A magnesium alloy for die casting and semi-solid injection molding and a method for preparing the same
By adding a moderate amount of Al and trace amounts of light rare earth elements, the problem of performance imbalance in magnesium alloys during die casting and semi-solid injection molding processes has been solved, resulting in a high-strength, high-plasticity, and low-cost alloy material suitable for new energy vehicles, drones, and other fields.
Patent Information
- Application Number
- CN202611420071.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-14
- Publication Date
- 2026-11-06
AI Technical Summary
Existing magnesium alloys are difficult to adapt to both die casting and semi-solid injection molding processes, resulting in high production costs and uneven alloy properties, which cannot meet the high strength and high plasticity requirements of new energy vehicles, drones and other fields.
By using a medium Al content and adding trace amounts of inexpensive light rare earth elements such as La, Ce, and Sm, and through precise control of the composition design, the microstructure of the alloy is refined and the mechanical properties are improved, taking into account both the fluidity and strength of the alloy, and it is compatible with two forming processes.
This technology achieves high strength and plasticity of magnesium alloys in die casting and semi-solid injection molding, reduces production costs, improves production efficiency, and meets the material performance requirements of new energy vehicles, robotic devices, drones, and other fields.
Smart Images
Figure CN123043386A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of magnesium alloys and their processing technology, and in particular to a high-strength magnesium alloy that can be used for die casting and semi-solid injection molding, and its preparation method. Background Technology
[0002] With the rapid development of emerging industries such as new energy vehicles, drones and the low-altitude economy, and androids, the demand for lightweight structures in equipment is continuously increasing. Magnesium alloys, as one of the lightest metallic structural materials currently available, possess high specific strength, high specific stiffness, and excellent thermal conductivity, heat dissipation, damping, vibration reduction, and electromagnetic shielding properties, making them ideal materials for achieving lightweighting and performance breakthroughs in these fields. Among these, the demand for magnesium alloy die-castings from strategic emerging industries such as new energy vehicles is growing rapidly, significantly exceeding that of wrought magnesium alloys. Typical applications of magnesium alloy die-castings include steering wheel frames, motor housings, and radiator shells for new energy vehicles; drone brackets and flight control computer chassis in the low-altitude economy; and various end-product categories such as laptop back panels in the 3C product market. With the continuous expansion of production capacity in downstream related industries, the market demand for high-performance magnesium alloy materials is rapidly increasing.
[0003] Currently, die casting remains the mainstream industrial production method for magnesium alloy castings, offering advantages such as high production efficiency, high dimensional accuracy, and stable surface quality, and can meet the integrated forming requirements of complex structural parts. In recent years, with the increasing demand for thin-walled, lightweight, and high-performance parts, magnesium alloy semi-solid injection molding technology has gradually emerged and achieved industrial application, and has now become the core production method for high-end parts in niche markets. Compared with traditional die casting processes, this technology has superior forming capabilities, better microstructure and properties, better product consistency, stronger controllability of process parameters, and better dimensional stability and performance consistency of parts, making it more suitable for the production of high-end precision parts.
[0004] Currently, die-cast magnesium alloys are mainly based on magnesium alloys such as AZ91D. However, due to the high requirements for alloys in semi-solid casting, it is difficult to achieve high solids content in AZ91D magnesium alloys, while low solids content can easily lead to insufficient product strength. To improve strength, existing semi-solid special magnesium alloys usually add refining elements (such as Zr and Sr), which increases the cost by more than 20% compared to conventional die-cast magnesium alloys. Furthermore, when used in traditional die casting, they exhibit poor melt flow, insufficient filling of thin-walled parts, and low yield. Special semi-solid magnesium alloys have complex composition designs, high costs, and are incompatible with traditional die casting processes. In addition, die casting is suitable for mass production at low cost, while semi-solid injection is suitable for complex, high-precision components. Companies typically need to prepare magnesium alloy ingots with different compositions, thus increasing inventory and raw material costs. Therefore, there is an urgent need for a universal magnesium alloy that can adapt to both processes to meet production needs. Summary of the Invention
[0005] The purpose of this invention is to provide a novel magnesium alloy material and its preparation method that can be used for both die casting and semi-solid injection molding, and a general-purpose magnesium alloy that can be adapted to both processes to meet production needs.
