High-copper high-scandium al-cu-mg casting alloy and heat treatment process for long-term thermal stability

Abstract

The application discloses a high-copper high-scandium Al-Cu-Mg casting alloy with long-term thermal stability and a heat treatment process. The composition of the casting alloy is as follows: Cu 5.0-6.6%, Mg 0.10-0.40%, Mn 0.20-0.50%, Ti 0.05-0.10%, Zr 0.10-0.25%, Sc 0.10-0.60%, and the rest is Al. According to some examples of the application, the morphology, content and distribution of the W phase are changed through the heat treatment process, and the room-temperature mechanical properties and thermal stability of the high-copper high-scandium Al-Cu-Mg casting alloy are improved. Firstly, the Sc and Zr atoms are precipitated in the form of Al3(Sc, Zr) through low-temperature homogenization, and the formation of the W phase in the medium-temperature homogenization process is reduced. The content of the Sc atoms is reduced under the medium-temperature condition, so that the content of the W phase is reduced and the W phase is dispersedly distributed; and secondly, according to the phase transition point of the W phase, part of the W phase is dissolved through high-temperature homogenization, a certain amount of Cu and Sc atoms are released, the θ' and Ω phases are precipitated in the aging process, the Sc atoms are segregated at the θ'-Al2Cu interface in the thermal exposure process, and thus the high-copper high-scandium Al-Cu-Mg casting alloy with long-term thermal stability is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new materials, and particularly relates to a high-copper high-scandium Al-Cu-Mg casting alloy with long-term thermal stability and a heat treatment process. BACKGROUND

[0002] The Al-Cu-Mg alloy belongs to the 2xxx aluminum alloy and is a typical age-hardening type aluminum alloy, and has the advantages of light weight, high strength, low density, excellent impact resistance and corrosion resistance, and good processing performance. In addition, due to the high heat resistance of the Al-Cu-Mg alloy, and the increasing demand for material lightweight, the development in the fields of military and aerospace attracts more attention of scientists. The Al-Cu-Mg alloy is one of the candidate materials for the second generation of civil supersonic aircraft fuselage construction, and can be used for the skin of high-speed civil transport aircraft, which is often exposed to an environment of more than 200 DEG C during long-term service, and the precipitated phase in the alloy is easy to coarsen, which leads to rapid softening and failure of the alloy. Therefore, the thermal stability of the precipitated phase is crucial to the heat resistance of the material.

[0003] The microstructure of the crystal can be improved in the process of extrusion of the deformed alloy, and the performance is often more excellent in combination with the corresponding heat treatment process. However, the deformed alloy needs to be extruded, which limits the shape of the profile, and is generally mainly in the form of a plate. In contrast, the casting alloy can be formed by casting once, and only the internal crystal structure can be adjusted by heat treatment. Although various profiles can be obtained by casting, higher requirements are put forward for the heat treatment process.

[0004] The Al-Cu-Mg casting aluminum alloy mainly contains Cu and Mg, has a large Cu / Mg ratio, and the main strengthening precipitated phases are θ' and Ω, and the precipitation sequences are SSSS→GP zone→ / θ''→θ'→θ and SSSS→{111} clusters→Ω (Al2Cu), respectively. The θ' phase is semi-coherent with the matrix, the Ω phase is completely coherent with the matrix, and the Ω phase is dispersed in the {111} AlThin hexagonal plates are formed on the plane. The omega phase is found in the aging microstructure of 2024 and 2124 alloys, and exhibits high thermal stability below 200℃. However, in the service environment of 300-400℃, the precipitated phase in Al-Cu-Mg alloy cannot maintain excellent thermal stability, and is prone to rapid coarsening, resulting in softening failure of the alloy. Therefore, the long-term service temperature of Al-Cu-Mg alloy should not exceed 200℃. Studies have found that Sc as a rare earth element often has a lower diffusion rate, and the interface energy is lower than that of the precipitated phase in the Al matrix, resulting in very slow coarsening kinetics of the alloy. And the coarsening rate of Sc-containing alloy is low during high-temperature service above 250℃, and Sc-containing alloy is the best choice for heat-resistant aluminum alloy. Related research has added Sc and Zr as a micro-alloying element to Al-Cu alloy, and the high-temperature performance has been significantly improved.

[0005] Although the addition of rare earth elements can improve the high-temperature mechanical properties, the interaction between Sc and Cu during heat treatment will form coarse W phase, reducing the content of Cu atoms in the matrix, and the number density of precipitated phase during aging process decreases, which seriously affects the room temperature mechanical properties of the alloy. Up to now, there has been no report on improving the W phase in high-copper high-scandium alloy. SUMMARY

[0006] The purpose of the present application is to overcome at least one of the deficiencies of the prior art and provide a high-copper high-scandium Al-Cu-Mg casting alloy with long-term thermal stability and a heat treatment process.

[0007] The technical solution adopted by the present application is:

[0008] In a first aspect, the present application provides:

[0009] A high-copper high-scandium Al-Cu-Mg casting alloy, which has a mass composition of: Cu 5.0-6.6%, Mg 0.10-0.40%, Mn 0.20-0.50%, Ti 0.05-0.10%, Zr 0.10-0.25%, Sc 0.10-0.60%, unavoidable impurities, and the rest is Al.

