A high-speed extrusion heat-resistant magnesium alloy and its preparation method

Abstract

This invention discloses a high-speed extrusion heat-resistant magnesium alloy and its preparation method, comprising 0.9wt% Bi, 0.8wt% Mn, 1.0wt% Al, 0.4wt% Ca, 0.3wt% Zn, with the balance being magnesium; this invention possesses good heat resistance and low-temperature high-speed extrusion forming capability.

Description

Technical Field

[0001] This invention belongs to the field of engineering and materials, and specifically relates to a heat-resistant magnesium alloy that can be extruded at high speed. Background Technology

[0002] Magnesium alloys, due to their excellent properties (such as lightweight, environmental friendliness, and high specific strength), have shown great potential in various applications in the 3C industry, transportation, and defense industry. In recent years, extruded magnesium alloys have become a research hotspot due to their superior mechanical properties and diverse product shapes. Currently, the AZ, ZM, and ZK series alloys are the most commonly produced commercially. However, these alloys exhibit poor formability under high-speed extrusion or low-temperature conditions. Furthermore, reducing extrusion speed or increasing extrusion temperature leads to increased costs or reduced final product efficiency, further hindering the application prospects of extruded magnesium alloys.

[0003] Mg in Mg-Al and Mg-Zn based alloys 17 Al 12 Both the Mg and Zn2 phases act as thermally unstable second phases, causing hot cracking during high-speed extrusion. This is mainly due to the increased extrusion temperature under high-speed extrusion conditions, which makes the thermally unstable phases easily dissolve into the matrix. Lowering the extrusion temperature seems to avoid this phenomenon, but it inevitably requires increasing the extrusion pressure. Even then, these alloys may still be difficult to extrude successfully. Therefore, there is an urgent need to develop new high-performance magnesium alloys with low-temperature, high-speed extrusion capabilities. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a high-speed extrusion heat-resistant magnesium alloy and its preparation method. The high-strength high-speed extrusion magnesium alloy of this invention has good heat resistance and low-temperature high-speed extrusion forming capability.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-speed extrudable heat-resistant magnesium alloy, comprising,

[0008] 0.9 wt% Bi, 0.8 wt% Mn, 1.0 wt% Al, 0.4 wt% Ca, 0.3 wt% Zn, balance magnesium.

[0009] A method for preparing high-strength, high-speed extruded Mg-Bi-based alloys, characterized by comprising the following steps:

[0010] According to the alloy composition ratio, pure magnesium ingots, pure aluminum ingots, pure zinc particles, master alloy Mg-10Bi, master alloy Mg-25Ca and master alloy Mg-10Mn are selected as raw materials, and the raw materials are preheated at the first set temperature.

[0011] Under the protective atmosphere of SF6 and CO2, pure magnesium is kept at a second set temperature and then heated to a third set temperature to melt the pure magnesium.

[0012] Pure aluminum ingots, pure zinc particles and three intermediate alloys are added, heated and melted, stirred and held at the fourth set temperature, and then argon gas is blown in for refining and slag removal to obtain a multi-element microalloyed magnesium alloy melt.

[0013] The obtained multi-component micro-alloyed magnesium alloy melt is poured into a steel mold to obtain a multi-component micro-alloyed magnesium alloy ingot;

[0014] The obtained magnesium alloy ingot was cut into Mg-Bi based alloy of a set size by wire electrode cutting, and then air-cooled to room temperature after solution treatment at the fifth set temperature to obtain a solution-treated magnesium alloy.

[0015] The obtained solid solution magnesium alloy was subjected to extrusion deformation treatment and then air-cooled to room temperature to obtain a multi-component high-strength extruded Mg-Bi based alloy.

[0016] In a preferred embodiment of the preparation method described in this invention, the magnesium alloy ingot and the extrusion die are preheated at a sixth set temperature before extrusion deformation.

[0017] In a preferred embodiment of the preparation method described in this invention, the extrusion temperature is 300°C, the extrusion ratio is 20:1, and the extrusion speed is 9 mm / s.

