CN108796324A - A kind of room temperature high-ductility magnesium-tin-yttrium-zircaloy and preparation method thereof - Google Patents

Abstract

The invention relates to a magnesium-tin-yttrium-zirconium alloy with high plasticity at room temperature and a preparation method thereof, belonging to the technical field of magnesium alloys. The magnesium alloy consists of the following components in terms of mass percentage: Sn 0.2-0.4%; Y 0.4-0.4% 0.9%; Zr 0.4‑0.6%; unavoidable impurities ≤ 0.15%; the balance is magnesium. By adding Sn, Y and Zr elements to the magnesium alloy and controlling the content of the three elements at the same time, not only can the final magnesium alloy be guaranteed to have high plasticity, the elongation rate is as high as 40%, and the magnesium alloy can also be guaranteed to have a medium yield strength. and tensile strength. When preparing the magnesium alloy, only a small amount of rare earth elements can be added to significantly change the plasticity of the magnesium alloy, and the preparation method is simple, only one traditional extrusion is required, and no complicated processing technology is required. Furnace and extruder are general-purpose equipment, which are highly portable and easy to implement in industry.

Description

A kind of magnesium-tin-yttrium-zirconium alloy with high plasticity at room temperature and preparation method thereof

technical field

The invention belongs to the technical field of magnesium alloys, in particular to a magnesium-tin-yttrium-zirconium alloy with high plasticity at room temperature and a preparation method thereof.

Background technique

Magnesium and magnesium alloys have the advantages of low density, high specific strength, high specific stiffness, and good electromagnetic shielding performance. They have extremely important application values and broad prospects in the fields of aerospace, automotive lightweight, and electronic communications.

Compared with cast magnesium alloys, wrought magnesium alloys have greater development potential, and better mechanical properties can be obtained by adjusting the material structure. Due to the close-packed hexagonal crystal structure of magnesium alloy, there are few slip systems at room temperature, which makes it difficult to process and deform. Therefore, deformed magnesium alloys need to be processed by hot deformation methods such as extrusion and rolling, but the limited slip system makes Magnesium alloys tend to form a strong basal texture after plastic deformation, and this strong basal texture will deteriorate the mechanical properties and room temperature formability of subsequent magnesium alloy sheets. In recent years, researchers have proposed the use of alloying methods to control the basal texture, thereby improving the mechanical properties and room temperature forming properties of magnesium alloys. The addition of rare earth elements in magnesium alloys can effectively weaken the basal texture and improve the plasticity and formability of magnesium alloys. However, due to the high price of rare earth elements, researchers are forced to develop low-cost high-performance magnesium alloys.

Contents of the invention

In view of this, one of the objectives of the present invention is to provide a room temperature high plasticity magnesium-tin-yttrium-zirconium alloy; the second purpose is to provide a room temperature high plasticity magnesium-tin-yttrium-zirconium alloy preparation method.

To achieve the above object, the present invention provides the following technical solutions:

1. A magnesium-tin-yttrium-zirconium alloy with high plasticity at room temperature. In terms of mass percentage, the magnesium alloy is composed of the following components: Sn 0.2-0.4%; Y 0.4-0.9%; Zr 0.4-0.6%; Avoid impurities ≤ 0.15%; the balance is magnesium.

Preferably, in terms of mass percentage, the magnesium alloy is composed of the following components: Sn 0.21%; Y 0.41%; Zr 0.46%; unavoidable impurities ≤ 0.15%; the balance is magnesium.

Preferably, in terms of mass percentage, the magnesium alloy is composed of the following components: Sn 0.38%; Y 0.90%; Zr 0.52%; unavoidable impurities ≤ 0.15%; the balance is magnesium.

