CN109136704B - High-strength single-phase (alpha-phase) magnesium-lithium alloy material and preparation method thereof - Google Patents
High-strength single-phase (alpha-phase) magnesium-lithium alloy material and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-strength single-phase (alpha-phase) magnesium-lithium alloy material and a preparation method thereof, belonging to the field of metal structure materials, wherein the magnesium-lithium alloy material comprises the following components in percentage by weight: li: 0-5.7 wt%; rare earth elements: 6.0-9.0 wt%; co: 3.0 to 6.0wt%, the balance being Mg and unavoidable impurities. The preparation method comprises the steps of carrying out vacuum melting on preheated metal raw materials to obtain alloy liquid, and then casting the alloy liquid into a mould to be cooled to obtain cast magnesium-lithium alloy; homogenizing the obtained as-cast magnesium-lithium alloy; carrying out low-temperature rolling on the homogenized magnesium-lithium alloy; wherein the low-temperature rolling adopts cross accumulation pack rolling. The magnesium-lithium alloy material is prepared by reasonably selecting alloy elements and controlling the content and the proportion of the alloy elements through vacuum casting, homogenization treatment and low-temperature rolling, and has the advantages of high cleanness, high strength and high plasticity.
Description
Technical Field
The invention belongs to the field of metal structure materials, and particularly relates to a high-strength single-phase (alpha-phase) magnesium-lithium alloy material and a preparation method thereof.
Background
In recent years, with the increasing shortage of energy, the traditional manufacturing industry brings serious environmental problems, and more researchers have to put the eyes on metal structural members which can be lightened, can save energy and reduce emission. As the lightest metal structure material (density 1.4-1.6 g/cm)3) The Mg-Li alloy not only has high specific strength and specific rigidity, but also has high specific strength and specific rigidityThe damping and noise reduction electromagnetic shielding device has the characteristics of damping and noise reduction, electromagnetic shielding, high-energy particle penetration resistance and the like. In recent years, by virtue of unique performance advantages, the magnesium-lithium alloy has wide application prospects in the fields of aerospace, weaponry, electronics 3C and the like. However, the current widespread use of magnesium-lithium alloys is limited by the generally low absolute strength of commercially available magnesium-lithium alloys (e.g., LA141, LA91, LAZ931, etc.). Therefore, the development of the high-strength magnesium-lithium alloy has important application value.
According to a magnesium-lithium binary phase diagram, when the content of lithium is lower than 5.7wt%, the alloy has a single-phase alpha-Mg structure with a close-packed hexagonal structure; when the lithium content is continuously increased, a body-centered cubic structure beta-Li phase begins to appear, and the alloy presents a typical alpha + beta double-phase structure; when the lithium content exceeds 10.3 wt%, the alloy exhibits a β -Li single-phase structure. The alloy with the alpha-phase matrix has high strength but poor ductility and toughness. Compared with the alpha phase, the beta phase is a relative 'softening phase', has a bcc crystal structure and more slip systems, so that the alloy with the beta phase matrix has better plastic deformation processability but lower strength. The magnesium-lithium alloy researched at the present stage is generally an alloy added with alloy elements such as Al, Zn-reinforced Mg-Li-Al base, Mg-Li-Zn base or Mg-Li-Al-Zn base and the like. However, the strengthening effect of the magnesium-lithium alloy added with the elements Al and Zn is very limited, metastable strengthening phases MgLi2Al and MgLi2Zn are precipitated, and during the aging process (even natural aging at room temperature), MgLi2Al and MgLi2Zn are converted into stable aging softening phases AlLi and MgLiZn, so that over-aging is easy to occur, and the long-term mechanical property of the magnesium-lithium alloy is unstable. The rare earth is an effective strengthening element of the magnesium alloy, and researches show that the strength of the magnesium-lithium alloy is improved to a certain extent by adding light rare earth such as Y, La, Ce and the like. The rare earth Y is a heavy rare earth element, and has higher solid solubility (12%) in Mg alloy. Y and Mg are both in a close-packed hexagonal structure, the lattice constant and the atomic radius are both close to those of Mg, and Y can be used as a crystal core of Mg. Y may form an intermetallic compound such as Al2Y or Al3Y with Al in the alloy. The intermetallic compounds such as Al2Y or Al3Y have high melting points, are formed before the alloy is solidified in the smelting process, can prevent the growth of Mg matrix grains, and have the function of refining the grains. In addition, the carbon fibers are distributed in the alloy matrix and have certain dispersion strengthening effect on the alloy. Dong and the like research the influence of the added (0-7%) Y element on the microstructure and the mechanical property of the Mg-7Li alloy, and the result shows that the cast Mg-7Li-1Y alloy has the highest elongation (30%) and the cast Mg-7Li-3Y alloy has the best mechanical property, and the tensile strength, the yield strength and the elongation at break of the cast Mg-7Li-1Y alloy respectively reach 160MPa, 144MPa and 22%. When the Y content exceeds 3%, the strength of the alloy is no longer significantly increased and the plasticity is also reduced (Journal of Alloys and Compounds,2010,506(1): 468-. Therefore, the development of the ultra-light high-strength magnesium-lithium alloy with stable performance has very important value.