[0018] In a preferred embodiment of the preparation method described in this invention, the first set temperature is 150°C and the preheating time is 90 min.

[0019] In a preferred embodiment of the preparation method described in this invention, the second set temperature is 500°C and the holding time is 60 min.

[0020] In a preferred embodiment of the preparation method described in this invention, the third set temperature is 750°C.

[0021] In a preferred embodiment of the preparation method described in this invention, the fourth set temperature is 720°C and the holding time is 20 min.

[0022] In a preferred embodiment of the preparation method described in this invention, the fifth set temperature is 500°C and the holding time is 12 hours.

[0023] In a preferred embodiment of the preparation method described in this invention, the sixth set temperature is 300℃ and the holding time is 2h.

[0024] The beneficial effects of this invention are as follows: The high-strength, high-speed extruded magnesium alloy of this invention has good heat resistance and low-temperature, high-speed extrusion forming capability due to the large number of micro / nano-scale second phases and the co-segregation of Ca and Zn atoms at grain boundaries and residual dislocations; by adding a certain amount of Bi, Mn, Al, Zn and Ca, highly thermally stable Mg2Bi2Ca, Al8Mn5 and α-Mn phases are formed as reinforcing phases, so that the Mg-Bi-Mn-Al-Ca-Zn alloy has excellent tensile mechanical properties. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0026] Figure 1 The images show the surface appearance and cross-sectional microstructure of the extruded Mg-Bi based alloy and AZ31 alloy. (a) and (b) are the surface appearance of the extruded bar, (c) and (d) are the cross-sectional views of the extruded BMAXZ11110 and AZ31 alloys, respectively; (e) is an enlarged view of (c); (f) and (g) are enlarged views of boxes 1 and 2 in (e), respectively; (h) is an enlarged view of (d); (i) and (j) are enlarged views of boxes 3 and 4 in (h), respectively.

[0027] Figure 2 These are optical microscope images of the core tissues of extruded Mg-Bi based alloy and AZ31 alloy. (a) and (b) are optical microscope images of the core tissues of extruded Mg-Bi based alloy; (c) and (d) are optical microscope images of the core tissues of AZ31 alloy.

[0028] Figure 3 These are electron backscatter diffraction (EBSD) images of the core of the extruded Mg-Bi based alloy and the AZ31 alloy. (a) and (b) are EBSD images of the longitudinal sections of the core of the extruded Mg-Bi based alloy and the AZ31 alloy, respectively. (c) is a histogram of grain size distribution. (d) and (e) are pole figures of the two alloys, which include the (0001), (11-20) and (10-10) planes, respectively.

[0029] Figure 4 These are scanning electron microscope (SEM) images of extruded Mg-Bi based alloys and AZ31 alloys. Among them, (a) to (j) are SEM analysis of extruded Mg-Bi based alloys, and (a) and (b) are SEM images; (c) to (h) are mapping scan images, showing the distribution of Mg, Bi, Mn, Al, Ca and Zn elements, respectively; (i) and (j) are the point scan results corresponding to A and B marked with circles in (b), respectively; (k) to (q) are SEM analysis of AZ31 alloys, and (k) to (l) are SEM images; (m) to (p) are mapping scan images, showing the distribution of Mg, Al, Zn and Mn elements, respectively; (q) is the point scan result corresponding to C marked with circles in (l).

[0030] Figure 5 These are transmission electron microscope (TEM) images of extruded Mg-Bi based alloys and AZ31 alloys. (a) and (b) are bright-field TEM images of AZ31 and extruded Mg-Bi based alloys, respectively; (c) is a high-resolution TEM image of A in the extruded Mg-Bi based alloy, including Fourier transform; (d) and (e) are bright-field and HAADF images of the DRX region of the AZ31 alloy, respectively; (f) and (g) are bright-field and HAADF images of the DRX region of the extruded Mg-Bi based alloy, respectively; (h) is the HAADF image of the three-pronged grain boundary in (g); (i) to (m) are the mapping scan results, showing the elemental distributions of Bi, Mn, Al, Ca, and Zn, respectively.

