CN104233024A - High-strength two-phase ultralight magnesium lithium alloy and preparation method thereof - Google Patents

Abstract

The invention relates to high-strength two-phase ultralight magnesium lithium alloy and a preparation method thereof and belongs to the technical field of light metal material preparation. The high-strength two-phase ultralight magnesium lithium alloy disclosed by the invention comprises the following components in mass percent: 6.0-9.0 percent of Li, 1.0-6.0 percent of Al, 0.01-1.0 percent of Y and 0.21-0.5 percent of Ca. According to the preparation method disclosed by the invention, magnesium lithium alloy is smelted in a general resistance furnace by adopting a flux-covering and gas protection method, so that the high-strength two-phase ultralight magnesium lithium alloy with the room temperature tensile strength of 162-190Mpa, the yield strength of 150-170Mpa, the percentage elongation of 15-30 percent and the density of 1.43-1.48g/cm<3> is obtained. The preparation process is simple; the obtained products are excellent in performance and industrial production is facilitated.

Description

A high-strength dual-phase ultra-light magnesium-lithium alloy and its preparation method

technical field

The invention relates to a high-strength dual-phase ultra-light magnesium-lithium alloy and a preparation method thereof, belonging to the technical field of light metal material preparation.

Background technique

In recent years, energy issues have become the focus of attention all over the world, and lightweight has become the development trend of modern vehicles and electronic industries. The magnesium-lithium alloy formed by adding lithium element (density 0.53g/cm3) to the magnesium alloy has a lower alloy density than the common AZ and ZK series magnesium alloys (the density of the AZ and ZK series magnesium alloys is about 1.8~ 1.9g/cm3), which has positive significance for lightweight. In addition to the advantages of low density, magnesium-lithium alloys also have high specific strength, specific stiffness, excellent shock resistance, good biocompatibility, and high-energy particle penetration resistance. They are used in aviation, aerospace, and weapon industries. One of the most ideal structural materials with great development potential in the fields of nuclear industry, automobile, 3C industry, medical equipment and so on.

However, the amount of lithium added will have an impact on the crystal structure of the magnesium-lithium alloy. When the lithium content is less than 5wt.%, the alloy consists of α-phase with close-packed hexagonal structure. When the lithium content exceeds 5wt.%, the alloy has a body-centered cubic β phase. Due to the limited deformation hardening strengthening effect of the continuous BCC structure of the lithium-rich β phase during severe deformation, the strength of the lithium-rich β phase is extremely low. Therefore, the strength at room temperature is extremely low, and the tensile strength of lithium-rich alloys is generally lower than 100 MPa, which greatly limits the wide application of such alloys. In order to improve the strength of magnesium-lithium alloys and expand their application range, the strength of magnesium-lithium alloys can be improved by means such as multi-element alloying, composite material strengthening and plastic deformation. Some scientific research personnel often adopt alloying method, try to improve the intensity index of magnesium embedment alloy by adding alloy element, the disclosed patent " a kind of high-strength magnesium embedment alloy " (application number: 200710144339.9, publication number: CNIO1121981, Public date: 2008.02.13) using Al, Zn, Ce as strengthening elements, the prepared alloy has a tensile strength of 245-300MPa, a yield strength of 230-280MPa, an elongation of 10-25%, and a density of 1.35-1.62g /cm ³ ; D.KXu et al. (DKXu, L.Liu, YB.xu, SeriptaMaterialia.285.57 (2007)), added Zn and Y to the magnesium-lithium alloy to strengthen the alloy, and obtained a higher strength and plasticity better alloy. However, since the amount of Zn added is more than 3wt%, not only the density of the alloy is increased, but also the microstructure and property stability of the alloy are poor, and the problem of overaging is easy to occur.

Rapid solidification-powder metallurgy can significantly refine grains and improve the strength and plasticity of alloys, but the cost is too high and the value of industrialization is not high.

Invention content:

Aiming at the shortcomings of existing magnesium-lithium alloys, the present invention provides a high-strength dual-phase ultra-light magnesium-lithium alloy and a preparation method thereof.

