Pre-aging and rotary extrusion synergistic strengthening and toughening magnesium alloy and preparation method thereof

Abstract

The invention discloses a pre-aging and rotary extrusion synergistic strengthening and toughening magnesium alloy and a preparation method thereof, and belongs to the technical field of metal material machining. The preparation method comprises the following steps: firstly carrying out homogenization treatment on a cast magnesium alloy, then carrying out two-stage aging treatment, and finally carrying out rotary extrusion deformation, so that precipitation strengthening and fine grain strengthening and toughening of the magnesium alloy are synergistically improved; according to the two-stage aging treatment, low-temperature aging treatment is conducted firstly, and then high-temperature aging treatment is conducted; according to the method disclosed by the invention, the type, the size, the distribution and the grain structure of a nano precipitated phase in a matrix are cooperatively regulated and controlled through the cooperative cooperation of the pre-aging process and the rotary extrusion process, so that good plasticity is kept while the alloy strength is remarkably improved, and the problem of inverted strong plasticity of the alloy is solved.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, specifically a magnesium alloy that is synergistically strengthened and toughened by pre-aging and rotary extrusion, and its preparation method. Background Technology

[0002] Magnesium alloys have the characteristics of low density, high specific strength / specific stiffness, good damping performance, excellent electronic shielding performance, and easy recycling. They have great potential in the fields of aerospace, defense and military industry and automotive lightweighting. However, they have problems such as low absolute strength, poor plasticity and poor formability, which restrict their widespread application.

[0003] Currently, the main method for strengthening and toughening magnesium alloys involves conventional plastic deformation combined with subsequent solution treatment and aging. However, this method suffers from problems such as insufficient dynamic recrystallization during plastic deformation, difficulty in uniformly dispersing nano-precipitates, and poor strength-plasticity matching. While aging alone can improve alloy strength to some extent, it easily leads to a decrease in alloy plasticity. In summary, existing technologies struggle to achieve coordinated and precise control over the grain structure and precipitate distribution of magnesium alloys, resulting in poor strength-plasticity matching and limited improvement in overall mechanical properties. Summary of the Invention

[0004] This invention overcomes the shortcomings of the prior art and proposes a magnesium alloy and its preparation method that is synergistically strengthened by pre-aging and rotary extrusion. By combining the "pre-aging" and "rotary extrusion" processes, the type, size, distribution and grain structure of nano-precipitates in the matrix are synergistically controlled, thereby significantly improving the strength of the alloy while maintaining good plasticity and resolving the contradiction of the inversion of strength and plasticity.

[0005] This invention is achieved through the following technical solution: A method for preparing magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion involves first homogenizing the cast magnesium alloy, then performing a two-stage aging treatment, and finally rotary extrusion deformation, thereby achieving synergistic improvement in precipitation strengthening and fine-grain toughening of the magnesium alloy; the two-stage aging treatment is to first perform low-temperature aging treatment and then high-temperature aging treatment.

[0006] Furthermore, the homogenization process involves maintaining the temperature at 500-550°C for 14-18 hours.

[0007] Furthermore, after homogenization treatment, the magnesium alloy is water quenched at a temperature of 70~80℃.

[0008] Furthermore, the low-temperature aging treatment is performed by holding at 150~180℃ for 48~52 hours; the high-temperature aging treatment is performed by holding at 200~220℃ for 15~20 hours.

[0009] Furthermore, the heating rate of the low-temperature aging treatment is 10~15℃ / min.

[0010] Furthermore, the heating rate of the high-temperature aging treatment is 10~20℃ / min.

[0011] Furthermore, rotary extrusion deformation is carried out on a press equipped with a rotary unit. The temperature of the rotary extrusion deformation is 400~440℃, and the speed of the press is 10~15rpm.

[0012] Furthermore, the punch pressing speed of the press is 1~1.5mm / s, and the die rotation speed is 7~9rpm.

