CN113249601B - Alloying method for inducing icosahedron quasicrystal phase in-situ self-generated strengthening cast aluminum-lithium alloy - Google Patents

Abstract

An alloying method for inducing icosahedral quasi-crystal phase in-situ in-situ strengthening of cast aluminum-lithium alloy relates to a method for inducing quasi-crystal phase in-situ in-situ strengthening of cast aluminum-lithium alloy. The invention aims to solve the problem that the large amount of precipitation of δ'-Al ₃ Li particles in the existing process of casting aluminum-lithium alloy will aggravate the tendency of coplanar slip, and the phenomenon of stress concentration at the grain boundary will become more obvious, which will lead to a significant decrease in the strength and toughness of the alloy. technical issues. The invention relates to an alloying method for inducing a quasi-crystal phase in-situ self-generated reinforced cast aluminum-lithium alloy. While the precipitation quantity of Al ₃ Li strengthening particles in the quasi-crystal reinforced cast aluminum-lithium alloy is suppressed, the icosahedral quasi-crystal phase T ₂ ‑ The amount of precipitation of Al ₆ CuLi ₃ is greatly increased, and the strength-plastic product of the alloy is increased by more than five times.

Description

A kind of alloying method for inducing icosahedral quasicrystal phase in situ self-strengthening cast aluminum-lithium alloy

technical field

The invention relates to a method for inducing a quasi-crystal phase in-situ in-situ strengthening and casting aluminum-lithium alloy.

Background technique

With the increasing shortage of petroleum resources and the increasingly complex structure of modern structural devices, especially in the high-end manufacturing fields of major equipment such as aerospace and military industry, the development of new preparation technologies and new materials is urgently needed. Aluminum-lithium alloy has the advantages of low density, high specific strength and specific stiffness, good corrosion resistance and good fatigue resistance. Using it to replace conventional aluminum alloy can reduce the quality of components by 10% to 20% and increase the stiffness by 15% to 20%. %, is an ideal aerospace structural material.

At present, the research and development of aluminum-lithium alloys is almost completely limited to deformed aluminum-lithium alloys. Aluminum-lithium alloy not only has excellent high-speed characteristics, but also has good casting performance, especially the ability of the alloy to replicate small structure cavities is generally better than that of ordinary aluminum alloys, which is conducive to the forming of thin-walled parts for aviation; At the same time, the allowable range of Li content in the cast aluminum-lithium alloy is wide, and the weight reduction effect of the component is more obvious. Therefore, it is of great significance to carry out research on cast aluminum-lithium alloys. Combining the unique advantages of casting forming technology with aluminum-lithium alloys with excellent performance is expected to accelerate the application process of cast aluminum-lithium alloy castings in the aerospace field. Different from deformed alloys, cast Al-Li alloys cannot be pre-deformed before aging, and the effective precipitation strengthening phases T ₁ -Al ₂ CuLi and S/S'-Al ₂ CuMg in the alloy are limited by the nucleation characteristics. Very rarely, the alloy can only rely on the dispersion strengthening of δ'-Al ₃ Li particles, which limits the application range of the alloy. In addition, compared with deformed alloys, the biggest problem of cast Al-Li alloys is their lower strength and toughness. The reason is that with the increase of Li content in the alloy, the precipitation of δ'-Al ₃ Li particles will aggravate the tendency of coplanar slip, and the crystallinity The stress concentration at the boundary becomes more and more obvious, which will lead to a significant decrease in the strength and toughness of the alloy. Therefore, in order to meet the demand for lightweight, high-strength and high-rigidity castings in the aerospace field, a cast aluminum-lithium alloy with excellent mechanical properties needs to be researched and developed.

SUMMARY OF THE INVENTION

The invention aims to solve the technology that the large amount of precipitation of δ'-Al3Li particles in the existing process of casting aluminum-lithium alloy will aggravate the tendency of coplanar sliding, the phenomenon of stress concentration at the grain boundary will become more obvious, and the strength and toughness of the alloy will be obviously decreased. The problem is to provide an alloying method for inducing icosahedral quasicrystal phase in situ to strengthen the cast aluminum-lithium alloy.

