CN106834846B - A kind of multicomponent heat-resistant corrosion-resistant magnesium alloy and preparation method - Google Patents

Abstract

The invention discloses a multi-element heat-resistant and corrosion-resistant magnesium alloy and a preparation method thereof. The alloy includes: 5.8-7.8% Al, 2.2-3.2% Sn, 0.2-1.0% Zn, 0.2-2.0% RE, 0.1- 0.3% Mn, the balance is Mg and unavoidable impurities with a total amount of ≤0.2%. Add tin, neodymium and/or samarium to the magnesium-aluminum base material to form high-melting point particle phases Nd ₅ Sn ₃ and Sm ₅ Sn ₃ , and further refine the high-melting point particle phase by adding zinc to improve the strong plasticity and heat resistance of the alloy At the same time, the remaining tin and magnesium combine to form Mg ₂ Sn, which further improves the performance of the alloy; adding manganese reduces the damage of impurity elements, improves the corrosion resistance of the alloy, and obtains heat and corrosion resistance by adjusting the ratio of elements magnesium alloy.

Description

A multi-component heat-resistant and corrosion-resistant magnesium alloy and its preparation method

technical field

The invention relates to the field of light metal materials and metallurgy technology. More specifically, the invention relates to a multi-element heat-resistant cast magnesium alloy and a preparation method thereof.

Background technique

With the increasing energy shortage and environmental pollution, the lightweight of the transportation field is inevitable, and it has attracted widespread attention as an environmentally friendly lightweight material. As the lightest metal structural material currently available, magnesium alloy has the advantages of high specific strength and specific stiffness, good anti-magnetic interference, excellent damping and shock absorption performance, high thermal conductivity and easy recycling. Transportation equipment manufacturing, home appliances, electronic communications, biomedicine and other fields have significant application value and huge application prospects, and have become one of the most promising metal materials in the 21st century. So far, the existing commercial magnesium alloys are still dominated by Mg-Al magnesium alloys of AZ91 and AM50, accounting for about 90% of the total magnesium alloys.

The Mg ₁₇ Al ₁₂ phase of the Mg-Al series magnesium alloy is mainly distributed in the grain boundary in the form of dissociated eutectic network, which deteriorates the corrosion resistance and high temperature strength of the alloy. For this reason, the majority of scientific researchers have carried out research on Mg-Al series magnesium alloys from the aspects of alloy composition design (alloying) and heat treatment (T6 treatment), aiming to improve their mechanical properties and corrosion resistance.

The addition of an appropriate amount of Sn to Mg-Al magnesium alloys can reduce the stacking fault energy of magnesium, which is beneficial to the realization of superplasticity, and has a certain solid solution strengthening effect; but when the content of Sn is high, large-sized Mg ₂ Sn aggregates in the crystal The boundary reduces the performance of the alloy; the single addition of Sn does not improve the corrosion resistance of the alloy significantly. The role of RE elements in Mg-Al magnesium alloys is mainly to improve the mechanical properties of the alloy through the formation of Al-RE phases and heat treatment, but the Al-RE phases are easily enriched at the alloy grain boundaries and have a large size, which reduces the alloy’s mechanical properties. precipitation strengthening effect. Zn element is one of the commonly used alloying elements in magnesium alloys, which is mainly used to improve the mechanical properties of the alloy. However, adding too much Zn will reduce the corrosion resistance of the alloy. The addition of Mn element can reduce the harmful effect of the impurity element Fe, and at the same time, the Al-Mn compound formed at the grain boundary is easier to passivate than the Mg ₁₇ Al ₁₂ phase, which improves the corrosion resistance of the magnesium alloy. The above shows that it is difficult to achieve a heat-resistant and corrosion-resistant magnesium alloy with certain mechanical properties by simply adding alloying elements to the Mg-Al alloy. Most studies focus on the formation and modification of the Al-RE phase, and do not take into account that the alloying element tin and neodymium or samarium form a second phase with a high melting point, and these second phases with a high melting point contribute to the improvement of the heat resistance of the alloy .

The Chinese patent "A high-strength cast magnesium alloy and its melting method" [Application No.: 200810230077.2] discloses a high-strength cast magnesium alloy. The mass percentages of its components are: Gd: 8.1-11.5% , Y: 1.0～4.5%, RE: 0.01～3.0%, Zn: 0.01～0.2%, Mn: 0～0.18%, Zr≤1.0%, and (Gd+Y+RE)≤15.5%; Mg and impurities: In the balance, the rare earth content of the alloy is high, and the grain size of the alloy is further refined by adding the alloy element Zr, which increases the cost of alloy preparation, and the alloy does not contain relatively cheap alloy elements Al and Sn.

