Microalloyed aluminum-copper-cerium heat-resistant aluminum alloy and preparation method thereof

Abstract

The invention belongs to the technical field of aluminum alloy materials, and particularly discloses a microalloyed aluminum-copper-cerium heat-resistant aluminum alloy and a preparation method thereof. The aluminum alloy comprises, by mass, 7%-9.5% of Cu, 1.3%-2.3% of Ce, 0.1%-0.5% of Mn, 0.1%-0.4% of Sc, 0.1%-0.4% of Zr, 0.1%-0.5% of Mg, 0.1%-0.3% of Si and the balance Al and inevitable impurities, the content relation of Cu and Ce is that Cu is equal to 2Ce + 4%-5%, and the content relation of Mg and Si is that Mg is larger than 1.5 Si. The aluminum alloy has high yield strength and high tensile strength in a high-temperature environment, the yield strength and the tensile strength at the temperature of 300 DEG C are 235-248 MPa and 245-257 MPa respectively, the ductility is 4-5%, the yield strength and the tensile strength at the temperature of 400 DEG C are 100-106 MPa and 105-110 MPa respectively, the ductility is 9-10%, and the aluminum alloy is obviously superior to a traditional ZL206 alloy and a traditional ZL207 alloy.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy materials, and in particular relates to a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy and a preparation method thereof. Background Art

[0002] Aluminum and aluminum alloys have the advantages of low melting point, low density, excellent electrical and thermal conductivity, and good machinability. Therefore, they are widely used in aerospace, automobiles, ships, electronic components, and daily necessities. With the rapid development of modern industry, the demand for aluminum alloys with excellent high-temperature mechanical properties continues to increase. However, the tensile strength of existing cast aluminum alloys at 300°C is lower than 180MPa, and the yield strength at 350°C has been limited to about 100MPa, which is difficult to meet application requirements. The main reason is that the dissolution or coarsening of the precipitated phase makes it difficult to restrict the deformation mechanism dominated by the grain boundary (GB) (including GB diffusion, GB migration, and grain rotation) at high temperature, resulting in dynamic softening of Al grains during high-temperature deformation. Previous work has focused more on improving the high-temperature strength of currently commonly used aluminum alloys by alloying them. Although it has a certain effect, it still cannot meet the demand. Unlike traditional aluminum alloys, Al-Cu-RE series alloys have excellent high-temperature strength. In particular, the Al-Cu-RE-Mn-Zr alloy exhibits good mechanical properties above 300 °C, and the intermetallic compounds at the grain boundaries and the nanophases inside the grains play a crucial role in the high-temperature deformation process, which is attributed to the pinning effect on the grain boundaries and dislocations.

[0003] Cheng Jianing and others improved the heat resistance of aluminum alloy by microalloying, thus developing ZL206 alloy, wherein the chemical composition of ZL206 is Cu: 7.6 ~ 8.4wt.%, RE: 1.5 ~ 2.3wt.%, Mn: 0.7 ~ 1.1wt.%, Zr: 0.1 ~ 0.25wt.%, Al is the balance, wherein RE is mixed rare earth, ZL206 alloy in T6 state, its high temperature tensile tensile strength at 300 ℃ is 161MPa. Similar ZL207 alloy has a high temperature tensile tensile strength of 115MPa at 300 ℃, a high temperature tensile tensile strength of 70MPa at 400 ℃, and an elongation of less than 2%, but the high temperature strength performance indicators of these aluminum alloy materials still cannot meet the latest requirements of the current automotive and aerospace fields. Therefore, developing or optimizing a new type of cast heat-resistant aluminum alloy so that the alloy can be used normally in an environment above 300 ℃ is a key issue that needs to be solved urgently. Summary of the invention

[0004] Aiming at the technical problem that the strength of the above-mentioned cast heat-resistant aluminum alloy cannot meet the industrial demand at 300℃~400℃ (tensile strength at 300℃ is less than 180MPa, and tensile strength at 400℃ is less than 70MPa), the present invention provides a microalloyed aluminum-copper-cerium series heat-resistant aluminum alloy and a preparation method thereof. The heat-resistant aluminum alloy has excellent high-temperature performance, high yield strength and high tensile strength under high temperature environment, the yield strength and tensile strength at 300℃ are 235~248MPa and 245~257MPa respectively, and the elongation is 4~5%, the yield strength and tensile strength at 350℃ are 165~173MPa and 172~178MPa respectively, and the elongation is 5~6%, the yield strength and tensile strength at 400℃ are 100~106MPa and 105~110MPa respectively, and the elongation is 9~10%, which is significantly better than the traditional ZL206 alloy (T6) and ZL207 alloy (T6).

[0005] The technical solution of the present invention is as follows:

[0006] The invention provides a microalloyed aluminum-copper-cerium series heat-resistant aluminum alloy, which comprises, by mass percentage, 7%-9.5% of Cu, 1.3%-2.3% of Ce, 0.1%-0.5% of Mn, 0.1%-0.4% of Sc, 0.1%-0.4% of Zr, 0.1%-0.5% of Mg, 0.1%-0.3% of Si, and the balance is Al and inevitable impurities, wherein the content relationship of Cu to Ce is Cu=2Ce+4-5%, and the content relationship of Mg to Si is Mg>1.5Si.