[0031] Figure 6 These are transmission electron microscope images of the unrecrystallized region of the extruded Mg-Bi based alloy. Among them, (a) is a bright-field TEM image; (b) to (d) are the bright-field, dark-field, and HAADF magnified images corresponding to the boxes in (a), respectively; (e) is the AB line scan result in (d); and (f) is a schematic diagram corresponding to (d), showing the nanoscale α-Mn phase and the co-segregation of Ca and Zn atoms at the residual dislocations.

[0032] Figure 7 These are the stress-strain curves of extruded Mg-Bi based alloy and AZ31 alloy under room temperature and 250℃ tensile engineering conditions.

[0033] Figure 8 The contribution values ​​of each strengthening mechanism to the room temperature and high temperature yield strength are (a) contribution value and (b) contribution value percentage.

[0034] Figure 9These are transmission electron microscope images of Mg-Bi based alloys, where (a) and (b) are TEM and HAADF images of the extruded BMZ110 alloy; (c) is a local TEM image near the grain boundary obtained from (b) and its row scan results; (dg) is a HAADF mapping scan image, showing the distribution of Mg, Bi, Mn and Zn elements in the box in (b).

[0035] Figure 10 These are the tensile true stress-strain curves of extruded BMZ110 and BM11 alloys.

[0036] Figure 11 The images show the microstructure and EBSD analysis of the extruded sample, where (a) is the longitudinal section OM image; (b) is the Schmidt factor distribution map of basal slip; (c) is the average size distribution map of recrystallized grains; (d) is the histogram of the Schmidt factor distribution of basal slip; and (e) are the (0001) and (10-10) pole figures. Detailed Implementation

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0040] Example 1:

[0041] A high-speed extrusion heat-resistant magnesium alloy comprising 0.9 wt% Bi, 0.8 wt% Mn, 1.0 wt% Al, 0.4 wt% Ca, 0.3 wt% Zn, with the balance being magnesium.

[0042] A method for preparing high-strength, high-speed extruded Mg-Bi-based alloys includes the following steps:

[0043] According to the alloy composition ratio, pure magnesium ingots, pure aluminum ingots, pure zinc particles, master alloy Mg-10Bi (wt.%), master alloy Mg-25Ca (wt.%) and master alloy Mg-10Mn (wt.%) were selected as raw materials. wt.% indicates the proportion of alloying elements in the magnesium alloy by mass percentage. The raw materials were preheated at 150℃ for 90 min.

[0044] Under the protective atmosphere of SF6 and CO2, with a volume ratio of SF6 to CO2 of 1:99, pure magnesium was kept at 500℃ for 60 minutes and then heated to 750℃ to melt the pure magnesium.

[0045] Pure aluminum ingots, pure zinc particles and three intermediate alloys were added, heated and melted, stirred and held at 720℃ for 20 minutes, and then argon gas was blown in for refining and slag removal to obtain a multi-element microalloyed magnesium alloy melt.

[0046] The obtained multi-component microalloyed magnesium alloy melt was poured into a Ф80×200mm (diameter×height) steel mold (preheated to 350℃) by gravity casting to obtain a multi-component microalloyed magnesium alloy ingot.

[0047] The obtained magnesium alloy ingot was cut into as-cast Mg-Bi based alloy with a diameter and height of 80 mm and 80 mm respectively by wire electrode cutting. After solution treatment, it was air-cooled to room temperature to obtain a solution-treated Mg-Bi based alloy.

[0048] The obtained solid solution Mg-Bi based alloy was subjected to extrusion deformation treatment and then air-cooled to room temperature to obtain a multi-component high-strength extruded Mg-Bi based alloy, namely a high-speed extruded heat-resistant magnesium alloy.

[0049] Before extrusion deformation, the solid solution Mg-Bi based alloy and the extrusion die are preheated at 300℃ for 2 hours; during the extrusion process, the extrusion temperature is 300℃, the extrusion ratio is 20:1, and the extrusion speed is 9mm / s.