[0006] This invention provides a magnesium alloy suitable for die casting and semi-solid injection molding, comprising the following components in the indicated mass percentages: Al 5.0%-9.0%, Zn 0.3%-1.2%, Mn 0.2%-0.8%, RE 0.5%-1.5%, Ca 0.1%-0.2%, and Sr 0.1%-0.2%. The RE comprises La 0.2%-0.6%, Ce 0.2%-0.6%, and Sm 0.1%-0.3%, with the balance being Mg and unavoidable impurities. The weight ratio of La to Ce is between (2:1) and (1:2).
[0007] The magnesium alloy die-cast parts have a maximum tensile strength of 288 MPa, a maximum yield strength of 196 MPa, and a maximum elongation of 11%.
[0008] The magnesium alloy semi-solid injection molded parts have a maximum tensile strength of 316 MPa, a maximum yield strength of 209 MPa, and a maximum elongation of 9%.
[0009] The present invention provides a die-casting preparation method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) Under a protective atmosphere, heat to 750℃~780℃ to melt all raw materials. After they are completely melted, cool down to 730℃~740℃ for refining. Use commercially available No. 5 flux as the refining agent. Refine twice, each time for 15min~20min. After refining, let stand for 1h~1.5h. (3) Control the melt temperature to 690℃~710℃, the mold temperature to 180℃~220℃, the injection speed to 3m / s~6m / s, and the injection pressure to 50MPa~200MPa, and perform high pressure die casting to obtain the finished product.
[0010] The protective gas is a mixture of CO2 and SF6.
[0011] This invention provides a semi-solid injection molding method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) Under a protective atmosphere, heat to 750℃~780℃ to melt all raw materials. After complete melting, cool to 730℃~740℃ for refining. Commercially available No. 5 flux is used as the refining agent. Refine twice, each time for 15min~20min. After refining, let stand for 1h~1.5h. The protective gas is a mixture of CO2 and SF6. (3) Control the melt temperature at 700℃~710℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 80A-120A, the frequency is set to 15Hz~20Hz, the duty cycle is set to 20%~50%, and the casting speed is 30mm / min-60mm / min. (4) The ingot is segmented and the outer skin is removed by machining. Then, the ingot is granulated using a magnesium alloy pelletizer. The particle size is 1.2mm~1.5mm in length, 1.2mm~1.5mm in width, and 1.5mm~2.0mm in height. (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 200℃~250℃, the temperature of the second stage is controlled at 450℃~480℃, the temperature of the third stage is controlled at 550℃~610℃, and the temperature of the fourth stage is controlled at 600℃~610℃. The injection pressure is 50MPa~150MPa, and the injection speed is 0.5m / s~3m / s. After injection into the mold, the material is held under pressure and cooled. The holding pressure is 50MPa~150MPa to obtain the finished product.
[0012] The advantages and beneficial effects of this invention are as follows: (1) The design adopts a medium Al content, which takes into account both the fluidity and mechanical properties of the alloy. It ensures good filling ability and meets the requirements of die casting and semi-solid forming processes, while avoiding the problem of reduced strength and plasticity of traditional high Al magnesium alloys. By adding trace amounts of rare earth elements to achieve microstructure refinement, replacing the traditional Zr refiner, the raw material preparation cost is effectively reduced. Rare earth elements can also promote spheroidization of semi-solid microstructure and inhibit grain coarsening, so that the alloy of this invention can be adapted to both die casting and semi-solid forming processes.
[0013] (2) Using abundant and inexpensive light rare earth elements for alloying will not significantly increase the production cost of alloys, and it is in line with the current status of rare earth resource development. It can effectively promote the high-value comprehensive utilization of light rare earth resources and has good industrial application and resource adaptability.