The alloying method for inducing an icosahedral quasicrystal phase in-situ self-strengthening cast aluminum-lithium alloy of the present invention is carried out according to the following steps:

1. Select pure aluminum, pure magnesium, pure lithium particles, Al-50Cu master alloy, Al-4Zr master alloy and aluminum-based master alloy containing alloying elements, and then remove the surface oxide scale and surface layer from the selected raw materials;

Wrap pure magnesium and pure lithium particles with aluminum foil respectively;

The aluminum-based master alloy containing alloying elements is an Al-10Ni master alloy, and the final prepared aluminum-lithium alloy is composed of: 1.8%-3.2% Li, 0.5%-2% Cu, 0.5% %～1.8% Mg, 0.04%～0.21% Zr, 0.2%～0.95% Ni, and the rest are Al;

The aluminum-based master alloy containing alloying elements can also be an Al-4V master alloy, and the final prepared aluminum-lithium alloy consists of: 1.8%-3.2% Li, 0.5%-2% Cu according to mass fraction , 0.5%-1.8% Mg, 0.04%-0.21% Zr, 0.2%-0.95% V, and the rest is Al;

2. Heat the crucible to 400℃～420℃ without load and keep the temperature for 2h～2.5h, increase the furnace temperature to 750℃～800℃, and then add the pure aluminum, Al-50Cu alloy, Al- 4Zr master alloy and aluminum-based master alloy containing alloying elements, after all melting, lower the furnace temperature to 720 ℃ ~ 730 ℃, use a graphite pressure cover to press the aluminum foil-wrapped pure magnesium and aluminum foil-wrapped pure lithium particles into the melt Introduce protective gas into the body, adjust the furnace temperature to 740 ℃ ~ 750 ℃ after the alloy is completely melted and add C ₂ Cl ₆ for degassing, let stand for 10 min ~ 15 min, adjust the furnace temperature to 720 ℃ ~ 725 ℃, put the melting The body is poured into a preheated mold to form an alloy ingot;

3. Heat treatment to the alloy ingot prepared in step 2. The heat treatment system is formulated in combination with the DSC results of the ingot to obtain an aluminum-lithium alloy.

The present invention proposes an alloying design method for inducing quasicrystal phase in-situ self-generated enhanced cast aluminum-lithium alloy based on the alloying-induced quasicrystal phase precipitation mechanism. The alloying elements include two types: one is the added alloying elements. The icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ or the precursor phase R-Al _4.8 CuLi ₃ can be induced to in-situ autogenerate, which reduces the precipitation of the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ in cast Al-Li alloys The required external conditions can expand the alloy composition range or process conditions required for the precipitation of the quasicrystal phase (or precursor); the second is that the added alloying elements can be doped into the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ In the lattice structure, the formation enthalpy of the precipitation of the quasicrystal phase is reduced; thus, the traditional casting method is used to produce an in-situ quasicrystal-enhanced cast aluminum-lithium alloy, which can not only significantly improve the strength of the cast aluminum-lithium alloy. It is tough and suitable for the preparation of large-scale and complex structural castings.

The in-situ solidification path involving the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ in the cast Al-Li alloy includes U ₈ type peritectic reaction:

The in-situ solidification path involving the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ in the cast Al-Li alloy includes U ₁₁ -type peritectic reaction:

The in-situ solidification path involving the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ in the cast Al-Li alloy includes P ₂ type peritectic reaction:

The alloying element characteristics described can be divided into two categories:

1. The intermetallic compound AlxMy (M refers to the added alloying element Ni or V) formed in the alloy after the alloying treatment of the present invention has a specific lattice structure/constant, which can be used as a heterogenous Cu/Mg-rich phase. Mass nucleation particles (similar to the "adsorption" effect) to change the alloy composition to deviate from the original solidification path, induce the above-mentioned U ₈ , U ₁₁ or P ₂ solidification reaction, and promote the icosahedral quasicrystal phase T ₂ -In situ self-generation of Al ₆ CuLi ₃ ;

2. The selected alloying elements should have the atomic radius and electronegativity similar to Cu, so the alloying elements will be doped in the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ lattice structure, reducing the quasi-crystal structure. The formation enthalpy of crystalline phase precipitation promotes the in-situ autogenesis of quasicrystalline phase.