A high-strength dual-phase ultra-light magnesium-lithium alloy according to the present invention comprises the following components in terms of mass percentage:

Li: 6.0-9.0%;

Al: 1.0-6.0%;

Y:0.01-1.0%;

Ca: 0.21-0.5%;

Unavoidable impurities ≤0.3%;

The remainder is Mg.

A high-strength dual-phase ultra-light magnesium-lithium alloy according to the present invention comprises the following components in terms of mass percentage:

Li: 7.0-8.0%;

Al: 2.0-3.5%;

Y: 0.01-0.75%;

Ca: 0.22-0.5%;

Unavoidable impurities ≤0.3%;

The remainder is Mg.

A high-strength dual-phase ultra-light magnesium-lithium alloy according to the present invention comprises the following components in terms of mass percentage:

Li: 7.5-8.0%;

Al: 2.5-3.2%;

Y: 0.25-0.55%;

Ca: 0.22-0.5%;

Unavoidable impurities ≤0.3%;

The remainder is Mg.

A high-strength two-phase ultra-light magnesium-lithium alloy described in the present invention, in the magnesium-lithium alloy, the α-phase and β-phase exist at the same time as the precipitation, wherein the α-phase is a solid solution based on Mg and has a close-packed hexagonal structure , the β phase is a Li-based solid solution with a body-centered cubic structure; the precipitated phase contains Al ₂ Y.

The high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention has a density of 1.43-1.48 g/cm ³ .

The high-strength dual-phase ultra-light magnesium-lithium alloy of the present invention has a room temperature tensile strength of 162-190Mpa, a yield strength of 150-170Mpa, and an elongation of 15%-30%.

A method for preparing a high-strength dual-phase ultra-light magnesium-lithium alloy of the present invention comprises the following steps:

Step 1 Ingredients

According to the designed alloy composition, prepare pure Mg, pure Li, pure Al, pure Ca and MgY master alloy respectively; and according to the total mass of the prepared pure Mg, pure Li, pure Al, pure Ca and MgY master alloy The 10%-12% of the covering agent is equipped with a covering agent; the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 1-5:1;

Step two casting

Under a protective atmosphere, raise the temperature of the melting furnace to 700-720°C, and then add the covering agent. After the covering agent melts, add the prepared pure Mg, pure Al, pure Ca and Mg-Y master alloy in sequence, and keep warm for 10- After 30 minutes, lower the temperature to 660-680°C, and add pure Li at this temperature, stir for 1-5 minutes after the pure Li melts, then raise the temperature to 700-720°C and keep it for 10-30 minutes, then cast to obtain a high-strength dual-phase Ultra-light magnesium-lithium alloy.

According to the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy of the present invention, the purity of pure Mg is ≥99.9%, the purity of pure Li is ≥99.9%, the purity of pure Al is ≥99.9%, and the purity of pure Ca is ≥99.9% %; the MgY master alloy is composed of 72.4-76.6% of Mg and 23.4-27.6% of Y in terms of mass percentage.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, in the actual operation process, the surface of pure magnesium, pure aluminum and MgY intermediate alloy needs to be polished to remove the oxide film on the surface, It reveals a silvery white metallic luster. Li is stored in a vacuum package and cut according to the amount when needed.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 1-5:1; preferably 2- 4:1; more preferably preferably 2.5-3.5:1.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, the protective atmosphere is formed by mixing argon and sulfur hexafluoride, wherein the volume content of sulfur hexafluoride is 0.2-0.7%.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, when pure Mg is added, the magnesium needs to pay attention to pressing the broken magnesium pieces into the bottom of the flux, and after the liquid level of the melt rises, the large Magnesium blocks are added.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, when sequentially adding the prepared pure Mg, pure Al, pure Ca and Mg-Y intermediate alloy, if sparks appear on the liquid surface, immediately Sprinkle a small amount of flux on the spark to cool down the fire.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, adding pure Li is to first place the lithium block in the feeding cover, and then press the lithium-adding cover into the melt; when the pure Li is melted After that, slowly pull out the lithium cap.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, when adding pure Li and stirring, on the one hand, the flow rate of the protective gas should be increased, and the flow rate should generally be controlled at 0.12-0.18m ³ /min On the other hand, control the stirring speed to 30-40r/min, if the speed is too high, it will easily cause the melt to splash. If sparks are found, immediately extinguish them with covering agent.

