CN110468317B - Magnesium alloy with excellent room temperature plasticity and preparation method thereof - Google Patents
Magnesium alloy with excellent room temperature plasticity and preparation method thereof Download PDFInfo
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Abstract
The invention provides a magnesium alloy with excellent room temperature plasticity, which is characterized in that the magnesium alloy is Mg-Bi-Gd-Mn magnesium alloy, and the magnesium alloy comprises the following components in percentage by weight: 1-3% of Bi, 1.5-4% of Gd, more than or equal to 1.5% of Gd, 0.05-0.15% of Mn and the balance of Mg, wherein the content ratio of Bi/Gd is 0.25-2. The elongation of the alloy at room temperature can reach more than 40 percent, the alloy shows excellent room temperature plasticity, and is a potential magnesium alloy material which can be further processed by room temperature plastic processing or superplastic forming technology; in addition, the alloy exhibits excellent flame retardant properties during casting and heat treatment.
Description
Technical Field
The invention relates to the field of metal materials and metal material processing, in particular to a magnesium alloy with excellent room temperature plasticity and a preparation method thereof.
Background
Energy, materials and information are three major pillars of human society development. With the increasing consumption of resources such as iron ore and the like and the increasing severity of the situation of energy conservation and emission reduction, the development and utilization of magnesium-based materials with rich resources are inevitable. In the metallic material, the magnesium density is about 1.74g/cm32/3 made of aluminum alloy and 1/4 made of steel, the magnesium alloy has a series of advantages of small density, high specific strength and specific stiffness, good electromagnetic shielding effect, good damping and shock absorption performance, easy recycling and the like, is known as a green metal engineering material in twenty-first century, and has wide application prospect in the fields of aerospace, weaponry, electronic communication, transportation and the like. But the reasons of lower absolute strength, poor corrosion resistance, poor room temperature forming capability and the like greatly limit the use of magnesium and the alloy thereof as novel greenApplication of color material.
In the aspect of developing high-room-temperature plastic magnesium alloy, because the crystal structures of magnesium and most of magnesium alloy are hexagonal close-packed, the magnesium and most of magnesium alloy mainly have basal plane slippage under the condition of low temperature (less than 220 ℃), the slippage system causes poor plasticity, and fiber texture or plate texture is easy to form in the extrusion or rolling process, so that the further plastic deformation capability of the alloy is poor. The cylindrical surface sliding system and the conical surface sliding system can be started only at a higher temperature, so that the plasticity of the magnesium alloy is improved. However, too high temperature of magnesium often causes coarsening of magnesium alloy grains, deteriorates the mechanical properties (strength) of the alloy, and increases the processing cost of the alloy. The development of the magnesium alloy with excellent plasticity at room temperature or lower temperature is beneficial to realizing the plastic processing of the magnesium alloy at low temperature or even room temperature, improving the product performance and quality, simultaneously reducing the production energy consumption and other costs, and greatly promoting the wide application of the magnesium and the magnesium alloy as a novel green material in the fields of automobiles, rail transit, aviation and the like. Therefore, the development of the magnesium alloy with high room temperature plasticity has important significance for further improving the strength of the magnesium alloy through low-temperature plastic deformation and further expanding the application field of the magnesium alloy.
In recent years, with the increasing demand for lightweight transportation vehicles, a great deal of research has been conducted to prepare high-room-temperature plastic magnesium alloys by various methods, and some high-room-temperature plastic magnesium alloys are developed at home and abroad.
Patent document 1 (publication No. CN102061414A) discloses a high-plasticity magnesium alloy and a method for producing the same, which comprises the following components: al: 0.5-2%, Mn: 2%, Ca: 0.02-0.1 percent, and the balance of magnesium, and the elongation at room temperature can reach 25 percent. The alloy has low cost, but the elongation is still low.
Patent document 2 (publication No. CN101381831A) discloses a high-plasticity magnesium alloy in which the proportions of magnesium, zinc, and zirconium are 80 to 83%, 12 to 15%, and 2 to 8%, respectively, and 23 to 27% by mass of Li, 7 to 9% by mass of manganese, and 4 to 6% by mass of yttrium. The alloy with the room temperature elongation of 42-49 is prepared by smelting, heat treatment and extrusion. However, the alloy contains a large amount of Li, and the smelting process needs to be firstly vacuumized or protected by introducing argon, and the oxygen content needs to be strictly controlled. On the other hand, the alloy contains a large amount of Y rare earth elements and Li, which causes the increase of the alloy cost.