[0050] Example 2:

[0051] Reference Figures 1 to 8 The difference between this embodiment and Embodiment 1 is that the multi-component high-strength extruded Mg-Bi based alloy prepared in Embodiment 1 was tested and compared with AZ31 alloy to verify that the high-strength extruded Mg-Bi based alloy has better performance.

[0052] Samples with a length of 7×5×3mm were machined from the extruded rod along the extrusion direction, and the microstructure and properties of the extruded magnesium alloy rod were analyzed.

[0053] like Figure 1As shown, compared with AZ31 alloy, the extruded magnesium alloy rods produced have recrystallized grain structures at both the edges and the core, with uniform microstructure, smaller average grain size, and higher thermal stability.

[0054] Figure 2 These are optical micrographs of the core structure of extruded Mg-Bi based alloy and AZ31 alloy. Under the same high-speed extrusion conditions, the extruded Mg-Bi based alloy has a finer grain structure, further indicating that the heat resistance of the extruded magnesium alloy rods prepared by this invention is higher than that of AZ31 alloy.

[0055] The sample was ground, cleaned, and dried, and then electropolished for 90 seconds using AC2 special electrolyte at a voltage of 20 V, a current of 0.03 A, and a temperature of -25 °C. The EBSD results are as follows: Figure 3 As shown, the extruded Mg-Bi based alloy obtained by the present invention exhibits a bimodal grain structure with a smaller average grain size, and the presence of non-recrystallization enhances the texture of the extruded magnesium alloy.

[0056] The crystal structure of the sample was observed using an electron microscope. As can be seen from the figure, the addition of Bi, Mn, Al and Ca elements can produce intermetallic compound second phases Mg2Bi2Ca and Al8Mn5, which have the effect of strengthening alloys.

[0057] The extruded magnesium alloy was observed using transmission electron microscopy (TEM). The metal sheet used for TEM observation was mechanically polished to 50 μm, then perforated into a 3 mm diameter disk. Subsequently, an ion thinning instrument was used to further thin the treated metal sheet to a thickness of 30 nm using an ion beam. The observation results are as follows: Figure 5 As shown, a certain number of nanoscale α-Mn phases and co-segregation of Ca and Zn elements at the grain boundaries were found in the prepared magnesium alloy.

[0058] Transmission electron microscopy was used to observe the non-dynamic recrystallization region of the extruded magnesium alloy. The results are as follows: Figure 6 As shown, a large number of residual dislocations and abundant α-Mn phases can be found inside the unrecrystallized grains. Ca and Zn elements exhibit co-aggregation at the residual dislocations, accompanied by the distribution of α-Mn phases along the residual dislocations.

[0059] The extruded magnesium alloy was processed into tensile test bars (Ф5×25mm) and subjected to tensile tests at room temperature and 250℃, with a strain rate of 1×10⁻⁶. -3 s -1Each tensile test was performed three times to ensure the accuracy of the experiment. The results are shown in Figure 7. The prepared magnesium alloy has a yield strength of 327.1 MPa, a tensile strength of 348.9 MPa, and an elongation of 5% at room temperature. At a high temperature of 250℃, the yield strength is 187.8 MPa, the tensile strength is 252.1 MPa, and the elongation is 42%.

[0060] The strengthening and toughening mechanism of the alloy was analyzed, and the tensile yield strength of the magnesium alloy was obtained from the following aspects:

[0061] ;

[0062] in, For tensile yield stress, and These represent the contributions of grain boundaries, precipitates, dislocations, solute atoms, and solute segregation effects to tensile yield strength, respectively.

[0063] like Figure 8 As shown, the prepared magnesium alloy has a high tensile yield strength at room temperature, with grain boundary strengthening being the main strengthening mechanism; at 250℃, solute segregation is the main strengthening mechanism, which enables the alloy to maintain a relatively high tensile yield strength and gives the prepared magnesium alloy high thermal stability.