[0010] In some examples of high-copper high-scandium Al-Cu-Mg casting alloy, the mass composition is: Cu 5.2-6.5%, Mg 0.16-0.40%, Mn 0.21-0.48%, Ti 0.06-0.10%, Zr 0.11-0.25%, Sc 0.24-0.55%, unavoidable impurities, and the rest is Al.

[0011] In some examples of the high-copper high-scandium Al-Cu-Mg casting alloy, the content of Cu is 5.5-6.6%, and the content of Sc is 0.30-0.55%.

[0012] In some examples of the high-copper high-scandium Al-Cu-Mg casting alloy, the unavoidable impurities are not more than 1%.

[0013] In a second aspect of the present application, there is provided:

[0014] The high-copper high-scandium Al-Cu-Mg casting alloy heat treatment process according to the first aspect of the present application comprises the following steps:

[0015] Raw material smelting: according to the composition of the high-copper high-scandium Al-Cu-Mg casting alloy, raw materials are weighed and smelted to obtain ingots;

[0016] Annealing treatment: the ingots are subjected to isothermal and non-isothermal multi-stage homogenization annealing at 300-570℃, and then water-cooled after annealing;

[0017] Aging treatment: the ingots after annealing treatment are subjected to two-stage aging treatment, and then water-cooled after taking out the sample;

[0018] Heat exposure treatment: the ingots after aging treatment are subjected to long-term heat exposure treatment, and then water-cooled after taking out the sample to obtain the high-copper high-scandium Al-Cu-Mg casting alloy.

[0019] In some examples of the heat treatment process, the annealing treatment is in the following order: 300-320℃ isothermal homogenization for 12-24h→300-400℃ non-isothermal homogenization treatment with a heating rate of 2-4℃ / min→390-410℃ isothermal homogenization for 24-48h→400-510℃ non-isothermal homogenization with a heating rate of 4-6℃ / min→500-510℃ isothermal homogenization for 12-24h→510-570℃ non-isothermal homogenization with a heating rate of 1-3℃ / min→560-570℃ isothermal homogenization for 12-16h.

[0020] In some examples of the heat treatment process, the annealing treatment is in the following order: 300-320℃ isothermal homogenization for 12-24h→300-400℃ non-isothermal homogenization treatment with a heating rate of 2℃ / min→390-410℃ isothermal homogenization for 24-48h→400-510℃ non-isothermal homogenization with a heating rate of 6℃ / min→500-510℃ isothermal homogenization for 12-24h→510-570℃ non-isothermal homogenization with a heating rate of 3℃ / min→560-570℃ isothermal homogenization for 12-16h.

[0021] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-3 h, at 160-185 DEG C for 0.5-56 h, and water cooling.

[0022] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0023] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0024] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0025] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0026] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0027] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0028] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0029] In some examples of the heat treatment process, the aging treatment is sequentially at 120-150 DEG C for 0.5-2 h, at 160-185 DEG C for 1-40 h, and water cooling.

[0030] Some examples of the present application, for the first time from the isothermal and non-isothermal homogenization combined heat treatment process to regulate the W phase morphology, content and distribution in high copper high scandium Al-Cu-Mg casting alloy, synergistic method to improve the room temperature mechanical properties and high temperature thermal stability of alloy. Because the best precipitation temperature range of Al3(Sc, Zr) / Al3Sc is 250℃ to 400℃, first isothermal homogenization at low temperature (about 300℃) to precipitate Al3(Sc, Zr) / Al3Sc. Then use non-isothermal homogenization to raise the temperature to about 400℃ and keep for about 48h, this process promotes Zr atoms to diffuse to Al3Sc particles, as much as possible to form Al3(Sc, Zr) particles. Continue to use non-isothermal to raise the temperature to medium temperature (about 510℃), promote Cu atoms to diffuse to Al matrix, achieve the effect of eliminating dendritic segregation. Isothermal homogenization at about 510℃ accelerates the dissolution process of solute atoms, making the alloy composition more uniform. Finally, use non-isothermal conditions to raise the temperature to high temperature (about 570℃), and isothermal homogenization at this temperature, the purpose is to dissolve part of the coarse W phase. On the one hand, the temperature reaches the phase transition point of W phase can promote the dissolution of W phase, greatly reduce the number, at the same time change the morphology and distribution of W phase. On the other hand, the dissolution of W phase will release part of Cu atoms and Sc atoms, increase the supersaturation of Cu atoms in Al matrix, the number density of precipitated phase increases during aging process. And the released Sc atoms can be used as a source of atoms to stabilize the interface of precipitated phase during heat exposure. In addition, Al3(Sc, Zr) has high thermal stability, further prevents θ' phase coarsening, improves the thermal stability of the alloy.