Patent document 3 (publication No. CN102925771A) discloses a high room temperature plasticity magnesium alloy material and a preparation method thereof: according to the mass percentage, Li1.0-5.0%, Al2.5-3.5%, Zn0.7-1.3%, Mn0.2-0.5%, impurity less than or equal to 0.3%, and the balance of magnesium. The alloy is prepared by smelting the pure lithium and AZ31 magnesium alloy in the formula under the conditions of vacuumizing and introducing inert gas, and the elongation of the obtained alloy at room temperature is between 14 and 31 percent. The alloy smelting process is complex, and the whole room temperature elongation is still low.
The related inventions of the prior related high room temperature plasticity have low room temperature plasticity, so that the requirements of industries such as consumer electronics and automobiles on low cost, easy processing and high performance of the high-strength magnesium alloy are better met, the magnesium alloy material with excellent room temperature plasticity is urgently required to be developed by applying a simple production and processing process, the further popularization and application of the magnesium alloy in the future are greatly expanded, and the invention has great economic and social significance.
Disclosure of Invention
The invention aims to provide a magnesium alloy with excellent room temperature plasticity and excellent flame retardant property and a preparation method thereof, aiming at the main problem of low room temperature plasticity of the existing magnesium alloy. The alloy is Mg-Bi-Gd-Mn alloy, in the alloy system, the wrought magnesium alloy with excellent room-temperature plasticity can be obtained by using an extremely simple processing means, the room-temperature elongation of the wrought magnesium alloy reaches more than 50%, and the wrought magnesium alloy has excellent flame retardant property.
In one aspect of the invention, the magnesium alloy with excellent room temperature plasticity is provided, and the magnesium alloy is Mg-Bi-Gd-Mn magnesium alloy, and comprises the following components in percentage by weight: 1-3% of Bi, 1.5-4% of Gd, more than or equal to 1.5% of Gd, 0.05-0.15% of Mn and the balance of Mg, wherein the content ratio of Bi/Gd is 0.25-2.
In another aspect of the present invention, there is provided a method for preparing a magnesium alloy having excellent room temperature plasticity, the method comprising the steps of:
1) preparing materials: taking a pure Mg ingot, a pure Bi block, a Mg-Gd intermediate alloy and a Mg-Mn intermediate alloy as raw materials, and mixing the raw materials according to the weight percentage of each component of the magnesium alloy;
2) smelting: setting the furnace temperature to 700-730 ℃, putting the preheated pure Mg ingot into a crucible of a smelting furnace when the furnace temperature is raised to the set temperature, and respectively adding the preheated pure Bi blocks and the preheated Mg-Gd intermediate alloy into the magnesium melt after the pure Mg ingot is molten; then, raising the smelting temperature to 750-760 ℃, preserving heat for 5-15 minutes, stirring for 3-10 minutes, standing for 3-10 minutes, adding an Mg-Mn intermediate alloy, preserving heat for 5-15 minutes, stirring for 3-10 minutes, reducing the furnace temperature to 740-750 ℃, standing for 3-10 minutes, and introducing argon for 1-3 minutes to carry out refining degassing treatment; standing for 3-10 minutes;
3) casting: casting the smelted magnesium alloy melt into a corresponding mould to prepare as-cast magnesium alloy;
4) and (3) heat treatment: carrying out solution heat treatment on the as-cast magnesium alloy obtained in the step 3), wherein the heat treatment temperature is 470-510 ℃, and the time is 7-12 hours;
5) cutting the cast ingot subjected to the solution treatment in the step 4) into corresponding blanks and peeling;
6) and (3) extrusion processing: heating the blank obtained in the step 5) to a required extrusion temperature within 30 minutes, putting the blank into an extrusion cylinder, and carrying out extrusion deformation processing, wherein the extrusion deformation speed is 0.1-20 m/min, the extrusion ratio is 10-40, and the extrusion temperature is 270-450 ℃, and finally obtaining the Mg-Bi-Gd-Mn wrought magnesium alloy.
Preferably, according to the preparation method of the high-toughness cast magnesium alloy, the Mg-Gd intermediate alloy is Mg-30Gd intermediate alloy;
preferably, according to the preparation method of the high-toughness cast magnesium alloy, the Mg-Mn intermediate alloy is Mg-5Mn intermediate alloy.
Preferably, according to the preparation method of the high-toughness cast magnesium alloy, the composition of the CO2/SF6 mixed gas is preferably in a volume ratio of CO2 to SF6 to 100 to 1.
Preferably, according to the preparation method of the high-toughness cast magnesium alloy, in the step 2), the preheating temperature of the pure Mg ingot is 200-300 ℃, the preheating temperature of the pure Bi block is 50-70 ℃, and the preheating temperature of the Mg-Gd intermediate alloy is 200-300 ℃.