[0064] As can be seen from the above, this invention not only achieves the preparation of extruded Mg-Bi based alloys with low total element content (≤3.4%), saving production costs, but also realizes low-temperature high-speed extrusion forming, which is superior to existing technologies, improves production efficiency, and has better thermal stability than existing technologies.

[0065] This invention achieves a synergistic effect of fine grain strengthening, second-phase strengthening, texture modification, and grain boundary co-segregation through the optimized alloy composition design and low-temperature high-speed extrusion process, resulting in a significant improvement in the thermal stability of magnesium alloys. The high-strength, high-speed extruded Mg-Bi-Mn-Al-Ca-Zn alloy produced exhibits a yield strength of 187.8 MPa, a tensile strength of 252.1 MPa, and an elongation of 42% at 250℃, which is more than three times the high-temperature yield strength of commercial AZ31 magnesium alloy. This invention solves the technical problems of poor heat resistance and low extrusion efficiency of magnesium alloys, and is conducive to the controllable industrial production of heat-resistant, high-strength, high-speed extruded Mg-Bi-based alloys.

[0066] Example 3:

[0067] Reference Figure 9 and Figure 10This is the third embodiment of the present invention. The difference between this embodiment and embodiment 1 is that this embodiment provides a high-speed extrusion heat-resistant magnesium alloy, which is composed of the following components: 1.0 wt% Bi, 1.0 wt% Mn, 0.3 wt% Zn, and the balance is magnesium.

[0068] The high-strength extruded Mg-Bi based alloy was compared with that prepared in Example 1 to verify that the addition of Al and Ca elements resulted in better performance of the high-strength extruded Mg-Bi based alloy. The preparation method includes the following steps:

[0069] According to the alloy composition ratio, pure magnesium ingots, pure zinc granules, master alloy Mg-10Bi (wt.%), and master alloy Mg-10Mn (wt.%) were selected as raw materials, where wt.% indicates the proportion of alloying elements in the magnesium alloy by mass percentage. The raw materials were preheated at 150℃ for 90 min.

[0070] Under the protective atmosphere of SF6 and CO2, with a volume ratio of SF6 to CO2 of 1:99, pure magnesium was kept at 500℃ for 60 minutes and then heated to 750℃ to melt the pure magnesium.

[0071] Pure zinc particles and two intermediate alloys were added, heated and melted, stirred and held at 720℃ for 20 minutes, and then argon gas was blown in for refining and slag removal to obtain a multi-element microalloyed magnesium alloy melt.

[0072] The obtained multi-component microalloyed magnesium alloy melt was poured into a Ф80×200mm (diameter×height) steel mold (preheated to 350℃) by gravity casting to obtain a multi-component microalloyed magnesium alloy ingot.

[0073] The obtained magnesium alloy ingot was cut into as-cast Mg-Bi based alloy with a diameter and height of 80 mm and 80 mm respectively by wire electrode cutting. After solution treatment at 500℃ for 12 h, it was air-cooled to room temperature to obtain a solution-treated Mg-Bi based alloy.

[0074] The obtained solid solution Mg-Bi based alloy is subjected to extrusion deformation treatment and then air-cooled to room temperature to obtain a multi-component high-strength extruded Mg-Bi based alloy, which can be used for high-speed extrusion of heat-resistant magnesium alloy.

[0075] Before extrusion deformation, the solid solution Mg-Bi based alloy and the extrusion die are preheated at 250℃ for 2 hours; during the extrusion process, the extrusion temperature is 250℃, the extrusion ratio is 28:1, and the extrusion speed is 5mm / s.

[0076] Samples with a length of 7×5×3mm were machined from the extruded rod along the extrusion direction, and the microstructure and properties of the extruded magnesium alloy rod were analyzed.

[0077] The prepared Mg-1Bi-1Mn-0.3Zn magnesium alloy was observed by transmission electron microscopy (TEM). The metal sheet used for TEM observation was mechanically polished to 50 μm, then perforated into a 3 mm diameter disk. Subsequently, an ion thinning instrument was used to further thin the treated metal sheet to a thickness of 30 nm using an ion beam. The observation results are as follows: Figure 9 As shown, a certain number of nanoscale α-Mn phases and co-segregation of Zn and Bi elements at the grain boundaries were found in the prepared magnesium alloy.

