High-strength and high-toughness magnesium-aluminum-based alloy capable of being extruded at high speed and preparation method thereof

Abstract

The invention discloses a high-strength and high-toughness magnesium-aluminum-based alloy capable of being extruded at a high speed and a preparation method thereof, the alloy comprises the following components in percentage by mass: 4-10 wt% of Al, 0.3-1.2 wt% of Zn, 0.3-1.3 wt% of Ca, 0.05-0.45 wt% of additive element, 0.15-0.45 wt% of Mn and the balance of magnesium, and the additive element is any one or a combination of more than two of La, Gd, Nd, Y, Sm and Dy. The preparation method comprises the steps of smelting, melt component regulation and control and standing treatment, pouring, heat treatment and high-speed extrusion processing. The extrusion speed of the alloy can reach 40 m / min or above, and the alloy has good strength and plasticity under the high-speed extrusion condition and can be used for transportation tools such as new energy automobiles, high-speed rails and airplanes and the field of tool and mold materials in the building field.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy extrusion processing, and in particular to a high-strength and tough magnesium-aluminum based alloy capable of high-speed extrusion and a preparation method thereof. Background Art

[0002] With the development of new energy vehicles, high-speed railways, airplanes and other means of transportation, as well as the development of lightweight technology for tooling materials in the construction field, the application of extruded magnesium alloys in the above fields has attracted more and more attention. At present, the proportion of magnesium alloy extrusion products in magnesium products is only ~3%, which is much lower than the ~25% proportion of extruded aluminum alloys in aluminum products. This is mainly because the mechanical properties and extrusion processing properties of extruded magnesium alloys are inferior to those of aluminum alloys. On the one hand, the maximum extrusion processing speed of magnesium alloys is significantly lower than that of aluminum alloys. The extrusion speed of commercial aluminum alloys such as 6061 and 6063 is generally 40-80m / min, while the maximum extrusion speed of commercial magnesium alloys such as AZ80 and ZK60 is only 6m / min. The maximum extrusion speed of commercial AZ31 alloy with low alloy content can reach ~23m / min, which is a significant improvement compared with AZ80 alloy, but it can only reach the extrusion speed of commercial aluminum alloys such as 6061 and 6063. On the other hand, the strength or plasticity of most magnesium alloys decreases significantly with the increase of extrusion speed, which becomes another bottleneck factor that seriously restricts the widespread application of magnesium alloy extruded profiles. For example, as the extrusion speed increases from 2.5m / min to 20m / min, magnesium alloys such as AZ31 lack a sufficient number of strengthening phases inside to hinder the growth of recrystallized grains, and cannot provide effective second-phase strengthening effects, resulting in their tensile yield strength (TYS) and elongation (EL) after high-speed extrusion processing dropping sharply from ~170MPa and ~17% to ~115MPa and ~3.5%, respectively.

[0003] In recent years, a growing number of researchers have devoted themselves to the development of high-speed extrusion magnesium alloys. Some studies have employed the strategy of reducing the content of alloying elements such as Al and Zn in magnesium alloys, increasing the maximum extrusion speed of low-alloyed magnesium alloys to 30-60 m / min. However, due to the low total content of alloying elements, most of which are less than 4% by weight, the strengthening effect is extremely limited, and the yield strength of most alloys after high-speed extrusion is below 200 MPa. For example, patent (publication number CN104032195A) discloses a high-efficiency, low-cost, high-performance thermally conductive magnesium alloy and its preparation method. The chemical composition, by weight, is: 0.1-0.8 wt% Al, 0.1-0.6 wt% Ca, 0.1-0.6 wt% Mn, 0.05-0.4 wt% La, with the remainder being Mg. This patent allows for production using a high-speed extrusion process with a maximum exit speed of no less than 20 m / min. The yield strength of the extruded material is approximately 180 MPa, which is significantly insufficient in strength. Patent CN114540683A discloses a microalloyed, corrosion-resistant, and low-cost magnesium alloy and its preparation method. The magnesium alloy comprises the following components by weight: aluminum: 0.55-1.2%, manganese: 0.5-0.65%, zinc: 0-0.4%, calcium: 0.01-0.03%, with the remainder being magnesium, additive elements, and unavoidable impurities. The additive elements are samarium and lanthanum, or a combination thereof, in amounts of 0.01-0.2% samarium and 0.01-0.2% lanthanum, calculated by mass percentage. The alloy can be extruded at an extrusion ratio of 20-150:1 and an extrusion speed of 20-70 m / min. However, the alloy has relatively low mechanical properties, with an average yield strength of 215 MPa and an elongation of 10.9%. Furthermore, the alloy requires solution and aging heat treatment after extrusion, which increases processing and material costs and easily leads to surface oxidation during subsequent heat treatment.

