High-strength and high-toughness magnesium alloy and preparation method thereof

Abstract

The present invention relates to the technical field of magnesium alloys, and in particular to a high-strength and high-toughness magnesium alloy and a preparation method thereof. The magnesium alloy comprises, by mass percentage, 2% to 12% of gadolinium, 0.5% to 6% of silver, 0.5% to 3% of manganese, 8% to 15% of aluminum, 0.5% to 3% of thallium, and 0.5% to 3% of tantalum, with the remainder being magnesium and inevitable impurities. The magnesium alloy matrix is formed by adding silver, aluminum, a magnesium-gadolinium master alloy, and a magnesium-manganese master alloy to molten magnesium, followed by melting, and then thalum and tantalum are added in combination to design and manufacture a magnesium alloy system of Mg-Gd-Ag-Mn-Al-Ti-Ta. The addition amounts of different metals are reasonably adjusted to adjust the microcrystalline structure of the alloy and improve the mechanical properties. The manufactured magnesium alloy has high tensile strength, high yield strength, and high elongation, i.e., high strength and high toughness.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloys, and in particular to a high-strength and high-toughness magnesium alloy and a preparation method thereof. Background Art

[0002] Magnesium alloy is the lightest metal structural material currently in industrial production, and its density is usually between 1.75 and 1.95 g·cm -3 It is far lower than other metal structural materials. Magnesium alloys have good specific strength and specific stiffness, good electromagnetic shielding performance and good processing and reprocessing performance. They have great development prospects in aerospace, future automobiles, high-altitude buildings, etc., and have positive significance for ensuring strength requirements, reducing weight and reducing energy consumption.

[0003] At present, a variety of magnesium alloys with high strength have been developed. However, the high modulus magnesium alloy materials that have been developed still generally have disadvantages such as low strength, low elongation, and poor toughness, which greatly hinder the expansion of the application of high modulus magnesium alloys in the field of science and technology. Rare earth elements have a special extranuclear electron configuration and can play a unique role in the field of materials and metallurgy research. Doping magnesium alloys with rare earth elements can produce high-strength magnesium alloys with strengths that can reach or exceed the strength of other metals. However, their elongation is generally low, usually less than 5%, and it is difficult to achieve both strength and toughness. These characteristics seriously restrict their development. At the same time, improving the elastic modulus and toughness of magnesium alloys is a difficult problem that magnesium alloys need to overcome. In order to meet the high-end requirements of the science and technology industry for the mechanical properties of magnesium alloys, the development and application of high modulus magnesium alloy materials that take into account both strength and toughness has become increasingly urgent.

[0004] Therefore, it is of great significance to rationally configure the proportions of different metals, rationally select rare earth elements, use metals that can refine grains, increase the bonding properties between metals, and increase ductility to dope magnesium metal, and melt and cast them together to prepare a magnesium alloy with both high strength and high toughness. Summary of the Invention

[0005] The object of the present invention is to provide a high-strength and high-toughness magnesium alloy and a preparation method thereof. The prepared magnesium alloy has high tensile strength, large yield strength, and large elongation, that is, high strength and high toughness.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A high-strength and high-toughness magnesium alloy comprising the following elements, calculated by mass percentage: gadolinium: 2% to 12%, silver: 0.5% to 6%, manganese: 0.5% to 3%, aluminum: 8% to 15%, thallium: 0.5% to 3%, tantalum: 0.5% to 3%, and the remainder being magnesium and unavoidable impurities;

[0008] A method for preparing a high-strength and high-toughness magnesium alloy comprises the following steps:

[0009] Step 1: Take a metal or alloy raw material, grind off the oxide layer on the surface of the material, and cut it into small pieces, which are respectively recorded as magnesium block, silver block, aluminum block, thallium block, tantalum block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block; wherein the relative mass ratio of magnesium element in the magnesium block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block is magnesium block: magnesium-gadolinium master alloy block: magnesium-manganese master alloy block = 90:2-8:2-5;

[0010] Step 2: Place the weighed magnesium block into a crucible, heat it to 660-700°C under an argon atmosphere, and keep it warm for 1-2 hours to completely melt the metal magnesium block. Then, add the weighed silver block, aluminum block, magnesium-gadolinium master alloy block, magnesium-manganese master alloy block, thallium block, and tantalum block into the crucible in sequence, heat it to 700-800°C, stir it intermittently, and remove the slag. After it is completely melted, continue to maintain the temperature unchanged, keep it warm for 15-30 minutes, cast it into a mold, and cool it at room temperature to form an ingot.