2. The preparation method of a room temperature high plasticity magnesium-tin-yttrium-zirconium alloy, the method comprising the following steps:

(1) Smelting: In a protective atmosphere, heat the pure magnesium ingot to 670-700°C, slag after the pure magnesium ingot is completely melted, then heat up to 710-730°C, add pure tin ingot, magnesium yttrium master alloy and magnesium-zirconium master alloy, fully stirred and smelted, and kept at 710-730°C for 20-30 minutes to obtain a magnesium alloy melt;

(2) Casting: cast the magnesium alloy melt obtained in the step (1) after slag casting, and get an ingot after air cooling;

(3) Machining: the ingot obtained in the step (2) is sawed, and the car is back for subsequent use;

(4) Homogenization treatment;

(5) Squeeze.

Preferably, in step (1), the protective atmosphere is a mixed gas formed of CO ₂ and SF ₆ at a volume ratio of 99:1.

Preferably, in step (1), the mass percent of the magnesium-yttrium master alloy yttrium is 28-30%.

Preferably, in step (1), the mass percentage of the magnesium-zirconium master alloy zirconium is 28-30%.

Preferably, in step (1), the specific method of adding the pure tin ingot, magnesium-yttrium master alloy and magnesium-zirconium master alloy is: after the pure tin ingot is melted, add the magnesium-yttrium master alloy after standing for 5 minutes, and then After the magnesium-yttrium master alloy is melted, the magnesium-zirconium master alloy is added after standing still for 5 minutes.

Preferably, in step (4), the homogenization treatment is specifically heat preservation at 350-370° C. for 12-24 hours.

Preferably, in step (5), the extrusion specifically includes: after preheating the extrusion die and the ingot treated in step (4) at 350-370°C for 1-2h, the extrusion temperature is 350- 370°C, the extrusion speed is 6-10m·min ^-1 , and the extrusion ratio is 33-55:1.

The beneficial effects of the present invention are: the present invention provides a magnesium-tin-yttrium-zirconium alloy with high plasticity at room temperature and a preparation method thereof, by adding Sn, Y and Zr elements to the magnesium alloy and simultaneously controlling the content of the three elements, Not only can it ensure that the final prepared magnesium alloy has high plasticity and the elongation rate is as high as 40%, but it can also ensure that the magnesium alloy has medium yield strength and tensile strength. The reason is that the content of the three elements added in pure magnesium is very small, and most of them are solid-dissolved in the magnesium matrix, so that the formation of the second phase is greatly reduced, so these rare first phases are reduced during the stretching process. The two phases are not enough to be the source of tensile cracks, thereby ensuring that the final prepared alloy has high plasticity, which is manifested by high elongation. In addition, because the Y element mainly exists in the form of solid solution in the magnesium matrix, it promotes the formation of rare earth texture during the extrusion process, weakens the basal texture of the alloy, and promotes the opening of the basal slip during tensile deformation, greatly Improve the plasticity of the alloy. In addition, the three elements dissolved in the magnesium matrix can play a solid solution strengthening effect to a certain extent. Among them, the Zr element exists in the form of α-Zr during the smelting process and acts as a nucleation point to refine the as-cast alloy. Grain size, which in turn makes the grain size of the extruded alloy smaller and promotes the improvement of the tensile strength of the alloy. The three elements solid-soluble in the magnesium matrix are enriched at the grain boundary in the form of atoms. On the one hand, it can effectively hinder the movement of the grain boundary and improve the tensile strength. The generation of grain boundary cracks during stretching can improve the strength of the alloy to a certain extent and at the same time greatly increase the plasticity of the alloy. The cost of raw materials used in the preparation of the magnesium alloy is low, only a small amount of rare earth elements can be added to significantly change the plasticity of the magnesium alloy, and the preparation method is simple, only one traditional extrusion is required, and no complicated processing is required The process, the smelting furnace and the extruder used are all conventional general-purpose equipment, which are highly portable and easy to realize in industry.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is the XRD figure of the magnesium-tin-yttrium-zirconium alloy sheet material prepared in embodiment 1, embodiment 2 and comparative example; ((a), (b), (c) are embodiment 1, embodiment successively 2 and the XRD pattern of the magnesium-tin-yttrium-zirconium alloy plate prepared in the comparative example)