[0004] Other research efforts have focused on the development of highly alloyed magnesium alloys for high-speed extrusion. For example, CN1876871 discloses a wrought magnesium alloy for high-speed extrusion. The alloy's components, by weight, are 2-5% Al, 0.1-0.7% Mn, with the remainder being magnesium and a small amount of unavoidable impurities. The alloy can be extruded at speeds up to 15 m / min, exhibiting a tensile strength of 255-285 MPa, a yield strength of 140-185 MPa, and an elongation of 10-20%. Overall, while the alloy is capable of high-speed extrusion, the achievable extrusion speed remains relatively low, and the resulting alloy exhibits relatively low strength. CN101805866A discloses a wrought magnesium alloy for high-speed extrusion. The alloy comprises, by weight, 2-9% Al, 0.1-1% Mn, 0.1-3% Si, 0.1-2% Ce, 0.1-1% Y, 0.1-1% Sr, and 0.1-1% Sb, with the remainder being magnesium and unavoidable impurities. The alloy can be extruded at speeds of no less than 15 m / min. However, the extrusion speed of this alloy is still relatively low, the elemental composition is relatively complex, and the Sr element is easily burned during alloying, directly increasing the cost of the alloy. The resulting alloy also has relatively low strength, with a yield strength of 160 MPa-220 MPa. The Sb element also has a certain degree of toxicity. CN101418404 discloses a wrought magnesium alloy for high-speed extrusion. Its components, by weight, are: 5-7 wt% Al, 2-3 wt% Zn, 7-9 wt% Mn, 3-4 wt% Li, 1-3% Zr, with the remainder being magnesium and unavoidable impurities. This alloy can achieve an extrusion speed of 20 m / min, with a tensile strength of 248-275 MPa, a yield strength of 142-178 MPa, and an elongation of 18-23.8%. However, the alloy has a relatively low yield strength, contains a high concentration of elements susceptible to burnout (3-4 wt% Li), and the Zr in the alloy is susceptible to mutual poisoning with the Al and Mn elements. ZL201510675184.6 discloses a deformable magnesium alloy capable of high-speed extrusion. The alloy is a Mg-Bi-Al-Zn-Mn magnesium alloy, and the mass percentages of its components are: Bi 2-10wt%, Al 0.5-5wt%, Zn 0.1-2wt%, Mn 0.1-1.0wt%, with the remainder being magnesium. On the one hand, the maximum extrusion speed of the alloy needs to be further improved. On the other hand, the Bi element used in large quantities in the alloy is relatively expensive, and the use of a large amount of Bi element for alloying will lead to excessively high costs. These factors restrict the further development and application of high-speed extrusion Mg-Bi-based alloys.

[0005] In summary, the existing technologies have the following obvious defects: (1) The strength of low-alloy high-speed extruded magnesium alloys is generally low, and the yield strength is generally less than 200 MPa; (2) The maximum speed of high-speed extrusion of high-alloyed magnesium-aluminum-based alloys is still less than (25 m / min), which needs to be further improved; (3) The yield strength of most high-aluminum content high-speed extruded magnesium alloys is low, less than 230 MPa; (4) The yield strength of most high-speed extruded magnesium alloys decreases significantly with the increase of extrusion speed, and it is urgent to find new high-speed extruded magnesium alloys whose mechanical properties do not decrease significantly under high-speed extrusion conditions; (5) The rare earth element content in some high-speed extruded magnesium alloys is too high (more than 0.5%), and the content of other more expensive elements (Zr, Sr, Bi, Li, etc.) is also high, which makes the material cost of high-speed extruded magnesium alloys high and leads to a decrease in the corrosion resistance of the alloy.

[0006] Therefore, if the content of rare alloying elements can be reduced through innovation in composition and processing technology on the basis of Mg-Al-based alloys, and at the same time its extrusion processing performance can be significantly improved, and the prepared alloy after high-speed extrusion processing can be given higher strength and other mechanical properties, it will be expected to significantly promote the promotion and application of extruded magnesium alloys. Summary of the Invention

[0007] In order to overcome the deficiencies in the background technology, the present invention discloses a high-speed extruded high-strength and high-toughness magnesium-aluminum based alloy and a preparation method thereof.

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0009] A high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion is disclosed. The alloy is a Mg-Al-based magnesium alloy, and its components by weight are: Al4-10wt%, Zn0.3-1.2wt%, Ca0.3-1.3wt%, added elements 0.05-0.45wt%, Mn0.15-0.45wt%, and the remainder is magnesium. The added elements are any one of La, Gd, Nd, Y, Sm, and Dy, or a combination of two or more thereof.

[0010] The method for preparing a high-strength and high-toughness magnesium-aluminum-based alloy capable of high-speed extrusion comprises the following steps:

[0011] 1) Melting: Under the protection of protective gas or covering agent, add pure magnesium and heat to 700-800℃ to melt it; then add metal Al and metal Zn in sequence. After they are melted, stir them mechanically or blow argon to make them uniform. Then add Mg-Ca master alloy, pure metal corresponding to the added element, or its corresponding magnesium-based master alloy; after they are melted, stir them mechanically or blow argon to make them uniform. Then, add alloying raw materials containing Mn under Ar gas stirring to make them fully melt and react in the alloy melt; adjust the melt temperature to between 680-760℃, perform refining and slag removal, then adjust the melt temperature to 680-730℃ and keep it warm for 10-30 minutes;

[0012] 2) Melt composition control and static treatment: Samples are taken from the melt, the alloy composition is tested, and the melt is controlled based on the test results. After the alloy composition reaches the target composition range, the melt temperature is adjusted to 670-720°C and the melt is allowed to stand for 20-120 minutes to obtain the target alloy melt;

[0013] 3) Casting: Using sand casting, metal mold casting or semi-continuous casting, the uniformly smelted magnesium alloy melt is cast to obtain a cast alloy ingot;

[0014] 4) Heat treatment: The alloy ingot obtained in step 3) is heat treated in a heat treatment furnace at a temperature of 380-450° C. for 5-36 hours, and then cooled to room temperature by air cooling or water cooling;

[0015] 5) High-speed extrusion processing: The heat-treated billet is cut into corresponding specifications and the surface oxide scale is removed. It is then heated to the extrusion temperature and placed in a deformation die for hot extrusion processing. The extrusion deformation speed is 10 to 45 m / min, the extrusion ratio is 5 to 100, and the extrusion temperature is 250 to 430°C. The hot-deformed billet is directly cooled to room temperature to obtain the high-speed extruded high-strength and toughness magnesium-aluminum-based alloy.

