Low-cost high-performance novel Mg-Al-Si-Ce alloy and preparation method thereof

Abstract

According to the low-cost and high-performance novel Mg-Al-Si-Ce alloy and the preparation method thereof, the content ranges of Al, Si and Ce are precisely regulated and controlled, vacuum melting, helium refining and multi-section hot extrusion processes are combined, fine and uniform distribution of an Mg2Si phase is successfully achieved, and meanwhile the room-temperature and high-temperature mechanical properties of the alloy are remarkably improved through the grain boundary strengthening effect of the Ce element; specifically, the tensile strength reaches 261 MPa, and the ductility is improved to 4.8% and is improved by about 30% compared with that of a traditional Mg-Al-Si alloy; in addition, a low-cost intermediate alloy and an optimized smelting process are adopted, so that the production cost is reduced by more than 15%. The alloy is particularly suitable for high-temperature bearing parts in the field of automobile lightweight, such as engine supports and gearbox shells, and has wide industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of alloys, and in particular to a low-cost, high-performance novel Mg-Al-Si-Ce alloy and a preparation method thereof. Background Art

[0002] As global extreme climate change intensifies, reducing CO2 emissions has become a pressing need for human survival. According to statistics, automobile exhaust contributes 25% of atmospheric CO2 emissions, and this proportion continues to rise as the number of cars on the road continues to grow. Against this backdrop, lightweighting vehicles has become a national strategic priority. Magnesium alloys, with their high specific strength and low density, are considered an ideal alternative to traditional steel. Currently, Mg-Al-based alloys, such as AZ91D, are widely used in automotive transmission housings, wheels, and other components. However, their low strength and upper operating temperature limit of only 120°C make them difficult to meet the demands of high-temperature operating conditions.

[0003] In order to solve the problem of insufficient performance of Mg-Al based alloys, researchers proposed to use in-situ self-generated Mg2Si as a strengthening phase. Mg2Si has high interfacial bonding strength with the matrix and can maintain low density characteristics, but under normal solidification conditions, Mg2Si tends to form coarse blocks or dendritic structures, resulting in a significant decrease in the tensile strength and elongation of the alloy at room temperature and high temperature. For example, the Mg-Al-Si alloy prepared by conventional casting technology in the prior art has a tensile strength of less than 200MPa and an elongation of less than 3% due to the uncontrollable morphology of Mg2Si. In addition, the addition of rare earth elements in the prior art is mostly concentrated on Al-based alloys, while there is little research on the coordinated regulation of rare earth Ce in Mg-Al-Si alloys, resulting in high alloy cost and poor process stability.

[0004] Therefore, how to precisely control the Mg2Si morphology and improve the comprehensive performance of Mg-Al-based alloys by optimizing the composition ratio and process parameters while ensuring low cost has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-cost, high-performance novel Mg-Al-Si-Ce alloy and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a low-cost, high-performance novel Mg-Al-Si-Ce alloy. The composition and content of the alloy are as follows, calculated by weight percentage: Al 4.75-5.22%, Si 0.95-1.14%, Ce 0.78-1.05%, and the remainder is Mg, with the total amount of impurity elements being ≤0.3%.

[0008] The present invention also provides a method for preparing a new type of Mg-Al-Si-Ce alloy with low cost and high performance, comprising the following steps:

[0009] S1. According to the theoretical calculated component ratio, preheat the weighed pure magnesium ingot, aluminum ingot and master alloy, put them into a vacuum induction melting furnace, evacuate the air and then introduce helium for protection;

[0010] S2. Adjust the melting power to 5 kW and 10 kW in sequence, each maintaining for 4 min, and then raise it to 15 kW until completely melted, and electromagnetically stir the melt;

[0011] S3. Before casting, introduce helium for refining the melt, control the melt temperature, and pour it into an ingot to obtain a new type of Mg-Al-Si-Ce alloy with low cost and high performance.

[0012] Preferably, in step S1, the master alloy is Al-24% Si master alloy and Mg-20% Ce master alloy.

[0013] Preferably, in step S1, the preheating temperature is 200 °C.

[0014] Preferably, in step S1, the vacuum induction melting furnace is a ZGSN-0.03 type intermediate frequency induction melting furnace.