Preferably, according to the preparation method of the high-toughness cast magnesium alloy, the smelting process in the step 2) is in CO2/SF6Under the protection of mixed gas.
Preferably, according to the method for preparing the high-toughness cast magnesium alloy of the present invention, the heat treatment of step 4) further comprises: quenching with warm water at 40-80 ℃.
Preferably, according to the preparation method of the high-toughness cast magnesium alloy, the whole heat treatment process of the step 4) does not need gas protection.
Preferably, according to the preparation method of the high-toughness cast magnesium alloy, the casting process in the step 3) does not need gas protection.
Compared with the prior art, the invention has the following beneficial effects:
1) the magnesium alloy of the invention takes Bi and GD elements as main alloying elements, is matched with a small amount of Mn element, and generates BiGd phase and Mg in situ in the casting processing process by simple alloying means3Bi2The two compete for growth and inhibit excessive growth of each other; the two second phases are dispersed and distributed on the substrate after the part which is not dissolved into the substrate in the extrusion process is crushed into micron-sized particles, a large amount of phase interfaces are provided, the dynamic recrystallization is promoted, and simultaneously, the two second phases and the dynamically precipitated nano-scale Mg which is dispersed and uniformly distributed in the thermal deformation process are dispersed and distributed3Bi2The phase coaction effectively pins the crystal boundary, hinders the movement of dislocation, and inhibits the growth of recrystallized grains, so that the deformed alloy has a uniform and fine complete recrystallization structure; on the other hand, Bi element and Gd element partially dissolved into the matrix can change the axial ratio of alpha-Mg phase in the alloy, thereby more slip systems are excited in extrusion processing, weak non-basal plane texture is formed in the alloy, and the generation of strong basal plane texture is avoided. The effects of grain and second phase refinement, texture optimization and the like are combined, so that room-temperature superplasticity deformation is developed in the alloy seriesThe magnesium alloy has a tensile elongation of 43% or more at room temperature (25 ℃).
2) The alloy of the invention has excellent flame retardant property, does not need protective gas in the casting stage and the heat treatment stage, ensures the stability of the alloy production process, reduces the processing cost and avoids the combustion problem in the alloy use process.
3) Mg in the alloy of the invention3Bi2The phase (melting point 823 ℃) and the BiGd phase have higher melting points, so that the alloy can be subjected to hot working deformation at higher temperature, thereby reducing the resistance to thermal deformation and improving the processing or production efficiency.
4) The magnesium alloy has simple preparation process, breaks through the limitation that fine grains are obtained by special processing modes such as large plastic deformation and the like required by most of high-room-temperature plastic magnesium alloys to improve the plasticity, can be continuously processed and produced by the existing magnesium alloy extrusion equipment without additional improvement, and has low requirement on production equipment.
Drawings
Fig. 1 is a microstructure of a magnesium alloy parallel to an extrusion direction according to example 1 of the present invention.
FIG. 2 is a microstructure of a magnesium alloy parallel to an extrusion direction according to example 2 of the present invention
Fig. 3 is a microstructure of a magnesium alloy parallel to an extrusion direction according to example 3 of the present invention.
Detailed Description
The present invention will be further described with reference to the following specific examples and drawings, wherein the following examples are all implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific procedures are provided, but the scope of the present invention is not limited to the following examples.
The room temperature plasticity of magnesium alloys is closely related to the grain size, grain uniformity, type, size, quantity, distribution of the second phase in the alloy, and the texture type of the alloy. High plasticity magnesium alloys require control and uniform fine grain structure, typically achieved by dynamic recrystallization during hot deformation. In the hot working process of extrusion and the like, the coarse second phase can be crushed and refined and is dispersed in the magnesium alloy matrix, so that the mechanical property of the alloy is further improved. If the growth of the dynamically recrystallized grains is suppressed, fine grains are easily obtained. And the second phase with better thermal stability can promote dynamic recrystallization nucleation in the extrusion process and inhibit the growth of recrystallized grains. The extruded magnesium alloy often has stronger basal plane texture, so that the room temperature plasticity of the alloy is reduced, and the texture of the alloy can be optimized to excite the alloy to activate more sliding systems under external force, so that the plastic deformation capacity of the alloy is improved.
The magnesium alloy of the invention takes Bi and GD as main alloying elements, the magnesium alloy is Mg-Bi-Gd-Mn magnesium alloy, and the components thereof by weight percentage (wt%) are as follows: 1-3% of Bi, 1.5-4% of Gd, more than or equal to 1.5% of Gd, 0.05-0.15% of Mn and the balance of Mg, wherein the content ratio of Bi/Gd is 0.25-2.