In the preparation method of a high-strength dual-phase ultra-light magnesium-lithium alloy described in the present invention, the relevant tools and molds used for smelting are all dried.

The advantages of the present invention are:

(1) In the magnesium-lithium alloy, the alloy is strengthened by adding alloying elements such as Y, Al, Ca, etc. of a specific composition to form intermetallic compounds through reasonable matching of the element types and the proportional relationship between the elements. A magnesium-lithium alloy with excellent plasticity and high strength is obtained through the synergistic effect between the components.

(2) The present invention strictly controls the content of Li in the alloy, and controls the alloy in the α+β phase region, so that the crystal grains can be refined, and the plasticity of the alloy can be retained while improving the strength of the alloy.

(3) The present invention strictly controls the content of Ca. Within a reasonable addition range, Ca can play a synergistic effect with other components, and then can refine the microstructure of the alloy and improve the mechanical properties of the alloy; when Ca is lower than When Ca is 0.21wt%, the effect of refining the microstructure of the alloy and improving the mechanical properties of the alloy is not obvious; when Ca is higher than 0.5wt%, especially higher than 1.0wt%, the plasticity of the alloy decreases significantly, and the finished product The density will also be higher than 1.48 g/cm ³ . In addition, Ca also plays a flame-retardant role in the alloy during the smelting process.

(4) The present invention adopts the addition of alloying elements in the form of Mg-Y master alloy, which avoids the disadvantages of high price and high melting point of pure Y. The cost of the alloy is greatly reduced, which is beneficial to commercial application.

(5) Because the present invention strictly limits the composition of the covering agent, the melting point of the covering agent is 660-680° C., and the density of the covering agent after melting is lower than the alloy density, which makes the covering agent cover the surface of the melt during the entire smelting process, isolating The air is suppressed to oxidize and burn the melt. The reason why the mixture of anhydrous lithium chloride and anhydrous lithium fluoride is selected as the covering agent is because an appropriate proportion of anhydrous lithium chloride and anhydrous lithium fluoride can be mixed with inclusions (the inclusions are brought in by raw materials and/or Smelting process) to form a slag with a density higher than that of the alloy liquid. Since the density of the slag is greater than that of the melt, the slag will sink to the bottom of the crucible to remove the slag. The invention strictly controls the mass ratio of anhydrous lithium chloride and anhydrous lithium fluoride in the covering agent. When the mass ratio of anhydrous lithium chloride and anhydrous lithium fluoride is less than 1:1, the covering agent has low viscosity and low density , The fluidity is excellent, which is easy to cause inclusions in the casting; when the mass ratio of anhydrous lithium chloride and anhydrous lithium fluoride is greater than 5:1, the density of the covering agent will increase greatly than the density of the magnesium-lithium alloy, and will occur during the smelting process. Continuous sinking requires continuous addition of covering agent, and part of the covering agent will remain in the solution as slag to form inclusions, thereby reducing the mechanical properties.

(6) The present invention is simple in operation and easy to carry out. The resulting alloy has high strength and good plasticity. The tensile strength at room temperature is 162-190Mpa, the yield strength is 150-170Mpa, the elongation is 15%-30%, and the density is 1.43-1.48g/cm ³ .

Description of drawings

Accompanying drawing 1 is the XRD figure of embodiment 3 gained as-cast alloy;

Accompanying drawing 2 is the obtained as-cast alloy microstructure picture of embodiment 3;

It can be seen from Figure 1 that the α phase and β phase in the obtained magnesium-lithium alloy exist at the same time as the precipitation, wherein the α phase is a Mg-based solid solution with a close-packed hexagonal structure, and the β phase is a Li-based solid solution , showing a body-centered cubic structure. At the same time, AlLi, Al2Y and MgAlLi2 also exist in a small amount in the alloy.