Chinese patent "A high-strength heat-resistant magnesium alloy and its melting method" [application number: 200610112622.9] discloses a high-strength heat-resistant magnesium alloy. 8wt%, Dy is 0~5wt%, Tb is 0~5wt%, Ho is 0~5wt%, Er is 0~5wt%, Tm is 0~5wt%, Nd is 2~4.5wt%, Sm is 0~5wt%. 3.5wt%, and the rest is Mg. This alloy can be used as a wrought magnesium alloy or as a casting. The alloy contains a high content of rare earth, which increases the cost of alloy preparation, does not contain alloy elements Al, Zn, Sn and Mn, and does not carry out relevant corrosion resistance testing.

Chinese patent "A heat-resistant magnesium-based rare earth alloy and its preparation method" [Application No.: 200610131696.7] proposes an alloy composition and weight percentage: 6-8% Gd, 1-5% R, 0.3-0.6% Zr, impurities The total amount of elements Ni, Cu, Fe, Si and Al is not more than 0.05%, and the rest is Mg; the general composition formula is: Mg-(6～8%)Gd-(1～5%)R-(0.3～0.6% ) Zr. Wherein, R represents Nd or Sm or MY or Dy or Ho or Er; the rare earth content in the alloy is controlled at 7% to 13%. The rare earth content of the alloy is high, which increases the cost of alloy preparation, and at the same time, a large amount of rare earth phase increases the cost of subsequent heat treatment of the alloy, and the alloy does not add elements Al, Zn, Sn and Mn.

Chinese patent "A Mg-Sn-Al Deformed Magnesium Alloy and Its Preparation Method" [Application No.: CN201310071667.6] discloses its raw material components and mass percentages: industrial pure tin: 4.00% to 10.00%; industrial pure tin: 4.00% to 10.00%; Pure aluminum: 1.00% to 6.00%; manganese: 0.01% to 1.00%; the rest is industrial pure magnesium and unavoidable impurities. The industrial pure magnesium, industrial pure aluminum and industrial pure tin are all above 99% pure; zinc purity Above 99.5%; manganese is added in the form of 4% magnesium-manganese master alloy. The alloy has a relatively high Sn content and is used as a deformed magnesium alloy without adding rare earth elements.

Patent 201110032706.1 discloses a high-strength, toughness, heat-resistant and corrosion-resistant rare earth magnesium alloy and its preparation method. Its mass percentage is composed of: 3-6% aluminum; 0.2-0.5% manganese, 1.0-2.5% rare earth, % of antimony, 0.3-0.8% of cadmium, and the rest being magnesium. The rare earth is a commercialized cerium-rich mixed rare earth (RE), and the mass percentage of the elemental composition of the commercialized cerium-rich mixed rare earth (RE) is: 25-35% lanthanum (La), 60-72% cerium (Ce), 3-8% praseodymium (Pr), 0-3% neodymium (Nd). Preparation method: according to the alloy material with the above ratio, under the protection smelting condition of SF6+CO2 mixed gas with a volume fraction of 0.5%, the magnesium is melted in the crucible, and at 660-680 ° C, the industrial pure aluminum, aluminum manganese intermediate Alloying elements are added in the form of alloy and Mg-RE intermediate alloy. After the added charge is completely dissolved into alloy melt, the temperature is raised, and then industrial pure antimony and pure cadmium are pressed into the alloy melt from the bell jar, and stirred and mixed. Uniform and continue to heat up, add refining agent to refine the magnesium alloy solution, and pour it after standing still to obtain this product. Advantages: Improve the strength and toughness of the alloy and the mechanical properties at room temperature and high temperature; make the strength and toughness, heat resistance and corrosion resistance of the alloy higher than the existing AE series magnesium alloys.

Contents of the invention

The purpose of the present invention is to provide a magnesium alloy, adding tin, neodymium and/or samarium into the magnesium-aluminum base material to form high-melting point particle phases Nd ₅ Sn ₃ and Sm ₅ Sn ₃ , and further refine the high-melting point particles by adding zinc phase, improve the strong plasticity, heat resistance and corrosion resistance of the alloy, and adjust the ratio between elements to obtain a heat-resistant and corrosion-resistant magnesium alloy.

Still another object of the present invention is to provide a kind of preparation method of magnesium alloy, control parameters such as argon flow rate, melt temperature when blowing argon, the time of blowing argon and the stirring speed of head blowing argon in the melt, Minimize the content of slag in the structure, which is beneficial to improve the performance of the alloy.