[0013] Furthermore, the method for preparing the cast magnesium alloy is as follows: weigh high-purity magnesium ingot, Mg-30Gd master alloy, Mg-25Y master alloy, pure zinc ingot, and Mg-30Zr grain refiner according to the mass percentage; place the magnesium ingot in a graphite crucible, introduce a mixed protective gas, and heat to melt; add Mg-30Gd and Mg-25Y master alloy in sequence, and after complete melting, add pure zinc ingot, and finally sprinkle in Mg-30Zr grain refiner; refine and remove slag, and cast ingot under protective gas to obtain a casting.

[0014] A magnesium alloy is prepared using the aforementioned method for synergistic strengthening and toughening of magnesium alloys through pre-aging and rotary extrusion.

[0015] The beneficial effects of this invention compared to the prior art are as follows: 1. Synergistic regulation mechanism of the present invention: The present invention creates a large number of uniform and dispersed nanomaterials in the matrix through "pre-aging". β The phase acts as a "pinning point"; the subsequent "rotational extrusion" under shear stress and strain promotes dynamic recrystallization and refines the grains on the one hand; on the other hand, it makes the existing nano-precipitated phases more uniformly distributed and may induce new precipitation behavior, thus achieving a synergistic effect of precipitation strengthening and grain refinement.

[0016] 2. The magnesium alloy prepared by this invention has significantly improved performance: the rare earth magnesium alloy rods prepared by this method have a tensile strength of over 450 MPa, a yield strength of over 380 MPa, and an elongation of over 12%, achieving a perfect combination of high strength and good plasticity. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the preparation method of the present invention; Figure 2 It is an alloy of Mg-9Gd-4Y-2Zn-0.5Zr. β 'Precipitation phase; Figure 3The optical microstructure (OM) and electron backscatter diffraction (EBSD) of the homogeneous Mg-9Gd-4Y-2Zn-0.5Zr are shown. Figure 4 Scanning electron microscopy (SEM) and EBSD of Mg-9Gd-4Y-2Zn-0.5Zr alloy after rotary extrusion deformation; Figure 5 The texture of the alloy after rotary extrusion deformation of Mg-9Gd-4Y-2Zn-0.5Zr; Figure 6 The room temperature tensile stress-strain curve of the Mg-9Gd-4Y-2Zn-0.5Zr alloy obtained in the embodiments of the present invention is shown. Detailed Implementation

[0018] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto. Example 1

[0019] See Figures 1 to 6 This embodiment proposes a method for preparing magnesium alloys that are synergistically strengthened and toughened by pre-aging and rotary extrusion, specifically comprising the following steps: Step 1: Alloy smelting and casting Weigh out the following components by mass percentage: 48.3% high-purity magnesium ingot (≥99.95%), 31.6% Mg-30Gd master alloy, 16.8% Mg-25Y master alloy, 0.51% pure zinc ingot, and 2.78% Mg-30Zr master alloy. Place the magnesium ingot in a graphite crucible, introduce a mixed protective gas of CO2 + 0.5% SF6, and heat to 750℃ to melt. Add the Mg-30Gd and Mg-25Y master alloys sequentially, and after complete melting, add the pure zinc ingot. Finally, sprinkle in the Mg-30Zr refining agent. Heat to 770℃ and refine for 10 minutes, using mechanical stirring to make the material composition more uniform. After standing for 20 minutes, remove the slag and pour the mixture into a metal mold at 2540℃ under a protective gas to obtain an ingot with a diameter of 80mm.

[0020] Step 2: Homogenization The ingot was placed in a box-type resistance furnace, heated to 520°C and held for 16 hours, and then quenched in water at 70°C. Through homogenization treatment, a large number of blocky second phases of the alloy were dissolved in the matrix to form a supersaturated solid solution.

[0021] Step 3: Pre-processing with two-stage aging 1) Low-temperature aging The homogenized alloy was placed in a forced-air drying oven and heated to 160°C at a rate of 10°C / min. It was held at that temperature for 48 hours and then cooled to room temperature in the furnace.