[0014] (3) Based on excellent forming performance, this invention relies on the high sphericity of semi-solid structure and the strengthening effect of rare earth second phase to take into account good mechanical properties. Whether it is die casting or semi-solid forming, it has high strength and plasticity, and its strength and plasticity are better than traditional single process special magnesium alloys. It can meet the comprehensive requirements of material performance in fields such as new energy vehicles, equipment robots, drones and low-altitude economy, and consumer electronics. Attached Figure Description
[0015] Figure 1 This is a scanned image of the microstructure of the magnesium alloy in Example 5 of the present invention; Figure 2 The XRD patterns of magnesium alloys in Examples 2-5 of this invention are shown below. Figure 3 These are the flowability test samples of magnesium alloy after semi-solid molding in Examples 1, 3 and 5 of this invention.
[0016] Among them, (a) is the flowability test sample of magnesium alloy after semi-solid molding in Example 1, (b) is the flowability test sample of magnesium alloy after semi-solid molding in Example 3, and (c) is the flowability test sample of magnesium alloy after semi-solid molding in Example 5. Detailed Implementation
[0017] This invention provides a novel magnesium alloy material and its preparation method suitable for both die casting and semi-solid injection molding. The magnesium alloy employs a moderate Al content and incorporates trace amounts of inexpensive light rare earth elements such as La, Ce, and Sm. Precise control of the composition achieves synergistic optimization of performance and processability. The moderate Al content avoids the molding challenges of excessively narrow solid-liquid phase regions and insufficient semi-solid slurry filling capacity in AZ alloys caused by low Al content. It also addresses the performance defects of high Al content, which, while offering excellent fluidity, leads to decreased strength and plasticity, thus achieving a balance between molding processability and mechanical properties. The added trace amounts of light rare earth elements promote the spheroidization transformation of the semi-solid non-dendritic structure and inhibit the coarsening and growth of spheroidal grains during heat treatment, providing an ideal slurry structure for semi-solid molding. Furthermore, the finely dispersed rare earth second phase provides second-phase strengthening, further enhancing the alloy's room-temperature and high-temperature mechanical properties. Simultaneously, the trace addition of rare earth elements minimizes their negative impact on the alloy's melt fluidity, ensuring the alloy's adaptability to both die casting and semi-solid molding. The magnesium alloy provided by this invention achieves the technical effect of "one alloy, two uses", effectively reducing the production and R&D costs of enterprises and improving production efficiency.
[0018] The present invention provides a magnesium alloy that can be used for die casting and semi-solid injection molding. The elemental composition, by mass percentage, includes: Al 5.0%-9.0%, Zn 0.3%-1.2%, Mn 0.2%-0.8%, RE 0.5%-1.5%, Ca 0.1%-0.2%, Sr 0.1%-0.2%, with the balance being Mg and unavoidable impurity elements.
[0019] The REs include La 0.2%-0.6%, Ce 0.2%-0.6%, and Sm 0.1%-0.3%.
[0020] The weight ratio of La to Ce is (2:1) to (1:2).
[0021] The present invention provides a die-casting preparation method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) Using a mixed gas with a volume ratio of CO2:SF6=99:1 as a protective atmosphere, heat the mixture to 750℃~780℃ to melt all raw materials. After complete melting, cool the mixture to 730℃~740℃ for refining. Use commercially available No. 5 flux as the refining agent. Refine twice, each time for 15min~20min. After refining, let it stand for 1h~1.5h. (3) Control the melt temperature to 690℃~710℃, the mold temperature to 180℃~220℃, the injection speed to 3m / s~6m / s, and the injection pressure to 50MPa~200MPa, and perform high pressure die casting to obtain the finished product.