As can be seen from Figure 2, the brighter area is the α phase, and the darker area is the β phase. The α phase presents irregular blocks or strips, and is relatively uniformly distributed on the β phase matrix.

Specific implementation plan:

Example 1:

The alloy consists of the following components by mass percentage:

Li: 7.91%

Al: 2.83%

Y:0.31%

Ca: 0.22%

Unavoidable impurities ≤0.3%

The rest is Mg.

Its preparation process is as follows:

Step 1 Ingredients

According to the designed alloy composition, prepare pure Mg, pure Li, pure Al, pure Ca and MgY master alloy respectively; and according to the total mass of the prepared pure Mg, pure Li, pure Al, pure Ca and MgY master alloy 10% of the covering agent is prepared; the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 1:1; the purity of the pure Mg is ≥99.9%, the purity of the pure Li is ≥99.9%, The purity of pure Al is ≥99.9%, the purity of pure Ca is ≥99.9%; the MgY master alloy is composed of 72.4% Mg and 27.6% Y in terms of mass percentage;

Step two casting

The gas mixed with argon and sulfur hexafluoride (in which the volume content of sulfur hexafluoride is 0.2%) is used as the protective gas. Under a protective atmosphere, raise the temperature of the smelting furnace to 700°C, and then add the covering agent. After the covering agent is completely melted, add the prepared pure Mg, pure Al, pure Ca and Mg-Y master alloy in sequence, and keep it for 20 minutes. Lower the temperature to 660°C. When the temperature drops to the specified temperature, place the lithium block in the feeding hood, and then press the lithium adding hood into the melt. After waiting for a few minutes, slowly pull out the lithium cap. Stir with a stirring bar for 20 min. Set the temperature to 700°C. When the temperature rises to the specified temperature, it is allowed to stand still for 20 minutes, and then cast to obtain a high-strength dual-phase ultra-light magnesium-lithium alloy. When adding pure Li for stirring, on the one hand, it is necessary to increase the flow rate of the protective gas, and generally control the flow rate at 0.12m ³ /min; If sparks are found, extinguish them immediately with covering agent.

The mechanical properties of the cast ingot were tested, and the tensile strength at room temperature was 183.5 MPa, the yield strength was 161.3 MPa, the elongation was 25.6%, and the density was 1.43 g/cm ³ .

Example 2:

The alloy consists of the following components by mass percentage:

Li: 7.82%

Al: 2.93%

Y:0.45%

Ca: 0.36%

Unavoidable impurities ≤0.3%

The remainder is Mg.

Its preparation process is as follows:

Step 1 Ingredients

According to the designed alloy composition, prepare pure Mg, pure Li, pure Al, pure Ca and MgY master alloy respectively; and according to the total mass of the prepared pure Mg, pure Li, pure Al, pure Ca and MgY master alloy 10% of the covering agent is prepared; the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 5:1; the purity of the pure Mg is ≥99.9%, the purity of the pure Li is ≥99.9%, The purity of pure Al is ≥99.9%, the purity of pure Ca is ≥99.9%; the MgY master alloy is composed of 76.6% Mg and 23.4% Y in terms of mass percentage;

Step two casting

The gas mixed with argon and sulfur hexafluoride (in which the volume content of sulfur hexafluoride is 0.7%) is used as the protective gas. Under a protective atmosphere, raise the temperature of the melting furnace to 720°C, and then add the covering agent. After the covering agent is completely melted, add the prepared pure Mg, pure Al, pure Ca and Mg-Y master alloy in sequence, and keep it for 10 minutes. Lower the temperature to 660°C. When the temperature drops to the specified temperature, place the lithium block in the feeding hood, and then press the lithium adding hood into the melt. After waiting for a few minutes, slowly pull out the lithium cap. Stir with a stirring bar for 30 min. Set the temperature to 720°C. When the temperature rises to the specified temperature, it is allowed to stand still for 30 minutes, and then cast to obtain a high-strength dual-phase ultra-light magnesium-lithium alloy. When adding pure Li for stirring, on the one hand, it is necessary to increase the flow rate of the protective gas, and generally control the flow rate at 0.18m ³ /min; If sparks are found, extinguish them immediately with covering agent.