In the invention, Mg, Bi, GD and Mn in the alloy melt undergo complex physical and chemical reactions under the conditions of melt temperature and medium, a BiGd phase with high thermal stability is generated in situ in the solidification process, and part of Bi element and Mg in the alloy generate Mg3Bi2And (4) phase(s). The competitive growth of the two phases avoids Mg3Bi2The excessive growth of the phase, the second phase which is not dissolved into the matrix in the extrusion process can be broken into micron-sized particles and then dispersed and distributed on the matrix, a large number of phase interfaces are provided, the dynamic recrystallization is promoted, and simultaneously, the phase interfaces and the dynamically precipitated nano-scale dispersed and uniformly distributed Mg in the thermal deformation process are uniformly distributed3Bi2The phase coaction effectively pins the crystal boundary, hinders the movement of dislocation, and inhibits the growth of recrystallized grains, so that the deformed alloy has a uniform and fine complete recrystallization structure; the combined existence of Gd element, Bi element and Mn element changes the axial ratio of alpha-Mg in the alloy, thereby changing the deformation mechanism of the alloy in the process of force action (extrusion), forming weak non-basal texture in the alloy, avoiding the existence of strong fiber texture, and optimizing the texture of the extruded alloy.
Next, a method for preparing the magnesium alloy having excellent room temperature plasticity according to the present invention will be described.
1) Preparing materials: pure Mg ingot, pure Bi block, Mg-Gd intermediate alloy and Mg-Mn intermediate alloy are used as raw materials, and the raw materials are mixed according to the weight percentage of each component of the magnesium alloy, namely 1-3% of Bi, 1.5-4% of Gd, more than or equal to 1.5% of Gd, 0.05-0.15% of Mn and the balance of Mg (wherein the content ratio of Bi/Gd is 0.25-2).
2) Smelting: setting the furnace temperature to 700-730 ℃, putting the preheated pure Mg ingot into a crucible of a smelting furnace when the furnace temperature is raised to the set temperature, and respectively adding the preheated pure Bi blocks and the preheated Mg-Gd intermediate alloy into the magnesium melt after the pure Mg ingot is molten; then, raising the smelting temperature to 750-760 ℃, preserving heat for 5-15 minutes, stirring for 3-10 minutes, standing for 3-10 minutes, adding an Mg-Mn intermediate alloy, preserving heat for 5-15 minutes, stirring for 3-10 minutes, reducing the furnace temperature to 740-750 ℃, standing for 3-10 minutes, and introducing argon for 1-3 minutes to carry out refining degassing treatment; and standing for 3-10 minutes.
The alloy is relatively uniform and stable during smelting, and the melting point (271.3 ℃) of the main alloying element Bi is relatively low, so that the alloy melt is easily uniform; meanwhile, due to the combined existence of Gd element and Bi element in the magnesium alloy, good flame retardant effect is achieved, and the melt is relatively stable.
3) Casting: and casting the smelted magnesium alloy melt into a corresponding mould to prepare the as-cast magnesium alloy.
4) And (3) heat treatment: carrying out solution heat treatment on the as-cast magnesium alloy obtained in the step 3), wherein the temperature of the solution heat treatment is 470-510 ℃, and the time is 7-12 hours.
5) Cutting the cast ingot subjected to the solution treatment in the step 4) into corresponding blanks and peeling.
6) And (3) extrusion processing: heating the blank obtained in the step 5) to a required extrusion temperature within 30 minutes, putting the blank into an extrusion cylinder, and carrying out extrusion deformation processing, wherein the extrusion deformation speed is 0.1-20 m/min, the extrusion ratio is 10-40, and the extrusion temperature is 270-450 ℃, and finally obtaining the Mg-Bi-Gd-Mn wrought magnesium alloy.
After the alloy is subjected to solid solution and extrusion forming, the elongation at room temperature (25 ℃) is more than 40%.
The present invention will be described in detail below by taking three alloy components, Mg-2Bi-3Gd-0.06Mn (wt%) (alloy 1), Mg-1.5Bi-1.5Gd-0.08Mn (alloy 2), and Mg-1Bi-1.5Gd-0.05Mn (wt%) (alloy 3), as typical examples.