Disclosure of Invention
The invention aims to provide a high-strength single-phase (alpha phase) magnesium-lithium alloy material which has corrosion resistance, ultralow density and high strength, wherein the matrix of the alloy is in an alpha phase structure by reasonably selecting alloy elements and controlling the content and the proportion of the alloy elements, and meanwhile, a long period structure phase is introduced into a magnesium-lithium alloy matrix.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 0-5.7 wt%; rare earth elements: 6.0-9.0 wt%; co: 3.0-6.0wt%, the balance being Mg and unavoidable impurities; the content of inevitable impurities in the magnesium-lithium alloy material is less than or equal to 0.03 wt%. According to the invention, through reasonably selecting alloy elements and controlling the content and proportion of the alloy elements, the matrix of the alloy is a single-phase (alpha-phase) structure, and simultaneously, a long-period structure formed by the action of Mg, rare earth and Co elements is introduced into the magnesium-lithium alloy matrix, so that the obvious strengthening effect of the low-density and long-period structure phase of the single-phase (alpha-phase) structure is fully combined, and the ultra-light magnesium-lithium alloy material with ultra-low density, high strength and high plasticity is prepared, and is suitable for the requirements of light weight and high strength materials.
Preferably, the yield strength of the magnesium-lithium alloy material is 250-280MPa, the tensile strength is 300-340MPa, and the elongation is 12-16%.
Preferably, the density of the magnesium-lithium alloy material is 1.4-1.5g/cm-3。
Preferably, the rare earth element is a heavy rare earth element selected from Y, Gd, Dy, Er or Tb. The solid solubility of different rare earth elements in magnesium is different, the solid solubility of light rare earth elements in magnesium is very small or even zero, the solid solubility of heavy rare earth elements except Yb is relatively large, the beneficial effect of adding rare earth on magnesium alloy is most obvious, and the rare earth has the effects of refining organization, purifying melt, improving the room temperature and high temperature strength of alloy, improving the plasticity and corrosion resistance of alloy and the like.
Preferably, the weight ratio of the rare earth element to the Co element in the magnesium-lithium alloy material is 1: 0.5-0.8. The long period structure is formed by the action of Mg, rare earth and Co, the reasonable weight ratio of the rare earth element to the Co element in the magnesium-lithium alloy material can introduce the long period structure phase into the magnesium-lithium alloy alpha phase matrix to the maximum extent in the vacuum casting process, the strength of the magnesium-lithium alloy material can be improved even if the addition amount of the rare earth element is high, atomic substitution can also occur during solid solution, atomic positions in the alloy phase can also be mutually substituted, supersaturated solid solution can be obtained, fine particles are formed, the dispersion strengthening effect is achieved, the strength of the magnesium-lithium alloy material is improved, the engineering application of the magnesium-lithium alloy material alloy is greatly promoted, the distribution of the alloy elements can be ensured to be uniform, the burning loss of the Li element under the high-temperature smelting condition can be reduced, the high-clean magnesium-lithium alloy material is obtained, and in addition, the H, Co and the Li in the melt can be effectively purified, O, S, and can form intermetallic compound with harmful metals Fe, Ni, Cu, etc. in the melt to form high-density intermetallic compound, which has density higher than that of alloy melt and deposits on the bottom of the melt to reduce the content of impurity elements Fe, Ni, Cu, etc. in the alloy, thus achieving the purpose of removing impurities and improving the corrosion resistance of the alloy.
Preferably, the magnesium-lithium alloy material comprises the following components in percentage by weight: li: 0-5.7 wt%; y: 6.0-9.0 wt%; co: 3.0-6.0wt%, the balance being Mg and unavoidable impurities; wherein the content of inevitable impurities is less than or equal to 0.03 wt%.
