In-situ nanoparticle and rare earth synergistically strengthened alloy casting and preparation method thereof

Abstract

The invention discloses an in-situ nanoparticle and rare earth synergistically strengthened alloy casting and a preparation method thereof, and relates to the technical field of aluminum alloy materials. The preparation method comprises the following steps: firstly, introducing binary in-situ nanoparticles such as ZrB2 and Al2O3 into an aluminum alloy; optimization is achieved by means of in-situ nanoparticles, and the mechanical property of the alloy can be greatly improved while the plasticity of the alloy is not reduced or slightly reduced; and by utilizing subzero treatment, the size of the in-situ nanoparticles is further reduced, so that the number density is increased. Secondly, the aluminum alloy is subjected to deep purification and composite modification refinement, Ce-rich mischmetal is added at high temperature after preliminary purification, and deep purification of aluminum alloy melt is achieved; then the aluminum alloy is subjected to heat treatment, element segregation in a casting part is eliminated, and the uniformity of rare earth elements in a matrix is improved; and finally, through aging, a high-temperature precipitated phase of submicron fine grains can stably exist near the recrystallization temperature, and the strength of the alloy casting is further improved. The alloy casting prepared by the method has the effect of high strength.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy materials, and in particular to an alloy casting synergistically strengthened with in-situ nanoparticles and rare earth and a preparation method thereof. Background Art

[0002] With the rapid and sustainable development of my country's aerospace, national defense, industry and other fields, the requirements for the comprehensive performance of materials are getting higher and higher. Nanoparticle-rare earth-metal matrix composites have attracted extensive attention because they can effectively combine the good thermal conductivity, electrical conductivity and plasticity of metals with the high temperature resistance, wear resistance and corrosion resistance of ceramics. Generally speaking, the smaller the size of the particles as the reinforcing phase, the better the reinforcing effect. Therefore, the preparation of in-situ nanoparticle-reinforced metal matrix composites with nanometer size, i.e., less than 100 nanometers, has become an important development direction of composite materials.

[0003] The comprehensive mechanical properties of high-strength aluminum alloys are mainly affected by the microstructure, which is closely related to the alloy composition design, the type and quantity of added elements for microalloying, the preparation technology and the heat treatment process. In recent years, how to further improve the physical, chemical, mechanical and other properties of aluminum alloy materials has become the first issue that researchers consider. As we all know, grain refinement is the key to improving the mechanical properties of materials. Usually, grain refinement and material strengthening are achieved by adding refiners and strengtheners containing ceramic particles. Summary of the invention

[0004] The purpose of the present invention is to provide an in-situ nanoparticle and rare earth synergistically strengthened alloy casting and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: an in-situ nanoparticle and rare earth synergistically strengthened alloy casting, wherein the casting is prepared by synergistically strengthening in-situ nanoparticle cryogenic treatment and rare earth refinement high temperature treatment.

[0006] Furthermore, the in-situ nanoparticles are binary in-situ nanoparticles such as introduced ZrB2 and A12O3.

[0007] Furthermore, the rare earth is Ce-rich mixed rare earth.

[0008] Furthermore, a method for preparing an alloy casting synergistically strengthened by in-situ nanoparticles and rare earths comprises the following preparation steps:

[0009] (1) Weigh 5 - 6 parts of K2ZrF6, 3 - 6 parts of KBF4, 10 - 12 parts of Na2B4O7 and 3 - 9 parts of Al2(SO4)3, dehydrate them at 100 - 200 °C for 5 h and then mix and grind them evenly; place the aluminum alloy in a crucible and heat it to melt, keep the temperature of the aluminum alloy liquid at 660 - 720 °C, press the mixed and ground reactant powder into the aluminum alloy liquid with a bell jar for full reaction, and introduce an inert gas into the melt to remove the slag generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. The helium gas flow rate is 6 - 10 L / min and the time is 10 - 30 min; after completion, first perform water quenching and then deep cryogenic treatment for 2 - 24 h to obtain an intermediate product;

[0010] (2) Heat the intermediate product to 620 °C, then add rich Ce mixed rare earth to remove fine A12O3 inclusions, let it stand for 10 - 15 min and then transfer it to a tundish to achieve deep purification of the aluminum alloy melt. After the reaction is completed, skim the slag, refine and degas, and cool it to 120 °C for aging treatment to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting;

[0011] (3) Perform homogenization treatment on the ingot. The homogenization treatment parameters are to treat it at 300 - 350 °C for 8 h and then at 450 °C for 10 h; after homogenization treatment, perform rolling. Anneal it before rolling at a temperature of 350 - 450 °C, and then perform rolling at a temperature of 400 °C; place the aluminum alloy casting in a furnace, heat it to 400 - 500 °C and keep it warm for 18 - 24 h, then cool it at a cooling rate of 40 - 50 °C / h to 300 - 350 °C, and then cool it at a cooling rate of 100 - 150 °C / h to 210 - 230 °C, keep it warm for 20 - 40 h and then cool it to room temperature at a cooling rate of 20 - 30 °C / h to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting.