Fig. 2 is the scanning electron micrograph of the magnesium-tin-yttrium-zirconium alloy sheet material prepared in embodiment 1;

Fig. 3 is the scanning electron micrograph of the magnesium-tin-yttrium-zirconium alloy sheet material prepared in embodiment 2;

Fig. 4 is the scanning electron micrograph of the magnesium-tin-yttrium-zirconium alloy sheet material prepared in the comparative example;

Fig. 5 is the scanning electron micrograph of the magnesium-tin-yttrium-zirconium alloy plate after stretching the magnesium alloy plate in the comparative example to 10% strain;

Fig. 6 is the microstructure and texture diagram of the magnesium-tin-yttrium-zirconium alloy plates prepared in Example 1, Example 2 and Comparative Example. ((a), (b), (c) the IPF figure of the magnesium-tin-yttrium-zirconium alloy sheet material prepared in successive embodiment 1, embodiment 2 and comparative example; (d), (e), (f ) the (0002) microscopic pole figure of the magnesium-tin-yttrium-zirconium alloy plate prepared in sequentially embodiment 1, embodiment 2 and comparative example)

Detailed ways

Preferred embodiments of the present invention will be described in detail below.

Example 1

A magnesium-tin-yttrium-zirconium alloy with high plasticity at room temperature, the magnesium alloy is composed of the following components in terms of mass percentage: Sn 0.21%; Y 0.41%; Zr 0.46%; unavoidable impurities ≤ 0.15%; the balance is magnesium.

The preparation method of this room temperature high plasticity magnesium-tin-yttrium-zirconium alloy is as follows:

(1) Smelting: Under the mixed gas of _CO2 and _SF6 at a volume ratio of 99:1, heat the pure magnesium ingot to 670°C, slag after the pure magnesium ingot is completely melted, and then raise the temperature to 720°C, First add pure tin ingot, after the pure tin ingot is melted, let it stand still for 5 minutes, then add the magnesium-yttrium master alloy, wait for the magnesium-yttrium master alloy to melt, then let it stand still for 5 minutes, finally add the magnesium-zirconium master alloy, fully stir and smelt, at 720 After being kept at ℃ for 20 minutes, a magnesium alloy melt was obtained, wherein the mass percentage of yttrium in the magnesium-yttrium master alloy was 28%; the mass percentage of zirconium in the magnesium-zirconium master alloy was 30%.

(2) Casting: cast the magnesium alloy melt obtained in the step (1) after slag casting, and get an ingot after air cooling;

(3) Machining: sawing and turning the ingot obtained in the step (2) to a diameter of 70mm and a height of 60mm for subsequent use;

(4) Homogenization treatment: keeping the ingot treated in step (3) at 350° C. for 12 hours.

(5) Extrusion: After preheating the extrusion die and the ingot treated in step (4) at 350°C for 1.5h, the extrusion temperature is 350°C and the extrusion speed is 6m·min ^-1 The extrusion is carried out under the condition of a ratio of 33:1 to obtain a magnesium-tin-yttrium-zirconium alloy plate.

Example 2

A room temperature high plasticity magnesium-tin-yttrium-zirconium alloy, the magnesium alloy is composed of the following components by mass percentage: Sn 0.38%; Y 0.90%; Zr 0.52%; unavoidable impurities ≤ 0.15%; magnesium.