According to the technical scheme of the invention, pure Mg (99.8 wt%) ingot, pure Bi (99 wt%) block, Mg-30Gd (Gd element actual detection content is 30.03 wt%) intermediate alloy and Mg-5Mn (Mn actual detection content is 4.98 wt%) intermediate alloy are used as alloying raw materials, and the alloying raw materials are smelted to prepare the low-cost magnesium alloy ingot; the blank after the solid solution treatment and the peeling treatment is put into a box-type resistance furnace to be rapidly heated to the extrusion temperature of 300 ℃, then the magnesium alloy blank is deformed and processed into a bar by adopting the extrusion processing, the extrusion speed is 5m/min, the extrusion ratio is 36, and the bar is air-cooled after the extrusion. And mechanical property test is carried out on the extruded bar, and the room temperature mechanical property test results of the examples and the comparative example AZ31 are shown in Table 1.
Example 1
(1) The Mg-2Bi-3Gd-0.06Mn (wt%) alloy is designed and selected to be matched into the magnesium alloy, and the preparation method comprises the following steps:
1) preparing materials: taking pure Mg ingot, pure Bi block, Mg-30Gd intermediate alloy and Mg-5Mn intermediate alloy as raw materials, carrying out surface pretreatment (such as removing dirt, oxide skin and the like, the same as in the following embodiment), and then batching according to the target components;
2) smelting: setting the furnace temperature to 700-730 ℃ (for example 700 ℃), putting a pure Mg ingot preheated to 200 ℃ into a crucible of a smelting furnace when the furnace temperature is raised to a preset temperature, and respectively adding a pure Bi block preheated to 50 ℃ and an Mg-Gd intermediate alloy preheated to 200 ℃ into a magnesium melt after the pure Mg ingot is molten; then, raising the smelting temperature to 750-760 ℃ (for example, 750 ℃), preserving heat for 10 minutes, then stirring for 5 minutes, standing for 5 minutes, adding Mg-5Mn intermediate alloy, preserving heat for 10 minutes, then stirring for 5 minutes, reducing the furnace temperature to 740-750 ℃ (for example, 740 ℃), standing for 10 minutes, and introducing argon for 2 minutes for refining and degassing treatment; and standing for 10 minutes. The whole smelting process is carried out in CO2/SF6Under the protection of mixed gas.
3) Casting: casting the magnesium alloy melt after standing into a corresponding mould to prepare as-cast magnesium alloy; wherein the casting process does not require gas shielding.
4) Homogenizing: heating the alloy ingot obtained in the step 3) to 480 ℃ along with the furnace, preserving the heat for 12 hours at the temperature for homogenization treatment, and then putting the sample into warm water at the temperature of 50 ℃ for quenching treatment, wherein the temperature rise time in the heating process is 60 minutes; the whole heat treatment process does not need gas protection and can be carried out in the natural atmosphere of a hearth.
5) Machining: turning to remove the oxide layer on the surface of the alloy cast ingot obtained in the step 4), and processing the alloy cast ingot into a size suitable for extrusion processing;
6) and (3) extrusion processing: extruding the alloy obtained in the step 5) into a bar by using an extruder, wherein the extrusion process comprises the following main process parameters: the blank temperature is 300 ℃, the extrusion container temperature is 300 ℃, the die temperature is 300 ℃, the extrusion speed is 7m/min, the extrusion ratio is 36, the deformed blank is heated for 30 minutes to reach the required extrusion temperature of 300 ℃, and the extruded material is cooled in air cooling, so that the magnesium alloy material with excellent room temperature plasticity is obtained.
(2) Alloy performance test and microstructure analysis
A sample having a length of 85mm was cut out from the extruded magnesium alloy rod obtained by the production method of example 1, and processed into a round bar-shaped tensile sample having a diameter of 6mm and a gauge length of 35mm, and a tensile test was conducted at room temperature (25 ℃ C.) at a tensile rate of 1mm/min with the axial direction of the sample round bar being the same as the extrusion flow line direction of the material. The magnesium alloy of the present invention was found to have a tensile strength of 175.9MPa, a yield strength of 117.6MPa, and an elongation of 40.8% (Table 1). The magnesium alloy obtained in this example has a large room temperature elongation. FIG. 1 shows the microstructure parallel to the extrusion direction of the Mg-2Bi-3Gd-0.06Mn (wt%) magnesium alloy prepared in this example, and it can be seen from the phase diagram that the alloy is completely dynamically recrystallized during the extrusion process, and the second phase is dispersed in the matrix. This is also the reason why the alloy has an ultra high strength.