[0011] Step 3: The ingot is subjected to heat solution treatment at 400-450°C for 5-7 hours, heated to 480-550°C, the extrusion ratio is set to 20:1-25:1, the extrusion speed is 2-4 mm / s, and extruded into a magnesium alloy rod. The rod is cooled to room temperature under a nitrogen atmosphere to obtain a high-strength and high-toughness magnesium alloy.

[0012] Further optimization is carried out, in the process of preparing magnesium alloy, silver, aluminum, thallium and tantalum are added in the form of pure metal during use, and the purity of metallic silver, metallic aluminum, metallic thallium and metallic tantalum is 99.99% or above; the gadolinium and manganese elements are added in the form of intermediate alloys during the preparation of magnesium alloy, namely magnesium-gadolinium intermediate alloy and magnesium-manganese intermediate alloy, and the remaining magnesium element is added in the form of pure metallic magnesium, and the purity of the magnesium block is 99.99% or above.

[0013] After further optimization, the gadolinium content in the magnesium-gadolinium master alloy is 10% to 40%.

[0014] After further optimization, the manganese content in the magnesium-manganese master alloy is 3% to 8%.

[0015] Further optimization, in step one, the surface oxide layer of the material is polished and cut into small pieces. Specifically, in a nitrogen atmosphere, a laser rust remover or sandpaper is used to remove the 1 to 50 μm thick oxide layer on the surface of the material. Then, in a nitrogen atmosphere, the raw material is cut into small pieces with a size of 5×5×5mm to 15×15×15mm.

[0016] Further optimization: in step 2, argon protection is used throughout the entire melting and casting process. After casting, argon protection is not required during the cooling process at room temperature.

[0017] For further optimization, in step 2, before casting, the mold used for casting needs to be preheated at 400-450°C.

[0018] Beneficial effects of the present invention:

[0019] 1. Adding metallic silver, metallic aluminum, magnesium-gadolinium master alloy, and magnesium-manganese master alloy to molten metallic magnesium and melting them to form a magnesium alloy matrix. Then, adding metallic thallium and metallic tantalum to the molten magnesium alloy matrix, a magnesium alloy system of Mg-Gd-Ag-Mn-Al-Ti-Ta is designed and manufactured. The amounts of different metal additions are rationally adjusted to adjust the microcrystalline structure of the alloy and improve the mechanical properties to manufacture a high-strength, high-toughness magnesium alloy. In addition, the use of magnesium-gadolinium master alloy and magnesium-manganese master alloy results in a master alloy with a melting point much lower than that of pure gadolinium and pure manganese, thereby reducing the melting temperature required for doping with gadolinium and manganese elements, making the entire preparation process more energy-efficient, simple, and efficient.

[0020] 2. Master alloys composed primarily of magnesium and gadolinium exhibit high strength; master alloys composed primarily of magnesium and manganese exhibit high strength, hardness, and good toughness. The magnesium-gadolinium and magnesium-manganese master alloys are melt-recast and then co-cast with magnesium, aluminum, and silver to form alloys characterized by high strength and toughness. The use of magnesium and aluminum provides a uniformly distributed foundation for the magnesium-gadolinium and magnesium-manganese master alloys. Furthermore, the use of aluminum increases the elastic modulus of the alloys, and the use of silver enhances the aging-strengthening effect of the magnesium-gadolinium and magnesium-manganese master alloys, ultimately further enhancing the strength of the magnesium alloy.

[0021] 3. Thallium is soft and tantalum is ductile. When used in the manufacture of magnesium alloys, it is evenly distributed in the matrix and has the effect of refining grains. Thallium also has the effect of solid solution strengthening, which inhibits the growth of recrystallized grains, making the grains uniform and the structure stable, which is beneficial to the microalloying of magnesium alloys and enhances the strength and toughness of magnesium alloys. Tantalum has good compatibility and adhesion with other metals, which helps the various components in the magnesium alloy to form a uniform and stable whole, and plays a role in volume expansion in magnesium alloys. In addition, the use of tantalum, due to its good toughness, helps the lubrication performance between the microcrystalline structure of magnesium alloys and improves the toughness of magnesium alloys.

[0022] 4. When preparing magnesium alloys, the purity of the pure metal used is 99.99% or above, and the impact of impurities in the raw materials on the performance of the magnesium alloy is minimized as much as possible. The use of gadolinium and manganese as additives, and the use of finished magnesium-gadolinium master alloys and magnesium-manganese master alloys, reduce the high melting temperature requirement of pure metallic gadolinium and pure metallic manganese. This allows the gadolinium and manganese elements to be doped into the magnesium alloy at a relatively low temperature during the preparation of the magnesium alloy, making the preparation process more efficient, simple, and energy-saving.