[0015] Preferably, in step S1, the evacuation pressure is 10 -2 Pa.

[0016] Preferably, in step S2, the stirring time is 10 min.

[0017] Preferably, in step S3, the refining time is 4 min.

[0018] Preferably, in step S3, the controlled melt temperature is 820 °C.

[0019] The present invention has achieved the following beneficial technical effects compared with the prior art:

[0020] A novel low-cost and high-performance Mg-Al-Si-Ce alloy provided by the present invention and its preparation method can successfully achieve the fine and uniform distribution of Mg2Si phase by precisely controlling the content ranges of Al, Si, and Ce, and combining vacuum melting, helium refining, and multi-stage hot extrusion processes. At the same time, by utilizing the grain boundary strengthening effect of Ce element, the room-temperature and high-temperature mechanical properties of the alloy are significantly improved. Specifically, the tensile strength reaches 261 MPa, the elongation rate is increased to 4.8%, which is about 30% higher than that of traditional Mg-Al-Si alloys. In addition, by using low-cost master alloys and optimized melting processes, the production cost is reduced by more than 15%. This alloy is particularly suitable for high-temperature load-bearing components in the field of automotive lightweight, such as engine brackets, transmission cases, etc., and has broad industrial application prospects. Detailed implementation manners

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] The purpose of the present invention is to provide a novel low-cost and high-performance Mg-Al-Si-Ce alloy and its preparation method to solve the problems existing in the prior art.

[0023] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the specific implementation manners.

[0024] Example 1:

[0025] This example provides a preparation method for a novel low-cost and high-performance Mg-Al-Si-Ce alloy, including the following steps:

[0026] S1. Weigh the raw materials by weight percentage: pure magnesium ingot (99.9 wt%), pure aluminum ingot (99.9 wt%), Al-24% Si master alloy, and Mg-20% Ce master alloy, so that the final composition is Al 4.75%, Si 0.95%, Ce 0.78%, the total amount of impurity elements is 0.3%, and the balance is Mg; preheat the raw materials to 200 °C, put them into a ZGSN-0.03 type vacuum induction melting furnace, evacuate to 10 -2 Pa, and introduce helium for protection;

[0027] S2. Adjust the power to 5 kW and 10 kW in sequence, each maintaining for 4 min, then raise it to 15 kW until completely melted, and perform electromagnetic stirring for 10 min;

[0028] S3. Introduce helium for refining for 4 min, and cast into an ingot when the melt temperature is 820 °C;

[0029] S4. The ingot is solution-treated at 360 °C for 2 h, and then hot-extruded into a Φ20 mm round bar at a die temperature of 385 °C, a rate of 1 mm / min, and an extrusion ratio of 13.4;

[0030] S5. Process into a tensile test bar with a 10-fold gauge length, and test it with a hydraulic servo universal testing machine. The tensile strength is 260 MPa, and the elongation is 4.8%.

[0031] Example 2:

[0032] This example provides a preparation method for a low-cost and high-performance new Mg-Al-Si-Ce alloy, including the following steps:

[0033] S1. Weigh the raw materials by weight percentage: pure magnesium ingot (99.9 wt%), pure aluminum ingot (99.9 wt%), Al-24% Si master alloy, and Mg-20% Ce master alloy, so that the final composition is Al 5%, Si 1%, Ce 0.9%, the total amount of impurity elements is 0.3%, and the balance is Mg; preheat the raw materials to 200 °C, put them into a ZGSN-0.03 type vacuum induction melting furnace, evacuate to 10 - 2 Pa, and introduce helium for protection;

[0034] S2. Adjust the power to 5 kW and 10 kW in sequence, each maintaining for 4 min, then increase to 15 kW until completely melted, and perform electromagnetic stirring for 10 min;

[0035] S3. Introduce helium for refining for 4 min, and cast into an ingot when the melt temperature is 820 °C;

[0036] S4. The ingot is solution-treated at 370 °C for 2 h, and then hot-extruded into a Φ20 mm round bar at a die temperature of 385 °C, a rate of 1 mm / min, and an extrusion ratio of 13.4;

[0037] S5. Process into a tensile test bar with a 10-fold gauge length, and test it with a hydraulic servo universal testing machine. The tensile strength is 261 MPa, and the elongation is 4.8%.