The invention aims to provide a preparation method of a high-strength single-phase (alpha phase) magnesium-lithium alloy material, which can form a novel long-period stacking ordered structure and uniform and fine crystal grains in a magnesium-lithium alloy, promote the introduction of a long-period structural phase into an alpha phase matrix of the magnesium-lithium alloy, improve the strength of the magnesium-lithium alloy material, maintain the plasticity in a relatively stable range and obtain a high-purity magnesium-lithium alloy material.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a preparation method of a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following steps:
putting the magnesium ingot and the magnesium-cobalt alloy ingot into a melting furnace, keeping the temperature, preheating, introducing protective gas, then continuously heating to 750-780 ℃ under the protective atmosphere, adding the magnesium-rare earth intermediate alloy, adding the lithium rod after melting, stirring for 10-15min at the temperature after the lithium rod is melted, and finally casting and cooling to obtain cast magnesium-lithium alloy;
homogenizing the obtained cast magnesium-lithium alloy at the temperature of 220-250 ℃ for 8-10 h;
carrying out low-temperature rolling on the homogenized magnesium-lithium alloy;
wherein, the low-temperature rolling adopts cross accumulation pack rolling.
The preparation method of the invention can ensure the uniform distribution of the alloy elements and simultaneously reduce the burning loss of the Li element under the high-temperature smelting condition to obtain the high-cleanness magnesium-lithium alloy material, meanwhile, a novel long-period stacking ordered structure and uniform and fine grains can be formed in the magnesium-lithium alloy, the microstructure endows the alloy with ultrahigh mechanical property, wherein the novel long-period stacking ordered structure can effectively block dislocation motion of a matrix in the plastic deformation process of the material, improve the strength of the alloy and form uniform and fine grains, in the plastic deformation process, uniform and fine crystal grains are beneficial to the plastic deformation of the alloy, on one hand, the number of crystal boundaries is increased, the strength of the alloy is improved, and the preparation method can also maintain the plasticity in a relatively stable range under the condition of improving the strength of the alloy, and improve the application of the magnesium-lithium alloy.
Preferably, the vacuum melting is performed by electromagnetic induction heating with a frequency of 0.05-0.08 MHz. The electromagnetic induction of the frequency can quickly raise the temperature to the melting temperature, then solute atoms Li, Y, Co and Mg in the disordered solid solution are transited to a regular arrangement state occupying a certain position from a statistical random distribution state, an ordering process occurs, the ordered solid solution is formed, the solute atoms exist in the magnesium-lithium alloy in the form of a lamellar long-period structure inside crystal grains, namely, a novel long-period stacking ordered structure is formed in the magnesium-lithium alloy, the novel structure is favorable for the alloy strength and plasticity and simultaneously prolongs the service life of the magnesium-lithium alloy material, in addition, the electromagnetic induction of the frequency section is used for heating, the long-period structure phase can be promoted to be introduced into an alpha-phase matrix of the magnesium-lithium alloy, and the strength of the magnesium-lithium alloy material is improved.
Preferably, the homogenization treatment temperature is 220-250 ℃, and the heat preservation time is 8-10 h. The structure of the as-cast magnesium-lithium alloy after condensation is in a non-equilibrium state with different degrees, the defects of segregation in the crystal, shrinkage porosity, shrinkage cavity and the like mainly exist, the performance of the magnesium-lithium alloy is influenced, and when homogenization treatment is carried out, elements in the alloy are subjected to solid diffusion, so that the defects of the magnesium-lithium alloy can be eliminated or alleviated, the chemical components and the structure of the alloy are homogenized, and the performance of the magnesium-lithium alloy is improved.
Preferably, the low-temperature rolling step comprises: the first-pass rolling temperature is 352-358 ℃, the rotating speed of the roller is 10-12r/min, the reduction is 20-25%, and the air cooling is carried out after the heat preservation is 12-14 min; the rolling temperature of the second pass is 348-; the rolling temperature of the last pass is 352-358 ℃, the rotating speed of the roller is 16-18r/min, the reduction is 10-12%, and the air cooling is carried out after the heat preservation is 12-14 min. The low-temperature rolling is beneficial to forming uniform and fine grains in the magnesium-lithium alloy, and in the plastic deformation process, the uniform and fine grains are beneficial to the plastic deformation of the alloy on the one hand, the number of crystal boundaries is increased, and the strength of the magnesium-lithium alloy is improved on the other hand.
