongation test method: According to the national standard GB / T228.2-2015 "Metallic Materials-Tensile Test-Part 2: High Temperature Test Method", the Shimadzu precision universal electronic tensile testing machine was used for testing. The tensile strength and elongation test results are shown in Table 1.

[0022] Table 1 Test results of tensile strength and elongation of high-strength extruded magnesium alloys prepared in Examples 1-3 The above shows and describes the main features, methods of use, basic principles and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements according to actual conditions, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high-strength extruded magnesium alloy, characterized in that: According to weight fraction, it includes the following components: Ce element 0.25%~1.45%, Yb element 0.5%~2.5%, Sn element 1%~2%, Al element 1.35%-1.95%, and the balance is metal Mg and some inevitable impurity elements; The tensile strength and elongation of the magnesium alloy at 275° C. are 373 MPa and 15.6% respectively, and the tensile strength and elongation at 300° C. are 321 MPa and 18.3% respectively.

2. A high-strength extruded magnesium alloy as claimed in claim 1, characterized in that: The content of the unavoidable impurity elements does not exceed 0.03%.

3. The method for preparing a high-strength extruded magnesium alloy according to claim 1, characterized in that: The following steps are involved: (1) Put the raw materials industrial pure Mg, Mg-15Yb, and Mg-15Ce master alloy into the In the crucible, a mixed gas of CO2 and SF6 is used for protection to melt and obtain alloy liquid A; Raise the temperature of alloy liquid A to 740~760℃, add pure tin and pure aluminum ingots, and keep Warm for 15-25 minutes to obtain alloy liquid B; The alloy liquid B is cooled to 700-730℃ to obtain alloy liquid C. Pour into a metal mold to obtain an alloy ingot; The alloy ingot obtained in step (3) is homogenized, hot extruded and timely After effective treatment, the prepared alloy is obtained.

4. The method for preparing a high-strength extruded magnesium alloy according to claim 3, characterized in that: The pure magnesium, pure aluminum, pure tin, magnesium-ytterbium, and magnesium-cerium master alloys in step (1) and step (2) are descaled and dried before use.

5. The method for preparing a high-strength extruded magnesium alloy according to claim 3, characterized in that: In step (3), the mold is preheated at 180-200°C before pouring.

6. The method for preparing a high-strength extruded magnesium alloy according to claim 3, characterized in that: In the step (4), the homogenization temperature is 480-500° C., and the homogenization time is 8-16 hours.

7. The method for preparing a high-strength extruded magnesium alloy according to claim 3, characterized in that: In the step (4), the hot extrusion temperature is 420-470° C., the extrusion ratio is 9.4-16.7, and the extrusion rate is 1.5-2.5 m / min.

8. The method for preparing a high-strength extruded magnesium alloy according to claim 3, characterized in that: In the step (4), the aging treatment temperature is 180-220° C., and the aging time is 16-24 hours.