[0022] This invention also provides a semi-solid injection molding method for the magnesium alloy, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) Using a mixed gas with a volume ratio of CO2:SF6=99:1 as a protective atmosphere, heat the mixture to 750℃~780℃ to melt all raw materials. After complete melting, cool the mixture to 730℃~740℃ for refining. Use commercially available No. 5 flux as the refining agent. Refine twice, each time for 15min~20min. After refining, let it stand for 1h~1.5h. (3) Control the melt temperature at 700℃~710℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 80A-120A, the frequency is set to 15Hz~20Hz, the duty cycle is set to 20%~50%, and the casting speed is 30mm / min-60mm / min. (4) The ingot is segmented and the outer skin is removed by machining. Then, the ingot is granulated using a magnesium alloy pelletizer. The particle size is 1.2mm~1.5mm in length, 1.2mm~1.5mm in width, and 1.5mm~2.0mm in height. (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 200℃~250℃, the temperature of the second stage is controlled at 450℃~480℃, the temperature of the third stage is controlled at 550℃~610℃, and the temperature of the fourth stage is controlled at 600℃~610℃. The injection pressure is 50MPa~150MPa, and the injection speed is 0.5m / s~3m / s. After injection into the mold, the material is held under pressure and cooled. The holding pressure is 50MPa~150MPa to obtain the finished product.
[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0024] Example 1: This embodiment provides a magnesium alloy that can be used for die casting and semi-solid injection molding. The elemental composition, by mass percentage, includes: Al 5.0%, Zn 0.3%, Mn 0.2%, La 0.2%, Ce 0.2%, Sm 0.1%, Ca 0.1%, Sr 0.1%, with the balance being Mg and unavoidable impurity elements.
[0025] This embodiment provides a die-casting preparation method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 750℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the temperature is lowered and the mixture is allowed to stand for 1 hour. (3) Control the melt temperature to 690℃, the mold temperature to 220℃, the injection speed to 3m / s, and the injection pressure to 150MPa, and perform high pressure die casting to obtain the finished product.
[0026] The die-cast part prepared in this embodiment has a tensile strength of 266 MPa, a yield strength of 186 MPa, and an elongation of 11%.
[0027] This embodiment also provides a semi-solid injection molding method for the magnesium alloy, including the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 780℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 740℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 15 minutes. After the refining is completed, the temperature is lowered and the mixture is allowed to stand for 1.5 hours. (3) Control the melt temperature at 700℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 120A, the frequency is set to 15Hz, the duty cycle is set to 20%, and the casting speed is 60mm / min. (4) The ingot is segmented and machined to remove the outer skin, and then granules are prepared using a magnesium alloy pelletizer; the particle size is 1.2 mm in length, 1.2 mm in width and 1.5 mm in height; (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 200℃, the temperature of the second stage is controlled at 450℃, the temperature of the third stage is controlled at 610℃, and the temperature of the fourth stage is controlled at 610℃. The injection pressure is 80MPa and the injection speed is 2m / s. After injection into the mold, the pressure is held and cooled. The holding pressure is 80MPa to obtain the finished product.
[0028] The semi-solid injection molded part prepared in this embodiment has a tensile strength of 285 MPa, a yield strength of 198 MPa, and an elongation of 9%.
[0029] Example 2: This embodiment provides a magnesium alloy that can be used for die casting and semi-solid injection molding. The elemental composition, by mass percentage, includes: Al 7.0%, Zn 1.0%, Mn 0.3%, La 0.3%, Ce 0.6%, Sm 0.2%, Ca 0.1%, Sr 0.1%, with the balance being Mg and unavoidable impurity elements.
[0030] This embodiment provides a die-casting preparation method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 750℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the mixture is left to stand for 1 hour. (3) Control the melt temperature to 710℃, the mold temperature to 220℃, the injection speed to 3m / s, and the injection pressure to 50MPa, and perform high pressure die casting to obtain the finished product.
[0031] The die-cast part prepared in this embodiment has a tensile strength of 268 MPa, a yield strength of 185 MPa, and an elongation of 11%.