The invention has the beneficial effects that: 1) the magnesium-lithium alloy material has the advantages that through reasonable selection of alloy elements and control of the content and the proportion of the alloy elements, the matrix of the alloy is a single-phase (alpha-phase) structure, and meanwhile, a long-period structural phase is introduced into the magnesium-lithium alloy matrix, so that the magnesium-lithium alloy material has the performances of ultralow density, high strength and high plasticity, and is suitable for the material requirements of light weight, high strength and high toughness; 2) the reasonable weight ratio of the rare earth element to the Co element in the magnesium-lithium alloy material can introduce a long-period structure phase into a magnesium-lithium alloy alpha-phase matrix to the maximum extent in the vacuum casting process, so that the strength of the magnesium-lithium alloy material is improved, and in addition, impurities can be removed and the corrosion resistance of the alloy is improved; 3) the preparation method adopts the modes of vacuum casting, homogenization treatment and hot extrusion to form a novel long-period stacking ordered structure in the magnesium-lithium alloy, and the novel structure is beneficial to improving the strength and the plasticity of the alloy at the same time; 4) the preparation method adopts the electromagnetic induction of a specific frequency band to carry out vacuum melting, is beneficial to solute atoms to form ordered solid solution, exists in the magnesium-lithium alloy in the form of lamellar long-period structure inside crystal grains, and can promote the long-period structure phase to be introduced into the matrix of the alpha + beta phase of the magnesium-lithium alloy, thereby improving the strength of the magnesium-lithium alloy material.
The invention adopts the technical scheme to provide the high-strength single-phase (alpha-phase) magnesium-lithium alloy material and the preparation method thereof, which make up the defects of the prior art, and have reasonable design and convenient operation.
Drawings
FIG. 1 is a microstructure diagram of a rolled magnesium-lithium alloy according to example 1 of the present invention;
FIG. 2 is a graph of true stress-true strain for rolled Mg-Li alloys in accordance with example 1 of the present invention.
Detailed Description
As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.
The term "comprising" is intended to include embodiments encompassed by the term "consisting essentially of and" consisting of. Similarly, the term "consisting essentially of is intended to encompass embodiments encompassed by the term" consisting of.
When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is described, the described range should be construed as including ranges of "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. Where numerical ranges are described herein, unless otherwise stated, the stated ranges are intended to include the endpoints of the ranges and all integers and fractions within the ranges.
Exemplary embodiments that embody features and advantages of the invention are described in detail below. It is to be understood that the invention is capable of other and different embodiments and its several details are capable of modification without departing from the scope of the invention, and that the description is intended to be illustrative in nature and not to be construed as limiting the invention.
The application discloses a high-strength single-phase (alpha-phase) magnesium-lithium alloy material, which comprises the following components in percentage by weight: li: 0-5.7 wt%; rare earth elements: 6.0-9.0 wt%; co: 3.0-6.0wt%, the balance being Mg and unavoidable impurities; the content of inevitable impurities in the magnesium-lithium alloy material is less than or equal to 0.03 wt%. According to the invention, through reasonably selecting alloy elements and controlling the content and proportion of the alloy elements, the matrix of the alloy is a single-phase (alpha-phase) structure, and simultaneously, a long-period structure formed by the action of Mg, rare earth and Co elements is introduced into the magnesium-lithium alloy matrix, so that the obvious strengthening effect of the low-density and long-period structure phase of the single-phase (alpha-phase) structure is fully combined, and the ultra-light magnesium-lithium alloy material with ultra-low density, high strength and high plasticity is prepared, and is suitable for the requirements of light weight and high strength materials.
The yield strength of the magnesium-lithium alloy material is 250-280MPa, the tensile strength is 300-340MPa, and the elongation is 12-16%; the density of the magnesium-lithium alloy material is 1.4-1.5g/cm-3。
The rare earth element is heavy rare earth element selected from Dy, Y, Er, Tb or Gd. The solid solubility of different rare earth elements in magnesium is different, the solid solubility of light rare earth elements in magnesium is very small or even zero, the solid solubility of heavy rare earth elements except Yb is relatively large, the beneficial effect of adding rare earth on magnesium alloy is most obvious, and the rare earth has the effects of refining organization, purifying melt, improving the room temperature and high temperature strength of alloy, improving the plasticity and corrosion resistance of alloy and the like.