In order to realize these objects and other advantages according to the present invention, a kind of multi-component heat-resistant and corrosion-resistant magnesium alloy is provided, comprising: 5.8～7.8% Al, 2.2～3.2% Sn, 0.2～1.0% Zn, 0.2～ 2.0% RE, 0.1-0.3% Mn, the rest is Mg and unavoidable total impurities ≤ 0.2%.

Preferably, the RE is Nd and/or Sm.

Preferably, Si≤0.1% in the impurities.

It is preferred to include: 7.0-7.8% Al, 2.5-3.0% Sn, 0.5-1.0% Zn, 0.8-1.6% RE, 0.1-0.3% Mn, the remainder being Mg and the unavoidable total amount ≤ 0.2% Impurities.

Preferably, the RE is 0.6-1.4% Nd and/or 0.3-0.6% Sm.

The purpose of the present invention is also achieved by a method for preparing a multi-element heat-resistant and corrosion-resistant magnesium alloy, comprising the following steps:

raw material preheating;

Put a protective atmosphere into the smelting furnace, put magnesium ingots and heat until completely melted, add aluminum ingots, zinc ingots and tin ingots at 670-690°C, dissolve completely and stir, then raise the temperature to 700-720°C, and then add Mg- Mn master alloy, Mg-Sm master alloy, Mg-Nd master alloy, then raise the temperature to 730-750°C to make the composition of the alloy melt uniform, then cool down to 680-700°C and blow argon into the melt for 1-5 minutes for refining , the alloy melt after slag removal is kept at 720-750°C for 10-30 minutes, and the alloy melt is cast into a mold with a preheating temperature of 200-300°C;

Put the casting into an electric furnace with a protective atmosphere for solution treatment, keep it at 410-430°C for 18-24 hours, then raise the temperature to 500-540°C with the furnace at a heating rate of 10-20°C/min and keep it for 1 ~3 hours, then quenched into water;

Put the casting after solid solution treatment into an aging treatment furnace, raise the temperature to 175-240°C and keep it warm for 36-84 hours, then take it out and air-cool it.

Preferably, the purity of magnesium ingots is ≥99.99%, the purity of aluminum ingots is ≥99.99%, the purity of zinc ingots is ≥99.99%, the purity of tin ingots is ≥99.99%, and the purity of Mg-Nd, Mg-Sm and Mg-Mn master alloys Impurity content ≤0.1%.

Preferably, the protective atmosphere in the alloy melting and casting step is a mixed gas of SF ₆ and CO ₂ , and the volume ratio of the SF ₆ and CO ₂ gas is 1:90-110.

Preferably, the refining argon flow rate is 5-20 ml/min.

Preferably, the preheating of the raw materials includes: placing the raw materials in an oven at 90-135° C. for 0.5-1 hour.

The present invention at least includes the following beneficial effects:

1. The alloy composition design principle of the present invention is multi-element alloying, rather than using a certain alloy element alone. For example, in the Mg-Al-Sn alloy, the Mg ₂ Sn phase is preferentially formed, but when the rare earth (RE) element is added, the electronegativity difference between Sn and RE is larger than that between Sn and Mg , the RE ₅ Sn ₃ phase is preferentially formed instead of the Mg ₂ Sn phase, and the remaining part of Sn reacts with Mg to form the Mg ₂ Sn phase; due to the small content of the alloying elements Sn and RE added in the alloy, the size of the second phase formed When the alloying element Zn is added, the RE ₅ Sn ₃ phase and Mg ₂ Sn phase will be further refined and distributed more diffusely in the grain boundary, which provides the size of the second phase for the subsequent solution treatment and aging treatment. Guarantee, correspondingly improve the heat resistance and corrosion resistance of the alloy. The addition of Mn further improves the corrosion resistance of the alloy.

2. The second phase RE ₅ Sn ₃ and Mg ₂ Sn refines the Mg ₁₇ Al ₁₂ phase. When the alloy is solidified, the second phase RE ₅ Sn ₃ and Mg ₂ Sn is preferentially generated at the grain boundary than the Mg ₁₇ Al ₁₂ phase , the large-sized, continuous Mg ₁₇ Al ₁₂ phase cannot be formed at the grain boundary. When the alloy is subjected to aging treatment, it is conducive to the small-sized precipitation of the Mg ₁₇ Al ₁₂ phase, thereby improving the strength, heat resistance and corrosion resistance of the alloy . As above, the addition of Zn element makes this effect more obvious.