[0016] Preferably, the protective gas in step 1) can be: a mixed gas of Ar+SF6, a mixed gas of SF6+CO2, or a mixed gas of Ar+SF6+CO2.

[0017] Preferably, the covering agent in step 1) may be RJ-5 or RJ-2.

[0018] Preferably, the Mg-Ca master alloy in step 1) is a Mg-20Ca master alloy, and the alloying raw material containing Mn is a Mg-Mn master alloy, or an Al-Mn master alloy, or anhydrous MnCl2.

[0019] Preferably, the refining in step 1) can be performed by adding a refining agent or blowing argon or a combination thereof.

[0020] Preferably, the mold in step 5) is a mold for forming plates, bars, tubes, wires, or profiles.

[0021] Preferably, the cooling after the deformation process in step 5) can be natural cooling in air, forced cooling by spraying water mist, or forced cooling by blowing air.

[0022] Preferably, the composition of the Mg-Al based deformable magnesium alloy used for high-speed extrusion further contains 0.001-0.2 wt % of Ag.

[0023] Preferably, in step 1), Mg-Ag master alloy is added simultaneously with the addition of Mg-Ca master alloy.

[0024] Due to the adoption of the above-mentioned technical solution, the present invention has the following beneficial effects:

[0025] (1) The present invention avoids the low thermal stability Mg in high aluminum magnesium alloy by comprehensive regulation of alloy composition and preparation method. 17 Al 12 Instead, a large number of micron-sized Al2Ca, Al-Mn-RE, Al-RE phases with high thermal stability and submicron-sized Al-Mn-RE phases and (Mg, Zn) 17 Al 12 phase, which is significantly different from the phase composition of other high-speed extruded magnesium alloys; at the same time, a part of the added elements and Ca elements dissolved in the matrix also improve the thermal stability of the alloy matrix, avoiding the alloy from cracking due to temperature rise during high-speed extrusion, and the alloy can still maintain a smooth surface at an extrusion speed of about 40m / min.

[0026] (2) The present invention constructs a fine grain structure in a high-speed extruded high-aluminum magnesium alloy through comprehensive regulation of alloy composition and preparation method, and at the same time, a large number of micro-nano dual-scale thermal stability materials are dispersed in the matrix. 17 Al 12 Higher strengthening phases, including Al2Ca, Al-Mn-RE, Al-RE phase, and submicron Al-Mn-RE phase and (Mg, Zn) 17 Al 12On the one hand, these second phases can refine the grain structure of high-speed extruded alloys, and on the other hand, they can also serve as strengthening phases to significantly improve the mechanical properties of the alloys. Under high-speed extrusion conditions of about 40m / min, the average grain size of the alloy is small; and part of the added elements and Ca elements dissolved in the matrix can not only play a role in solid solution strengthening, but also promote the excitation of the matrix, including<c+a> A variety of plastic deformation mechanisms, including dislocations, give the alloy excellent strength and plasticity, with a yield strength of about 250MPa and an elongation of about 15%; the extrusion speed is higher than that of other high-aluminum-magnesium alloys, and the yield strength is significantly higher than that of most high-speed extruded magnesium alloys. At the same time, it has good plasticity and has broken through two technical difficulties: high-aluminum-magnesium alloys are difficult to extrude at a basic speed of more than 30m / min, and the yield strength is significantly reduced after extrusion processing at a high-speed extrusion speed of more than 20m / min. It has made significant progress.

[0027] (3) Most magnesium alloys exhibit significant differences in mechanical properties under different extrusion speed conditions, particularly their strength, which decreases dramatically with increasing extrusion speed. However, another significant advantage of the high-speed extruded magnesium alloy of the present invention is that its mechanical properties at an extrusion speed of approximately 40 m / min are similar to those at an extrusion speed of 3.24 m / min, indicating that its mechanical properties are relatively stable over this wide processing speed range. This significant advantage facilitates the production of extruded products with stable performance. It is significantly superior to existing alloys such as commercial AZ31.

[0028] (4) The cost of most alloying elements in the alloy of the present invention is very low, and the amount of rare earth elements used is very limited, controlled within 0.5%, and the cost is significantly lower than that of Mg-Bi based alloys.

[0029] (5) The heat treatment process before extrusion of the alloy of the present invention is relatively simple. After extrusion processing, good mechanical properties can be obtained in the prepared state without subsequent heat treatment processing, which can reduce processing costs and avoid oxidation of the alloy during subsequent heat treatment.

[0030] (6) The alloying of trace 0.001-0.2wt% Ag elements will not lead to a significant increase in the cost of alloy materials, but it has significant beneficial effects. It is dissolved in the matrix. On the one hand, it can further improve the thermal stability of the matrix and improve its plastic deformation ability during high-speed extrusion processing. On the other hand, it can also play a certain solid solution strengthening effect, giving the high-speed extrusion alloy more excellent strength and plasticity.