The invention relates to an alloying method for inducing a quasicrystal phase in-situ in-situ reinforced cast aluminum-lithium alloy. While the precipitation quantity of Al ₃ Li strengthening particles in the quasicrystal reinforced cast aluminum-lithium alloy is suppressed, the icosahedral quasicrystal phase T ₂ - The amount of precipitation of Al ₆ CuLi ₃ is greatly increased, and the strength-plastic product of the alloy is increased by more than five times.

The present invention focuses on an alloying method (including types and additions of alloying elements, etc.) that can induce in-situ icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ in aluminum-lithium alloys. There is a preparation process and equipment for aluminum-lithium alloy, which does not significantly increase the production cost of the alloy.

Description of drawings

Fig. 1 is the Al-rich end phase diagram of the aluminum-lithium alloy prepared in test 1;

Fig. 2 is the TEM of the aluminum-lithium alloy prepared in experiment two;

Fig. 3 is the TEM of the aluminum-lithium alloy prepared in test one;

Fig. 4 is the selected area diffraction pattern of the round rod-shaped precipitated phase in Fig. 3;

Fig. 5 is the atomic arrangement TEM of the round rod-shaped precipitated phase in Fig. 3;

Figure 6 is an engineering tensile stress-strain curve diagram;

Figure 7 is a comparison of the area enclosed by the alloy tensile curve.

Detailed ways

Embodiment 1: This embodiment is an alloying method for inducing icosahedral quasicrystal phase in-situ self-strengthening cast aluminum-lithium alloy, which is specifically carried out according to the following steps:

1. Select pure aluminum, pure magnesium, pure lithium particles, Al-50Cu master alloy, Al-4Zr master alloy and aluminum-based master alloy containing alloying elements, and then remove the surface oxide scale and surface layer from the selected raw materials;

Wrap pure magnesium and pure lithium particles with aluminum foil respectively;

The aluminum-based master alloy containing alloying elements is an Al-10Ni master alloy, and the final prepared aluminum-lithium alloy is composed of: 1.8%-3.2% Li, 0.5%-2% Cu, 0.5% %～1.8% Mg, 0.04%～0.21% Zr, 0.2%～0.95% Ni, and the rest are Al;

The aluminum-based master alloy containing alloying elements can also be an Al-4V master alloy, and the final prepared aluminum-lithium alloy consists of: 1.8%-3.2% Li, 0.5%-2% Cu according to mass fraction , 0.5%-1.8% Mg, 0.04%-0.21% Zr, 0.2%-0.95% V, and the rest is Al;

2. Heat the crucible to 400℃～420℃ without load and keep the temperature for 2h～2.5h, increase the furnace temperature to 750℃～800℃, and then add the pure aluminum, Al-50Cu alloy, Al- 4Zr master alloy and aluminum-based master alloy containing alloying elements, after all melting, lower the furnace temperature to 720 ℃ ~ 730 ℃, use a graphite pressure cover to press the aluminum foil-wrapped pure magnesium and aluminum foil-wrapped pure lithium particles into the melt Introduce protective gas into the body, adjust the furnace temperature to 740 ℃ ~ 750 ℃ after the alloy is completely melted and add C ₂ Cl ₆ for degassing, let stand for 10 min ~ 15 min, adjust the furnace temperature to 720 ℃ ~ 725 ℃, put the melting The body is poured into a preheated mold to form an alloy ingot;

3. Heat-treating the alloy ingot prepared in step 2 to obtain an aluminum-lithium alloy.

Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the aluminum-based master alloy containing alloying elements described in step 1 is an Al-10Ni master alloy, and the final prepared aluminum-lithium alloy is divided by mass. The array is: 2.51% Li, 1.11% Cu, 1.38% Mg, 0.21% Zr, 0.24% Ni, and the rest is Al. Others are the same as the first embodiment.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the aluminum-based master alloy containing alloying elements described in step 1 is an Al-10Ni master alloy, and the final prepared aluminum-lithium alloy has The mass fraction composition is: 2.35% Li, 0.96% Cu, 1.22% Mg, 0.19% Zr, 0.44% Ni, and the rest is Al. Others are the same as in the first or second embodiment.