[0007] The present invention also provides a method for preparing the above-mentioned microalloyed aluminum-copper-cerium series heat-resistant aluminum alloy, comprising the following steps:

[0008] (1) Melting and casting alloy: heating to 700-720°C, melting pure Al ingot and keeping the temperature for 30 min-1 h; adding pure Cu ingot, pure Mg ingot, Al-30wt.%Ce master alloy ingot, Al-10wt.%Mn master alloy ingot and Al-50wt.%Si master alloy ingot in turn every 10-20 min, stirring and melting, and then heating to 740-760°C, adding Al-2wt.%Sc master alloy ingot and Al-10wt.%Zr master alloy ingot in turn, stirring until all are melted, and keeping the temperature; then adding refining agent and hexachloroethane in turn for degassing and deslagging, standing and keeping the temperature for 10-15 min after slagging, and finally casting into a mold preheated at 200°C-300°C to obtain an aluminum alloy ingot, and quenching the aluminum alloy ingot once solidified;

[0009] (2) Solution treatment: The aluminum alloy ingot is placed at 200°C to 300°C for 12 to 24 hours, then heated to 350°C to 450°C for 5 to 15 hours, then heated to 520°C to 537°C for 5 to 15 hours, and finally quenched;

[0010] (3) Low temperature aging: The quenched aluminum alloy ingot is placed at 160°C to 200°C for 3 to 18 hours and then quenched to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0011] In one embodiment of the present invention, the process further includes mechanically grinding the surface of each metal raw material to remove the oxide scale on the surface before smelting in step (1), and then taking the amount according to the mass percentage of the aluminum alloy.

[0012] In one embodiment of the present invention, the purity of the pure Al ingot, pure Cu ingot, pure Mg ingot, Al-30wt.%Ce master alloy ingot, Al-10wt.%Mn master alloy ingot, Al-50wt.%Si master alloy ingot, Al-2wt.%Sc master alloy ingot and Al-10wt.%Zr master alloy ingot in step (1) are all greater than 99.5%.

[0013] In one embodiment of the present invention, the temperature of the alloy melt during casting in step (1) is 740°C to 760°C.

[0014] In one embodiment of the present invention, the quenching methods in steps (2) to (3) are all water quenching.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The invention discloses a microalloyed aluminum-copper-cerium heat-resistant aluminum alloy. The solidification phase diagram confirms that Cu / Ce>2. Meanwhile, in order to prevent excessive Cu from being unable to dissolve during solution treatment, the content of copper and cerium elements is Cu=2Ce+4-5%, so as to regulate the volume fraction ratio of the nano-precipitated phase and the micro-metallic compound. The nano-precipitated phase is θ′-Al2Cu, and the micro-metallic compound is Al8Cu4Ce. The mechanism of θ′-Al2Cu nano-precipitate phase improving high temperature strength is precipitation strengthening, the mechanism of micron intermetallic compound improving high temperature strength is load transfer and inhibiting grain boundary sliding, and the volume fraction of nano-precipitate phase and micron intermetallic compound can increase at the same time, so that the two strengthening mechanisms of precipitation strengthening and load transfer can produce the best synergistic effect at the same time, and improve the high temperature mechanical properties of the alloy. At the same time, in order to solve the problem of the strength drop caused by the dissolution of θ′-Al2Cu nano-precipitate phase due to temperature increase, L12 nano-precipitate phase forming elements are also added to the aluminum alloy. The L12 nano-precipitate phase significantly improves the long-term service ability of the heat-resistant cast aluminum alloy at high temperature. Finally, Mg and Si are added for microalloying, and the content relationship of Mg and Si is Mg>1.5Si. The heat-resistant aluminum alloy of the present invention has the microstructural characteristics of various intermetallic compounds, which are specifically manifested in: the macroscopic microstructure morphology is equiaxed crystal, and there is coarsely precipitated Al3 (Sc, Zr) in the crystal, which is an α-Al nucleating agent; a large number of nano-scale dispersed precipitation phases are precipitated inside the grains; granular and lamellar Al are continuously distributed along the grain boundaries. 24 Ce3Cu8Mn、Al 16 The CeCu4Mn2 and Al8CeCu4 micron-scale heat-resistant intermetallic compound skeletons have high yield strength and high tensile strength under high temperature environment. The yield strength and tensile strength at 300°C are 235-248MPa and 245-257MPa respectively, and the elongation is 4-5%. The yield strength and tensile strength at 350°C are 165-173MPa and 172-178MPa respectively, and the elongation is 5-6%. The yield strength and tensile strength at 400°C are 100-106MPa and 105-110MPa respectively, and the elongation is 9-10%, which is significantly better than traditional ZL206 alloy (T6) and ZL207 alloy (T6).