[0012] Further, in the step (1), the aluminum alloy has the following composition: copper 0.04% - 0.06%, magnesium 0.2% - 0.3%, iron 0.1% - 0.2%, silicon 0.05% - 0.1%, erbium 0.015% - 0.03%, titanium 0.015% - 0.03%, zinc 0.15% - 0.25%, manganese 0.15% - 0.20%, and the balance is aluminum.

[0013] Further, in the step (1), the inert gas is helium.

[0014] Further, in the step (1), the deep cryogenic treatment is to perform liquid deep cryogenic treatment by putting it into liquid nitrogen, and the temperature of the liquid nitrogen is -196 °C to -180 °C.

[0015] Further, in the step (2), the rare earth is 0.2 wt% of the intermediate product.

[0016] Further, the aging treatment time in step (2) is 4 to 24 h.

[0017] Further, the annealing time in step (3) is 2 to 4 h.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0019] The present invention synergistically strengthens alloy castings by in-situ nanoparticle cryogenic treatment and rare earth refinement high-temperature treatment to achieve high strength.

[0020] First, binary in-situ nanoparticles such as ZrB2 and A12O3 are introduced into the aluminum alloy, significantly refining the grain structure. The as-cast aluminum alloy obtained has a room-temperature tensile strength > 320 MPa, a yield strength > 250 MPa, and an elongation rate ≥ 6%; optimization is achieved by means of in-situ nanoparticles: the in-situ nanoparticles are ceramic phases with small sizes and excellent mechanical properties, which can greatly improve the filling ability of die-cast alloys, refine the solidification structure of aluminum alloys, and can significantly improve their mechanical properties without reducing or slightly reducing the plasticity of the alloy; by using cryogenic treatment, the size of the in-situ nanoparticles is further reduced, thereby increasing the number density, improving the dislocation density, and making the distribution more uniform, optimizing the strength of the alloy casting.

[0021] Second, the deep purification and composite modification refinement of the aluminum alloy are carried out. The aluminum alloy melt is preliminarily purified by powder refining in a melting furnace, and then a Ce-rich mixed rare earth is added at high temperature to remove fine inclusions, achieving deep purification of the aluminum alloy melt. The size of the inclusions in the melt is less than 20 μm, and the density of the hydrogen-measuring sample is greater than 2.65 g / cm 3 ; then the aluminum alloy is heat-treated to eliminate element segregation in the casting and improve the uniformity of rare earth elements in the matrix; finally, through aging, submicron-scale fine-grained high-temperature precipitation phases can stably exist near the recrystallization temperature, with large radii and small volume fractions, and combine with the in-situ generated nano-fine grains as the main phase to inhibit matrix recrystallization, further improving the strength of the alloy casting. Specific embodiments

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Example 1

[0024] (1) The aluminum alloy has the following composition by weight: copper 0.04%, magnesium 0.2%, iron 0.1%, silicon 0.05%, erbium 0.015%, titanium 0.015%, zinc 0.15%, manganese 0.15%, and the balance is aluminum. Weigh 5 parts of K2ZrF6, 3 parts of KBF4, 10 parts of Na2B4O7, and 3 parts of Al2(SO4)3. After dehydrating at 100 °C for 5 h, mix and grind them evenly. Place the aluminum alloy in a crucible and heat it to melt. Keep the temperature of the aluminum alloy liquid at 660 °C. Press the mixed and ground reactant powder into the aluminum alloy liquid with a bell jar for full reaction. Pass helium gas into the melt to remove the slag generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. The helium gas flow rate is 6 L / min and the time is 10 min. After completion, first perform water quenching, then perform cryogenic treatment for 2 h, and place it in liquid nitrogen for cryogenic treatment by the liquid method. The liquid nitrogen temperature is -180 °C to obtain an intermediate product;

[0025] (2) Heat the intermediate product to 620 °C, then add 0.2 wt% of Ce-rich mixed rare earth to remove fine A12O3 inclusions. After standing for 10 min, transfer it to a tundish to achieve deep purification of the aluminum alloy melt. After the reaction is completed, skim the slag, refine and degas, and cool down to 120 °C for aging treatment for 4 h to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting;

[0026] (3) Perform homogenization treatment on the ingot. The homogenization treatment parameters are to treat at 300 °C for 8 h, and then treat at 450 °C for 10 h. After homogenization treatment, perform rolling. Anneal for 2 h before rolling at a temperature of 350 °C, and then perform rolling at a temperature of 400 °C. Place the aluminum alloy casting in a furnace, heat it to 400 °C, and after holding for 18 h, cool it down to 300 °C at a cooling rate of 40 °C / h, then cool it down to 210 °C at a cooling rate of 100 °C / h, hold for 20 h, and then cool it to room temperature at a cooling rate of 20 °C / h to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting.