Embodiment 4: The difference between this embodiment and one of Embodiments 1 to 3 is that the aluminum-based master alloy containing alloying elements described in step 1 is an Al-10Ni master alloy, and the final prepared aluminum-lithium alloy is According to the mass fraction, the composition is: 2.62% Li, 1.03% Cu, 1.53% Mg, 0.18% Zr, 0.91% Ni, and the rest is Al. Others are the same as one of Embodiments 1 to 3.

Embodiment 5: The difference between this embodiment and Embodiment 4 is that the aluminum-based master alloy containing alloying elements described in step 1 is an Al-4V master alloy, and the final prepared aluminum-lithium alloy includes by mass fraction 0.2% of V. Others are the same as the fourth embodiment.

Embodiment 6: The difference between this embodiment and Embodiment 5 is that the method for removing the surface oxide scale and the surface layer in step 1 is: firstly wash with 0.2% NaOH aqueous solution, dry and polish. Others are the same as the fifth embodiment.

Embodiment 7: The difference between this embodiment and Embodiment 6 is that: in step 2, the crucible is heated to 400°C without load and kept for 2 hours, the furnace temperature is increased to 750°C, and the pure product weighed in step 1 is added into the crucible. Aluminum, Al-50Cu alloy, Al-4Zr master alloy and aluminum-based master alloy containing alloying elements are all melted, and the furnace temperature is lowered to 720 °C, and the pure magnesium wrapped in aluminum foil and pure magnesium wrapped in aluminum foil are covered by a graphite pressure cover. Lithium particles are all pressed into the melt and a protective gas is introduced. When the alloy is completely melted, the furnace temperature is adjusted to 740°C and C ₂ Cl ₆ is added for degassing. After standing for 10 minutes, the furnace temperature is adjusted to 720° C. The melt is poured into a preheated mold to form an alloy ingot. Others are the same as the sixth embodiment.

Embodiment 8: This embodiment is different from Embodiment 7 in that the weight of C ₂ Cl ₆ added in step 2 is 6/1000 of the weight of the aluminum-lithium alloy. Others are the same as in the seventh embodiment.

Embodiment 9: This embodiment differs from Embodiment 8 in that the protective gas described in step 2 is argon. Others are the same as the eighth specific embodiment.

Embodiment 10: This embodiment differs from Embodiment 9 in that the temperature of the preheating mold in step 2 is 200°C. Others are the same as in the ninth embodiment.

The present invention was verified with the following experiments:

Test 1: This test is an alloying method for inducing icosahedral quasicrystal phase in situ to strengthen cast Al-Li alloys. This test uses Ni alloying to induce icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ Strengthen the cast aluminum-lithium alloy and determine the appropriate amount of Ni alloying addition. Specifically, follow these steps:

1. Select pure aluminum, pure magnesium, pure lithium particles, Al-50Cu master alloy, Al-4Zr master alloy and aluminum-based master alloy containing alloying elements, and then remove the surface oxide scale and surface layer from the selected raw materials;

Wrap pure magnesium and pure lithium particles with aluminum foil respectively;

The aluminum-based master alloy containing alloying elements is an Al-10Ni master alloy;

The method of removing the surface oxide scale and the surface layer in step 1 is as follows: firstly wash with NaOH aqueous solution with a mass concentration of 0.2%, dry at 120°C, and polish with 400# sandpaper;

2. Heat the crucible to 400°C without load and keep it for 2h, adjust the furnace temperature to 750°C, and then add the pure aluminum, Al-50Cu alloy, Al-4Zr master alloy and alloying elements weighed in step 1 into the crucible. After all the aluminum-based master alloys are melted, lower the furnace temperature to 720°C. Use a graphite pressure cover to press the aluminum foil-wrapped pure magnesium and aluminum foil-wrapped pure lithium particles into the melt and pass argon gas. When the alloy is completely melted After adjusting the furnace temperature to 740°C and adding C ₂ Cl ₆ for degassing, let stand for 10 minutes, adjust the furnace temperature to 720° C, and pour the melt into a preheated mold to form an alloy ingot; in step 2, add C ₂ The weight of Cl ₆ is six thousandths of the weight of the aluminum-lithium alloy; the temperature of the preheating mold in step 2 is 200°C;

3. Heat treatment to the alloy ingot prepared in step 2 to obtain an aluminum-lithium alloy. The heat treatment process is solution treatment + water quenching at 25° C. + aging treatment, see Table 2 for details.