[0078] The prepared Mg-1Bi-1Mn-0.3Zn magnesium alloy was processed into a tensile test bar (Ф5×25mm) and subjected to a room temperature tensile test with a strain rate of 1.2×10⁻⁶. -3 s -1 Each tensile test was performed three times to ensure the accuracy of the experiment. The results are shown in Figure 10. The obtained magnesium alloy has a yield strength of 283.4 MPa, a tensile strength of 366.2 MPa, and an elongation of 26% at room temperature.

[0079] As can be seen from the above, the addition of Al and Ca elements gives the high-strength extruded Mg-Bi-based alloy better performance, increasing the room temperature yield strength by 43.7 MPa. This invention achieves a synergistic effect of fine-grain strengthening, second-phase strengthening, and grain boundary co-segregation through alloy composition optimization design, resulting in a significant improvement in the room temperature yield strength of magnesium alloys. This contributes to the development of new high-performance low-alloy Mg-Bi-based wrought alloys, enabling their widespread industrial application.

[0080] Example 4:

[0081] Reference Figure 11 This is the third embodiment of the present invention. The difference between this embodiment and embodiment 1 is that this embodiment provides a high-speed extrusion heat-resistant magnesium alloy, which is composed of the following components: 0.9wt% Bi, 0.8wt% Mn, 1.0wt% Al, 0.4wt% Ca, 0.3wt% Zn, with the balance being magnesium.

[0082] Its preparation method includes the following steps:

[0083] According to the alloy composition ratio, pure magnesium ingots, pure aluminum ingots, pure zinc granules, master alloys Mg-10Bi (wt.%), Mg-25Ca (wt.%), and Mg-10Mn (wt.%) were selected as raw materials. wt.% indicates the percentage of alloying elements in the magnesium alloy by mass. The raw materials were preheated at 150℃ for 90 min.

[0084] Under the protective atmosphere of SF6 and CO2, with a volume ratio of SF6 to CO2 of 1:99, pure magnesium was kept at 500℃ for 60 minutes and then heated to 750℃ to melt the pure magnesium.

[0085] Pure aluminum ingots, pure zinc particles and three intermediate alloys were added, heated and melted, stirred and held at 720℃ for 20 minutes, and then argon gas was blown in for refining and slag removal to obtain a multi-element microalloyed magnesium alloy melt.

[0086] The obtained multi-component microalloyed magnesium alloy melt was poured into a Ф80×200mm (diameter×height) steel mold (preheated to 350℃) by gravity casting to obtain a multi-component microalloyed magnesium alloy ingot.

[0087] The obtained magnesium alloy ingot was cut into as-cast Mg-Bi based alloy with a diameter and height of 80 mm and 80 mm respectively by wire electrode cutting. After solution treatment at 500℃ for 12 h, it was air-cooled to room temperature to obtain a solution-treated Mg-Bi based alloy.

[0088] The obtained solid solution Mg-Bi based alloy was subjected to extrusion deformation treatment and then air-cooled to room temperature to obtain a multi-component high-strength extruded Mg-Bi based alloy.

[0089] Before extrusion deformation, the solid solution Mg-Bi based alloy and the extrusion die are preheated at 300℃ for 2 hours; during extrusion, the extrusion temperature is 300℃, the extrusion ratio is 20:1, and the extrusion speed is 0.5mm / s.

[0090] Samples with a length of 7×5×3mm were machined from the extruded rod along the extrusion direction, and the microstructure and properties of the extruded magnesium alloy rod were analyzed.

[0091] The sample was ground, cleaned, and dried, and then electropolished for 90 seconds using a special AC2 electrolyte at a voltage of 20 V, a current of 0.03 A, and a temperature of -25 °C. The electron backscatter diffraction pattern is shown below. Figure 11 As shown, the extruded Mg-Bi based alloy exhibits a bimodal grain structure with a small average grain size of 0.89 μm. The presence of non-recrystallization results in enhanced texture and a low average Schmidt factor for basal slip in the extruded magnesium alloy.