[0023] 5. In a nitrogen atmosphere, the raw materials are polished to remove the oxide layer on the surface of the metal or alloy to avoid the introduction of impurities from the oxide layer into the magnesium alloy preparation process. The raw materials are cut into small pieces in a nitrogen atmosphere to ensure that the small pieces are not oxidized by oxygen in the air. At the same time, the smaller volume is conducive to the melting of metal blocks or alloy blocks, which is conducive to energy saving in the actual operation of preparing magnesium alloys.

[0024] 6. Argon is used for protection during the melting and casting process to prevent oxygen in the air from entering the molten metal, avoid the formation of metal oxides, and avoid the formation of impurities in the magnesium alloy, thereby ensuring the purity and mechanical properties of the magnesium alloy. During the hot solution treatment process, nitrogen is used for protection. While achieving the purpose of protecting the magnesium alloy, cheaper nitrogen replaces argon, further reducing manufacturing costs. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] A high-strength and high-toughness magnesium alloy comprising the following elements, calculated by mass percentage: 2% gadolinium, 0.5% silver, 0.5% manganese, 8% aluminum, 0.5% thallium, 0.5% tantalum, and the remainder being magnesium and unavoidable impurities.

[0028] Silver, aluminum, thallium, and tantalum are added in the form of pure metals during the preparation of the magnesium alloy, and the purity of the metallic silver, metallic aluminum, metallic thallium, and metallic tantalum is 99.99%. The gadolinium and manganese elements are added in the form of master alloys during the preparation of the magnesium alloy, namely magnesium-gadolinium master alloy and magnesium-manganese master alloy, respectively. The remaining magnesium element is added in the form of pure metallic magnesium, and the purity of the magnesium block is 99.99%.

[0029] The gadolinium content in the magnesium-gadolinium master alloy is 10%; the manganese content in the magnesium-manganese master alloy is 3%;

[0030] A method for preparing a high-strength and high-toughness magnesium alloy comprises the following steps:

[0031] Step 1: Take a metal or alloy raw material, polish the surface oxide layer of the material, and cut it into small pieces. Specifically, in a nitrogen atmosphere, use a laser rust remover or sandpaper to remove the 1 μm thick oxide layer on the surface of the material. Then, in a nitrogen atmosphere, cut the raw material into small pieces with a size of 5×5×5 mm; record them as magnesium block, silver block, aluminum block, thallium block, tantalum block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block respectively; the relative mass ratio of magnesium element in the magnesium block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block is magnesium block:magnesium-gadolinium master alloy block:magnesium-manganese master alloy block = 90:2:2;

[0032] Step 2: Place the weighed magnesium block into a crucible, and under the protection of an argon atmosphere, heat it to 660°C and keep it warm for 1 hour to completely melt the metal magnesium block. Then, add the weighed silver block, aluminum block, magnesium-gadolinium master alloy block, magnesium-manganese master alloy block, thallium block, and tantalum block into the crucible in sequence, heat it to 700°C, stir it intermittently, and remove the slag. After it is completely melted, continue to maintain the temperature unchanged, keep it warm for 15 minutes, cast it into a mold, and cool it at room temperature to form an ingot. During the entire melting and casting process, argon protection is used throughout. After casting, argon protection is not required during the cooling process at room temperature. Before casting, the casting mold needs to be preheated at 400°C.

[0033] Step 3: The ingot is subjected to heat solution treatment at 400°C for 5 hours, heated to 480°C, and extruded into a magnesium alloy rod with an extrusion ratio of 20:1:1 and an extrusion speed of 2 mm / s. The rod is cooled to room temperature under a nitrogen atmosphere to obtain a high-strength and high-toughness magnesium alloy.

[0034] Example 2

[0035] A high-strength and high-toughness magnesium alloy comprising the following elements, calculated by mass percentage: gadolinium: 12%, silver: 6%, manganese: 3%, aluminum: 15%, thallium: 3%, tantalum: 3%, and the remainder being magnesium and unavoidable impurities;

[0036] Silver, aluminum, thallium, and tantalum are added in the form of pure metals during the preparation of the magnesium alloy, and the purity of the metallic silver, metallic aluminum, metallic thallium, and metallic tantalum is 99.99%. The gadolinium and manganese elements are added in the form of master alloys during the preparation of the magnesium alloy, namely magnesium-gadolinium master alloy and magnesium-manganese master alloy, respectively. The remaining magnesium element is added in the form of pure metallic magnesium, and the purity of the magnesium block is 99.99%.