The weight ratio of the rare earth element to the Co element in the magnesium-lithium alloy material is 1: 0.5-0.8. The long period structure is formed by the action of Mg, rare earth and Co, the reasonable weight ratio of the rare earth element to the Co element in the magnesium-lithium alloy material can introduce the long period structure phase into the magnesium-lithium alloy alpha phase matrix to the maximum extent in the vacuum casting process, the strength of the magnesium-lithium alloy material can be improved even if the addition amount of the rare earth element is high, atomic substitution can also occur during solid solution, atomic positions in the alloy phase can also be mutually substituted, supersaturated solid solution can be obtained, fine particles are formed, the dispersion strengthening effect is achieved, the strength of the magnesium-lithium alloy material is improved, the engineering application of the magnesium-lithium alloy material alloy is greatly promoted, the distribution of the alloy elements can be ensured to be uniform, the burning loss of the Li element under the high-temperature smelting condition can be reduced, the high-clean magnesium-lithium alloy material is obtained, and in addition, the H, Co and the Li in the melt can be effectively purified, O, S, and can form intermetallic compound with harmful metals Fe, Ni, Cu, etc. in the melt to form high-density intermetallic compound, which has density higher than that of alloy melt and deposits on the bottom of the melt to reduce the content of impurity elements Fe, Ni, Cu, etc. in the alloy, thus achieving the purpose of removing impurities and improving the corrosion resistance of the alloy.
The magnesium-lithium alloy material comprises the following components in percentage by weight: li: 0-5.7 wt%; y: 6.0-9.0 wt%; co: 3.0-6.0wt%, the balance being Mg and unavoidable impurities; the content of inevitable impurities in the magnesium-lithium alloy material is less than or equal to 0.03 wt%.
The application also discloses a preparation method of the high-strength single-phase (alpha-phase) magnesium-lithium alloy material, which comprises the following steps,
1) weighing raw materials according to the mass ratio, putting a magnesium ingot and a magnesium-cobalt alloy ingot into a smelting furnace, heating the smelting furnace to 200 ℃, and preserving heat and preheating for 10-20 min; 2) then the temperature of the smelting furnace is raised to 300 ℃, and SF with the volume ratio of 1:99 is introduced6:CO2Mixing protective gas, introducing at a speed of 200cm3And/min, keeping the pressure in the furnace at 1 atmosphere, regulating and controlling by a vent valve, continuously heating to 750-780 ℃ in protective atmosphere, adding a magnesium-rare earth intermediate alloy, adding a lithium rod after the magnesium-rare earth intermediate alloy is melted, stirring for 10-15min at the temperature after the lithium rod is melted, and finally casting into a mold to be cooled to obtain the cast magnesium-lithium alloy. The vacuum melting adopts electromagnetic induction heating with the frequency of 0.05-0.08 MHz. The electromagnetic induction of the frequency can quickly raise the temperature to the melting temperature, then solute atoms Li, Y, Co and Mg in the disordered solid solution are transited to a regular arrangement state occupying a certain position from a statistical random distribution state to generate an ordering process to form the ordered solid solution, and the ordered solid solution exists in the magnesium-lithium alloy in a lamellar long-period structure form inside crystal grains, namely a novel long-period stacking ordered structure is formed in the magnesium-lithium alloy, the novel structure is favorable for the alloy strength and plasticity and simultaneously prolongs the service life of the magnesium-lithium alloy material;
2) homogenizing the obtained cast magnesium-lithium alloy at the temperature of 220-250 ℃ for 8-10 h. The structure of the as-cast magnesium-lithium alloy after condensation is in a non-equilibrium state with different degrees, the defects of segregation, shrinkage porosity, shrinkage cavity and the like in the crystal mainly exist, the performance of the magnesium-lithium alloy is influenced, and when homogenization treatment is carried out, elements in the alloy are subjected to solid diffusion, so that the defects of the magnesium-lithium alloy can be eliminated or alleviated, the chemical components and the structure of the alloy are homogenized, and the performance of the magnesium-lithium alloy is improved;
3) carrying out low-temperature rolling on the homogenized magnesium-lithium alloy; wherein the low-temperature rolling adopts cross accumulation pack rolling.