[0092] The extruded magnesium alloy was machined into a tensile test bar (Ф5×25mm) and subjected to a room temperature tensile test with a strain rate of 1×10⁻⁶. -3 s -1Each tensile test was conducted three times to ensure the accuracy of the experiment. The Mg-0.9Bi-0.8Mn-1.0Al-0.4Ca-0.3Zn alloy extruded at a speed of 0.5 mm / s had a yield strength of 425 MPa and a tensile strength of 438 MPa at room temperature, but the elongation was only 2%, which severely limited the application of the Mg-0.9Bi-0.8Mn-1.0Al-0.4Ca-0.3Zn alloy. At the same time, the low extrusion speed reduced production efficiency.

[0093] As can be seen from the above, increasing the extrusion speed results in better overall mechanical properties for the high-strength extruded Mg-Bi based alloy, with elongation more than doubling. This invention achieves a synergistic match between strength and plasticity in the Mg-0.9Bi-0.8Mn-1.0Al-0.4Ca-0.3Zn alloy by optimizing extrusion process parameters. Simultaneously, the low-temperature, high-speed extrusion process significantly improves the production efficiency of magnesium alloys. Therefore, this low-alloy magnesium-bismuth alloy with excellent overall mechanical properties will contribute to enriching the series of high-performance, low-cost wrought magnesium alloys, enabling widespread industrial applications.

[0094] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a high-speed extruded heat-resistant magnesium alloy, characterized in that: The heat-resistant magnesium alloy comprises 0.9 wt% Bi, 0.8 wt% Mn, 1.0 wt% Al, 0.4 wt% Ca, 0.3 wt% Zn, with the balance being magnesium; include The following steps, According to the alloy composition ratio, pure magnesium ingots, pure aluminum ingots, pure zinc particles, master alloy Mg-10Bi, master alloy Mg-25Ca and master alloy Mg-10Mn are selected as raw materials, and the raw materials are preheated at the first set temperature. Under the protective atmosphere of SF6 and CO2, pure magnesium is kept at a second set temperature and then heated to a third set temperature to melt the pure magnesium. Pure aluminum ingots, pure zinc particles and three intermediate alloys are added, heated and melted, stirred and held at the fourth set temperature, and then argon gas is blown in for refining and slag removal to obtain a multi-element microalloyed magnesium alloy melt. The obtained multi-component microalloyed magnesium alloy melt is poured into a steel mold to obtain a multi-component microalloyed magnesium alloy ingot; The obtained magnesium alloy ingot was cut into Mg-Bi based alloy of a set size by wire electrode cutting, and then air-cooled to room temperature after solution treatment at the fifth set temperature to obtain a solution-treated magnesium alloy. The obtained solid solution magnesium alloy was subjected to extrusion deformation treatment and then air-cooled to room temperature. The extrusion temperature was 300℃, the extrusion ratio was 20:1, and the extrusion speed was 9mm / s to obtain a multi-component high-strength extruded Mg-Bi-based alloy.

2. The method as described in claim 1, characterized in that: Before extrusion deformation, the magnesium alloy ingot and extrusion die are preheated at the sixth set temperature.

3. The method as described in claim 1 or 2, characterized in that: The first set temperature is 150℃, and the preheating time is 90min.

4. The method as described in claim 1 or 2, characterized in that: The second set temperature is 500℃, and the holding time is 60 minutes.

5. The method as described in claim 1 or 2, characterized in that: The third set temperature is 750℃.

6. The method as described in claim 1 or 2, characterized in that: The fourth set temperature is 720℃, and the holding time is 20 minutes.

7. The method as described in claim 1 or 2, characterized in that: The fifth setting temperature is 500℃, and the heat preservation time is 12h.

8. The method as described in claim 2, characterized in that: The sixth setting temperature is 300℃, and the holding time is 2 hours.

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