The mechanical properties of the cast ingot were tested, and the tensile strength at room temperature was 188.7MPa, the yield strength was 165.4MPa, the elongation was 22.3%, and the density was 1.46g/cm ³ .

Example 3:

The alloy consists of the following components by mass percentage:

Li: 7.66%

Al: 3.11%

Y:0.52%

Ca: 0.44%

Unavoidable impurities ≤0.3%

The rest is Mg.

Its preparation process is as follows:

Step 1 Ingredients

According to the designed alloy composition, prepare pure Mg, pure Li, pure Al, pure Ca and MgY master alloy respectively; and according to the total mass of the prepared pure Mg, pure Li, pure Al, pure Ca and MgY master alloy 10% of the covering agent is equipped with a covering agent; the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 3:1; the purity of the pure Mg is ≥99.9%, the purity of the pure Li is ≥99.9%, The purity of pure Al is ≥99.9%, and the purity of pure Ca is ≥99.9%; the MgY master alloy is composed of 75% Mg and 25% Y in terms of mass percentage;

Step 2 Casting

The gas mixed with argon and sulfur hexafluoride (in which the volume content of sulfur hexafluoride is 0.5%) is used as the protective gas. Under a protective atmosphere, raise the temperature of the melting furnace to 720°C, and then add the covering agent. After the covering agent is completely melted, add the prepared pure Mg, pure Al, pure Ca and Mg-Y master alloy in sequence, and keep it for 20 minutes. Lower the temperature to 680°C. When the temperature drops to 680°C, place the lithium block in the feeding hood, and then press the lithium adding hood into the melt. After waiting for a few minutes, slowly pull out the lithium cap. Stir with a stirring bar for 20 min. Set the temperature to 720°C. When the temperature rises to the specified temperature, it is allowed to stand still for 20 minutes, and then cast to obtain a high-strength dual-phase ultra-light magnesium-lithium alloy. When adding pure Li for stirring, on the one hand, the flow rate of the protective gas should be increased, and the flow rate should generally be controlled at 0.15m ³ /min; If sparks are found, extinguish them immediately with covering agent.

The mechanical properties of the cast ingot were tested, and the tensile strength at room temperature was 187.4MPa, the yield strength was 170.3MPa, the elongation was 20.8%, and the density was 1.48g/cm ³ .

Example 4:

The alloy consists of the following components by mass percentage:

Li: 8.92%

Al: 2.13%

Y:0.23%

Ca: 0.25%

Unavoidable impurities ≤0.3%

The remainder is Mg.

Its preparation process is as follows:

Step 1 Ingredients

According to the designed alloy composition, prepare pure Mg, pure Li, pure Al, pure Ca and MgY master alloy respectively; and according to the total mass of the prepared pure Mg, pure Li, pure Al, pure Ca and MgY master alloy 10% of the covering agent is equipped with a covering agent; the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 3:1; the purity of the pure Mg is ≥99.9%, the purity of the pure Li is ≥99.9%, The purity of pure Al is ≥99.9%, and the purity of pure Ca is ≥99.9%; the MgY master alloy is composed of 75% Mg and 25% Y in terms of mass percentage;

Step 2 Casting

The gas mixed with argon and sulfur hexafluoride (in which the volume content of sulfur hexafluoride is 0.5%) is used as the protective gas. Under a protective atmosphere, raise the temperature of the melting furnace to 720°C, and then add the covering agent. After the covering agent is completely melted, add the prepared pure Mg, pure Al, pure Ca and Mg-Y master alloy in sequence, and keep it for 20 minutes. Lower the temperature to 680°C. When the temperature drops to 680°C, place the lithium block in the feeding hood, and then press the lithium adding hood into the melt. After waiting for a few minutes, slowly pull out the lithium cap. Stir with a stirring bar for 20 min. Set the temperature to 720°C. When the temperature rises to the specified temperature, it is allowed to stand still for 20 minutes, and then cast to obtain a high-strength dual-phase ultra-light magnesium-lithium alloy. When adding pure Li and stirring, on the one hand, the flow rate of the protective gas should be increased, and the flow rate should generally be controlled at 0.15m ³ /min; If sparks are found, extinguish them immediately with covering agent.