[0032] This embodiment also provides a semi-solid injection molding method for the magnesium alloy, including the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 760℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the mixture is left to stand for 1 hour. (3) Control the melt temperature at 705℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 120A, the frequency is set to 20Hz, the duty cycle is set to 50%, and the casting speed is 30mm / min. (4) The ingot is segmented and machined to remove the outer skin, and then granules are prepared using a magnesium alloy pelletizer; the particle size is 1.2 mm in length, 1.2 mm in width and 1.5 mm in height; (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 250℃, the temperature of the second stage is controlled at 480℃, the temperature of the third stage is controlled at 595℃, and the temperature of the fourth stage is controlled at 605℃. The injection pressure is 90MPa and the injection speed is 2m / s. After injection into the mold, the pressure is held and cooled. The holding pressure is 90MPa to obtain the finished product.
[0033] The semi-solid injection molded part prepared in this embodiment has a tensile strength of 286 MPa, a yield strength of 199 MPa, and an elongation of 8%.
[0034] Example 3: This embodiment provides a magnesium alloy that can be used for die casting and semi-solid injection molding. The elemental composition, by mass percentage, includes: Al 7.0%, Zn 0.8%, Mn 0.5%, La 0.5%, Ce 0.5%, Sm 0.3%, Ca 0.1%, Sr 0.2%, with the balance being Mg and unavoidable impurity elements.
[0035] This embodiment provides a die-casting preparation method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 780℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 740℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 15 minutes. After the refining is completed, the mixture is left to stand for 1.5 hours. (3) Control the melt temperature to 710℃, the mold temperature to 180℃, the injection speed to 3m / s, and the injection pressure to 150MPa, and perform high pressure die casting to obtain the finished product.
[0036] The die-cast part prepared in this embodiment has a tensile strength of 283 MPa, a yield strength of 191 MPa, and an elongation of 11%.
[0037] This embodiment also provides a semi-solid injection molding method for the magnesium alloy, including the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 750℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the mixture is left to stand for 1 hour. (3) Control the melt temperature at 710℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 80A, the frequency is set to 15Hz, the duty cycle is set to 20%, and the casting speed is 60mm / min. (4) The ingot is segmented and machined to remove the outer skin, and then granules are prepared using a magnesium alloy pelletizer; the particle size is 1.5 mm in length, 1.5 mm in width and 2.0 mm in height. (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 200℃, the temperature of the second stage is controlled at 450℃, the temperature of the third stage is controlled at 550℃, and the temperature of the fourth stage is controlled at 600℃. The injection pressure is 50MPa and the injection speed is 0.5m / s. After injection into the mold, the material is held under pressure and cooled. The holding pressure is 50MPa to obtain the finished product.
[0038] The semi-solid injection molded part prepared in this embodiment has a tensile strength of 301 MPa, a yield strength of 209 MPa, and an elongation of 9%.
[0039] Example 4: This embodiment provides a magnesium alloy that can be used for die casting and semi-solid injection molding. The elemental composition, by mass percentage, includes: Al 8.0%, Zn 0.3%, Mn 0.8%, La 0.6%, Ce 0.3%, Sm 0.3%, Ca 0.2%, Sr 0.1%, with the balance being Mg and unavoidable impurity elements.
[0040] This embodiment provides a die-casting preparation method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 760℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the mixture is left to stand for 1 hour. (3) Control the melt temperature to 710℃, the mold temperature to 220℃, the injection speed to 6m / s, and the injection pressure to 200MPa, and perform high-pressure die casting to obtain the finished product; The die-cast part prepared in this embodiment has a tensile strength of 287 MPa, a yield strength of 196 MPa, and an elongation of 7%.