The preparation method of this room temperature high plasticity magnesium-tin-yttrium-zirconium alloy is as follows:

(1) Smelting: Under the mixed gas formed by _CO2 and _SF6 at a volume ratio of 99:1, heat the pure magnesium ingot to 700°C, slag after the pure magnesium ingot is completely melted, and then raise the temperature to 730°C, First add pure tin ingot, after the pure tin ingot is melted, let it stand still for 5 minutes, then add the magnesium-yttrium master alloy, wait for the magnesium-yttrium master alloy to melt, then let it stand still for 5 minutes, finally add the magnesium-zirconium master alloy, fully stir and smelt, at 730 After being kept at ℃ for 30 minutes, a magnesium alloy melt is obtained, wherein the mass percentage of yttrium in the magnesium-yttrium master alloy is 30%; the mass percentage of zirconium in the magnesium-zirconium master alloy is 28%.

(2) Casting: cast the magnesium alloy melt obtained in the step (1) after slag casting, and get an ingot after air cooling;

(3) Machining: sawing and turning the ingot obtained in the step (2) to a diameter of 70mm and a height of 60mm for subsequent use;

(4) Homogenization treatment: keeping the ingot treated in step (3) at 370° C. for 24 hours.

(5) Extrusion: After preheating the extrusion die and the ingot treated in step (4) at 370°C for 2 hours, the extrusion temperature is 370°C, the extrusion speed is 10m·min ^-1 , and the extrusion ratio Extrusion is carried out under the condition of 55:1 to obtain a magnesium-tin-yttrium-zirconium alloy plate.

comparative example

A magnesium-tin-yttrium-zirconium alloy with medium Sn and Y content, the magnesium alloy is composed of the following components in terms of mass percentage: Sn 2.1%; Y 2.0%; Zr 0.56%; unavoidable impurities ≤ 0.15%; The balance is magnesium. Refer to Example 1 for the preparation method of the alloy.

Utilize X-ray diffractometer (Rigaku D/Max 2500) to analyze the magnesium-tin-yttrium-zirconium alloy sheet material prepared in embodiment 1, embodiment 2 and comparative example respectively, the result is as shown in Figure 1, wherein, (a), (b), and (c) in 1 are successively the XRD patterns of the magnesium-tin-yttrium-zirconium alloy plates prepared in Example 1, Example 2 and Comparative Examples, as can be seen from Figure 1, Example 1 Only α-Mg matrix is found in the magnesium-tin-yttrium-zirconium alloy plate prepared in ₃ Y ₅ and the second phase of MgSnY, but no diffraction peaks containing Zr elements were found. Judging by the peak intensity and the number of diffraction peaks of the XRD figure, the diffraction peak intensity of the MgSnY ternary phase in the magnesium-tin-yttrium-zirconium alloy plate in Example 2 is weak and the number is small, while the magnesium-tin phase in the comparative example - The phase has a large peak intensity and a large number in the yttrium-zirconium alloy plate. Therefore, it can be concluded that Sn ₃ Y ₅ is preferentially formed during the solidification process of the alloy, and the MgSnY ternary phase gradually forms with the increase of Sn and Y content.

Using a TESCAN VEGA 3LMH scanning electron microscope, the magnesium-tin-yttrium-zirconium alloy sheet prepared in Example 1, Example 2, and the comparative example and the magnesium-tin-yttrium-zirconium alloy sheet prepared in the comparative example after stretching the magnesium alloy sheet to 10% strain were respectively analyzed. Tin-yttrium-zirconium alloy plate is analyzed, and the results are as shown in Figure 2, Figure 3, Figure 4 and Figure 5, wherein, as can be seen from Figure 2, the magnesium-tin-yttrium-zirconium alloy plate prepared in Example 1 is the first The quantity of two phases is quite few, and this agrees with the result that there is no other second phase except α-Mg phase in its XRD figure; As can be seen from Fig. 3 and Fig. 4, the magnesium-prepared in embodiment 2 and comparative example- The quantity of the second phase in the tin-yttrium-zirconium alloy plate gradually increases, and the morphology of the second phase presents irregular fine particles, which are distributed in a streamline along the direction of extrusion, and the magnesium-tin prepared in the comparative example - The amount of the second phase in the yttrium-zirconium alloy plate is much greater than the amount of the second phase in the magnesium-tin-yttrium-zirconium alloy plate prepared in Example 2, and there are more large and irregular second phases, which It is also consistent with the results shown in the XRD patterns of the two plates.