Example 2
(1) The preparation method comprises the following steps:
1) preparing materials: taking pure Mg ingot, pure Bi block, Mg-30Gd intermediate alloy and Mg-5Mn intermediate alloy as raw materials, performing surface pretreatment (such as removing dirt, oxide skin and the like), and mixing according to the target components;
2) smelting: setting the furnace temperature to 700-730 ℃ (for example 720 ℃), putting a pure Mg ingot preheated to 200 ℃ into a crucible of a smelting furnace when the furnace temperature is raised to a preset temperature, and respectively adding a pure Bi block preheated to 50 ℃ and an Mg-Gd intermediate alloy preheated to 200 ℃ into a magnesium melt after the pure Mg ingot is molten; then, raising the smelting temperature to 750-760 ℃ (for example 755 ℃), preserving heat for 10 minutes, then stirring for 5 minutes, standing for 5 minutes, adding Mg-5Mn intermediate alloy, preserving heat for 10 minutes, then stirring for 5 minutes, reducing the furnace temperature to 740-750 ℃ (for example 740 ℃), standing for 10 minutes, and introducing argon for 2 minutes for refining and degassing treatment; and standing for 10 minutes. The whole smelting process is carried out in CO2/SF6Under the protection of mixed gas;
3) casting: casting the magnesium alloy melt after standing into a corresponding mould to prepare as-cast magnesium alloy; the casting process does not need gas protection;
4) homogenizing: heating the alloy ingot obtained in the step 3) to 480 ℃ along with the furnace, preserving the heat for 12 hours at the temperature for homogenization treatment, and then putting the sample into warm water at the temperature of 50 ℃ for quenching treatment, wherein the temperature rise time in the heating process is 60 minutes; the whole heat treatment process does not need gas protection and can be carried out in the natural atmosphere of a hearth.
5) Machining: turning to remove the oxide layer on the surface of the alloy cast ingot obtained in the step 4), and processing the alloy cast ingot into a size suitable for extrusion processing;
6) and (3) extrusion processing: extruding the alloy obtained in the step 5) into a bar by using an extruder, wherein the extrusion process comprises the following main process parameters: the blank temperature is 300 ℃, the extrusion container temperature is 300 ℃, the die temperature is 300 ℃, the extrusion speed is 5m/min, the extrusion ratio is 36, the deformed blank is heated for 30 minutes to reach the required extrusion temperature of 300 ℃, and the extruded material is cooled in air cooling, so that the magnesium alloy material with excellent room temperature plasticity is obtained.
(2) Alloy performance test and microstructure analysis
A specimen having a length of 85mm was cut out from the extruded magnesium alloy rod obtained by the production method of example 2, and processed into a round bar-shaped tensile specimen having a diameter of 6mm and a gauge length of 35mm, and a tensile test was conducted at room temperature (25 ℃ C.) at a tensile rate of 1mm/min with the axial direction of the round bar specimen being the same as the extrusion flow line direction of the material. The magnesium alloy of the present invention was found to have a tensile strength of 169.4MPa, a yield strength of 113.2MPa, and an elongation of 42.5% (Table 1). The magnesium alloy obtained in this example has a large room temperature elongation. FIG. 2 is the microstructure morphology of the Mg-1.5Bi-1.5Gd-O.08Mn (wt%) magnesium alloy prepared in this example parallel to the extrusion direction, and it can be seen from the phase diagram that the alloy is completely dynamically recrystallized during the extrusion process, and the second phase is dispersed in the matrix.
Example 3
(1) The Mg-1Bi-1.5Gd-0.05Mn (wt%) alloy component is designed and selected to be matched into the magnesium alloy, and the preparation method comprises the following steps:
1) preparing materials: taking pure Mg ingot, pure Bi block, Mg-30Gd intermediate alloy and Mg-5Mn intermediate alloy as raw materials, performing surface pretreatment (such as removing dirt, oxide skin and the like), and mixing according to the target components;
2) smelting: setting the furnace temperature to 700-730 ℃ (for example 730 ℃), putting a pure Mg ingot preheated to 200 ℃ into a crucible of a smelting furnace when the furnace temperature is raised to a preset temperature, and respectively adding a pure Bi block preheated to 50 ℃ and an Mg-Gd intermediate alloy preheated to 200 ℃ into a magnesium melt after the pure Mg ingot is molten; then, raising the smelting temperature to 750-760 ℃ (760 ℃ for example), preserving heat for 10 minutes, stirring for 5 minutes, standing for 5 minutes, adding Mg-5Mn intermediate alloy, preserving heat for 10 minutes, stirring for 5 minutes, reducing the furnace temperature to 740-750 ℃ (750 ℃ for example), standing for 10 minutes, and introducing argon for 2 minutes for refining and degassing treatment; and standing for 10 minutes. The whole smelting process is carried out in CO2/SF6Under the protection of mixed gas;
3) casting: casting the magnesium alloy melt after standing into a corresponding mould to prepare as-cast magnesium alloy; gas protection is not needed in the casting process;
4) homogenizing: heating the alloy ingot obtained in the step 3) to 480 ℃ along with the furnace, preserving the heat for 12 hours at the temperature for homogenization treatment, and then putting the sample into warm water at the temperature of 50 ℃ for quenching treatment, wherein the temperature rise time is 60 minutes; the whole heat treatment process does not need gas protection and can be carried out in the natural atmosphere of a hearth.