[0041] This embodiment also provides a semi-solid injection molding method for the magnesium alloy, including the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 760℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 740℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the mixture is left to stand for 1 hour. (3) Control the melt temperature at 710℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 120A, the frequency is set to 15Hz, the duty cycle is set to 20%, and the casting speed is 60mm / min. (4) The ingot is segmented and machined to remove the outer skin, and then granules are prepared using a magnesium alloy pelletizer; the particle size is 1.2 mm in length, 1.2 mm in width and 1.5 mm in height; (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 250℃, the temperature of the second stage is controlled at 480℃, the temperature of the third stage is controlled at 590℃, and the temperature of the fourth stage is controlled at 600℃. The injection pressure is 100MPa and the injection speed is 2m / s. After injection into the mold, the material is held under pressure and cooled. The holding pressure is 100MPa to obtain the finished product.
[0042] The semi-solid injection molded part prepared in this embodiment has a tensile strength of 316 MPa, a yield strength of 206 MPa, and an elongation of 7%.
[0043] Example 5: This embodiment provides a magnesium alloy that can be used for die casting and semi-solid injection molding. The elemental composition, by mass percentage, includes: Al 9.0%, Zn 1.2%, Mn 0.4%, La 0.6%, Ce 0.4%, Sm 0.2%, Ca 0.1%, Sr 0.1%, with the balance being Mg and unavoidable impurity elements.
[0044] This embodiment provides a die-casting preparation method for magnesium alloys that can be used for die casting and semi-solid injection molding, comprising the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 760℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the mixture is left to stand for 1 hour. (3) Control the melt temperature to 710℃, the mold temperature to 220℃, the injection speed to 3m / s, and the injection pressure to 200MPa, and perform high pressure die casting to obtain the finished product.
[0045] The die-cast part prepared in this embodiment has a tensile strength of 288 MPa, a yield strength of 196 MPa, and an elongation of 11%.
[0046] This embodiment also provides a semi-solid injection molding method for the magnesium alloy, including the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy and Mg-Sr master alloy according to the above composition ratio for later use. (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 760℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the mixture is left to stand for 1 hour. (3) Control the melt temperature at 710℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 120A, the frequency is set to 15Hz, the duty cycle is set to 20%, and the casting speed is 60mm / min. (4) The ingot is segmented and machined to remove the outer skin, and then granules are prepared using a magnesium alloy pelletizer; the particle size is 1.2 mm in length, 1.2 mm in width and 1.5 mm in height; (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 250℃, the temperature of the second stage is controlled at 480℃, the temperature of the third stage is controlled at 600℃, and the temperature of the fourth stage is controlled at 610℃. The injection pressure is 150MPa and the injection speed is 3m / s. After injection into the mold, the pressure is held and cooled. The holding pressure is 150MPa to obtain the finished product.
[0047] The semi-solid injection molded part prepared in this embodiment has a tensile strength of 310 MPa, a yield strength of 198 MPa, and an elongation of 9%.
[0048] like Figure 2 As shown, this magnesium alloy system contains both Al-RE intermetallic compound phases and Al-Ca and Al-Sr second phases. Figure 1 The microstructure of the molded sample shows that the Al-RE phase generated in the alloy is dispersed. This dispersed precipitated second phase can effectively hinder dislocation movement through the coupling effect of grain refinement strengthening and precipitation strengthening. When moving dislocations encounter rigid second phase particles that are difficult to cut, the dislocations cannot pass directly through the particles, but instead bend and bypass between the particles. The finer and more dispersed the second phase particles are, the more significant the strengthening effect, thereby significantly improving the mechanical strength of the alloy matrix. After introducing Ca and Sr elements into the alloy, on the one hand, the growth and agglomeration of the Al-RE phase can be significantly inhibited through the solute dragging effect, realizing the size refinement and distribution control of the Al-RE phase. When Ca, Sr and other elements are introduced into the alloy, these solute atoms agglomerate at the Al-RE phase / matrix interface, generating significant solute dragging pressure and hindering the migration of the phase interface. On the other hand, the in-situ generated Al-Ca and Al-Sr phases can serve as efficient heterogeneous nucleation nuclei for the magnesium matrix, greatly increasing the nucleation rate during solidification, and ultimately achieving overall grain refinement of the alloy, providing an microstructure basis for the alloy to simultaneously achieve high strength and excellent ductility and toughness.