[0027] Example 2

[0028] (1) The aluminum alloy has the following composition: copper 0.05%, magnesium 0.25%, iron 0.15%, silicon 0.075%, erbium 0.0225%, titanium 0.0225%, zinc 0.20%, manganese 0.175%, and the balance is aluminum. Weigh 5.5 parts of K2ZrF6, 4.5 parts of KBF4, 11 parts of Na2B4O7 and 4.5 parts of Al2(SO4)3. After dehydrating at 150 °C for 5 h, mix and grind them evenly. Place the aluminum alloy in a crucible and heat it to melt. Keep the temperature of the aluminum alloy liquid at 690 °C. Press the mixed and ground reactant powder into the aluminum alloy liquid with a bell jar for full reaction. Pass helium gas into the melt to remove the slag generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. The helium gas flow rate is 8 L / min and the time is 20 min. After completion, first perform water quenching, then perform cryogenic treatment for 13 h, and place it in liquid nitrogen for cryogenic treatment by the liquid method. The liquid nitrogen temperature is -188 °C to obtain an intermediate product;

[0029] (2) Heat the intermediate product to 620 °C, then add 0.2 wt% of Ce-rich mixed rare earth to remove fine A12O3 inclusions. After standing for 12 min, transfer it to a tundish to achieve deep purification of the aluminum alloy melt. After the reaction is completed, skim the slag, refine and degas, and cool down to 120 °C for aging treatment for 14 h to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting;

[0030] (3) Perform homogenization treatment on the ingot. The homogenization treatment parameters are treating at 325 °C for 8 h and then at 450 °C for 10 h. After homogenization treatment, perform rolling. Anneal for 3 h at a temperature of 400 °C before rolling, and then perform rolling at a temperature of 400 °C. Place the aluminum alloy casting in a furnace, heat it to 450 °C, hold for 21 h, then cool down at a rate of 45 °C / h to 325 °C, and then cool down at a rate of 125 °C / h to 220 °C. After holding for 30 h, cool down to room temperature at a rate of 25 °C / h to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting.

[0031] Example 3

[0032] (1) The aluminum alloy has the following composition by weight: 0.06% copper, 0.3% magnesium, 0.2% iron, 0.1% silicon, 0.03% erbium, 0.03% titanium, 0.25% zinc, 0.20% manganese, and the balance is aluminum. Weigh 6 parts of K2ZrF6, 6 parts of KBF4, 12 parts of Na2B4O7, and 9 parts of Al2(SO4)3. After dehydrating at 200°C for 5 hours, mix and grind them evenly. Place the aluminum alloy in a crucible and heat it to melt. Keep the temperature of the aluminum alloy liquid at 720°C. Press the mixed and ground reactant powder into the aluminum alloy liquid with a bell jar for full reaction. Pass helium gas into the melt to remove the slag generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. The helium gas flow rate is 10 L / min, and the time is 30 min. After completion, first perform water quenching, then perform cryogenic treatment for 24 hours, and place it in liquid nitrogen for cryogenic treatment by the liquid method. The liquid nitrogen temperature is -196°C to obtain an intermediate product;

[0033] (2) Heat the intermediate product to 620°C, then add 0.2 wt% of Ce-rich rare earth mixture to remove fine A12O3 inclusions. After standing for 15 minutes, transfer it to a tundish to achieve deep purification of the aluminum alloy melt. After the reaction, skim the slag, refine and degas, and cool down to 120°C for aging treatment for 24 hours to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting;

[0034] (3) Perform homogenization treatment on the ingot. The homogenization treatment parameters are: treat at 350°C for 8 hours, and then treat at 450°C for 10 hours. After homogenization treatment, perform rolling. Before rolling, anneal for 4 hours at a temperature of 450°C, and then perform rolling at a temperature of 400°C. Place the aluminum alloy casting in a furnace, heat it to 500°C, hold for 24 hours, then cool down at a rate of 50°C / h to 350°C, and then cool down at a rate of 150°C / h to 230°C. After holding for 40 hours, cool down to room temperature at a rate of 30°C / h to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting.