[0017] At the same time, the present invention prepares the aluminum alloy through a short-time heat treatment process, which saves production cycle and energy consumption for industrial applications as much as possible, including but not limited to pre-aging treatment at 200°C to 300°C / 12h to 24h to form high-density solute atomic clusters, pre-aging treatment at 350°C to 450°C / 5h to 15h, using high-density solute atomic clusters as heterogeneous nucleation particles to form high-density thermally stable insoluble L12 Al3 (Sc, Zr) nano-precipitation phases, using 520°C to 537°C solid solution segregation Cu, and ensuring that the high-density L12 Al3 (Sc, Zr) nano-precipitation phase is not significantly coarsened, using a low-temperature aging treatment process of 160 to 200°C / 3 to 18h, using L12Al3 (Sc, Zr) nano-precipitation phases as heterogeneous nucleation particles to precipitate precipitation phases, and solving the outstanding problem of limited high-temperature life of the alloy. The macroscopic microstructure of the alloy of the present invention is equiaxed crystals, and there is coarsely precipitated Al3 (Sc, Zr) in the crystals, which is an α-Al nucleating agent; there are a large number of nano-scale dispersed precipitation phases in the grains; and there are granular and lamellar Al2O3 phases continuously distributed along the grain boundaries. 24 MnCu8Ce3、Al 16 Cu4Mn2Ce and Al8CeCu4 micron-scale heat-resistant intermetallic compound network; and the mechanical properties of the alloy at 300℃~400℃ were significantly improved by microalloying with a small amount of Mg and Si. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The equilibrium solidification phase diagram of Al-Ce-Cu ternary alloy in a microalloyed aluminum-copper-cerium series heat-resistant aluminum alloy according to an embodiment of the present invention;

[0019] Figure 2 The microstructure diagrams of the copper-cerium series heat-resistant aluminum alloys of Example 1 and Comparative Examples 1-3 of the present invention;

[0020] Figure 3 Graphs showing high temperature tensile properties of the copper-cerium based heat-resistant aluminum alloys of Example 1 of the present invention and Comparative Examples 1-3 at (a) 300°C and (b) 400°C. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0023] A microalloyed aluminum-copper-cerium heat-resistant aluminum alloy according to an embodiment of the present invention comprises, by mass percentage, Cu7% to 9.5%, Ce 1.3% to 2.3%, Mn 0.1% to 0.5%, Sc 0.1% to 0.4%, Zr 0.1% to 0.4%, Mg 0.1% to 0.5%, Si 0.1% to 0.3%, and the balance is Al and unavoidable impurities, wherein the content relationship of Cu to Ce is Cu=2Ce+4-5%, and the content relationship of Mg to Si is Mg>1.5Si. The preparation method comprises the following steps:

[0024] (1) Before smelting, the surfaces of the metal raw materials are first mechanically polished to remove the surface oxide scale, and then the amount is taken according to the mass percentage of the aluminum alloy; the metal raw materials are pure Al ingots, pure Cu ingots, pure Mg ingots, Al-30wt.%Ce master alloy ingots, Al-10wt.%Mn master alloy ingots, Al-50wt.%Si master alloy ingots, Al-2wt.%Sc master alloy ingots and Al-10wt.%Zr master alloy ingots, and the purity is greater than 99.5%.

[0025] (2) Melting and casting alloy: taking a pure Al ingot and placing it in an iron crucible, heating it to 700-720°C, melting the pure Al ingot and then keeping it warm for 30 minutes to 1 hour; adding pure Cu ingot, pure Mg ingot, Al-30wt.%Ce master alloy ingot, Al-10wt.%Mn master alloy ingot and Al-50wt.%Si master alloy ingot in turn every 10-20 minutes, stirring and melting, and then continuing to heat to 740-760°C, adding Al-2wt.%Sc master alloy ingot and Al-10wt.%Zr master alloy ingot in turn, stirring until all are melted, and continuing to keep warm; then adding refining agent and hexachloroethane in turn for degassing and deslagging, standing and keeping warm for 10-15 minutes after slagging, and finally casting it into a mold preheated at 200°C-300°C to obtain an aluminum alloy ingot, and quenching the aluminum alloy ingot with room temperature water once it solidifies, and the casting temperature is 740°C-760°C;

[0026] (3) Solution treatment: The aluminum alloy ingot is placed at 200°C to 300°C for 12h to 24h, then heated to 350°C to 450°C for 5h to 15h, then heated to 520°C to 537°C for 5h to 15h, and finally quenched with room temperature water;

[0027] (4) Low temperature aging: The quenched aluminum alloy ingot is placed at 160°C to 200°C for 3-18 hours and then quenched to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0028] The aluminum alloy of the microalloyed aluminum-copper-cerium series heat-resistant aluminum alloy of the present invention, the intermetallic compound needs to have sufficiently high thermal stability (thermal stability temperature limit ~ 400 ° C), and in order to ensure a sufficient number of intermetallic compound phases to inhibit grain boundary sliding and provide sufficient strengthening, the total molar fraction of the intermetallic compound (heat-resistant phase) needs to meet ≥ 2%; on the other hand, nano-aging precipitation phases need to be precipitated in the crystal to make the alloy meet the basic room temperature strength requirements, and multi-step heat treatment can be performed to regulate its organizational morphology. Secondly, the intermetallic compound formed during the solidification process cannot remove the L12 nano-precipitation phase forming elements used to further strengthen the alloy. When Mg and Si are used for microalloying, in order to ensure that there are no silicon particles, the content relationship of Mg and Si is Mg>1.5Si. At the same time, a multi-step aging treatment is carried out. First, the high thermal stability L12 nano-precipitation phase in the crystal is precipitated uniformly in large quantities under pre-aging treatment, and then the traditional high temperature solid solution-low temperature aging (T6) treatment is carried out to allow the low thermal stability nano-precipitation phase in the crystal for room temperature strengthening to precipitate in large quantities. In addition, excessive coarsening of the low thermal stability nano-precipitation phase can be avoided, thereby obtaining the maximum nano-precipitation strengthening effect.