[0031] (7) The alloy of the present invention contains a certain amount of Ca element, which can give the alloy good flame retardant properties, making the alloy safe during preparation, storage, transportation and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is an optical microstructure diagram of the alloy of Example 1 of the present invention;

[0033] Figure 2 This is an optical microstructure diagram of the alloy of Example 10 of the present invention;

[0034] Figure 3 is a typical tensile stress-strain curve of the alloy of Example 10 of the present invention;

[0035] Figure 4 This is a typical tensile stress-strain curve of the alloy in Example 13 of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Example 1:

[0038] A high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion is disclosed. The alloy is a Mg-Al-based magnesium alloy, and its components by weight are: Al4-10wt%, Zn0.3-1.2wt%, Ca0.3-1.3wt%, added elements 0.05-0.45wt%, Mn0.15-0.45wt%, and the remainder is magnesium. The added elements are any one of La, Gd, Nd, Y, Sm, and Dy, or a combination of two or more thereof.

[0039] The target composition of this example is Mg-6.80Al-0.78Zn-0.16Mn-0.23Gd-0.90Ca (wt%). The following raw materials are used to achieve this target composition: Mg, Al, Zn, Mg-5Mn, Mg-30Gd, and Mg-20Ca. The impurity content in the pure metal raw materials is no more than 0.05%, and the impurity content in the master alloy raw materials is no more than 0.1%. The preparation method includes the following steps:

[0040] 1) Melting: Under the protection of RJ-5, add pure magnesium and heat to 770℃ to melt it; then add metal Al and metal Zn in sequence and continue to heat and melt at 770℃; after they are melted, blow argon into the melt to stir it uniformly, then add Mg-20Ca master alloy and Mg-30Gd master alloy; after they are melted, blow argon into the melt to stir it uniformly, then add Mg-5Mn under Ar gas stirring to fully melt and react in the alloy melt; adjust the melt temperature to 740℃, blow argon into it for refining for 8 minutes, then adjust the melt temperature to 720℃ and keep it warm for 10-30 minutes;

[0041] 2) Melt composition control and static treatment: Samples were taken from the melt, and the alloy composition was detected to be Mg-6.82Al-0.77Zn-0.17Mn-0.25Gd-0.92Ca (wt%), which was basically consistent with the target composition. The melt temperature was adjusted to 690°C and the melt was allowed to stand for 90 minutes to obtain the target alloy melt.

[0042] 3) Casting: Using a semi-continuous casting method, the uniformly smelted magnesium alloy melt is cast to obtain a cast alloy ingot with a diameter of 110 mm;

[0043] 4) Heat treatment: The alloy ingot obtained in step 3) was divided into billets with a height of 120 mm, and heat treated in a heat treatment furnace at a temperature of 420° C. for 36 hours, and then water-cooled to room temperature;

[0044] 5) High-speed extrusion processing: The heat-treated billet is cut into specifications with a diameter of 35 mm and a height of 110 mm, and the surface oxide scale is removed. Then, it is heated to 300°C and hot extruded. The extrusion head movement speed is 15 m / min, the extrusion ratio is 36, the extrusion temperature is 300°C, and the extrusion speed is 32.4 m / min. After hot extrusion, it is naturally cooled in air to obtain the high-speed extruded high-strength and toughness magnesium-aluminum-based alloy.

[0045] The surface of the alloy extruded sample is bright and crack-free, and its optical microstructure is as follows Figure 1 As shown in the figure, the alloy has undergone complete recrystallization, and its average grain size is about 7.72μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase and (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 248 MPa, 377 MPa and 15%, respectively.

[0046] Example 2:

[0047] A high-speed extrusion high-strength and tough magnesium-aluminum based alloy is provided. The alloy is a Mg-Al based magnesium alloy. The weight percentages of the components are: Al 4-10wt%, Zn 0.3-1.2wt%, Ca 0.3-1.3wt%, added elements 0.05-0.45wt%, Mn 0.15-0.45wt%, and the remainder is magnesium. The added elements are any one of La, Gd, Nd, Y, Sm, and Dy, or a combination of two or more thereof.

[0048] The target components of this embodiment are:

[0049] Mg-6.80Al-0.78Zn-0.16Mn-0.23Gd-0.90Ca (wt%);

[0050] The following raw materials are used according to the target composition: Mg, Al, Zn, anhydrous MnCl2, Mg-30Gd, and Mg-20Ca. The impurity content in the pure metal raw materials is not higher than 0.05%, and the impurity content in the anhydrous MnCl2 and master alloy raw materials is not higher than 0.1%. The preparation method includes the following steps:

[0051] 1) Melting: Under the protection of SF6 and CO2 mixed gas, add pure magnesium and heat to 760℃ to melt it; then add metal Al and metal Zn in sequence and continue to heat and melt at 760℃; after they are melted, mechanically stir for 3 minutes to make them uniform, then add Mg-20Ca master alloy and Mg-30Gd master alloy; after they are melted, mechanically stir for 3 minutes to make them uniform, then add anhydrous MnCl2 under Ar gas stirring to fully melt and react in the alloy melt; adjust the melt temperature to 740℃, add refining agent and refine for 8 minutes, then adjust the melt temperature to 710℃ and keep warm for 10-30 minutes;

[0052] 2) Melt composition control and static treatment: Samples were taken from the melt, and the alloy composition was detected to be Mg-6.85Al-0.78Zn-0.19Mn-0.25Gd-0.91Ca (wt%), which was basically consistent with the target composition. The melt temperature was adjusted to 695°C and the melt was allowed to stand for 90 minutes to obtain the target alloy melt.