[0038] Example 3:

[0039] This example provides a preparation method for a low-cost and high-performance new Mg-Al-Si-Ce alloy, including the following steps:

[0040] S1. Weigh the raw materials by weight percentage: pure magnesium ingot (99.9 wt%), pure aluminum ingot (99.9 wt%), Al-24% Si master alloy and Mg-20% Ce master alloy, so that the final composition is Al 5.22%, Si 1.14%, Ce 1.05%, the total amount of impurity elements is 0.3%, and the balance is Mg; preheat the raw materials to 200 °C, put them into a ZGSN-0.03 type vacuum induction melting furnace, evacuate to 10 -2 Pa, and introduce helium for protection;

[0041] S2. Adjust the power to 5 kW and 10 kW in sequence, each maintaining for 4 min, increase to 15 kW until completely melted, and perform electromagnetic stirring for 10 min;

[0042] S3. Introduce helium for refining for 4 min, and pour the melt into an ingot when the melt temperature is at 820 °C;

[0043] S4. The ingot is solution-treated at 380 °C for 2 h, and then hot-extruded into a Φ20 mm round bar at a die temperature of 385 °C, a rate of 1 mm / min, and an extrusion ratio of 13.4;

[0044] S5. Process into a tensile test bar with a 10-fold gauge length, and test it with a hydraulic servo universal testing machine. The tensile strength is 259 MPa and the elongation is 4.9%.

[0045] Comparative Example

[0046] The main difference between this comparative example and Examples 1-3 is that Ce element is not added. The final composition is Al 5%, Si 1%, the total amount of impurity elements is 0.3%, and the balance is Mg; under the same process, Mg2Si is in a thick dendritic shape, and the tensile strength is only 198 MPa and the elongation is 2.7%.

[0047] The above examples show that the present invention significantly improves the comprehensive performance of the alloy through Ce addition and process optimization.

[0048] The present invention uses specific examples to elaborate on the principle and implementation mode of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A new type of low-cost and high-performance Mg-Al-Si-Ce alloy, characterized in that, By weight percentage, the composition and content of the alloy are as follows: Al 4.75 - 5.22%, Si 0.95 - 1.14%, Ce 0.78 - 1.05%, the balance being Mg, and the total amount of impurity elements ≤ 0.3%.

2. A preparation method of a novel Mg-Al-Si-Ce alloy with low cost and high performance, characterized in that, It includes the following steps: S1. According to the theoretical calculated composition ratio, preheat the weighed pure magnesium ingot, aluminum ingot and master alloy, put them into a vacuum induction melting furnace, evacuate and then introduce helium for protection; S2. Adjust the melting power to 5 kW and 10 kW in sequence, each maintaining for 4 min, and then raise it to 15 kW until completely melted, and electromagnetic stir the melt; S3. Before casting, introduce helium for refining into the melt, control the melt temperature, and cast into ingots to obtain a low-cost and high-performance new type of Mg-Al-Si-Ce alloy.

3. The preparation method of the low-cost and high-performance novel Mg-Al-Si-Ce alloy according to claim 2, wherein, In step S1, the master alloy is Al-24% Si master alloy and Mg-20% Ce master alloy.

4. The preparation method of the low-cost and high-performance novel Mg-Al-Si-Ce alloy according to claim 2, wherein, In step S1, the preheating temperature is 200 °C.

5. The preparation method of the low-cost and high-performance novel Mg-Al-Si-Ce alloy according to claim 2, characterized in that, In step S1, the vacuum induction melting furnace is a ZGSN-0.03 type intermediate frequency induction melting furnace.

6. The preparation method of the low-cost and high-performance novel Mg-Al-Si-Ce alloy according to claim 2, wherein, In step S1, the pressure for vacuum pumping is 10 -2 Pa.

7. The preparation method of the low-cost and high-performance novel Mg-Al-Si-Ce alloy according to claim 2, characterized in that, In step S2, the stirring time is 10 min.

8. The preparation method of the low-cost and high-performance novel Mg-Al-Si-Ce alloy according to claim 2, characterized in that, In step S3, the refining time is 4 min.

9. The preparation method of the low-cost and high-performance novel Mg-Al-Si-Ce alloy according to claim 2, characterized in that, In step S3, the controlled melt temperature is 820 °C.