[0029] At the same time, combined with the solidification phase diagram, such as Figure 1 As shown, the Al-Ce-Cu ternary alloy is rich in aluminum, and Al8CeCu4 and Al2Cu phases are precipitated. In order to make the alloy produce an aging strengthening effect, a concentration of Cu / Ce>2 is required. At the same time, in order to avoid the excessive Cu from being unable to dissolve during the solution treatment, the content relationship of Cu and Ce is required to be Cu=2Ce+4~5. Adding a small amount of Mn (0.1%~0.5%) further accelerates and strengthens the aging hardening effect during aging, and improves the stability of the precipitated phase through solute interface segregation during thermal exposure. The composite addition of Sc and Zr promotes the formation of equiaxed crystals, refines the grain size, and precipitates thermally stable L12 Al3 (Sc, Zr) nano-precipitates during pre-aging. When Mg and Si are used for microalloying, in order to ensure that there are no silicon particles, the content relationship of Mg and Si is Mg>1.5Si. Finally, the composition of the aluminum-copper-cerium series high-strength high-temperature casting heat-resistant aluminum alloy is designed, so that Al is precipitated along the grain boundary during solidification. 24 MnCu8Ce3、Al 16 Cu4Mn2Ce and Al8CeCu4 intermetallic compound phases; a large number of nano-scale dispersed precipitate phases are precipitated in the crystal; Al3(Sc,Zr) is first precipitated as a nucleating agent to promote the formation of equiaxed crystals and refine the grain size.

[0030] Example 1

[0031] A microalloyed aluminum-copper-cerium heat-resistant aluminum alloy according to Example 1 of the present invention comprises, by mass percentage, Cu 8.5%, Ce 1.9%, Mn 0.45%, Sc 0.26%, Zr 0.19%, Mg 0.24%, Si 0.13%, and the balance is aluminum. The preparation method thereof comprises the following steps:

[0032] (1) Before smelting, the weight of each ingot is about 2.5 kg, the surface of each metal raw material is first mechanically polished to remove the surface oxide scale, and then the amount is taken according to the above mass ratio; the metal raw materials are pure Al ingots, pure Cu ingots, pure Mg ingots, Al-30wt.%Ce master alloy ingots, Al-10wt.%Mn master alloy ingots, Al-50wt.%Si master alloy ingots, Al-2wt.%Sc master alloy ingots and Al-10wt.%Zr master alloy ingots, and the purity is greater than 99.5%;

[0033] (2) placing a high-purity Al ingot in an iron crucible and heating it to 720° C. to melt it, and then keeping it warm for 30 minutes; sequentially adding preheated pure Cu, pure Mg, Al-30wt.%Ce, Al-10wt.%Mn master alloy ingots and Al-50wt.%Si master alloy ingots to the melt, stirring and melting them, and keeping them warm for 10 to 20 minutes each time; heating the melt to 760° C., sequentially adding preheated Al-2wt.%Sc and Al-10wt.%Zr master alloy ingots to the melt, stirring them until they are completely melted, and keeping them warm for 10 minutes; sequentially adding a refining agent and hexachloroethane to degas and deslag, standing and keeping warm for 10 to 15 minutes after slagging, and finally casting into a mold preheated at 200° C. to 300° C. to obtain an aluminum alloy ingot; and quenching the aluminum alloy ingot once it solidifies.

[0034] (3) Solution treatment: keep the alloy ingot at 200℃~300℃ for 12h~24h, then heat it to 350℃~450℃ and keep it for 5h~15h, then heat it to 520℃~537℃ and keep it for 5h~15h, and finally quench it in room temperature water;

[0035] (4) Low temperature aging: The alloy ingot is then kept in an oil bath furnace at 160°C to 200°C for 3 to 18 hours, and then quenched into room temperature water to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0036] (3) Organization and performance testing

[0037] The microstructure of the microalloyed aluminum-copper-cerium heat-resistant aluminum alloy of Example 1 is as follows: Figure 2As shown in Figure d, the microstructure of the heat-resistant aluminum alloy strengthened by a variety of intermetallic compounds is obtained, that is, the macroscopic microstructure of the material is equiaxed crystals (grain size ~75μm), coarsely precipitated Al3(Sc,Zr) intermetallic compounds exist in the α-Al matrix as nucleating agents, a high number density of nanoscale precipitates are distributed in the crystals, and micrometer-scale Al is distributed nearly continuously on the grain boundaries. 16 Cu4Mn2Ce、Al 24 Cu8Ce3Mn and Al8CeCu4 intermetallic compound networks.