[0053] 3) Casting: The uniformly smelted magnesium alloy melt is cast by gravity casting to obtain a cast alloy ingot with a diameter of 65 mm;

[0054] 4) Heat treatment: The alloy ingot obtained in step 3) was divided into billets with a height of 80 mm, and heat treated in a heat treatment furnace at a temperature of 420° C. for 24 hours, and then water-cooled to room temperature;

[0055] 5) High-speed extrusion processing: The heat-treated billet was cut into specifications of 59 mm in diameter and 70 mm in height, and the surface oxide scale was removed. The billet was then heated to 320°C and hot extruded at an extrusion head speed of 20 m / min, an extrusion ratio of 36, an extrusion temperature of 320°C, and an extrusion speed of 43.2 m / min. After hot extrusion, water mist was sprayed for forced cooling to obtain the high-speed extruded high-strength and toughness magnesium-aluminum-based alloy.

[0056] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 7.75μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase and (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 244 MPa, 372 MPa and 14%, respectively.

[0057] Example 3:

[0058] The target components of this embodiment are:

[0059] Mg-5.8Al-0.76Zn-0.16Mn-0.23Gd-0.7Ca (wt%);

[0060] The same preparation process as in Example 2 was used to prepare a high-speed extrusion sample whose actual composition (Mg-5.84Al-0.77Zn-0.17Mn-0.24Gd-0.69Ca, wt %) was substantially consistent with the target composition.

[0061] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 7.9μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase and (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 241 MPa, 363 MPa and 14%, respectively.

[0062] Example 4:

[0063] The target components of this embodiment are:

[0064] Mg-4.8Al-0.48Zn-0.3Mn-0.23Gd-0.6Ca (wt%);

[0065] The same preparation process as in Example 2 was used to prepare a high-speed extrusion sample whose actual composition (Mg-4.82Al-0.50Zn-0.29Mn-0.21Gd-0.59Ca, wt %) was substantially consistent with the target composition.

[0066] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 7.95μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase and (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 238 MPa, 361 MPa and 13%, respectively.

[0067] Example 5:

[0068] The target components of this embodiment are:

[0069] Mg-4.8Al-0.48Zn-0.3Mn-0.23Gd-0.6Ca (wt%):

[0070] The same preparation process as in Example 2 was used to prepare a high-speed extrusion sample whose actual composition (Mg-4.82Al-0.50Zn-0.29Mn-0.21Gd-0.59Ca, wt %) was substantially consistent with the target composition.

[0071] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 8.3μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase and (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 233 MPa, 358 MPa and 14%, respectively.

[0072] Example 6:

[0073] The target components of this embodiment are:

[0074] Mg-7.5Al-0.38Zn-0.3Mn-0.34Gd-0.66Ca (wt%);

[0075] The same preparation process as in Example 2 was used to prepare a high-speed extrusion sample whose actual composition (Mg-7.4Al-0.36Zn-0.32Mn-0.33Gd-0.67Ca, wt %) was substantially consistent with the target composition.

[0076] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 5.2μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase with (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 254 MPa, 390 MPa and 15%, respectively.

[0077] Example 7:

[0078] The target components of this embodiment are:

[0079] Mg-8.5Al-0.98Zn-0.3Mn-0.34Gd-1.16Ca (wt%);

[0080] The same preparation process as in Example 2 was used to prepare a high-speed extrusion sample whose actual composition (Mg-8.6Al-0.97Zn-0.31Mn-0.33Gd-1.18Ca, wt %) was substantially consistent with the target composition.

[0081] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 6.8μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase and (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 261MPa, 415MPa and 13%, respectively.

[0082] Example 8:

[0083] The target components of this embodiment are:

[0084] Mg-7.7Al-0.9Zn-0.3Mn-0.3La-0.6Ca (wt%);

[0085] The same preparation process as in Example 1 was adopted, except that the Mg-30Gd master alloy was replaced with Mg-30La master alloy to prepare a high-speed extrusion sample having an actual composition (Mg-7.72Al-0.89Zn-0.31Mn-0.29La-0.58Ca, wt%) that was substantially consistent with the target composition.

[0086] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 7.1μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4La, Al-La phase, and submicron-sized Al8Mn4La phase with (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 247 MPa, 375 MPa and 15%, respectively.

[0087] Example 9:

[0088] The target components of this embodiment are:

[0089] Mg-7.7Al-0.9Zn-0.3Mn-0.3La-0.6Ca (wt%);

[0090] The same preparation process as in Example 2 was adopted, except that the Mg-30Gd master alloy was replaced with a Mg-30La master alloy, to prepare a high-speed extrusion sample having an actual composition (Mg-7.71Al-0.89Zn-0.32Mn-0.31La-0.61Ca, wt %) substantially consistent with the target composition.

[0091] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 7.3μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4La, Al-La phase, and submicron-sized Al8Mn4La phase with (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 245MPa, 373MPa and 13%, respectively.

[0092] Example 10:

[0093] The target components of this embodiment are:

[0094] Mg-7.2Al-0.82Zn-0.3Mn-0.3Sm-0.75Ca (wt%);

[0095] The same preparation process as in Example 1 was adopted, except that the Mg-30Gd master alloy was replaced with the Mg-30Sm master alloy to prepare a high-speed extrusion sample having an actual composition (Mg-7.19Al-0.81Zn-0.31Mn-0.31Sm-0.77Ca, wt %) that was substantially consistent with the target composition.

[0096] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 9.31μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Sm, Al-Sm phase, and submicron-sized Al8Mn4Sm phase with (Mg, Zn) 17 Al 12 Phase. The room temperature tensile test measured the alloy yield strength, tensile strength and elongation to be 246MPa, 386MPa and 17% respectively. Its optical microstructure is as follows Figure 2 Its tensile stress-strain curve is shown as Figure 3 shown.