Because a large number of fine and dispersed second phases can effectively pin the grain boundaries, thereby refining the grain size of the alloy and improving the strength of the alloy, but at the same time, a large number of large and irregular second phases are in the process of stretching. It will become the source of tensile cracks and reduce the plasticity of the alloy to a large extent. It can be seen from Figure 5 that there are obvious cracks in the bulk second phase, which shows that a large number of large irregular second phases can become the source of tensile cracks during the stretching process, which reduces the plasticity of the alloy.

Utilize JEOL JSM-7800F field emission electron microscope to carry out microstructure and texture analysis to the magnesium-tin-yttrium-zirconium alloy plate prepared in embodiment 1, embodiment 2 and comparative example respectively, the result is as shown in Figure 6, Figure 6 Among (a), (b), (c) the IPF figure of the magnesium-tin-yttrium-zirconium alloy sheet material that prepares in embodiment 1, embodiment 2 and comparative example successively, by (a) among Fig. 6, (b ), (c) it can be seen that with the increase of Sn element content, the grain size becomes smaller and smaller, and the average grain size decreases from ~10μm to ~6μm. Particles can effectively promote the formation of dynamic recrystallization, and at the same time, they are pinned to the grain boundary to hinder the growth of recrystallized grains. In addition, part of the Zr element exists in the form of α-Zr in the magnesium melt, which becomes the nucleation point of the magnesium crystal, and refines the grain size of the as-cast magnesium-tin-yttrium-zirconium alloy. The grains can be further refined during the process. Among Fig. 6 (d), (e), (f) the (0002) microcosmic pole figure of the magnesium-tin-yttrium-zirconium alloy plate that prepares in embodiment 1, embodiment 2 and comparative example successively, by in Fig. 6 (d), (e) and (f), it can be seen that the three alloy sheets all exhibit typical bimodal texture characteristics, and the maximum pole density appears at the position where ~20° deflection occurs along the extrusion direction, but the pole density increases with decrease with the increase of Sn content.

Adopt CMT5105-300kN microcomputer control electronic universal testing machine to commercial AZ31 magnesium alloy sheet material, the microalloying magnesium-tin-yttrium alloy (Mg-0.4Sn-0.7Y) that does not contain Zr element and embodiment 1, 2 and comparative embodiment The magnesium-tin-yttrium-zirconium alloy plates prepared in the tensile test were carried out, and the results are shown in Table 1.

As can be seen from Table 1, the elongation of the microalloyed magnesium-tin-yttrium alloy (Mg-0.4Sn-0.7Y) and the magnesium-tin-yttrium-zirconium alloy plate prepared in Examples 1 and 2 without Zr element is obvious Higher than the elongation of the magnesium-tin-yttrium-zirconium alloy sheet prepared in the commercial AZ31 and comparative examples, especially the elongation of the magnesium alloy sheet prepared in Example 2 is as high as 40.1%, and the yield strength and tensile strength are respectively Increased to 180.3MPa and 300.8MPa, this excellent mechanical properties and elongation are conducive to further improvement of bending and cupping forming performance. Although the comparative example contains a large amount of fine second phases, which can significantly enhance its yield strength, its texture strength is obviously weakened, and under the combined effect of the two, the strength is still lower than that prepared in Examples 1 and 2. Strength of magnesium-tin-yttrium-zirconium alloy sheets. In addition, due to the appearance of the bulky second phase in the magnesium-tin-yttrium-zirconium alloy sheet in the comparative example, it becomes the source of tensile cracks during the stretching process, greatly reducing its plasticity. For the microalloyed magnesium-tin-yttrium alloy without Zr element, even though it has a higher elongation, the yield strength shown by the alloy is far lower than that of the magnesium-tin-yttrium alloy prepared in Examples 1 and 2. Yttrium-zirconium alloy plate, this is due to the addition of Zr element, which can effectively refine the grain, and can contribute part of the plasticity while improving the tensile strength of the alloy. Therefore, the microalloyed magnesium-tin- Both yttrium alloy and magnesium-tin-yttrium-zirconium alloy with high Sn content are not suitable for practical industrial applications, while the magnesium-tin-yttrium-zirconium alloy plate in the present invention can obtain high plasticity medium after a hot extrusion process High-strength magnesium-tin-yttrium-zirconium alloy sheet has high industrial application value.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (10)