[0038] Figure 3 The tensile stress-strain curves of the microalloyed aluminum-copper-cerium heat-resistant aluminum alloys of Example 1 and Comparative Examples 1-3 at 300°C and 400°C are shown. The mechanical properties test results show that the yield strength and tensile strength of the heat-resistant aluminum alloy of Example 1 at room temperature are 358MPa and 397MPa, respectively, at 300°C, the yield strength and tensile strength are 242MPa and 250MPa, respectively, at 350°C, the yield strength and tensile strength are 169MPa and 175MPa, respectively, and at 400°C, the yield strength and tensile strength are 102MPa and 107MPa, respectively. Compared with Comparative Examples 1-3, the performance in the temperature range of room temperature to 400°C is significantly improved. Compared with the current ZL206 alloy (T6), the tensile strength at 300℃ is increased by 57%, and the tensile strength at 350℃ is increased by 46%; compared with the current ZL207 alloy (T6), the tensile strength at 300℃ and 400℃ is increased by 127% and 53% respectively.

[0039] Example 2

[0040] A microalloyed aluminum-copper-cerium heat-resistant aluminum alloy according to Example 2 of the present invention comprises, by mass percentage, Cu 9.1%, Ce 2.2%, Mn 0.33%, Sc 0.18%, Zr 0.26%, Mg 0.34%, Si 0.18%, and the balance is aluminum. The preparation method thereof comprises the following steps:

[0041] (1) Before smelting, the weight of each ingot is about 2.5 kg, the surface of each metal raw material is first mechanically polished to remove the surface oxide scale, and then the amount is taken according to the above mass ratio; the metal raw materials are pure Al ingots, pure Cu ingots, pure Mg ingots, Al-30wt.%Ce master alloy ingots, Al-10wt.%Mn master alloy ingots, Al-50wt.%Si master alloy ingots, Al-2wt.%Sc master alloy ingots and Al-10wt.%Zr master alloy ingots, and the purity is greater than 99.5%;

[0042] (2) placing a high-purity Al ingot in an iron crucible and heating it to 720° C. to melt it, and then keeping it warm for 30 minutes; sequentially adding preheated pure Cu, pure Mg, Al-30wt.%Ce, Al-10wt.%Mn master alloy ingots and Al-50wt.%Si master alloy ingots to the melt, stirring and melting them, and keeping them warm for 10 to 20 minutes each time; heating the melt to 760° C., sequentially adding preheated Al-2wt.%Sc and Al-10wt.%Zr master alloy ingots to the melt, stirring them until they are completely melted, and keeping them warm for 10 minutes; sequentially adding a refining agent and hexachloroethane to degas and deslag, standing and keeping warm for 10 to 15 minutes after slagging, and finally casting into a mold preheated at 200° C. to 300° C. to obtain an aluminum alloy ingot; and quenching the aluminum alloy ingot once it solidifies.

[0043] (3) Solution treatment: keep the alloy ingot at 200℃~300℃ for 12h~24h, then heat it to 350℃~450℃ and keep it for 5h~15h, then heat it to 520℃~537℃ and keep it for 5h~15h, and finally quench it in room temperature water;

[0044] (4) Low temperature aging: The alloy ingot is then kept in an oil bath furnace at 160°C to 200°C for 3 to 18 hours, and then quenched into room temperature water to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0045] (3) Performance testing

[0046] The mechanical properties test results show that the yield strength and tensile strength of the heat-resistant aluminum alloy of Example 2 at room temperature are 367MPa and 410MPa, respectively, at 300°C, the yield strength and tensile strength are 248MPa and 256MPa, respectively, at 350°C, the yield strength and tensile strength are 174MPa and 178MPa, respectively, and at 400°C, the yield strength and tensile strength are 106MPa and 110MPa, respectively. Compared with Comparative Examples 1-3, the performance in the temperature range of room temperature to 400°C is significantly improved.

[0047] Example 3

[0048] A microalloyed aluminum-copper-cerium heat-resistant aluminum alloy according to Example 3 of the present invention comprises, by mass percentage, Cu7.6%, Ce1.5%, Mn0.28%, Sc0.332%, Zr0.17%, Mg0.45%, Si0.21%, and the balance is aluminum. The preparation method thereof comprises the following steps:

[0049] (1) Before smelting, the weight of each ingot is about 2.5 kg, the surface of each metal raw material is first mechanically polished to remove the surface oxide scale, and then the amount is taken according to the above mass ratio; the metal raw materials are pure Al ingots, pure Cu ingots, pure Mg ingots, Al-30wt.%Ce master alloy ingots, Al-10wt.%Mn master alloy ingots, Al-50wt.%Si master alloy ingots, Al-2wt.%Sc master alloy ingots and Al-10wt.%Zr master alloy ingots, and the purity is greater than 99.5%;

[0050] (2) placing a high-purity Al ingot in an iron crucible and heating it to 720° C. to melt it, and then keeping it warm for 30 minutes; sequentially adding preheated pure Cu, pure Mg, Al-30wt.%Ce, Al-10wt.%Mn master alloy ingots and Al-50wt.%Si master alloy ingots to the melt, stirring and melting them, and keeping them warm for 10 to 20 minutes each time; heating the melt to 760° C., sequentially adding preheated Al-2wt.%Sc and Al-10wt.%Zr master alloy ingots to the melt, stirring them until they are completely melted, and keeping them warm for 10 minutes; sequentially adding a refining agent and hexachloroethane to degas and deslag, standing and keeping warm for 10 to 15 minutes after slagging, and finally casting into a mold preheated at 200° C. to 300° C. to obtain an aluminum alloy ingot; and quenching the aluminum alloy ingot once it solidifies.