[0097] Example 11:

[0098] The target components of this embodiment are:

[0099] Mg-7.2Al-0.82Zn-0.3Mn-0.3Sm-0.75Ca (wt%);

[0100] The same preparation process as in Example 2 was adopted, except that the Mg-30Gd master alloy was replaced with a Mg-30Sm master alloy, to prepare a high-speed extrusion sample having an actual composition (Mg-7.21Al-0.81Zn-0.30Mn-0.30Sm-0.74Ca, wt %) substantially consistent with the target composition.

[0101] The surface of the extruded sample of the alloy is bright and crack-free. The alloy has undergone complete recrystallization, and its average grain size is about 6.5μm. The second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Sm, Al-Sm phase, and submicron-sized Al8Mn4Sm phase with (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 234 MPa, 377 MPa and 17%, respectively.

[0102] Example 12:

[0103] The target components of this embodiment are:

[0104] Mg-7.2Al-0.82Zn-0.3Mn-0.3Y-0.75Ca (wt%);

[0105] The same preparation process as in Example 1 was adopted, except that the Mg-30Gd master alloy was replaced with Mg-30Y master alloy to prepare a high-speed extrusion sample having an actual composition (Mg-7.19Al-0.83Zn-0.29Mn-0.31Y-0.76Ca, wt %) that was substantially consistent with the target composition.

[0106] The surface of the extruded sample of the alloy is bright and crack-free, and the alloy has undergone complete recrystallization. The room temperature tensile test shows that the alloy's yield strength, tensile strength and elongation are 239MPa, 415MPa and 15% respectively.

[0107] Example 13:

[0108] The target components of this embodiment are:

[0109] Mg-7.2Al-0.82Zn-0.3Mn-0.3Nd-0.75Ca (wt%);

[0110] The same preparation process as in Example 1 was adopted, except that the Mg-30Gd master alloy was replaced with Mg-30Nd master alloy to prepare a high-speed extrusion sample having an actual composition (Mg-7.21Al-0.81Zn-0.31Mn-0.31Nd-0.74Ca, wt%) that was substantially consistent with the target composition.

[0111] The surface of the extruded sample of the alloy is bright and crack-free, and the alloy has undergone complete recrystallization. The room temperature tensile test measured the alloy's yield strength, tensile strength and elongation to be 251MPa, 387MPa and 15% respectively. Its tensile stress-strain curve is shown in Figure 4 shown.

[0112] Example 14:

[0113] The target components of this embodiment are:

[0114] Mg-7.2Al-0.82Zn-0.3Mn-0.3Nd-0.75Ca (wt%);

[0115] The same preparation process as in Example 2 was adopted, except that the Mg-30Gd master alloy was replaced with Mg-30Nd master alloy to prepare a high-speed extrusion sample having an actual composition (Mg-7.21Al-0.81Zn-0.31Mn-0.31Nd-0.74Ca, wt%) that was substantially consistent with the target composition.

[0116] The surface of the extruded sample of the alloy is bright and crack-free, and the alloy has undergone complete recrystallization. The room temperature tensile test shows that the alloy's yield strength, tensile strength and elongation are 253MPa, 367MPa and 17% respectively.

[0117] Example 15:

[0118] The target components of this embodiment are:

[0119] Mg-7.2Al-0.82Zn-0.3Mn-0.3Dy-0.75Ca (wt%);

[0120] The same preparation process as in Example 1 was adopted, except that the Mg-30Gd master alloy was replaced with a Mg-30Dy master alloy to prepare a high-speed extrusion sample having an actual composition (Mg-7.19Al-0.83Zn-0.28Mn-0.28Dy-0.73Ca, wt %) substantially consistent with the target composition.

[0121] The surface of the extruded sample of the alloy is bright and crack-free, and the alloy has undergone complete recrystallization. The room temperature tensile test shows that the alloy's yield strength, tensile strength and elongation are 243MPa, 381MPa and 17% respectively.

[0122] Example 16:

[0123] The target ingredients of this embodiment are:

[0124] Mg-7.2Al-0.82Zn-0.3Mn-0.3Dy-0.75Ca (wt%);

[0125] The same preparation process as in Example 2 was adopted, except that the Mg-30Gd master alloy was replaced with Mg-30Dy master alloy to prepare a high-speed extrusion sample having an actual composition (Mg-7.18Al-0.81Zn-0.31Mn-0.31Dy-0.76Ca, wt %) that was substantially consistent with the target composition.

[0126] The surface of the extruded sample of the alloy is bright and crack-free, and the alloy has undergone complete recrystallization. The room temperature tensile test shows that the alloy's yield strength, tensile strength and elongation are 239MPa, 379MPa and 15% respectively.

[0127] Example 17:

[0128] The target components of this embodiment are:

[0129] Mg-7.2Al-0.82Zn-0.3Mn-0.15Nd-0.1Y-0.75Ca (wt%);

[0130] The same preparation process as in Example 1 was adopted, except that the Mg-30Gd master alloy was replaced with Mg-30Nd master alloy and Mg-30Y master alloy to prepare high-speed extrusion samples whose actual composition (Mg-7.23Al-0.80Zn-0.30Mn-0.16Nd-0.12Y-0.73Ca, wt %) was basically consistent with the target composition.

[0131] The surface of the extruded sample of the alloy is bright and crack-free, and the alloy has undergone complete recrystallization. The room temperature tensile test shows that the alloy's yield strength, tensile strength and elongation are 255MPa, 397MPa and 17% respectively.