The low-temperature rolling comprises the following steps: the first-pass rolling temperature is 352-358 ℃, the rotating speed of the roller is 10-12r/min, the reduction is 20-25%, and the air cooling is carried out after the heat preservation is 12-14 min; the rolling temperature of the second pass is 348-; the rolling temperature of the last pass is 352-358 ℃, the rotating speed of the roller is 16-18r/min, the reduction is 10-12%, and the air cooling is carried out after the heat preservation is 12-14 min. The low-temperature rolling is beneficial to forming uniform and fine grains in the magnesium-lithium alloy, and in the plastic deformation process, the uniform and fine grains are beneficial to the plastic deformation of the alloy, on the one hand, the number of crystal boundaries is increased, and the strength of the magnesium-lithium alloy is improved.
The present invention is further described in detail with reference to the following examples:
example 1:
a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 5.7wt%, Y: 9.0wt%, Co: 6.0wt% and the balance of Mg and inevitable impurities, wherein the content of the inevitable impurities is less than or equal to 0.03 wt%.
A preparation method of a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following steps,
1) vacuum smelting the preheated metal raw material to obtain alloy liquid, heating the alloy liquid by adopting electromagnetic induction with the frequency of 0.065MHz, and then casting the alloy liquid into a mould to be cooled to obtain as-cast magnesium-lithium alloy;
2) homogenizing the obtained cast magnesium-lithium alloy at 240 ℃ for 9 h;
3) rolling the homogenized magnesium-lithium alloy at low temperature, wherein the first-pass rolling temperature is 355 ℃, the roller rotating speed is 11r/min, the reduction is 22.5%, and air cooling is carried out after heat preservation is carried out for 13 min; the rolling temperature of the second pass is 350 ℃, the rotating speed of the roller is 15r/min, the reduction is 16.5%, the temperature is kept for 4min, then air cooling is carried out, and the rolling is repeated for 4 passes; the final pass rolling temperature is 355 ℃, the roller rotating speed is 17r/min, the reduction is 11%, the magnesium-lithium alloy is obtained after heat preservation is carried out for 13min, the microstructure of the rolled magnesium-lithium alloy Mg-5.7Li-9Y-6Co is shown in figure 1, as can be seen from figure 1, the rolled magnesium-lithium alloy Mg-5.7Li-9Y-6Co contains a large amount of long-period stacking ordered structures, the true stress-true strain curve of the extruded magnesium-lithium alloy Mg-5.7Li-9Y-6Co is shown in figure 2, as can be seen from figure 2, the yield strength of the magnesium-lithium alloy material is 280MPa, the tensile strength is 340MPa, and the elongation is 12.7%; the density of the magnesium-lithium alloy material is 1.5g/cm-3。
Example 2:
a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 2.6 wt%; tb: 7.5 wt%; co: 4.5 wt%, and the balance of Mg and inevitable impurities, the content of the inevitable impurities being less than or equal to 0.03 wt%.
A preparation method of a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following steps,
1) vacuum smelting the preheated metal raw material to obtain alloy liquid, heating the alloy liquid by adopting electromagnetic induction with the frequency of 0.05MHz in the vacuum smelting, and then casting the alloy liquid into a mould to be cooled to obtain as-cast magnesium-lithium alloy;
2) homogenizing the obtained cast magnesium-lithium alloy for 8 hours at the temperature of 220 ℃;
3) rolling the homogenized magnesium-lithium alloy at low temperature, wherein the first-pass rolling temperature is 352 ℃, the roller rotating speed is 10r/min, the reduction is 20%, and air cooling is carried out after heat preservation is carried out for 12 min; the rolling temperature of the second pass is 348 ℃, the rotating speed of the roller is 14r/min, the reduction is 15%, the temperature is kept for 3min, then air cooling is carried out, and the rolling is repeated for 3 passes; and the rolling temperature of the last pass is 352 ℃, the rotating speed of the roller is 16r/min, the reduction is 10%, and the air cooling is carried out after the heat preservation is carried out for 12 min. The yield strength of the magnesium-lithium alloy material is 265MPa, the tensile strength is 334MPa, and the elongation is 14.8%; the density of the magnesium-lithium alloy material is 1.46g/cm-3。
Example 3:
a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 0.1 wt%; y: 6.0 wt%; co: 3.0 wt% and the balance of Mg and inevitable impurities, wherein the content of the inevitable impurities is less than or equal to 0.03 wt%.