[0049] like Figure 3 As shown, the flowability of the magnesium alloys in Examples 1, 3, and 5 after semi-solid injection molding can be compared by the flow length of the samples. The increase in Al content is beneficial to increasing the flowability of the alloy during semi-solid molding. Based on the filling completion of the samples, it can be seen that the medium Al content magnesium alloy provided by the present invention, which is suitable for both die casting and semi-solid injection molding, has good flowability.
[0050] Comparative Example 1: This comparative example provides an AZ91D die-cast magnesium alloy, the elemental composition of which, by mass percentage, comprises: Al 9.0%, Zn 0.5%, Mn 0.4%, with the balance being Mg and unavoidable impurity elements. The preparation method of this alloy includes the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, and Mg-Mn master alloy according to the above composition ratio for later use; (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 750℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 730℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 20 minutes. After the refining is completed, the temperature is lowered and the mixture is allowed to stand for 1 hour. (3) Control the melt temperature to 690℃, the mold temperature to 220℃, the injection speed to 3m / s, and the injection pressure to 150MPa, and perform high pressure die casting to obtain the finished product.
[0051] The AZ91D die-cast magnesium alloy obtained in this comparative example has a tensile strength of 280 MPa, a yield strength of 180 MPa, and an elongation of 9%.
[0052] Comparative Example 2: This comparative example provides an AZ91D semi-solid injection-molded magnesium alloy, the elemental composition of which, by mass percentage, comprises: Al 9.0%, Zn 0.5%, Mn 0.4%, with the balance being Mg and unavoidable impurity elements. The preparation method of this alloy includes the following steps: (1) Weigh out pure magnesium, pure aluminum, pure zinc, and Mg-Mn master alloy according to the above composition ratio for later use; (2) A mixed gas with a volume ratio of CO2:SF6=99:1 is used as a protective atmosphere. Under this protective atmosphere, the temperature is raised to 780℃ to melt all the raw materials. After they are completely melted, the temperature is lowered to 740℃ for refining. Commercially available No. 5 flux is used as the refining agent. The refining is carried out in two stages, each refining for 15 minutes. After the refining is completed, the temperature is lowered and the mixture is allowed to stand for 1.5 hours. (3) Control the melt temperature at 700℃, and then perform electromagnetic semi-continuous casting to prepare the billet. The current is set to 120A, the frequency is set to 15Hz, the duty cycle is set to 20%, and the casting speed is 60mm / min. (4) The ingot is segmented and machined to remove the outer skin, and then granules are prepared using a magnesium alloy pelletizer; the particle size is 1.2 mm in length, 1.2 mm in width and 1.5 mm in height; (5) The granules are injected into the injection molding machine barrel. The barrel heats the granules through four stages of heating. The temperature of the first stage is controlled at 200℃, the temperature of the second stage is controlled at 450℃, the temperature of the third stage is controlled at 610℃, and the temperature of the fourth stage is controlled at 610℃. The injection pressure is 80MPa and the injection speed is 2m / s. After injection into the mold, the pressure is held and cooled. The holding pressure is 80MPa to obtain the finished product.
[0053] The AZ91D semi-solid injection molded magnesium alloy obtained in this comparative example has a tensile strength of 270 MPa, a yield strength of 185 MPa, and an elongation of 6%.
Claims
1. A magnesium alloy suitable for die casting and semi-solid injection molding, characterized in that, It can meet the requirements of both die casting and semi-solid injection molding processes. The elemental composition of the magnesium alloy, by mass percentage, includes: Al 5.0%-9.0%, Zn 0.3%-1.2%, Mn 0.2%-0.8%, RE 0.5%-1.5%, Ca 0.1%-0.2%, Sr 0.1%-0.2%, with the balance being Mg and unavoidable impurities. The REs include La 0.2%-0.6%, Ce 0.2%-0.6%, and Sm 0.1%-0.3%.