[0051] (3) Solution treatment: keep the alloy ingot at 200℃~300℃ for 12h~24h, then heat it to 350℃~450℃ and keep it for 5h~15h, then heat it to 520℃~537℃ and keep it for 5h~15h, and finally quench it in room temperature water;

[0052] (4) Low temperature aging: The alloy ingot is then kept in an oil bath furnace at 160°C to 200°C for 3 to 18 hours, and then quenched into room temperature water to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0053] (3) Performance testing

[0054] The mechanical properties test results show that the yield strength and tensile strength of the heat-resistant aluminum alloy of Example 3 at room temperature are 342MPa and 383MPa respectively, at 300°C, the yield strength and tensile strength are 236MPa and 246MPa respectively, at 350°C, the yield strength and tensile strength are 161MPa and 172MPa respectively, and at 400°C, the yield strength and tensile strength are 100MPa and 105MPa respectively. Compared with Comparative Examples 1-3, the performance in the temperature range of room temperature to 400°C is significantly improved.

[0055] Comparative Example 1

[0056] Comparative Example 1 is an aluminum-copper-cerium series heat-resistant aluminum alloy, which includes, by weight percentage, Cu: 8.7%, Ce: 1.9%, Mn: 0.45%, Sc: 0.32%, Zr: 0.27%, and the balance is Al. The preparation method thereof includes the following steps:

[0057] (1) Before smelting, the weight of each ingot is about 2.5 kg, the surface of each metal raw material is first mechanically polished to remove the surface oxide scale, and then the amount is taken according to the above mass ratio; the metal raw materials are pure Al ingots, pure Cu ingots, Al-30wt.%Ce master alloy ingots, Al-10wt.%Mn master alloy ingots, Al-2wt.%Sc master alloy ingots and Al-10wt.%Zr master alloy ingots, and the purity is greater than 99.5%;

[0058] (2) placing a high-purity Al ingot in an iron crucible and heating it to 720°C for melting, and then keeping it warm for 30 minutes; sequentially adding the preheated pure Cu, Al-30wt.%Ce, and Al-10wt.%Mn master alloy ingots into the melt and stirring and melting them, and keeping them warm for 10 to 20 minutes each time; heating the melt to 760°C, sequentially adding the preheated Al-2wt.%Sc and Al-10wt.%Zr master alloy ingots into the melt and stirring until they are completely melted, and keeping them warm for 10 minutes; sequentially adding a refining agent and hexachloroethane for degassing and deslagging, standing and keeping warm for 10 to 15 minutes after slagging, and finally casting into a mold preheated at 200°C to 300°C to obtain an aluminum alloy ingot; quenching the aluminum alloy ingot once solidified.

[0059] (3) Solution treatment: keep the alloy ingot at 200℃~300℃ for 12h~24h, then heat it to 350℃~450℃ and keep it for 5h~15h, then heat it to 520℃~537℃ and keep it for 5h~15h, and finally quench it in room temperature water;

[0060] (4) Low temperature aging: The alloy ingot is then kept in an oil bath furnace at 160°C to 200°C for 3-18 hours, and quenched into room temperature water to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0061] Organization and performance testing

[0062] The microstructure of the aluminum-copper-cerium heat-resistant aluminum alloy of Comparative Example 1 is as follows: Figure 2 As shown in a, a variety of intermetallic compound-reinforced heat-resistant aluminum alloy microstructures were obtained, that is, the macroscopic microstructure of the material is equiaxed crystals (grain size ~ 50μm), coarsely precipitated Al3(Sc,Zr) intermetallic compounds exist in the α-Al matrix as nucleating agents, high number density of nanoscale θ′ / θ"-Al2Cu and L12 Al3(Sc,Zr) precipitation phases are distributed in the crystal, and micron-scale Al is distributed nearly continuously on the grain boundary. 16 Cu4Mn2Ce、Al24 Cu8Ce3Mn and Al8CeCu4 intermetallic compound networks.

[0063] like Figure 3 As shown, the yield strength and tensile strength of the heat-resistant aluminum alloy of Comparative Example 1 are 280MPa and 357MPa at room temperature, 200MPa and 210MPa at 300°C, 134MPa and 150MPa at 350°C, and 106MPa and 114MPa at 400°C.