3. In the alloy preparation method, especially the argon blowing refining step in the casting method, the purpose is to remove the slag in the alloy melt, the argon flow rate, the melt temperature when blowing argon, the time of blowing argon and the Parameters such as the stirring speed of the argon head in the melt determine the content of slag in the as-cast microstructure of the alloy when it solidifies. Appropriate process parameters are conducive to minimizing the content of slag in the structure and improving the performance of the alloy; for example : If the argon flow rate is too fast, the alloy will be further oxidized, or if the argon flow rate is too slow, there will be residual slag left in the alloy structure, both of which are not conducive to the microstructure of the alloy, and will deteriorate the strength and heat resistance of the alloy. performance and corrosion resistance. The optimization of parameters such as temperature and time of solution treatment and aging treatment in the alloy preparation method further ensures the effect of precipitation strengthening.

Through the multi-element alloying composition design, the alloy obtained a dispersed high-temperature second phase during solidification, realizing solid solution strengthening, fine-grain strengthening and second phase strengthening; further through heat treatment, aging strengthening was achieved and the alloy’s strength was improved. Heat resistance, while significantly improving the corrosion resistance of the alloy.

Other advantages, objectives and features of the present invention will partly be embodied through the following descriptions, and partly will be understood by those skilled in the art through the study and practice of the present invention.

Description of drawings

Fig. 1 is a precipitated phase morphology diagram of the multi-component heat-resistant and corrosion-resistant magnesium alloy of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings, so that those skilled in the art can implement it with reference to the description.

It should be understood that terms such as "having", "comprising" and "including" as used herein do not entail the presence or addition of one or more other elements or combinations thereof.

The invention provides a multi-component heat-resistant and corrosion-resistant magnesium alloy, which comprises: 5.8-7.8% Al, 2.2-3.2% Sn, 0.2-1.0% Zn, 0.2-2.0% RE, 0.1-0.3% Mn, The remainder is Mg and unavoidable impurities in a total amount≤0.2%, wherein the RE is Nd or Sm or a mixture of Nd and Sm, and Si≤0.1% in the impurities.

In another embodiment, the multi-component heat-resistant and corrosion-resistant magnesium alloy includes: 7.0-7.8% Al, 2.5-3.0% Sn, 0.5-1.0% Zn, 0.8-1.6% RE, 0.1-0.3% Mn, and the rest Mg and unavoidable impurities with a total amount≤0.2%, wherein, the RE is 0.5-1.0% Nd and/or 0.3-0.6% Sm, and Si≤0.1% in the impurities.

The optimization process of heat and corrosion resistance of Mg alloy is as follows:

1. Mg-Al alloy substrate

Adding aluminum to magnesium can improve the solid solution strengthening effect of the alloy. When the mass of Al and Mg is 1:11-15.5, the casting performance and corrosion resistance of the magnesium alloy can be improved, and the weight of the alloy can be realized. But the Mg ₁₇ Al ₁₂ phase deteriorates the corrosion resistance and high temperature strength of the alloy.

2. Mg-Al-Sn alloy:

The element Sn is added to the Mg-Al alloy substrate, wherein, based on the mass of Al:Mg:Sn=1:11-15.5:0.38-0.41, the co-doping of Sn and Al is beneficial to the improvement of plasticity.

Table 1 Mass fraction ratio of Mg-Al-Sn alloy

Example Mg(wt%) Al(wt%) Sn(wt%) 1 91.48 6.0 2.4 2 90.77 6.5 2.6 3 90.06 7.0 2.8 4 89.35 7.5 3 5 88.62 8.0 3.2

The alloy obtained in embodiment 1-5 carries out room temperature tensile test, high temperature (175 ℃) tensile test and corrosion full immersion test, wherein, the test data of corrosion resistance is according to GB10124-1988 metal material laboratory uniform corrosion full immersion test method obtained, and the test results are summarized in Table 2.

Table 2 Mass fraction ratio of Mg-Al-Sn alloy

It can be seen from Table 2 that as the Sn content increases from 2.4% to 3.0%, the tensile properties and corrosion resistance of the alloy at room temperature and high temperature are improved, but when the Sn content increases to 3.2%, the mechanical properties of the alloy decrease instead. The reason is as follows: the grains of Mg-Al-Sn alloy are further refined than that of Mg-Al alloy. Since the diffusion rate of Sn in Mg is slow, it is not easy to cause the grain growth of the precipitated phase due to overaging, because in the alloy melt During the solidification process, part of Sn is preferentially combined with Mg to form Mg ₂ Sn phase with high melting point and dispersed distribution. This phase can be used as the heterogeneous nucleation core of divorced eutectic Mg ₁₇ Al ₁₂ phase, which can play a role in solid solution strengthening and refinement of magnesium alloys. The effect of the grain and the refinement of the Mg ₁₇ Al ₁₂ phase can also hinder the movement of dislocations and improve the high-temperature strength and plasticity of the alloy when the alloy is deformed at high temperature. When the content of Sn element is high, the formed Mg ₂ Sn phase will be coarsened, which will split the matrix and reduce the mechanical properties of the alloy.