A preparation method of a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following steps,
1) vacuum smelting the preheated metal raw material to obtain alloy liquid, heating the alloy liquid by adopting electromagnetic induction with the frequency of 0.08MHz in the vacuum smelting, and then casting the alloy liquid into a mould to be cooled to obtain as-cast magnesium-lithium alloy;
2) homogenizing the obtained cast magnesium-lithium alloy for 10 hours at the temperature of 250 ℃;
3) rolling the homogenized magnesium-lithium alloy at low temperature, wherein the first-pass rolling temperature is 358 ℃, the roller rotating speed is 12r/min, the reduction is 25%, and air cooling is carried out after heat preservation is carried out for 14 min; the rolling temperature of the second pass is 352 ℃, the rotating speed of the roller is 16r/min, the reduction is 18%, the temperature is kept for 5min, then air cooling is carried out, and the rolling is carried out for 5 passes repeatedly; and the rolling temperature of the last pass is 358 ℃, the rotating speed of the roller is 18r/min, the reduction is 12%, and the air cooling is carried out after the heat preservation is carried out for 14 min. The yield strength of the magnesium-lithium alloy material is 263MPa, the tensile strength is 337MPa, and the elongation is 15.7%; the density of the magnesium-lithium alloy material is 1.44g/cm-3。
Comparative example 1:
a kind ofThe high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 5.7wt%, Y: 9.0wt%, Co: 4.5 wt% and the balance of Mg and inevitable impurities, wherein the content of the inevitable impurities is less than or equal to 0.03 wt%. The preparation method is the same as that of the embodiment 3, the yield strength of the magnesium-lithium alloy material is 233MPa, the tensile strength is 287MPa, and the elongation is 11.4%; the density of the magnesium-lithium alloy material is 1.57g/cm-3。
Comparative example 2:
a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 5.7wt%, Y: 9.0wt%, Co: 7.2 wt% and the balance of Mg and inevitable impurities, wherein the content of the inevitable impurities is less than or equal to 0.03 wt%. The preparation method is the same as that of the embodiment 3, the yield strength of the magnesium-lithium alloy material is 245MPa, the tensile strength is 278MPa, and the elongation is 10.7%; the density of the magnesium-lithium alloy material is 1.6g/cm-3。
The strength and plasticity of the magnesium-lithium alloy materials of comparative examples 1 and 2 are inferior to those of example 1, which shows that the reasonable weight ratio of rare earth elements and Co elements in the magnesium-lithium alloy materials can introduce a long period structure phase into a magnesium-lithium alloy alpha phase matrix to the maximum extent in the vacuum casting process, and the strength of the magnesium-lithium alloy materials is improved.
Comparative example 3:
a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 5.7wt%, Y: 9.0wt%, Co: 6.0wt% and the balance of Mg and inevitable impurities, wherein the content of the inevitable impurities is less than or equal to 0.03 wt%.
A preparation method of a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following steps,
1) vacuum melting the preheated metal raw material to obtain alloy liquid, heating the alloy liquid by adopting electromagnetic induction with the frequency of 0.04MHz in the vacuum melting, and then casting the alloy liquid into a mould to be cooled to obtain as-cast magnesium-lithium alloy;
2) homogenizing the obtained cast magnesium-lithium alloy at 240 ℃ for 9 h;
3) homogenizing the mixtureRolling the treated magnesium-lithium alloy at low temperature, wherein the first-pass rolling temperature is 355 ℃, the roller rotating speed is 11r/min, the reduction is 22.5%, and air cooling is carried out after heat preservation is carried out for 13 min; the rolling temperature of the second pass is 350 ℃, the rotating speed of the roller is 15r/min, the reduction is 16.5%, the temperature is kept for 4min, then air cooling is carried out, and the rolling is repeated for 4 passes; the rolling temperature of the last pass is 355 ℃, the rotating speed of the roller is 17r/min, the reduction is 11%, the temperature is kept for 13min, and then air cooling is carried out to obtain the magnesium-lithium alloy, wherein the yield strength of the magnesium-lithium alloy material is 240MPa, the tensile strength is 298MPa, and the elongation is 10.7%; the density of the magnesium-lithium alloy material is 1.52g/cm-3。
Comparative example 4:
a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following components in percentage by weight: li: 5.7wt%, Y: 9.0wt%, Co: 6.0wt% and the balance of Mg and inevitable impurities, wherein the content of the inevitable impurities is less than or equal to 0.03 wt%.