[0035] Comparative Example 1

[0036] The difference between Comparative Example 1 and Example 2 lies in step (1). Modify step (1) as follows: The aluminum alloy composition is 0.05% copper, 0.25% magnesium, 0.15% iron, 0.075% silicon, 0.0225% erbium, 0.0225% titanium, 0.20% zinc, 0.175% manganese, and the balance is aluminum. Place the aluminum alloy in a crucible and heat it to melt. Keep the temperature of the aluminum alloy liquid at 690 °C, and introduce helium gas into the melt to remove the slag generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. The helium gas flow rate is 8 L / min, and the time is 20 min. After completion, first perform water quenching, and then perform cryogenic treatment for 13 h. Put it into liquid nitrogen for cryogenic treatment by the liquid method. The liquid nitrogen temperature is -188 °C to obtain an intermediate product. The remaining steps are the same as those in Example 2.

[0037] Comparative Example 2

[0038] The difference between Comparative Example 2 and Example 2 lies in step (1). Modify step (1) as follows: The aluminum alloy composition is 0.05% copper, 0.25% magnesium, 0.15% iron, 0.075% silicon, 0.0225% erbium, 0.0225% titanium, 0.20% zinc, 0.175% manganese, and the balance is aluminum. Weigh 5.5 parts of K2ZrF6, 4.5 parts of KBF4, 11 parts of Na2B4O7, and 4.5 parts of Al2(SO4)3. Dehydrate at 150 °C for 5 h and then mix and grind evenly. Place the aluminum alloy in a crucible and heat it to melt. Keep the temperature of the aluminum alloy liquid at 690 °C, and press the mixed and ground reactant powder into the aluminum alloy liquid with a bell jar for full reaction. Introduce helium gas into the melt to remove the slag generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. The helium gas flow rate is 8 L / min, and the time is 20 min to obtain an intermediate product. The remaining steps are the same as those in Example 2.

[0039] Comparative Example 3

[0040] The difference between Comparative Example 3 and Example 2 lies in step (2). Modify step (2) as follows: Heat the intermediate product to 620 °C, let it stand for 12 min and then transfer it to a tundish to achieve deep purification of the aluminum alloy melt. After the reaction is completed, skim the slag, refine and degas, and cool down to 120 °C for aging treatment for 14 h to obtain an in-situ nano-particle and rare earth synergistically strengthened alloy casting. The remaining steps are the same as those in Example 2.

[0041] Comparative Example 4

[0042] The difference between Comparative Example 4 and Example 2 lies in step (3). Step (3) is modified as follows: Place the ingot in a furnace, heat it to 450 °C, hold for 21 h, then cool it at a rate of 45 °C / h to 325 °C, and then cool it at a rate of 125 °C / h to 220 °C. After holding for 30 h, cool it at a rate of 25 °C / h to room temperature to obtain an in-situ nano-particle and rare earth co-strengthened alloy casting; the remaining steps are the same as those in Example 2.

[0043] Effect Example

[0044] The following Table 1 shows the performance analysis results of an in-situ nano-particle and rare earth co-strengthened alloy casting using Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention.

[0045] Table 1

[0046] Tensile strength (MPa) Yield strength (MPa) Elongation at break (%) Example 1 462 370 10.6 Example 2 468 380 10.6 Example 3 467 380 10.4 Comparative Example 1 351 270 7.8 Comparative Example 2 435 340 9.2 Comparative Example 3 401 290 8.5 Comparative Example 4 420 310 8.8

[0047] From the comparison of the experimental data of the strength of the examples and comparative examples, it can be found that by introducing binary in-situ nano-particles such as ZrB2 and A12O3 into aluminum alloy in the present invention, the grain structure is significantly refined. With the help of in-situ nano-particles, the following optimizations are achieved: The in-situ nano-particles are ceramic phases with small sizes and excellent mechanical properties, which can greatly improve the filling ability of die-cast alloys, refine the solidification structure of aluminum alloys, and can significantly improve their mechanical properties while not reducing or slightly reducing the plasticity of the alloy; by cryogenic treatment, the size of the in-situ nano-particles is further reduced, thus increasing the number density, improving the dislocation density, and making the distribution more uniform, optimizing the strength of the alloy casting. Secondly, through the deep purification and composite modification refinement of aluminum alloy, the aluminum alloy melt is preliminarily purified by powder refining in a melting furnace, and then a Ce-rich mixed rare earth is added at high temperature to remove fine A12O3 inclusions, realizing the deep purification of the aluminum alloy melt. Then, the aluminum alloy is heat-treated to eliminate element segregation in the casting and improve the uniformity of rare earth elements in the matrix; finally, through aging, sub-micron fine-grained high-temperature precipitation phases can stably exist near the recrystallization temperature, with large radii and small volume fractions. As the main phase inhibiting matrix recrystallization, combined with in-situ generated nano-fine grains, the strength of the alloy casting is further improved.