Fig. 1 is the Al-rich terminal phase diagram of the Al-Li alloy prepared in Experiment 1 (including the in-situ solidification path involving the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ ).

Test 2: This test is a comparative test. The difference from test 1 is that no aluminum-based master alloy containing alloying elements was added in step 1, and the mass fraction of each element was different. See Table 1 for details. Others are the same as test 1.

Fig. 2 is the TEM of the aluminum-lithium alloy prepared in the second experiment, and Fig. 3 is the TEM of the aluminum-lithium alloy prepared in the experiment one. It can be seen from the figure that a large number of small spherical δ'-Al ₃ Li particles ( The diameter of about 15nm) was mostly transformed into the round rod-like precipitate phase (section diameter of about 35nm) in the aluminum-lithium alloy in experiment one. FIG. 4 is a selected area diffraction pattern of the round rod-shaped precipitates in FIG. 3 . It can be seen that the diffraction spots of these round rod-shaped precipitates have a fivefold symmetrical structure.

Using the atomic arrangement of the round rod-like precipitates in high-resolution TEM Fig. 3, see Fig. 5, it is found that the atomic structure of these precipitates is a structure in which twenty atoms surround a central atom. From FIGS. 5 and 4 , it can be determined that these round rod-like precipitates are icosahedral quasicrystal phases T ₂ -Al ₆ CuLi ₃ . From this, it can be determined that Ni is an alloying element that can induce quasicrystal phase in situ in-situ enhanced cast Al-Li alloys, and the optimal addition amount should be 0.251wt.%.

Experiment 3: The difference between this experiment and experiment 1 is that the mass fraction of each element in step 1 is different, see Table 1 for details. Others are the same as test 1.

Experiment 4: The difference between this experiment and experiment 1 is that the mass fraction of each element in step 1 is different, see Table 1 for details. Others are the same as test 1.

Fig. 6 is an engineering tensile stress-strain curve diagram, curve 1 is the aluminum-lithium alloy prepared in test two, curve 2 is the aluminum-lithium alloy prepared in test one, curve 3 is the aluminum-lithium alloy prepared in test three, curve 4 It is the aluminum-lithium alloy prepared in test four.

Figure 7 is a comparison diagram of the area enclosed by the tensile curve of the alloy. The enclosed area describes the strong-plastic product of the alloy. Its physical meaning is to characterize the comprehensive properties of the alloy's strength and plasticity. Curve 1 is the aluminum-lithium prepared in test 2. Alloy, curve 2 is the aluminum-lithium alloy prepared in test one.

Table 1

Note: The remainder of the alloy composition is aluminum.

Table 2

It can be seen from Table 1 that the alloying method for inducing quasicrystal phase in-situ enhanced cast aluminum-lithium alloy according to the present invention, compared with the comparative test, the tensile strength of quasicrystal-strengthened cast aluminum-lithium alloy is increased by ~ 20MPa, and the tensile strength is increased by ~ 50MPa, the elongation is ~62.5%, the strength and plastic product is increased by more than five times, and the effect of test 1 is the best.

In particular, the intermetallic compound Al ₃ Ni phase formed in the alloy after Ni alloying treatment has an orthorhombic structure, and the lattice constants are a=6.6114nm, b=7.3662nm, c=4.8112nm, compared with α -Al matrix (cubic crystal structure, lattice constant is a=b=4.0494nm), more easily used as Cu-rich phase (mainly Al ₂ Cu phase, body-centered cubic structure, lattice constant is a=b=6.063nm, c=4.872nm) heterogeneous nucleation particles (similar to the effect of "adsorbing" Cu atoms in the matrix), which can change the alloy composition to deviate from the original solidification path, induce the occurrence of _U8 -type solidification reaction, and promote the icosahedron In situ autogenesis of the quasicrystal phase T ₂ -Al ₆ CuLi ₃ .