3. Mg-Al-Sn-RE alloy:

The element RE is added to the Mg-Al-Sn alloy, and the experiment is shown in the table below:

Table 3 Orthogonal test conditions

Table 4 Orthogonal test table

A B C D. 6 A(1) B(1) C(1) D(1) 7 A(1) B(2) C(2) D(2) 8 A(1) B(3) C(3) D(3) 9 A(1) B(4) C(4) D(4) 10 A(2) B(1) C(2) D(3) 11 A(2) B(2) C(1) D(4) 12 A(2) B(3) C(4) D(1) 13 A(2) B(4) C(3) D(2) 14 A(3) B(1) C(3) D(4) 15 A(3) B(2) C(4) D(3) 16 A(3) B(3) C(1) D(2) 17 A(3) B(4) C(2) D(1) 18 A(4) B(1) C(4) D(2) 19 A(4) B(2) C(3) D(1) 20 A(4) B(3) C(2) D(4) twenty one A(4) B(4) C(1) D(3)

The magnesium alloys in different proportions of Examples 6-21 in Table 4 were tested, and the test items included room temperature tensile test, high temperature (175°C) tensile test and corrosion full immersion test, wherein the test data of corrosion resistance was according to GB10124 - Obtained by the uniform corrosion full immersion test method of the Metal Materials Laboratory in 1988.

Table 5 Performance Test Summary Table

The extreme difference analysis of high temperature tensile strength and corrosion resistance performance in the orthogonal test is carried out, and the analysis data is summarized in Table 6.

Table 6 Data Summary of Range Analysis

It can be seen from Table 6 that the optimal ratio for high-temperature mechanical properties is C3A1D2B4, that is, the mass fraction of Mg-Al-Sn-RE in the alloy is 7.7% Al, 2.1% Sn, 1.2% RE (0.8% Nd and 0.4% Sm ), the remainder is Mg and unavoidable impurities with a total amount of ≤0.2%. Adding a certain amount of rare earth elements, when the alloy elements Sn and RE (Nd and Sm) are added to the alloy melt, the formation enthalpy of Sn and RE (Nd and Sm) compounds is much smaller than the formation enthalpy of Sn and Mg and the formation enthalpy of Sn, Nd , the electronegativity relationship between Sm and Mg, Sn is preferentially combined with RE (Nd and Sm) to form the second phase of RE ₅ Sn ₃ high melting point dispersed distribution, and the remaining part of Sn combines with Mg to form Mg ₂ Sn phase and Sn’s Part of it is solid-soluble in the magnesium alloy matrix. Using Nd, Sm and Sn to greatly improve the high-temperature performance of the alloy, and adjusting the ratio, the formed RE ₅ Sn ₃ phase will enhance the age hardening effect and greatly improve the high-temperature performance of the alloy. Not only can it effectively improve the casting performance of the alloy , and the formation of RE ₅ Sn ₃ not only reduces the content of Mg ₁₇ Al ₁₂ phase, refines the alloy structure, makes the Mg ₁₇ Al ₁₂ phase fine and dispersed, and improves the high temperature performance of the alloy. Compared with lanthanum, cerium and praseodymium, rare earth elements neodymium and samarium have a stronger strengthening effect in magnesium alloys, but the addition of high content rare earth elements will increase the cost of magnesium alloys, and too much RE ₅ Sn ₃ phase will aggregate and coarsen , detrimental to the mechanical properties of the alloy.

By comparing Table 6 and Table 2, it can be seen that the addition of rare earth elements will improve the corrosion resistance of the alloy to a certain extent, but the effect is limited.

3. Mg-Al-Sn-RE-Zn

On the basis of the optimal mass fraction of Mg-Al-Sn-RE alloy, a certain amount of Zn was added, and the effect of Zn on the mechanical properties of the alloy and the refinement of RE ₅ Sn ₃ phase was discussed through orthogonal experiments:

Table 7 Orthogonal test conditions

Table 8 Orthogonal test table

A B C D. E. 6 A(1) B(1) C(1) D(1) E(1) 7 A(1) B(2) C(2) D(2) E(2) 8 A(1) B(3) C(3) D(3) E(3) 9 A(1) B(4) C(4) D(4) E(4) 10 A(2) B(1) C(2) D(4) E(3) 11 A(2) B(2) C(1) D(3) E(4) 12 A(2) B(3) C(4) D(2) E(1) 13 A(2) B(4) C(3) D(1) E(2) 14 A(3) B(1) C(3) D(2) E(4) 15 A(3) B(2) C(1) D(1) E(3) 16 A(3) B(3) C(4) D(4) E(2) 17 A(3) B(4) C(2) D(3) E(1) 18 A(4) B(1) C(4) D(3) E(2) 19 A(4) B(2) C(3) D(4) E(1) 20 A(4) B(3) C(2) D(1) E(4) twenty one A(4) B(4) C(1) D(2) E(3)

The magnesium alloys in different proportions of Examples 6-21 in Table 4 were tested, and the test items included room temperature tensile test, high temperature (175°C) tensile test and corrosion full immersion test, wherein the test data of corrosion resistance was according to GB10124 - Obtained by the uniform corrosion full immersion test method of the Metal Materials Laboratory in 1988.