5) Machining: turning to remove the oxide layer on the surface of the alloy cast ingot obtained in the step 4), and processing the alloy cast ingot into a size suitable for extrusion processing;
6) and (3) extrusion processing: extruding the alloy obtained in the step 5) into a bar by using an extruder, wherein the extrusion process comprises the following main process parameters: the blank temperature is 300 ℃, the extrusion container temperature is 300 ℃, the die temperature is 300 ℃, the extrusion speed is 7m/min, the extrusion ratio is 36, the deformed blank is heated for 30 minutes to reach the required extrusion temperature of 300 ℃, and the extruded material is cooled in air cooling, so that the magnesium alloy material with excellent room temperature plasticity is obtained.
(2) Alloy performance test and microstructure analysis
A sample of 85mm in length was cut out from the extruded magnesium alloy rod obtained by the production method according to example 3, processed into a round bar-shaped tensile sample of 6mm in diameter and 35mm in gauge length, and subjected to a tensile test at room temperature (25 ℃ C.) at a tensile rate of 1mm/min with the axial direction of the round bar of the sample being the same as the extrusion flow line direction of the material. The magnesium alloy of the present invention was found to have a tensile strength of 165.3MPa, a yield strength of 101.4MPa and an elongation of 43.4% (Table 1). The magnesium alloy obtained in this example has a large room temperature elongation. FIG. 3 is a microstructure of Mg-1Bi-1.5Gd-0.05Mn (wt%) magnesium alloy parallel to the extrusion direction prepared in this example, and it can be seen from the phase diagram that the alloy of this example undergoes complete dynamic recrystallization during extrusion and the second phase is dispersed in the matrix, similarly to the alloys of examples 1 and 2.
Comparative example
The comparative example is a current commercial extruded magnesium alloy: mg-2.8Al-0.9Zn-0.3Mn (wt%) AZ31 magnesium alloy. The comparative example (obtained under the same processing conditions as example 2) had a tensile strength of 223.7MPa, a yield strength of 203.5MPa, and an elongation of 20.2% (Table 1). The comparison shows that the room temperature elongation of the magnesium alloy is remarkably improved compared with that of the proportional alloy.
TABLE 1 results of mechanical properties at room temperature for examples and comparative examples
The raw materials and equipment used in the above examples are obtained by known means, and the procedures used are within the skill of those in the art. In addition, the respective numerical values given in the above preparation methods are merely examples, and the present invention is not limited thereto.
The magnesium alloy with excellent room temperature plasticity plays a good role in flame retardance due to the combined existence of Gd element and Bi element in the magnesium alloy, the melt is relatively stable, and the elongation of the alloy at room temperature (25 ℃) is more than 40% after solid solution and extrusion forming.
In addition, the magnesium alloy of the invention has excellent flame retardant property, and does not need protective gas in the casting stage and the heat treatment stage, thereby not only ensuring the stability of the alloy production process, reducing the processing cost, but also avoiding the combustion problem in the alloy use process.
In addition, the magnesium alloy has simple preparation process, breaks through the limitation that fine grains are obtained by special processing modes such as large plastic deformation and the like required by most of high-room-temperature plastic magnesium alloys to improve the plasticity, can be continuously processed and produced by the conventional magnesium alloy extrusion equipment without additional improvement, and has low requirement on production equipment
The high room temperature plasticity flame-retardant magnesium alloy has excellent room temperature plasticity and flame retardant property, has low economic cost and environmental cost in the processing process, can avoid hidden danger of combustion in the use process, and can be used as a part material of transportation, aerospace, computers, communication and consumer electronics products.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. A magnesium alloy having excellent room-temperature plasticity, characterized in that the magnesium alloy is a Mg-Bi-Gd-Mn magnesium alloy, the contents of Bi, Gd, and Mn in weight percent are 1%, 1.5%, and 0.05%, respectively, and the balance is Mg, the elongation of the magnesium alloy reaches 43.4%, and the magnesium alloy is produced by the steps of: 1) preparing materials; 2) smelting; 3) casting; 4) heat treatment; 5) cutting the cast ingot subjected to the solution treatment in the step 4) into corresponding blanks and peeling; 6) the extrusion processing is carried out on the mixture,
in the extrusion processing of the step 6), the blank obtained in the step 5) is heated to the required extrusion temperature within 30 minutes, and is placed into an extrusion cylinder for extrusion deformation processing, wherein the extrusion deformation speed is 0.1-20 m/min, the extrusion ratio is 10-40, and the extrusion temperature is 270-450 ℃, and finally the Mg-Bi-Gd-Mn wrought magnesium alloy is obtained.