[0048] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. An in-situ nanoparticle and rare earth synergistically strengthened alloy casting, characterized in that: The casting is prepared by synergistic strengthening of in-situ nano-particle deep cryogenic treatment and rare earth refinement high temperature treatment.

2. The in-situ nanoparticle and rare earth synergistically strengthened alloy casting according to claim 1, characterized in that: The in-situ nanoparticles are binary in-situ nanoparticles such as introduced ZrB2 and A12O3.

3. The in-situ nanoparticle and rare earth synergistically strengthened alloy casting according to claim 1, characterized in that: The rare earth is Ce-rich mixed rare earth.

4. A method for preparing an alloy casting synergistically strengthened by in-situ nanoparticles and rare earth, characterized in that: The method comprises the following preparation steps: (1) Weigh 5-6 parts of K2ZrF6, 3-6 parts of KBF4, 10-12 parts of Na2B4O7 and 3-9 parts of Al2(SO4)3, dehydrate at 100-200°C for 5 hours, and then mix and grind them evenly; place the aluminum alloy in a crucible for heating and melting, and keep the aluminum alloy liquid temperature at 660-720°C. Press the mixed and ground reactant powder into the aluminum alloy liquid with a bell jar for full reaction, and pass an inert gas into the melt to remove slag generated during the high-temperature smelting and reaction of the alloy and hydrogen dissolved in the melt. The helium flow rate is 6-10 L / min, and the time is 10-30 minutes; after completion, quench with water, and then deep cryogenically treat for 2-24 hours to obtain an intermediate product; (2) heating the intermediate product to 620°C, then adding Ce-rich mixed rare earth to remove fine Al2O3 inclusions, leaving it to stand for 10 to 15 minutes and then transferring it to a tundish to achieve deep purification of the aluminum alloy melt, slagging after the reaction, refining and degassing, cooling it to 120°C for aging treatment, and obtaining an in-situ nanoparticle and rare earth synergistically strengthened alloy casting; (3) The ingot is homogenized at a temperature of 300-350°C for 8 hours and then at 450°C for 10 hours; the ingot is rolled after the homogenization and annealed before rolling at a temperature of 350-450°C and then rolled at 400°C; the aluminum alloy casting is placed in a furnace, heated to 400-500°C, kept at this temperature for 18-24 hours, cooled to 300-350°C at a cooling rate of 40-50°C / h, then cooled to 210-230°C at a cooling rate of 100-150°C / h, kept at this temperature for 20-40 hours, and then cooled to room temperature at a cooling rate of 20-30°C / h to obtain an alloy casting synergistically strengthened by in-situ nanoparticles and rare earths.

5. The method for preparing an alloy casting synergistically strengthened by in-situ nanoparticles and rare earth according to claim 4, characterized in that: The aluminum alloy composition in step (1) comprises 0.04% to 0.06% copper, 0.2% to 0.3% magnesium, 0.1% to 0.2% iron, 0.05% to 0.1% silicon, 0.015% to 0.03% erbium, 0.015% to 0.03% titanium, 0.15% to 0.25% zinc, 0.15% to 0.20% manganese, and the balance is aluminum.

6. The method for preparing an in-situ nanoparticle and rare earth synergistically strengthened alloy casting according to claim 4, characterized in that: In the step (1), the inert gas is helium.

7. The method for preparing an alloy casting synergistically strengthened by in-situ nanoparticles and rare earth according to claim 4, characterized in that: The cryogenic treatment in step (1) is performed by placing the cryogenic treatment in liquid nitrogen, and the temperature of the liquid nitrogen is -196°C to -180°C.

8. The method for preparing an alloy casting synergistically strengthened by in-situ nanoparticles and rare earth according to claim 4, characterized in that: In the step (2), the rare earth accounts for 0.2 wt% of the intermediate product.

9. The method for preparing an alloy casting synergistically strengthened by in-situ nanoparticles and rare earth according to claim 4, characterized in that: The aging treatment time in step (2) is 4 to 24 hours.

10. The method for preparing an alloy casting synergistically strengthened by in-situ nanoparticles and rare earth according to claim 4, characterized in that: The annealing time in step (3) is 2 to 4 hours.