[0132] Example 18:

[0133] The target components of this embodiment are:

[0134] Mg-7.2Al-0.82Zn-0.3Mn-0.3Nd-0.2La-0.75Ca (wt%);

[0135] Using the same preparation process as Example 2, but replacing the Mg-30Gd master alloy with Mg-30Nd and Mg-30La master alloys, high-speed extrusion samples were prepared with an actual composition (Mg-7.17Al-0.84Zn-0.28Mn-0.28Nd-0.18La-0.77Ca, wt%) substantially consistent with the target composition. The extruded samples exhibited a bright, crack-free surface, demonstrating complete recrystallization. Room-temperature tensile testing revealed yield strength, tensile strength, and elongation of 263 MPa, 399 MPa, and 14%, respectively.

[0136] Example 19:

[0137] A high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion is disclosed. The alloy is a Mg-Al-based magnesium alloy, and its components by weight are: Al4-10wt%, Zn0.3-1.2wt%, Ca0.3-1.3wt%, added elements 0.05-0.45wt%, Ag0.001-0.2wt%, Mn0.15-0.45wt%, and the remainder is magnesium. The added elements are any one of La, Gd, Nd, Y, Sm, and Dy, or a combination of two or more thereof.

[0138] The target components of this embodiment are:

[0139] Mg-6.80Al-0.78Zn-0.16Mn-0.23Gd-0.90Ca-0.05Ag (wt%), using the following raw materials according to the target composition: Mg, Al, Zn, Mg-5Mn, Mg-30Gd, Mg-20Ca, Mg-20Ag, wherein the impurity content in the pure metal raw materials is not higher than 0.05%, and the impurity content in the master alloy raw materials is not higher than 0.1%. The preparation method includes the following steps:

[0140] 1) Melting: Under the protection of RJ-5, add pure magnesium and heat to 770℃ to melt it; then add metal Al and metal Zn in sequence and continue to heat and melt at 770℃; after they are melted, blow argon into the melt to stir it uniformly, then add Mg-20Ca master alloy, Mg-20Ag master alloy, and Mg-30Gd master alloy; after they are melted, blow argon into it to stir it uniformly, and then add Mg-5Mn under Ar gas stirring to allow it to fully react and dissolve in the alloy melt; adjust the melt temperature to 740℃, blow argon into it to refine for 8 minutes, then adjust the melt temperature to 720℃ and keep it warm for 10-30 minutes;

[0141] 2) Melt composition control and static treatment: Samples were taken from the melt, and the alloy composition was detected to be Mg-6.82Al-0.77Zn-0.17Mn-0.25Gd-0.92Ca-0.051Ag (wt%), which was basically consistent with the target composition. The melt temperature was adjusted to 690°C and the melt was allowed to stand for 90 minutes to obtain the target alloy melt.

[0142] 3) Casting: Using a semi-continuous casting method, the uniformly smelted magnesium alloy melt is cast to obtain a cast alloy ingot with a diameter of 110 mm;

[0143] 4) Heat treatment: The alloy ingot obtained in step 3) was divided into billets with a height of 120 mm, and heat treated in a heat treatment furnace at a temperature of 420° C. for 36 hours, and then water-cooled to room temperature;

[0144] 5) High-speed extrusion processing: The heat-treated billet is cut into specifications with a diameter of 35 mm and a height of 110 mm, and the surface oxide scale is removed. Then, it is heated to 300°C and hot extruded. The extrusion head movement speed is 15 m / min, the extrusion ratio is 36, the extrusion temperature is 300°C, and the extrusion speed is 32.4 m / min. After hot extrusion, it is naturally cooled in air to obtain the high-speed extruded high-strength and toughness magnesium-aluminum-based alloy.

[0145] The surface of the alloy extruded sample is bright and crack-free, and its optical microstructure is as follows Figure 1 As shown in the figure, the alloy has undergone complete recrystallization, and its average grain size is about 5.42μm. The Ag element is dissolved in the matrix, and the second phase in the alloy includes micron-sized Al2Ca, Al8Mn4Gd, Al-Gd phase, and submicron-sized Al8Mn4Gd phase with (Mg, Zn) 17 Al 12 The room temperature tensile test showed that the yield strength, tensile strength and elongation of the alloy were 278 MPa, 397 MPa and 19%, respectively.

[0146] Comparative Example 1:

[0147] The extrusion ram was set at a speed of 1.5 mm / min. The billet composition and other conditions were identical to those in Example 1. Extrusion experiments were conducted at a corresponding extrusion speed of 3.24 m / min. The resulting low-speed extruded alloy had a bright surface. Room-temperature tensile tests revealed yield strength, tensile strength, and elongation of 253 MPa, 387 MPa, and 15%, respectively.

[0148] Comparative Example 2:

[0149] The extrusion ram was set at a speed of 1.5 mm / min. The billet composition and other conditions were identical to those in Example 8. An extrusion experiment was conducted at a corresponding extrusion speed of 3.24 m / min. The resulting low-speed extruded alloy had a bright surface. Room-temperature tensile testing revealed yield strength, tensile strength, and elongation of 252 MPa, 379 MPa, and 14%, respectively.

[0150] Comparative Example 3:

[0151] Commercial AZ80 alloy was used, and the indenter moving speed was set to 4.5 mm / s. Other solution treatment and extrusion conditions were the same as those in Example 1. Extrusion processing was performed at an extrusion speed of 9.72 m / min, and the extruded sample cracked.

[0152] Comparative Example 4:

[0153] The raw materials selected were Mg, Al, Zn, Mg-5Mn, Mg-30Y, and Mg-20Ca. The same casting and heat treatment methods as in Example 1 were used to prepare a Mg-7.71Al-0.92Zn-0.28Mn-0.51Y-0.62Ca alloy. The pressure head movement speed was set to 4.5 mm / s, and the other extrusion conditions were the same as in Example 1. Extrusion processing was performed, and the corresponding extrusion speed was 9.72 m / min. The extruded sample cracked.