The mechanical properties of the cast ingot were tested, and the tensile strength at room temperature was 164.5 MPa, the yield strength was 151.2 MPa, the elongation was 29.1%, and the density was 1.46 g/cm ³ .

Comparative example 1

The alloy consists of the following components by mass percentage:

Li: 7.82%

Al: 2.93%

Y:0.45%

Unavoidable impurities ≤0.3%

The remainder is Mg.

The process and process parameters used in the preparation process are completely consistent with those in Example 1. After the ingot is obtained, the mechanical properties of the ingot are detected, and the tensile strength at room temperature is 164.5MPa, the yield strength is 143.2MPa, and the elongation is 20.3%. , the density is 1.46g/cm ³ . It can be seen from Example 1 and Comparative Example 1 that due to the lack of addition of Ca element, the comprehensive mechanical properties of the alloy have declined in an all-round way.

Comparative example 2

The alloy consists of the following components by mass percentage:

Li: 7.82%

Al: 2.93%

Y:0.45%

Ca: 1.2%

Unavoidable impurities ≤0.3%

The remainder is Mg.

During its preparation, the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 8:1; other processes and process parameters are completely consistent with those in Example 2, and the mechanical properties of the ingot are detected after the ingot is obtained. , the tensile strength at room temperature is 195.7 MPa, the yield strength is 170.8 MPa, the elongation is 8.7%, and the density is 1.46 g/cm ³ .

It can be seen from Example 2 and Comparative Example 2 that due to the addition of too much Ca element, although the strength of the alloy is slightly improved, the plasticity of the alloy decreases sharply, and the comprehensive mechanical properties of the alloy still decrease.

Comparative example 3

The alloy consists of the following components by mass percentage:

Li: 10%

Al: 7%

Y: 1.2%

Ca: 0.1%

Unavoidable impurities ≤0.3%

The remainder is Mg.

Its preparation process is as follows:

Step 1 Ingredients

According to the designed alloy composition, prepare pure Mg, pure Li, pure Al, pure Ca and MgY master alloy respectively; and according to the total mass of the prepared pure Mg, pure Li, pure Al, pure Ca and MgY master alloy 10% of the covering agent is equipped with a covering agent; the covering agent is composed of anhydrous lithium chloride and anhydrous lithium fluoride in a mass ratio of 0.5:1; the purity of the pure Mg is ≥99.9%, the purity of the pure Li is ≥99.9%, The purity of pure Al ≥ 99.9%, the purity of pure Ca ≥ 99.9%; the MgY master alloy is composed of 75% Mg and 25% Y in terms of mass percentage;

Step 2 Casting

The gas mixed with argon and sulfur hexafluoride (the volume content of sulfur hexafluoride is 1%) is used as the protective gas. Under a protective atmosphere, raise the temperature of the melting furnace to 720°C, and then add the covering agent. After the covering agent is completely melted, add the prepared pure Mg, pure Al, pure Ca and Mg-Y master alloy in sequence, and keep it for 20 minutes. Lower the temperature to 680°C. When the temperature drops to 680°C, place the lithium block in the feeding hood, and then press the lithium adding hood into the melt. After waiting for a few minutes, slowly pull out the lithium cap. Stir with a stirring bar for 20 min. Set the temperature to 720°C. When the temperature rises to the specified temperature, it is allowed to stand still for 20 minutes, and then cast to obtain a high-strength dual-phase ultra-light magnesium-lithium alloy. When adding pure Li for stirring, on the one hand, the flow rate of the protective gas should be increased, and the flow rate should generally be controlled at 0.15m ³ /min; If sparks are found, extinguish them immediately with covering agent.