[0037] The gadolinium content in the magnesium-gadolinium master alloy is 40%; the manganese content in the magnesium-manganese master alloy is 8%;

[0038] A method for preparing a high-strength and high-toughness magnesium alloy comprises the following steps:

[0039] Step 1: Take a metal or alloy raw material, polish the surface oxide layer of the material, and cut it into small pieces. Specifically, in a nitrogen atmosphere, use a laser rust remover or sandpaper to remove the 50 μm thick oxide layer on the surface of the material. Then, in a nitrogen atmosphere, cut the raw material into small pieces with a size of 15×15×15 mm; record them as magnesium block, silver block, aluminum block, thallium block, tantalum block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block respectively; the relative mass ratio of magnesium element in the magnesium block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block is magnesium block:magnesium-gadolinium master alloy block:magnesium-manganese master alloy block = 90:8:5;

[0040] Step 2: Place the weighed magnesium block into a crucible, and under the protection of an argon atmosphere, heat it to 700°C and keep it warm for 2 hours to completely melt the metal magnesium block. Then, add the weighed silver block, aluminum block, magnesium-gadolinium master alloy block, magnesium-manganese master alloy block, thallium block, and tantalum block into the crucible in sequence, heat it to 800°C, stir it intermittently, and remove the slag. After it is completely melted, continue to maintain the temperature unchanged, keep it warm for 30 minutes, cast it into a mold, and cool it at room temperature to form an ingot. During the entire melting and casting process, argon protection is used throughout. After casting, argon protection is not required during the cooling process at room temperature. Before casting, the casting mold needs to be preheated at 450°C.

[0041] Step 3: The ingot is subjected to heat solution treatment at 450°C for 7 hours, heated to 550°C, and extruded into a magnesium alloy rod with an extrusion ratio of 20:25:1 and an extrusion speed of 4 mm / s. The rod is cooled to room temperature under a nitrogen atmosphere to obtain a high-strength and high-toughness magnesium alloy.

[0042] Example 3

[0043] A high-strength and high-toughness magnesium alloy comprising the following elements, calculated by mass percentage: gadolinium: 8%, silver: 3%, manganese: 2%, aluminum: 12%, thallium: 2%, tantalum: 2%, and the remainder being magnesium and unavoidable impurities;

[0044] Silver, aluminum, thallium, and tantalum are added in the form of pure metals during the preparation of the magnesium alloy, and the purity of the metallic silver, metallic aluminum, metallic thallium, and metallic tantalum is 99.99%. The gadolinium and manganese elements are added in the form of master alloys during the preparation of the magnesium alloy, namely magnesium-gadolinium master alloy and magnesium-manganese master alloy, respectively. The remaining magnesium element is added in the form of pure metallic magnesium, and the purity of the magnesium block is 99.99%.

[0045] The gadolinium content in the magnesium-gadolinium master alloy is 20%; the manganese content in the magnesium-manganese master alloy is 5%;

[0046] A method for preparing a high-strength and high-toughness magnesium alloy comprises the following steps:

[0047] Step 1: Take a metal or alloy raw material, grind off the surface oxide layer of the material, and cut it into small pieces. Specifically, in a nitrogen atmosphere, use a laser rust remover or sandpaper to remove the 20 μm thick oxide layer on the surface of the material. Then, in a nitrogen atmosphere, cut the raw material into small pieces with a size of 10×10×10 mm; record them as magnesium block, silver block, aluminum block, thallium block, tantalum block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block respectively; wherein the relative mass ratio of magnesium element in the magnesium block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block is magnesium block:magnesium-gadolinium master alloy block:magnesium-manganese master alloy block = 90:5:3;

[0048] Step 2: Place the weighed magnesium block into a crucible, and under the protection of an argon atmosphere, heat it to 680°C and keep it warm for 2 hours to completely melt the metal magnesium block. Then, weigh the silver block, aluminum block, magnesium-gadolinium master alloy block, magnesium-manganese master alloy block, thallium block, and tantalum block are added to the crucible in sequence, heated to 750°C, stirred intermittently, and slag removed. After complete melting, continue to maintain the temperature unchanged, keep warm for 20 minutes, cast it into a mold, and cool it at room temperature to form an ingot. During the entire melting and casting process, argon protection is used throughout. After casting, argon protection is not required during the cooling process at room temperature. Before casting, the mold used for casting needs to be preheated at 420°C.