[0154] Comparative Example 5:

[0155] The raw materials selected were Mg, Al, Zn, Mg-5Mn, Mg-30Y, and Mg-20Ca. The same casting and heat treatment methods as in Example 1 were adopted to prepare Mg-9Al-0.8Zn-0.3Mn-0.9Ca-0.6Y alloy. The pressing head moving speed was set to 4.5 mm / s. The other extrusion conditions were the same as in Example 1. Extrusion processing was carried out, and the corresponding extrusion speed was 9.72 m / min. The extruded sample cracked.

[0156] Comparative Example 6:

[0157] The raw materials selected were Mg, Al, Zn, mixed rare earth (RE) containing 75wt% Ce and 25wt% La, Mg-5Mn, Mg-30Y, and Mg-20Ca, and the same casting and heat treatment methods as in Example 1 were adopted to prepare Mg-7.7Al-0.9Zn-0.3Mn-0.5Y-0.5RE-0.9Ca alloy; the pressing head moving speed was set to 4.5mm / s, and the other extrusion conditions were the same as in Example 1, and extrusion processing was carried out, the corresponding extrusion speed was 9.72m / mi, and the extruded sample cracked.

[0158] By comparison, it can be seen that the alloy of the present invention uses fewer rare earth elements but can give the alloy better high-speed extrusion processing performance, which is a more significant innovation.

[0159] The parts of the present invention that are not described in detail are prior art. It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure marks in the claims should not be regarded as limiting the claims involved.

Claims

1. A high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion, the alloy being a Mg-Al-based magnesium alloy, characterized in that: The mass percentages of its components are: Al4-10wt%, Zn0.3-1.2wt%, Ca0.3-1.3wt%, added elements 0.05-0.45%wt%, Mn0.15-0.45%wt, and the rest is magnesium. The added elements are any one of La, Gd, Nd, Y, Sm, and Dy, or a combination of two or more thereof.

2. The method for preparing the high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 1, characterized in that: The following steps are involved: 1) Melting: Under the protection of protective gas or covering agent, add pure magnesium and heat to 700-800℃ to melt it; then add metal Al and metal Zn in sequence. After they are melted, stir them mechanically or blow argon to make them uniform. Then add Mg-Ca master alloy, pure metal corresponding to the added element, or its corresponding magnesium-based master alloy; after they are melted, stir them mechanically or blow argon to make them uniform. Then, add alloying raw materials containing Mn under Ar gas stirring to make them fully melt and react in the alloy melt; adjust the melt temperature to between 680-760℃, perform refining and slag removal, then adjust the melt temperature to 680-730℃ and keep it warm for 10-30 minutes; 2) Melt composition control and static treatment: Samples are taken from the melt, the alloy composition is tested, and the melt is controlled based on the test results. After the alloy composition reaches the target composition range, the melt temperature is adjusted to 670-720°C and the melt is allowed to stand for 20-120 minutes to obtain the target alloy melt; 3) Casting: Using sand casting, metal mold casting or semi-continuous casting, the uniformly smelted magnesium alloy melt is cast to obtain a cast alloy ingot; 4) Heat treatment: The alloy ingot obtained in step 3) is heat treated in a heat treatment furnace at a temperature of 380-450° C. for 5-36 hours, and then cooled to room temperature by air cooling or water cooling; 5) High-speed extrusion processing: The heat-treated billet is cut into corresponding specifications and the surface oxide scale is removed. It is then heated to the extrusion temperature and placed in a deformation die for hot extrusion processing. The extrusion deformation speed is 10 to 45 m / min, the extrusion ratio is 5 to 100, and the extrusion temperature is 250 to 430°C. The hot-deformed billet is directly cooled to room temperature to obtain the high-speed extruded high-strength and toughness magnesium-aluminum-based alloy.

3. The method for preparing a high-strength and high-toughness magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 2, wherein: The protective gas in step 1) can be: a mixed gas of Ar+SF6, a mixed gas of SF6+CO2, or a mixed gas of Ar+SF6+CO2.

4. The method for preparing a high-strength and high-toughness magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 2, wherein: The covering agent in step 1) can be RJ-5 or RJ-2.

5. The method for preparing a high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 2, wherein: The Mg-Ca master alloy in step 1) is a Mg-20Ca master alloy, and the alloying raw material containing Mn is a Mg-Mn master alloy, or an Al-Mn master alloy, or anhydrous MnCl2.

6. The method for preparing a high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 2, wherein: The refining in step 1) can be refining by adding a refining agent or refining by blowing argon gas, or a combination thereof.

7. The method for preparing a high-strength and high-toughness magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 2, wherein: The mold in step 5) is a mold for forming plates, bars, pipes, wires, or profiles.

8. The method for preparing a high-strength and high-toughness magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 2, wherein: The cooling after the deformation process in step 5) can be natural cooling in the air, forced cooling by spraying water mist, or forced cooling by blowing air.

9. The high-strength and tough magnesium-aluminum-based alloy capable of high-speed extrusion according to claim 1, characterized in that: Its components also contain Ag 0.001-0.2wt%.

10. The method for preparing a high-strength and high-toughness magnesium-aluminum-based alloy capable of high-speed extrusion according to any one of claims 2 to 8, characterized in that: In step 1), when the Mg-Ca master alloy is added, the Mg-Ag master alloy is added at the same time.

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