A preparation method of a high-strength single-phase (alpha-phase) magnesium-lithium alloy material comprises the following steps,
1) vacuum smelting the preheated metal raw material to obtain alloy liquid, heating the alloy liquid by adopting electromagnetic induction with the frequency of 0.1MHz in the vacuum smelting, and then casting the alloy liquid into a mould to be cooled to obtain as-cast magnesium-lithium alloy;
2) homogenizing the obtained cast magnesium-lithium alloy at 240 ℃ for 9 h;
3) rolling the homogenized magnesium-lithium alloy at low temperature, wherein the first-pass rolling temperature is 355 ℃, the roller rotating speed is 11r/min, the reduction is 22.5%, and air cooling is carried out after heat preservation is carried out for 13 min; the rolling temperature of the second pass is 350 ℃, the rotating speed of the roller is 15r/min, the reduction is 16.5%, the temperature is kept for 4min, then air cooling is carried out, and the rolling is repeated for 4 passes; the rolling temperature of the last pass is 355 ℃, the rotating speed of the roller is 17r/min, the reduction is 11%, the temperature is kept for 13min, and then air cooling is carried out to obtain the magnesium-lithium alloy, wherein the yield strength of the magnesium-lithium alloy material is 253MPa, the tensile strength is 287MPa, and the elongation is 8.6%; the density of the magnesium-lithium alloy material is 1.54g/cm-3。
The magnesium-lithium alloy materials of comparative examples 1 and 2 have inferior strength and plasticity to those of example 1, which shows that the reasonable weight ratio of rare earth element and Co element in the magnesium-lithium alloy material can improve the strength of the magnesium-lithium alloy material. The electromagnetic induction of the frequency can enable solute atoms Li, Y, Co and Mg in the disordered solid solution to form the ordered solid solution, and the ordered solid solution exists in the magnesium-lithium alloy in the form of lamellar long-period structure inside crystal grains, namely, a novel long-period stacking ordered structure is formed in the magnesium-lithium alloy, so that the introduction of a long-period structure phase into an alpha-phase matrix of the magnesium-lithium alloy can be promoted, and the alloy strength and the plasticity are improved.
Conventional techniques in the above embodiments are known to those skilled in the art, and therefore, will not be described in detail herein.
The above embodiments are merely illustrative, and not restrictive, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the protection scope of the present invention should be defined by the claims.
Claims (4)
1. A high-strength single-phase alpha-phase magnesium-lithium alloy material is characterized in that: comprises the following components in percentage by weight: li: 0.1-5.7 wt%; rare earth elements: 6.0-9.0 wt%; co: 3.0-6.0wt%, the balance being Mg and unavoidable impurities; the content of inevitable impurities in the magnesium-lithium alloy material is less than or equal to 0.03 wt%; the yield strength of the magnesium-lithium alloy material is 250-280MPa, the tensile strength is 300-340MPa, and the elongation is 12-16%; the density of the magnesium-lithium alloy material is 1.4-1.5g/cm3(ii) a The weight ratio of rare earth elements to Co elements in the magnesium-lithium alloy material is 1: 0.5-0.8; the preparation method of the magnesium-lithium alloy material comprises the steps of low-temperature rolling; the low-temperature rolling comprises the following steps: the first-pass rolling temperature is 352-358 ℃, the rotating speed of the roller is 10-12r/min, the reduction is 20-25%, and the air cooling is carried out after the heat preservation is 12-14 min; the rolling temperature of the second pass is 348-; the rolling temperature of the last pass is 352-358 ℃, the rotating speed of the roller is 16-18r/min, the reduction is 10-12%, and the air cooling is carried out after the heat preservation is 12-14 min.
2. The high-strength single-phase alpha-phase magnesium-lithium alloy material according to claim 1, wherein: the rare earth element is a heavy rare earth element selected from Y, Gd, Dy, Er or Tb.
3. A high strength single phase α -phase magnesium lithium alloy material according to claim 1 or 2, wherein: the magnesium-lithium alloy material comprises the following components in percentage by weight: li: 0.1-5.7 wt%; y: 6.0-9.0 wt%; co: 3.0-6.0wt%, the balance being Mg and unavoidable impurities; the content of the inevitable impurities is less than or equal to 0.03 wt%.
4. The method for preparing the high-strength single-phase alpha-phase magnesium-lithium alloy material according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:
1) putting the magnesium ingot and the magnesium-cobalt alloy ingot into a melting furnace, keeping the temperature, preheating, introducing protective gas, then continuously heating to 750-;
2) homogenizing the obtained cast magnesium-lithium alloy at the temperature of 220-250 ℃ for 8-10 h;
3) carrying out low-temperature rolling on the homogenized magnesium-lithium alloy;
and the low-temperature rolling in the step 3) adopts cross accumulation pack rolling.
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