Table 9 Performance Test Summary Table

Table 9 is compared with Table 5. It can be seen that the addition of Zn improves the mechanical properties of the alloy at room temperature and high temperature, and improves the corrosion resistance of the alloy.

Table 10 Range Analysis Data Summary

As can be seen in Table 9 and Table 10, for improving the mechanical properties of the alloy, the optimal combination is C3D4A2E2B4, because: ①The addition of Zn can refine the RE ₅ Sn ₃ phase, and the scanning electron microscope of the sample is shown in Figure 1 , the alloy grains are refined; ② also has a solid solution strengthening effect, improving the mechanical properties of the alloy; comparing the optimal ratio of C3A1D2B4 in Example 6-21, it can be seen that Zn makes the Sm effect on the alloy by refining the RE ₅ Sn ₃ phase. The influence of mechanical properties exceeds that of element Sn, enhancing the influence of rare earth elements on the mechanical properties of the alloy. Furthermore, the optimal combination for improving the corrosion resistance of the alloy is: A1B2D1C1F2. It can be seen that in the Mg-Al-Sn-RE-Zn alloy, the mechanical properties and corrosion resistance cannot be combined. At the same time, it also has high corrosion resistance, and Mn is added to the Mg-Al-Sn-RE-Zn alloy.

4. Mg-Al-Sn-RE-Zn-Mn alloy:

On the basis of the optimal mechanical ratio of the Mg-Al-Sn-RE-Zn alloy, reduce the Mg content and add Mn to improve the corrosion resistance of the alloy, see Table 11 for details.

Table 11 Summary of corrosion resistance test data for alloys with manganese added

As shown in Table 11, the addition of manganese can improve the corrosion resistance of the alloy. By comparing Table 9, when the Mn content is 0.1-0.3%, the corrosion resistance of the alloy can be significantly improved, and the Mn element can reduce the easy corrosion of Fe in impurities. corrosion performance, but when the content is too high, it will have a certain impact on the high temperature performance of the alloy, preferably 0.2% by mass fraction.

It can be seen from the above that adding tin, neodymium and/or samarium to the magnesium-aluminum base material forms high-melting point particle phases Nd ₅ Sn ₃ and Sm ₅ Sn ₃ , and further refines the high-melting point particle phase by adding zinc to improve the strong plasticity of the alloy , heat resistance and corrosion resistance; at the same time, the remaining tin and magnesium combine to form Mg ₂ Sn, which further improves the performance of the alloy; adding manganese reduces the damage of impurity elements and improves the corrosion resistance of the alloy. Heat and corrosion-resistant magnesium alloy, when the mass ratio is 7.7% Al, 2.3% Sn, 0.8% Zn, 1.4% RE (0.8% Nd, 0.4% Sm), 0.2% Mn, the unavoidable total amount of 0.16% impurities and When Mg remains, a Mg alloy with good mechanical properties and corrosion resistance is obtained.

The invention also discloses a method for preparing a multi-component heat-resistant and corrosion-resistant magnesium alloy, which includes the following steps:

1) Raw material preparation

According to the chemical composition and mass percentage of the designed alloy, pure magnesium, pure aluminum, pure zinc, pure tin, Mg-Nd master alloy, Mg-Sm master alloy, and Mg-Mn master alloy are weighed as raw materials; among them, the purity of the magnesium ingot is ≥ 99.99%, the purity of aluminum ingots is ≥99.99%, the purity of zinc ingots is ≥99.99%, the purity of tin ingots is ≥99.99%, and the impurity content of Mg-Nd, Mg-Sm and Mg-Mn master alloys is ≤0.1%.