U ₈ type peritectic reaction:

Experiment 5: The difference between this experiment and experiment 1 is: this experiment uses V alloying to induce icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ in situ to enhance the cast aluminum-lithium alloy, and determine the optimal addition amount of V alloying .

In particular, compared with the Al matrix, the selected V element has an atomic radius and electronegativity similar to Cu (Cu: atomic radius 0.157 nm, electronegativity 1.90; V: atomic radius 0.192 nm, electronegativity 1.63; Al: atomic radius 0.182 nm, electronegativity 1.61).

According to the interaction strength formula between elements:

In the formula, _RA and RB are the atomic radii of solute _A and solvent _B , respectively, NA and NB are the electronegativity of solute A and solvent _B , respectively, W _AB is the interaction strength of elements A and B, the The parameter can semi-quantitatively characterize the propensity of elements to form compounds. It can be known from the calculation of the above formula that W _Al-V =0.1375; W _Cu-V =2.802.

Therefore, it can be inferred that the V element is easy to combine with the Cu element to form a compound, that is to say, it is inferred that V can be doped in the icosahedral quasicrystal phase T ₂ -Al ₆ CuLi ₃ lattice structure, replacing part of the Cu atoms to occupy the center of the lattice, reducing the quasi-crystal lattice structure. The formation enthalpy of crystalline phase precipitation can promote the in-situ autogenesis of quasicrystalline phase, and the optimal addition amount of V is 0.2 wt.%.

Claims (1)

1. An alloying method for inducing the in-situ self-generation of icosahedron quasicrystal phase to strengthen the cast Al-Li alloy features that the in-situ self-generation of icosahedron quasicrystal phase containing Li is promoted by alloying treatment to suppress delta' -Al₃Due to the large precipitation of Li particles, the alloy structure is more uniform, and the toughness of the alloy can be greatly improved;

the standard stoichiometric ratio of the icosahedron quasicrystal phase is: al, Cu, Li, 6:1: 3;

the judgment basis of the elements used in the alloying treatment is as follows: w_Al-X<W_Cu-XWherein X represents an alloying element V;

the preparation process of the alloying treatment quasicrystal phase in-situ autogenous reinforced cast aluminum-lithium alloy is carried out according to the following steps:

firstly, selecting pure aluminum, pure magnesium, pure lithium particles, Al-50Cu intermediate alloy, Al-4Zr intermediate alloy and commercial aluminum-based intermediate alloy containing alloying elements, and then removing surface oxide skin and a surface layer of the selected raw materials; the aluminum-based intermediate alloy containing alloying elements is Al-4V intermediate alloy;

respectively wrapping pure magnesium and pure lithium particles by using aluminum foil;

secondly, heating the crucible to 400-420 ℃ in no-load mode, preserving heat for 2-2.5 hours, raising the temperature of the furnace to 750-800 ℃, and then adding the first step scale into the crucibleTaking pure aluminum, Al-50Cu alloy, Al-4Zr intermediate alloy and aluminum-based intermediate alloy containing alloying elements, reducing the furnace temperature to 720-730 ℃ after the pure aluminum, the Al-50Cu alloy, the Al-4Zr intermediate alloy and the aluminum-based intermediate alloy containing the alloying elements are completely melted, pressing pure magnesium wrapped by aluminum foil and pure lithium wrapped by the aluminum foil into the melt by utilizing a graphite pressure cover, introducing protective gas, adjusting the furnace temperature to 740-750 ℃ after the alloy is completely melted, and adding C₂Cl₆Degassing, standing for 10-15 min, adjusting the furnace temperature to 720-725 ℃, and pouring the melt into a preheated mold to form an alloy ingot;

thirdly, carrying out heat treatment on the alloy ingot prepared in the second step to obtain an aluminum-lithium alloy; the aluminum lithium alloy comprises the following components in percentage by mass: 1.8 to 3.2 percent of Li, 0.5 to 2 percent of Cu, 0.5 to 1.8 percent of Mg, 0.04 to 0.21 percent of Zr, 0.2 to 0.95 percent of V, and the balance of Al.

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