[0049] Step 3: The ingot is subjected to heat solution treatment at 430°C for 6 hours, heated to 500°C, and extruded into a magnesium alloy rod with an extrusion ratio of 20:15:1 and an extrusion speed of 3 mm / s. The rod is cooled to room temperature under a nitrogen atmosphere to obtain a high-strength and high-toughness magnesium alloy.

[0050] Comparative Example 1: Compared with Example 1, no metal thallium and metal tantalum were added, and other conditions were the same;

[0051] Comparative Example 2: Commercially available magnesium alloy, model AZ91D;

[0052] Test: The magnesium alloys prepared in Examples 1 to 3 and the magnesium alloys in Comparative Example 1 and Comparative Example 2 were subjected to performance tests, and the results are shown in the table:

[0053] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Tensile strength (MPa) 410 440 430 350 253 Yield strength (MPa) 240 270 260 170 158 Elongation (%) 8 12 9 5 4

[0054] As shown in the above table, the magnesium alloy prepared by the method of the present invention has higher tensile strength, greater yield strength and greater elongation, indicating that it has high strength and high toughness.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-strength and high-toughness magnesium alloy, characterized in that: Calculated by mass percentage, it includes the following elements: gadolinium: 2% to 12%, silver: 0.5% to 6%, manganese: 0.5% to 3%, aluminum: 8% to 15%, thallium: 0.5% to 3%, tantalum: 0.5% to 3%, and the rest is magnesium and unavoidable impurities; A method for preparing a high-strength and high-toughness magnesium alloy comprises the following steps: Step 1: Take a metal or alloy raw material, grind off the oxide layer on the surface of the material, and cut it into small pieces, which are respectively recorded as magnesium block, silver block, aluminum block, thallium block, tantalum block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block; wherein the relative mass ratio of magnesium element in the magnesium block, magnesium-gadolinium master alloy block, and magnesium-manganese master alloy block is magnesium block: magnesium-gadolinium master alloy block: magnesium-manganese master alloy block = 90:2-8:2-5; Step 2: Place the weighed magnesium block into a crucible, heat it to 660-700°C under the protection of an argon atmosphere, and keep it warm for 1-2 hours to completely melt the metal magnesium block. Then, add the weighed silver block, aluminum block, magnesium-gadolinium master alloy block, magnesium-manganese master alloy block, thallium block, and tantalum block into the crucible in sequence, heat it to 700-800°C, stir it intermittently, and remove the slag. After it is completely melted, continue to maintain the temperature unchanged, keep it warm for 15-30 minutes, cast it into a mold, and cool it at room temperature to form an ingot. Step 3: The ingot is subjected to heat solution treatment at 400-450°C for 5-7 hours, heated to 480-550°C, the extrusion ratio is set to 20:1-25:1, the extrusion speed is 2-4 mm / s, and extruded into a magnesium alloy rod. The rod is cooled to room temperature under a nitrogen atmosphere to obtain a high-strength and high-toughness magnesium alloy.

2. The high-strength and high-toughness magnesium alloy according to claim 1, characterized in that: The silver, aluminum, thallium and tantalum elements are added in the form of pure metals during use in the process of preparing the magnesium alloy, and the purity of the metallic silver, metallic aluminum, metallic thallium and metallic tantalum is 99.99% or above; the gadolinium and manganese elements are added in the form of master alloys during the preparation of the magnesium alloy, namely magnesium-gadolinium master alloy and magnesium-manganese master alloy, respectively. The remaining magnesium element is added in the form of pure metallic magnesium, and the purity of the magnesium block is 99.99% or above.

3. The high-strength and high-toughness magnesium alloy according to claim 1, characterized in that: The gadolinium content in the magnesium-gadolinium master alloy is 10% to 40%.

4. The high-strength and high-toughness magnesium alloy according to claim 1, characterized in that: The manganese content in the magnesium-manganese master alloy is 3% to 8%.

5. The high-strength and high-toughness magnesium alloy according to claim 1, characterized in that: In step one, the surface oxide layer of the material is polished and cut into small pieces. Specifically, in a nitrogen atmosphere, a laser rust remover or sandpaper is used to remove the 1 to 50 μm thick oxide layer on the surface of the material. Then, in a nitrogen atmosphere, the raw material is cut into small pieces with a size of 5×5×5mm to 15×15×15mm.

6. The high-strength and high-toughness magnesium alloy according to claim 1, characterized in that: In the step 2, argon protection is used throughout the entire melting and casting process. After casting, argon protection is not required during the cooling process at room temperature.

7. The high-strength and high-toughness magnesium alloy according to claim 1, characterized in that: In the step 2, before casting, the mold used for casting needs to be preheated at 400-450°C.