[0064] Comparative Example 2

[0065] Comparative Example 2 is an aluminum-copper-cerium series heat-resistant aluminum alloy, which includes, by weight percentage, Cu: 8.4%, Ce: 1.7%, Mn: 0.37%, Sc: 0.26%, Zr: 0.24%, Mg: 0.28%, and the balance is Al. The preparation method thereof includes the following steps:

[0066] (1) Before smelting, the weight of each ingot is about 2.5 kg, the surface of each metal raw material is first mechanically polished to remove the surface oxide scale, and then the amount is taken according to the above mass ratio; the metal raw materials are pure Al ingots, pure Cu ingots, pure Mg ingots, Al-30wt.%Ce master alloy ingots, Al-10wt.%Mn master alloy ingots, Al-2wt.%Sc master alloy ingots and Al-10wt.%Zr master alloy ingots, and the purity is greater than 99.5%;

[0067] (2) placing a high-purity Al ingot in an iron crucible and heating it to 720°C to melt it, then keeping it warm for 30 minutes; sequentially adding preheated pure Cu, pure Mg, Al-30wt.%Ce, and Al-10wt.%Mn master alloy ingots to the melt, stirring and melting them, and keeping them warm for 10 to 20 minutes each time; heating the melt to 760°C, sequentially adding preheated Al-2wt.%Sc and Al-10wt.%Zr master alloy ingots to the melt, stirring them until they are completely melted, and keeping them warm for 10 minutes; sequentially adding a refining agent and hexachloroethane to degas and deslag, standing and keeping warm for 10 to 15 minutes after slagging, and finally casting into a mold preheated at 200°C to 300°C to obtain an aluminum alloy ingot; quenching the aluminum alloy ingot once solidified.

[0068] (3) Solution treatment: keep the alloy ingot at 200℃~300℃ for 12h~24h, then heat it to 350℃~450℃ and keep it for 5h~15h, then heat it to 520℃~537℃ and keep it for 5h~15h, and finally quench it in room temperature water;

[0069] (4) Low temperature aging: The alloy ingot is then kept in an oil bath furnace at 160°C to 200°C for 3-18 hours, and quenched into room temperature water to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0070] Organization and performance testing

[0071] The microstructure of the microalloyed aluminum-copper-cerium heat-resistant aluminum alloy of Comparative Example 2 is as follows: Figure 2 As shown in Fig. 2, the microstructure of the heat-resistant aluminum alloy strengthened by various intermetallic compounds is obtained, that is, the macroscopic microstructure of the material is equiaxed crystals (grain size ~ 64 μm), the coarsely precipitated Al3(Sc, Zr) intermetallic compounds exist in the α-Al matrix as nucleating agents, the nanoscale precipitate phase is distributed with a high number density in the crystal, and the micrometer-scale Al is distributed nearly continuously on the grain boundary. 16 Cu4Mn2Ce、Al 24 Cu8Ce3Mn and Al8CeCu4 intermetallic compound networks.

[0072] like Figure 3 As shown, the yield strength and tensile strength of the heat-resistant aluminum alloy of Comparative Example 2 are 291 MPa and 336 MPa at room temperature, 193 MPa and 204 MPa at 300°C, 140 MPa and 148 MPa at 350°C, and 98 MPa and 103 MPa at 400°C. Compared with Comparative Example 1, the microalloying of Mg does not seem to have a significant effect.

[0073] Comparative Example 3

[0074] Comparative Example 3: Aluminum-copper-cerium heat-resistant aluminum alloy AlCu 8.4 Ce 1.8 Mn 0.5 Sc 0.28 Zr 0.26 Si 0.16 , according to weight percentage: Cu: 8.4%, Ce: 1.8%, Mn: 0.41%, Sc: 0.28%, Zr: 0.26%, Si: 0.16%, and the balance is Al. The preparation method includes the following steps;

[0075] (1) Before smelting, the weight of each ingot is about 2.5 kg, the surface of each metal raw material is first mechanically polished to remove the surface oxide scale, and then the amount is taken according to the above mass ratio; the metal raw materials are pure Al ingots, pure Cu ingots, pure Mg ingots, Al-30wt.%Ce master alloy ingots, Al-10wt.%Mn master alloy ingots, Al-2wt.%Sc master alloy ingots and Al-10wt.%Zr master alloy ingots, and the purity is greater than 99.5%;

[0076] (2) placing a high-purity Al ingot in an iron crucible and heating it to 720°C to melt it, then keeping it warm for 30 minutes; sequentially adding preheated pure Cu, pure Mg, Al-30wt.%Ce, and Al-10wt.%Mn master alloy ingots to the melt, stirring and melting them, and keeping them warm for 10 to 20 minutes each time; heating the melt to 760°C, sequentially adding preheated Al-2wt.%Sc and Al-10wt.%Zr master alloy ingots to the melt, stirring them until they are completely melted, and keeping them warm for 10 minutes; sequentially adding a refining agent and hexachloroethane to degas and deslag, standing and keeping warm for 10 to 15 minutes after slagging, and finally casting into a mold preheated at 200°C to 300°C to obtain an aluminum alloy ingot; quenching the aluminum alloy ingot once solidified.