1. a kind of room temperature high-ductility magnesium-tin-yttrium-zircaloy, which is characterized in that by mass percentage, the magnesium alloy is by such as The following group is grouped as：Sn 0.2-0.4%；Y 0.4-0.9%；Zr 0.4-0.6%；Inevitable impurity≤0.15%；Surplus is Magnesium.

2. a kind of room temperature high-ductility magnesium-tin-yttrium-zircaloy as described in claim 1, which is characterized in that by mass percentage Meter, the magnesium alloy are grouped as by following group：Sn 0.21%；Y 0.41%；Zr 0.46%；Inevitable impurity≤ 0.15%；Surplus is magnesium.

3. a kind of room temperature high-ductility magnesium-tin-yttrium-zircaloy as described in claim 1, which is characterized in that by mass percentage Meter, the magnesium alloy are grouped as by following group：Sn 0.38%；Y 0.90%；Zr 0.52%；Inevitable impurity≤ 0.15%；Surplus is magnesium.

4. a kind of preparation method of room temperature high-ductility magnesium-tin-yttrium-zircaloy of claim 1-3 any one of them, feature exist In described method includes following steps：

(1) melting：Under protective atmosphere, pure magnesium ingot is heated to 670-700 DEG C, the slag hitting after the pure magnesium ingot all fusing, 710-730 DEG C is then heated to, pure tin ingot, magnesium yttrium intermediate alloy and Mg-Zr intermediate alloy is added, melting is sufficiently stirred, in 710- Magnesium alloy melt is obtained after keeping the temperature 20-30min at 730 DEG C；

(2) it casts：By moulding by casting after the magnesium alloy melt slag hitting obtained in step (1), ingot casting is obtained after air-cooled；

(3) it machines：It will be spare after the ingot casting sawing obtained in step (2), railway carriage；

(4) Homogenization Treatments；

(5) it squeezes.

5. method as claimed in claim 4, which is characterized in that in step (1), the protective atmosphere is CO₂And SF₆By volume Than 99：1 mixed gas formed.

6. method as claimed in claim 4, which is characterized in that in step (1), the quality percentage of the magnesium yttrium intermediate alloy yttrium Than for 28-30%.

7. method as claimed in claim 4, which is characterized in that in step (1), the quality percentage of the Mg-Zr intermediate alloy zirconium Than for 28-30%.

8. method as claimed in claim 4, which is characterized in that in step (1), the addition pure tin ingot, magnesium yttrium intermediate alloy Concrete mode with Mg-Zr intermediate alloy is：After pure tin ingot fusing, magnesium yttrium intermediate alloy is added after standing 5min, then wait for After the magnesium yttrium intermediate alloy fusing, then Mg-Zr intermediate alloy is added after standing 5min.

9. method as claimed in claim 4, which is characterized in that in step (4), the Homogenization Treatments are specially in 350- 12-24h is kept the temperature at 370 DEG C.

10. method as claimed in claim 4, which is characterized in that in step (5), the extruding is specially：By extrusion die and It is 350-370 DEG C squeezing temperature after the ingot casting of step (4) processing preheats 1-2h at 350-370 DEG C, extrusion speed 6- 10m·min^-1, extrusion ratio 33-55:It is carried out under the conditions of 1.