[0022] 2) High-temperature aging The low-temperature aged alloy was placed back in a forced-air drying oven, heated to 210℃ at a rate of 10℃ / min, held at that temperature for 16 hours, and then air-cooled to room temperature.

[0023] Step 4: Rotary Extrusion Rotary extrusion deformation was carried out on a 1250T press equipped with a rotary unit. The press provided a torque of 40T·m and a rotation speed of 10rpm. The die preheating temperature was 420℃, the billet heating temperature was 420℃, and the holding time was 2 hours. The punch pressing speed was 1mm / s, the cumulative strain was 0.8, the die rotation speed was 7rpm, and the deformed billet was water quenched at room temperature.

[0024] Step 5: Tissue Characterization and Performance Testing The microstructure of the wrought magnesium alloy was tested using SEM, EBSD, and TEM. TEM showed that the β' phase was uniformly distributed in the α-Mg matrix. Samples were taken for mechanical property testing. The alloy had a tensile strength of 452 MPa, a yield strength of 387 MPa, and an elongation of 12.3%. Example 2

[0025] This embodiment proposes a method for preparing magnesium alloys that are synergistically strengthened and toughened by pre-aging and rotary extrusion, specifically comprising the following steps: Step 1: Alloy smelting and casting Weigh out the following components by mass percentage: 48.3% high-purity magnesium ingot (≥99.95%), 31.6% Mg-30Gd master alloy, 16.8% Mg-25Y master alloy, 0.51% pure zinc ingot, and 2.78% Mg-30Zr master alloy. Place the magnesium ingot in a graphite crucible, introduce a mixed protective gas of CO2 + 0.5% SF6, and heat to 750℃ to melt. Add the Mg-30Gd and Mg-25Y master alloys sequentially, and after complete melting, add the pure zinc ingot. Finally, sprinkle in the Mg-30Zr refining agent. Heat to 770℃ and refine for 10 minutes, using mechanical stirring to make the material composition more uniform. After standing for 30 minutes, remove the slag and pour the mixture into a metal mold at 2540℃ under a protective gas to obtain an ingot with a diameter of 80mm.

[0026] Step 2: Homogenization The ingots were placed in a box-type resistance furnace, heated to 550°C and held for 14 hours, and then quenched in water at 70°C.

[0027] Step 3: Pre-processing with two-stage aging 1) Low-temperature aging The homogenized alloy was placed in a forced-air drying oven and heated to 150°C at a rate of 15°C / min. It was held at that temperature for 48 hours and then cooled to room temperature in the furnace.

[0028] 2) High-temperature aging The low-temperature aged alloy was placed back in a forced-air drying oven, heated to 200℃ at a rate of 20℃ / min, held at that temperature for 20 hours, and then air-cooled to room temperature.

[0029] Step 4: Rotary Extrusion Rotary extrusion deformation was carried out on a 1250T press equipped with a rotary unit. The press provided a torque of 40T·m and a rotation speed of 15rpm. The die preheating temperature was 400℃, the billet heating temperature was 400℃, and the holding time was 3 hours. The punch pressing speed was 1.5mm / s, the die rotation speed was 9rpm, and the deformed billet was water quenched at room temperature. Example 3

[0030] This embodiment proposes a method for preparing magnesium alloys that are synergistically strengthened and toughened by pre-aging and rotary extrusion, specifically comprising the following steps: Step 1: Alloy smelting and casting Weigh out the following components by mass percentage: 48.3% high-purity magnesium ingot (≥99.95%), 31.6% Mg-30Gd master alloy, 16.8% Mg-25Y master alloy, 0.51% pure zinc ingot, and 2.78% Mg-30Zr master alloy. Place the magnesium ingot in a graphite crucible, introduce a mixed protective gas of CO2 + 0.5% SF6, and heat to 750℃ to melt. Add the Mg-30Gd and Mg-25Y master alloys sequentially, and after complete melting, add the pure zinc ingot. Finally, sprinkle in the Mg-30Zr refining agent. Heat to 770℃ and refine for 10 minutes, using mechanical stirring to make the material composition more uniform. After standing for 30 minutes, remove the slag and pour the mixture into a metal mold at 2540℃ under a protective gas to obtain an ingot with a diameter of 80mm.