[0077] (3) Solution treatment: keep the alloy ingot at 200℃~300℃ for 12h~24h, then heat it to 350℃~450℃ and keep it for 5h~15h, then heat it to 520℃~537℃ and keep it for 5h~15h, and finally quench it in room temperature water;

[0078] (4) Low temperature aging: The alloy ingot is then kept in an oil bath furnace at 160°C to 200°C for 3 to 18 hours, and then quenched into room temperature water to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

[0079] Organization and performance testing

[0080] The microstructure of the aluminum-copper-cerium heat-resistant aluminum alloy of Comparative Example 3 is as follows: Figure 2 As shown in Figure 3, a variety of intermetallic compound-reinforced heat-resistant aluminum alloy microstructures were obtained, that is, the macroscopic microstructure of the material was equiaxed crystals (grain size ~ 69 μm), coarsely precipitated Al3 (Sc, Zr) intermetallic compounds existed in the α-Al matrix as nucleating agents, coarse strip-like precipitation phases with low number density were distributed in the crystals, and micron-scale Al 16 Cu4Mn2Ce、Al 24 Cu8Ce3Mn and Al8CeCu4 intermetallic compound networks.

[0081] like Figure 3 As shown, the yield strength and tensile strength of the heat-resistant aluminum alloy of Comparative Example 3 are 270MPa and 354MPa at room temperature, 147MPa and 160MPa at 300°C, 121MPa and 133MPa at 350°C, and 90MPa and 99MPa at 400°C. Compared with Comparative Example 1, the micro-alloying of Si "poisons" the performance of the alloy in the temperature range of 300°C to 400°C, and seems to eliminate the strengthening increment brought by the L12Al3 (Sc, Zr) nanoprecipitate phase.

[0082] Table 1

[0083]

[0084]

[0085] It can be seen from Table 1 that the heat-resistant aluminum alloy of the present invention has a tensile strength of nearly 57% at 300°C and a tensile strength of nearly 46% at 350°C compared with the current ZL206 alloy (T6); and has a tensile strength of nearly 127% and 57% at 300°C and 400°C respectively compared with the current ZL207 alloy (T6). Compared with reference documents 1-3, the heat-resistant aluminum alloy of the present invention significantly improves the tensile strength of the alloy at 300°C and 350°C by adding only a small amount of microalloying elements.

[0086] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A microalloyed aluminum-copper-cerium heat-resistant aluminum alloy, characterized in that: Calculated by mass percentage, it includes Cu 7% to 9.5%, Ce 1.3% to 2.3%, Mn 0.1% to 0.5%, Sc 0.1% to 0.4%, Zr 0.1% to 0.4%, Mg 0.1% to 0.5%, Si 0.1% to 0.3%, and the balance is Al and unavoidable impurities, wherein the content relationship of Cu to Ce is Cu=2Ce+4~5%, and the content relationship of Mg to Si is Mg>1.5Si.

2. A method for preparing a microalloyed aluminum-copper-cerium heat-resistant aluminum alloy as claimed in claim 1, characterized in that: The following steps are involved: (1) Melting and casting alloy: heating to 700-720°C, melting pure Al ingot and keeping the temperature for 30 min-1 h; adding pure Cu ingot, pure Mg ingot, Al-30wt.%Ce master alloy ingot, Al-10wt.%Mn master alloy ingot and Al-50wt.%Si master alloy ingot in turn every 10-20 min, stirring and melting, and then heating to 740-760°C, adding Al-2wt.%Sc master alloy ingot and Al-10wt.%Zr master alloy ingot in turn, stirring until all are melted, and keeping the temperature; then adding refining agent and hexachloroethane in turn for degassing and deslagging, standing and keeping the temperature for 10-15 min after slagging, and finally casting into a mold preheated at 200°C-300°C to obtain an aluminum alloy ingot, and quenching the aluminum alloy ingot once solidified; (2) Solution treatment: The aluminum alloy ingot is placed at 200°C to 300°C for 12 to 24 hours, then heated to 350°C to 450°C for 5 to 15 hours, then heated to 520°C to 537°C for 5 to 15 hours, and finally quenched; (3) Low temperature aging: The quenched aluminum alloy ingot is placed at 160°C to 200°C for 3 to 18 hours and then quenched to obtain a micro-alloyed aluminum-copper-cerium series heat-resistant aluminum alloy.

3. The method for preparing a microalloyed aluminum-copper-cerium heat-resistant aluminum alloy according to claim 2, characterized in that: The method also includes mechanically grinding the surface of each metal raw material to remove the surface oxide scale before smelting in step (1), and then taking the amount according to the mass percentage of the aluminum alloy.

4. The method for preparing a microalloyed aluminum-copper-cerium heat-resistant aluminum alloy according to claim 2, characterized in that: The purity of the pure Al ingot, pure Cu ingot, pure Mg ingot, Al-30wt.%Ce master alloy ingot, Al-10wt.%Mn master alloy ingot, Al-50wt.%Si master alloy ingot, Al-2wt.%Sc master alloy ingot and Al-10wt.%Zr master alloy ingot in step (1) is all greater than 99.5%.

5. The method for preparing a microalloyed aluminum-copper-cerium series heat-resistant aluminum alloy according to claim 2, characterized in that: The temperature of the alloy melt during casting in step (1) is 740°C to 760°C.

6. The method for preparing a microalloyed aluminum-copper-cerium heat-resistant aluminum alloy according to claim 2, characterized in that: The quenching method in steps (2) to (3) is water quenching.

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