2. A magnesium alloy according to claim 1, which can be used for die casting and semi-solid injection molding, characterized in that, The magnesium alloy die-cast parts have a maximum tensile strength of 288 MPa, a maximum yield strength of 196 MPa, and a maximum elongation of 11%.
3. A magnesium alloy according to claim 1, which can be used for die casting and semi-solid injection molding, characterized in that, The magnesium alloy semi-solid injection molded parts have a maximum tensile strength of 316 MPa, a maximum yield strength of 209 MPa, and a maximum elongation of 9%.
4. A method for preparing a magnesium alloy suitable for die casting and semi-solid injection molding as described in any one of claims 1 to 3, characterized in that, The magnesium alloy is a die-cast magnesium alloy part or a semi-solid injection-molded magnesium alloy part, and the method includes the following steps: S1 prepares the raw materials according to the target alloy element composition; S2 is heated to melt all raw materials under a protective atmosphere. After complete melting, it is cooled down and refined twice. After refining, it is left to stand. The method for preparing the magnesium alloy die-cast part further includes step S3-1: S3-1 controls the melt temperature to 690℃~710℃, the mold temperature to 180℃~220℃, the injection speed to 3m / s~6m / s, and the injection pressure to 50MPa~200MPa for high-pressure die casting to obtain die-cast parts. The method for preparing the magnesium alloy semi-solid injection molded part further includes steps S3-2, S4 and S5: S3-2 controls the melt temperature and performs electromagnetic semi-continuous casting to prepare ingots; S4 segments the ingot and removes the outer skin by machining, and then uses a magnesium alloy pelletizer to prepare granules; S5 injects the granules into the injection molding machine barrel. The barrel uses four stages of induction heating to heat the granules. The temperature of the first stage is controlled at 200℃~250℃, the temperature of the second stage is controlled at 450℃~480℃, the temperature of the third stage is controlled at 550℃~610℃, and the temperature of the fourth stage is controlled at 600℃~610℃. After injection into the mold, the material is held under pressure and cooled to obtain a semi-solid injection molded part.
5. The method for preparing a magnesium alloy suitable for die casting and semi-solid injection molding according to claim 4, characterized in that, The S1 batching process involves weighing pure magnesium, pure aluminum, pure zinc, Mg-Mn master alloy, Mg-La master alloy, Mg-Ce master alloy, Mg-Sm master alloy, Mg-Ca master alloy, and Mg-Sr master alloy according to the target alloy element composition for later use.
6. The method for preparing a magnesium alloy suitable for die casting and semi-solid injection molding according to claim 4, characterized in that, In S2, the temperature for melting all raw materials is 750℃~780℃, and the refining temperature is 730℃~740℃; The refining process is as follows: using No. 5 flux as the refining agent, the refining is carried out in two stages, with each refining time lasting 15 to 20 minutes. After refining, the standing time is 1 to 1.5 hours.
7. The method for preparing a magnesium alloy suitable for die casting and semi-solid injection molding according to claim 4, characterized in that, The protective atmosphere is a mixture of CO2 and SF6.
8. A method for preparing a magnesium alloy suitable for die casting and semi-solid injection molding according to claim 4, characterized in that, In S3-2, the melt temperature is 700℃~710℃, the current for electromagnetic semi-continuous casting is set to 80A-120A, the frequency is set to 15Hz~20Hz, the duty cycle is set to 20%~50%, and the casting speed is 30mm / min-60mm / min.
9. A method for preparing a magnesium alloy suitable for die casting and semi-solid injection molding according to claim 4, characterized in that, The dimensions of the granules are: length 1.2mm~1.5mm, width 1.2mm~1.5mm, height 1.5mm~2.0mm.
10. A method for preparing a magnesium alloy suitable for die casting and semi-solid injection molding according to claim 4, characterized in that, In S5, the injection pressure is 50MPa~150MPa, the injection speed is 0.5m / s~3m / s, and the holding pressure is 50MPa~150MPa.