Put the raw materials of the above components into an oven at 90-135°C to preheat for 0.5-1 hour;

2) Alloy casting

First, put the pure magnesium ingot into the mixed protective gas of SF ₆ and CO ₂ with a volume ratio of 1:90~110, heat it in the melting furnace with protective atmosphere until it is completely melted, add aluminum ingot, zinc Ingots and tin ingots, after the alloy is completely dissolved and fully stirred, the temperature is raised to 700-720°C, and Mg-Mn master alloy, Mg-Sm master alloy, and Mg-Nd master alloy are added in sequence, and the temperature is raised to 730-750°C. Stir after all the alloy materials are melted to make the composition _of the alloy melt uniform, then cool down to 680-700°C and blow argon gas into the melt, wherein the argon gas is high-purity argon gas (≥ 99.99%), the argon flow rate is 5-20 ml/min, after refining for 1-5 minutes, the slag is removed, and then the alloy melt is kept at 720-750°C for 10-30 minutes, and the alloy melt is cast to the preheating temperature In the pure copper mold or cast iron mold at 200~300℃.

3) Solution treatment T6

Put the casting into an electric furnace with a mixed protective gas of SF ₆ and CO ₂ with a volume ratio of 1:90-110, keep it at 410-430°C for 18-24 hours, and then heat it with the furnace at 10-20°C/min Raise the temperature to 500-540°C and keep it warm for 1-3 hours, then quench into water.

4) Aging treatment

Put the solid solution treated casting into an aging treatment furnace, raise the temperature to 175-240°C and keep it warm for 36-84 hours, then take it out and air-cool to obtain a high-strength, heat-resistant and corrosion-resistant magnesium alloy.

Example 25

According to the mass fraction of 7.3% Al, 3.0% Sn, 0.8% Zn, 1.2% RE (0.8% Nd and 0.4% Sm) and 0.2% Mn, the rest is Mg and the unavoidable total amount of impurities ≤ 0.2% for batching , put the ingredients in an oven at 120°C and bake for 50 minutes, then put the pure magnesium ingot into a resistance crucible furnace, heat it to completely melt under the protection of SF ₆ : CO ₂ volume ratio of 1:100, and then raise the temperature to 680°C , add pure aluminum, pure zinc, pure tin, fully stir the alloy liquid after dissolution, add Mg-Nd, Mg-Sm and Mg-Mn intermediate alloys at 700°C, stir the alloy liquid fully after the alloy is completely melted, and cool down to 680°C Carry out argon refining for 2 minutes, remove surface scum, argon flow rate is 8 ml/min, then rise to 745 ° C for 20 minutes, then cast into 200 ° C cast iron mold; then put the casting into the dry high-purity nitrogen In an electric furnace with atmosphere, keep it at 420°C for 20 hours, then raise the temperature to 510°C with the furnace at a heating rate of 10°C per minute and hold it for 3 hours, then quench it into water; then put the casting after solid solution treatment into a 225°C Aging treatment furnace and heat preservation for 72 hours, then take out and air-cool, to obtain excellent multi-element, high-strength, heat-resistant and corrosion-resistant magnesium alloy.

The magnesium alloy obtained in Example 25 is tested, and the test items include room temperature tensile test, high temperature (175° C.) tensile test and corrosion full immersion test. Its corrosion resistance is 2.679 (mm/a), and the prepared alloy Has excellent heat and corrosion resistance.

Example 26

According to the mass fraction of 7.3% Al, 3.0% Sn, 0.8% Zn, 1.2% RE (0.8% Nd and 0.4% Sm) and 0.2% Mn, the rest is Mg and the unavoidable total amount of impurities ≤ 0.2% for batching , put the ingredients in an oven at 120°C and bake for 50 minutes, then put the pure magnesium ingot into a resistance crucible furnace, heat it to completely melt under the protection of SF ₆ : CO ₂ volume ratio of 1:100, and then raise the temperature to 680°C , add pure aluminum, pure zinc, pure tin, fully stir the alloy liquid after dissolution, add Mg-Nd, Mg-Sm and Mg-Mn intermediate alloys at 710°C, stir the alloy liquid fully after the alloy is completely melted, and cool down to 690°C Carry out argon refining for 3 minutes, remove surface scum, argon flow rate is 15 ml/min, then rise to 745 ℃ for 20 minutes, then cast into 200 ℃ cast iron mold; then put the casting into the dry high-purity nitrogen In an electric furnace with an atmosphere, keep it at 420°C for 20 hours, then raise the temperature to 520°C with the furnace at a heating rate of 15°C per minute and hold it for 2 hours, and then quench it into water; then put the casting after solid solution treatment into a 240°C Aging treatment furnace and heat preservation for 72 hours, then take out and air-cool to obtain excellent multi-element, high-strength, heat-resistant and corrosion-resistant magnesium alloy.