[0031] Step 2: Homogenization The ingots are placed in a box-type resistance furnace, heated to 500°C and held for 18 hours, and then quenched in water at 80°C.

[0032] Step 3: Pre-processing with two-stage aging 1) Low-temperature aging The homogenized alloy was placed in a forced-air drying oven and heated to 180°C at a rate of 12°C / min. It was held at that temperature for 52 hours and then cooled to room temperature in the furnace.

[0033] 2) High-temperature aging The low-temperature aged alloy was placed back in a forced-air drying oven, heated to 220°C at a rate of 15°C / min, held at that temperature for 15 hours, and then air-cooled to room temperature.

[0034] Step 4: Rotary Extrusion Rotary extrusion deformation was carried out on a 1250T press equipped with a rotary unit. The press provided a torque of 40T·m and a rotation speed of 12rpm. The die preheating temperature was 440℃, the billet heating temperature was 440℃, and the holding time was 3 hours. The punch pressing speed was 1.5mm / s, the die rotation speed was 9rpm, and the deformed billet was water quenched at room temperature.

[0035] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

[0036] To provide the public with a thorough understanding of the present invention, specific details have been described in detail in the above preferred embodiments. However, those skilled in the art can fully understand the invention even without these detailed descriptions. Several improvements and modifications can be made without departing from the principles of the invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a magnesium alloy that is synergistically strengthened and toughened by pre-aging and rotary extrusion, characterized in that, The cast magnesium alloy is first homogenized, then subjected to a two-stage aging treatment, and finally subjected to rotary extrusion deformation, so that the magnesium alloy can achieve precipitation strengthening and fine grain toughness improvement in a synergistic manner; the two-stage aging treatment is to first perform low-temperature aging treatment and then high-temperature aging treatment.

2. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 1, characterized in that, The homogenization process involves holding the temperature at 500-550℃ for 14-18 hours.

3. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 2, characterized in that, After homogenization, the magnesium alloy is water quenched at a temperature of 70~80℃.

4. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 1, characterized in that, The low-temperature aging treatment is performed by holding at 150~180℃ for 48~52 hours; the high-temperature aging treatment is performed by holding at 200~220℃ for 15~20 hours.

5. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 4, characterized in that, The heating rate of the low-temperature aging treatment is 10~15℃ / min.

6. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 4, characterized in that, The heating rate of the high-temperature aging treatment is 10~20℃ / min.

7. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 1, characterized in that, Rotary extrusion deformation is carried out on a press equipped with a rotary unit. The temperature of the rotary extrusion deformation is 400~440℃, and the speed of the press is 10~15rpm.

8. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 7, characterized in that, The punch pressing speed of the press is 1~1.5mm / s, and the die rotation speed is 7~9rpm.

9. The method for preparing a magnesium alloy with synergistic strengthening and toughening through pre-aging and rotary extrusion according to claim 1, characterized in that, The method for preparing the cast magnesium alloy is as follows: weigh high-purity magnesium ingot, Mg-30Gd master alloy, Mg-25Y master alloy, pure zinc ingot, and Mg-30Zr grain refiner according to the mass percentage; place the magnesium ingot in a graphite crucible, introduce a mixed protective gas, and heat to melt; add Mg-30Gd and Mg-25Y master alloy in sequence, and after complete melting, add pure zinc ingot, and finally sprinkle in Mg-30Zr grain refiner; refine and remove slag, and cast ingot under protective gas to obtain the cast ingot.

10. A magnesium alloy prepared by a method for pre-aging and rotary extrusion synergistic strengthening of magnesium alloy as described in any one of claims 1-9.

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