2. A method for preparing a magnesium alloy having excellent room temperature plasticity, characterized by comprising the steps of:
1) preparing materials: taking a pure Mg ingot, a pure Bi block, a Mg-Gd intermediate alloy and a Mg-Mn intermediate alloy as raw materials, and mixing the raw materials according to the weight percentage of each component of the magnesium alloy in the claim 1;
2) smelting: setting the furnace temperature to 700-730 ℃, putting the preheated pure Mg ingot into a crucible of a smelting furnace when the furnace temperature is raised to the set temperature, and respectively adding the preheated pure Bi blocks and the preheated Mg-Gd intermediate alloy into the magnesium melt after the pure Mg ingot is molten; then, raising the smelting temperature to 750-760 ℃, preserving heat for 5-15 minutes, stirring for 3-10 minutes, standing for 3-10 minutes, adding an Mg-Mn intermediate alloy, preserving heat for 5-15 minutes, stirring for 3-10 minutes, reducing the furnace temperature to 740-750 ℃, standing for 3-10 minutes, and introducing argon for 1-3 minutes to carry out refining degassing treatment; standing for 3-10 minutes;
3) casting: casting the smelted magnesium alloy melt into a corresponding mould to prepare as-cast magnesium alloy;
4) and (3) heat treatment: carrying out solution heat treatment on the as-cast magnesium alloy obtained in the step 3), wherein the heat treatment temperature is 470-510 ℃, and the time is 7-12 hours;
5) cutting the cast ingot subjected to the solution treatment in the step 4) into corresponding blanks and peeling;
6) and (3) extrusion processing: heating the blank obtained in the step 5) to the required extrusion temperature within 30 minutes, putting the blank into an extrusion cylinder for extrusion deformation processing, wherein the extrusion deformation speed is 0.1-20 m/min, the extrusion ratio is 10-40, the extrusion temperature is 270-450 ℃, and finally obtaining the Mg-Bi-Gd-Mn wrought magnesium alloy,
wherein the elongation of the obtained Mg-Bi-Gd-Mn wrought magnesium alloy reaches 43.4 percent.
3. The method of claim 2, wherein the Mg-Gd intermediate alloy is a Mg-30Gd intermediate alloy.
4. The method for preparing magnesium alloy according to claim 2, wherein the Mg-Mn master alloy is Mg-5Mn master alloy.
5. The method for preparing a magnesium alloy according to claim 2, wherein in the step 2), the preheating temperature of the pure Mg ingot is 200 to 300 ℃, the preheating temperature of the pure Bi block is 50 to 70 ℃, and the preheating temperature of the Mg-Gd intermediate alloy is 200 to 300 ℃.
6. The method for preparing magnesium alloy according to claim 2, wherein the melting process in step 2) is performed in the presence of CO2/SF6Under the protection of mixed gas.
7.The method of claim 6, wherein the CO is2/SF6The volume ratio of the mixed gas is CO2∶SF6＝100∶1。
8. The method for preparing a magnesium alloy according to claim 2, wherein the heat treatment of step 4) further comprises: quenching with warm water at 40-80 ℃.
9. The method for preparing the magnesium alloy according to claim 2, wherein the whole heat treatment process of the step 4) does not need gas protection.
10. The method for preparing a magnesium alloy according to claim 2, wherein the step 3) of casting does not require gas protection.
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| WO2019017307A1 (en) * | 2017-07-18 | 2019-01-24 | 国立研究開発法人物質・材料研究機構 | Magnesium-based alloy wrought product and method for producing same |
| CN109371301A (en) * | 2018-12-04 | 2019-02-22 | 北京极泰冷锻科技有限公司 | A kind of room temperature high plastic magnesium alloy and preparation method thereof |
| CN109402429A (en) * | 2018-11-19 | 2019-03-01 | 河北工业大学 | A kind of high plastic magnesium alloy and preparation method thereof |
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| CN108220725A (en) * | 2018-04-09 | 2018-06-29 | 河北工业大学 | A kind of preparation method of high-performance magnesium-alloy bar |
| CN109402429A (en) * | 2018-11-19 | 2019-03-01 | 河北工业大学 | A kind of high plastic magnesium alloy and preparation method thereof |
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