After the ingot was obtained, the mechanical properties of the ingot were tested, and the tensile strength at room temperature was 190.5 MPa, the yield strength was 176.2 MPa, the elongation was 10.1%, and the density was 1.49 g/cm ³ .

It can be seen from Example 3 and Comparative Example 3 that although the Li content increases, the Al content is too high, which greatly affects the plasticity of the alloy, so the plasticity of the alloy drops sharply, and the strength does not change much. The mechanical properties of the alloy decrease.

Claims (9)

1. the magnesium lithium alloy that high-strength two-phase is ultralight, is characterized in that: comprise following component by percentage to the quality:

Li:6.0-9.0％；

Al:1.0-6.0％；

Y:0.01-1.0％；

Ca:0.21-0.5％；

Inevitable impurity≤0.3%;

All the other are Mg.

2. the magnesium lithium alloy that a kind of high-strength two-phase according to claim 1 is ultralight, is characterized in that: comprise following component by percentage to the quality:

Li:7.0-8.0％；

Al:2.0-3.5％；

Y:0.01-0.75％；

Ca:0.22-0.5％；

Inevitable impurity≤0.3%;

All the other are Mg.

3. the magnesium lithium alloy that a kind of high-strength two-phase according to claim 2 is ultralight, is characterized in that: comprise following component by percentage to the quality:

Li:7.5-8.0％；

Al:2.5-3.2％；

Y:0.25-0.55％；

Ca:0.22-0.5％；

Inevitable impurity≤0.3%;

All the other are Mg.

4. the magnesium lithium alloy that a kind of high-strength two-phase according to claim 1-3 any one is ultralight, it is characterized in that: in described magnesium lithium alloy, α phase, β phase and precipitated phase exist simultaneously, wherein α phase take Mg as the sosoloid of base, in close-packed hexagonal structure, β phase take Li as the sosoloid of base, in body-centered cubic structure, described precipitated phase comprises Al ₂y.

5. the magnesium lithium alloy that a kind of high-strength two-phase according to claim 1-3 any one is ultralight, is characterized in that: its density is 1.43-1.48g/cm ³.

6. the magnesium lithium alloy that a kind of high-strength two-phase according to claim 1-3 any one is ultralight, is characterized in that: the room temperature tensile intensity of described magnesium lithium alloy is 162-190Mpa, yield strength is 150-170Mpa, unit elongation is 15%-30%.

7. prepare a method for the magnesium lithium alloy that high-strength two-phase is ultralight as described in claim 1-3 any one, it is characterized in that: comprise the steps:

Step one is prepared burden

By the alloy compositions of design, join respectively and get pure Mg, pure Li, pure Al, pure Ca and MgY master alloy; And by join the pure Mg got, pure Li, pure Al, pure Ca, MgY master alloy the 10%-12% of total mass join and get insulating covering agent; Described insulating covering agent by Lithium chloride (anhydrous) and anhydrous lithium fluoride in mass ratio 1-5:1 form;

Step 2 founding

Under protective atmosphere; smelting furnace is warming up to 700-720 DEG C, then adds insulating covering agent, after to be covered dose of fusing; add successively join the pure Mg got, pure Al, pure Ca and Mg-Y master alloy; after insulation 10-30min, be cooled to 660-680 DEG C, and add pure Li at such a temperature; 1-5min is stirred after pure Li fusing; then be warming up to 700-720 DEG C and the standing 10-30min of insulation, casting, obtains the magnesium lithium alloy that high-strength two-phase is ultralight.

8. a kind of method preparing the ultralight magnesium lithium alloy of high-strength two-phase according to claim 7, is characterized in that: purity >=99.9% of pure Mg, purity >=99.9% of pure Li, purity >=99.9% of pure Al, purity >=99.9% of pure Ca; Described MgY master alloy is made up of the Y of Mg and the 23.4-27.6% of 72.4-76.6% by mass percentage.

9. a kind of method preparing the ultralight magnesium lithium alloy of high-strength two-phase according to claim 7, is characterized in that: described protective atmosphere to be mixed with sulfur hexafluoride by argon gas and forms, and wherein the volume content of sulfur hexafluoride is 0.2-0.7%.