Example 27

According to the mass fraction of 7.3% Al, 3.0% Sn, 0.8% Zn, 1.2% RE (0.8% Nd and 0.4% Sm) and 0.2% Mn, the rest is Mg and the unavoidable total amount of impurities ≤ 0.2% for batching , put the ingredients in an oven at 120°C and bake for 50 minutes, then put the pure magnesium ingot into a resistance crucible furnace, heat it to completely melt under the protection of SF ₆ : CO ₂ volume ratio of 1:100, and then raise the temperature to 680°C , add pure aluminum, pure zinc, pure tin, fully stir the alloy liquid after dissolution, add Mg-Nd, Mg-Sm and Mg-Mn intermediate alloys at 720°C, stir the alloy liquid fully after the alloy is completely melted, and cool down to 700°C Carry out argon refining for 5 minutes, remove surface scum, argon flow rate is 20 ml/min, then rise to 745 ° C for 20 minutes, then cast into 200 ° C cast iron mold; then put the casting into a dry high-purity nitrogen In an electric furnace with an atmosphere, keep it at 420°C for 20 hours, then raise the temperature to 520°C with the furnace at a heating rate of 15°C per minute and hold it for 2 hours, then quench it into water; then put the casting after solid solution treatment into a 180°C Aging treatment furnace and heat preservation for 84 hours, then take it out and air-cool to obtain excellent multi-element, high-strength, heat-resistant and corrosion-resistant magnesium alloy.

The preparation method of the magnesium alloy of the present invention, especially the argon blowing refining step in the melting and casting method, controls the argon flow rate, the melt temperature when blowing argon, the time of blowing argon and the position of the argon blowing head in the melt. Stirring speed and other parameters, suitable process parameters are beneficial to minimize the content of slag in the structure, the purpose is to remove the slag in the alloy melt, which determines the content of slag in the as-cast microstructure of the alloy when it solidifies, and is conducive to improving alloy properties. The optimization of parameters such as temperature and time of solution treatment and aging treatment in the alloy preparation method further ensures the effect of precipitation strengthening.

Although embodiments of the present invention have been disclosed above, it is not limited to the applications set forth in the specification and examples. It can be fully applied to various fields suitable for the present invention. Additional modifications can readily be made by those skilled in the art. Therefore, the invention should not be limited to the specific details and examples shown and described herein, without departing from the general concept defined by the claims and their equivalents.

Claims (4)

1. A method for preparing a multi-component heat-resistant and corrosion-resistant magnesium alloy, preparing a multi-component heat-resistant and corrosion-resistant magnesium alloy, which comprises: 5.8-7.8% Al, 2.2-3.2% Sn, 0.2-1.0% Zn, 0.2-2.0% RE, 0.1-0.3% Mn, the remainder is Mg and unavoidable impurities ≤ 0.2% in total; It is characterized by including: Put a protective atmosphere into the smelting furnace, put magnesium ingots and heat until completely melted, add aluminum ingots, zinc ingots and tin ingots at 670-690°C, dissolve completely and stir, then raise the temperature to 700-720°C, and then add Mg- Mn master alloy, Mg-Sm master alloy, Mg-Nd master alloy, then raise the temperature to 730-750°C to make the composition of the alloy melt uniform, then cool down to 680-700°C and blow argon into the melt for 1-5 minutes for refining , the alloy melt after slag removal is kept at 720-750°C for 10-30 minutes, and the alloy melt is cast into a mold with a preheating temperature of 200-300°C; the argon flow rate is 5-20 ml/ minute; Put the casting into an electric furnace with a protective atmosphere for solution treatment, keep it at 410-430°C for 18-24 hours, then raise the temperature to 500-540°C with the furnace at a heating rate of 10-20°C/min and keep it for 1 ~3 hours, then quenched into water; Put the casting after solid solution treatment into an aging treatment furnace, raise the temperature to 175-240°C and keep it warm for 36-84 hours, then take it out and air-cool it. 2. The preparation method of multi-component heat-resistant and corrosion-resistant magnesium alloy according to claim 1, characterized in that: the purity of magnesium ingots is ≥99.99%, the purity of aluminum ingots is ≥99.99%, the purity of zinc ingots is ≥99.99%, and the purity of tin ingots is ≥99.99%. The purity ≥99.99%, the impurity content of Mg-Nd, Mg-Sm and Mg-Mn master alloys ≤0.1%. 3. The preparation method of the multi-element heat-resistant and corrosion-resistant magnesium alloy according to claim 2 is characterized in that: the protective atmosphere in the alloy melting and casting step is SF ₆ and CO ₂ mixed gas, said SF ₆ and CO ₂ gas The volume ratio is 1:90~110. 4 . The method for preparing a multi-component heat-resistant and corrosion-resistant magnesium alloy according to claim 3 , further comprising preheating the raw materials: putting the raw materials in an oven at 90-135° C. for 0.5-1 hour.