[0031] Some examples of the present application, by low temperature homogenization, Sc and Zr atoms are precipitated in the form of Al3(Sc, Zr) / Al3Sc, in the medium temperature homogenization to reduce the interaction with Cu atoms to form W phase, and improve the morphology and distribution of W phase. In high temperature homogenization, part of the W phase is dissolved to release Cu atoms and Sc atoms.

[0032] Some examples of the present application, low temperature short time aging (150℃, 0.5-3h) can promote the formation of GP zone, at the same time, the fine and dispersed GP zone provides a large number of nucleation sites for θ' phase, increases the number density of precipitated phase, and improves the mechanical properties of the alloy.

[0033] In some examples of the present application, the microstructure of the homogenization process is regulated by optimizing the heat treatment process, which not only meets the beneficial effects of micro-alloying and deformation, but also meets the high-strength and heat-resistant characteristics of the cast alloy in room temperature / high temperature environment. The microstructure design idea is to combine multi-stage isothermal homogenization and non-isothermal homogenization, to preferentially precipitate Al3(Sc,Zr) / Al3Sc in the low temperature range, and to control the formation of W phase under medium temperature conditions. The high temperature process further dissolves the W phase, releases part of the Cu and Sc atoms, and achieves the purpose of improving the morphology, content and distribution of the W phase. Finally, it promotes the increase of the number density of precipitates in the aging process, improves the room temperature mechanical properties, and the released Sc atoms stabilize the θ' / Al interface during thermal exposure, inhibit the coarsening of θ', and greatly improve the thermal stability. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Figure 1 is a microstructure diagram of a high-copper high-scandium Al-Cu-Mg cast alloy prepared according to Example 1. DETAILED DESCRIPTION

[0035] In a first aspect of the present application, there is provided:

[0036] A high-copper high-scandium Al-Cu-Mg cast alloy, which has a mass composition of: Cu 5.0-6.6%, Mg 0.10-0.40%, Mn 0.20-0.50%, Ti 0.05-0.10%, Zr 0.10-0.25%, Sc 0.10-0.60%, unavoidable impurities, and the balance being Al.

[0037] In some examples of the high-copper high-scandium Al-Cu-Mg cast alloy, the mass composition is: Cu 5.2-6.5%, Mg 0.16-0.40%, Mn 0.21-0.48%, Ti 0.06-0.10%, Zr 0.11-0.25%, Sc 0.24-0.55%, unavoidable impurities, and the balance being Al.

[0038] In some examples of the high-copper high-scandium Al-Cu-Mg cast alloy, the content of Cu is 5.5-6.6%, and the content of Sc is 0.30-0.55%. This is conducive to obtaining a high-copper high-scandium Al-Cu-Mg cast alloy with better performance.

[0039] In some examples of the high-copper high-scandium Al-Cu-Mg cast alloy, the unavoidable impurities are not more than 1%. The less the amount of impurities, the more stable the quality of the product.

[0040] In a second aspect of the present application, there is provided:

[0041] The heat treatment process of the high-copper high-scandium Al-Cu-Mg casting alloy in the first aspect of the present application comprises the following steps:

[0042] Raw material smelting: according to the composition of the high-copper high-scandium Al-Cu-Mg casting alloy, raw materials are weighed and smelted to obtain ingots;

[0043] Annealing treatment: the ingots are subjected to isothermal and non-isothermal multi-stage homogenization annealing at 300-570℃, and then water-cooled after annealing;

[0044] Aging treatment: the ingots after annealing treatment are subjected to two-stage aging treatment, and then water-cooled after taking out the sample;

[0045] Heat exposure treatment: the ingots after aging treatment are subjected to long-term heat exposure treatment, and then water-cooled after taking out the sample to obtain the high-copper high-scandium Al-Cu-Mg casting alloy.

[0046] In some examples of the heat treatment process, the annealing treatment is in the order of: 300-320℃ isothermal homogenization for 12-24h→300-400℃ non-isothermal homogenization treatment with a heating rate of 2-4℃ / min→390-410℃ isothermal homogenization for 24-48h→400-510℃ non-isothermal homogenization with a heating rate of 4-6℃ / min→500-510℃ isothermal homogenization for 12-24h→510-570℃ non-isothermal homogenization with a heating rate of 1-3℃ / min→560-570℃ isothermal homogenization for 12-16h.

[0047] In some examples of the heat treatment process, the annealing treatment is in the order of: 300-320℃ isothermal homogenization for 12-24h→300-400℃ non-isothermal homogenization treatment with a heating rate of 2℃ / min→390-410℃ isothermal homogenization for 24-48h→400-510℃ non-isothermal homogenization with a heating rate of 6℃ / min→500-510℃ isothermal homogenization for 12-24h→510-570℃ non-isothermal homogenization with a heating rate of 3℃ / min→560-570℃ isothermal homogenization for 12-16h.

[0048] In some examples of the heat treatment process, the aging treatment is in the order of: 120-150℃ for 0.5-3h, 160-185℃ for 0.5-56h, and water-cooled.

[0049] In some examples of the heat treatment process, the aging treatment is in the order of: 120-150℃ for 0.5-2h, 160-185℃ for 1-40h, and water-cooled.

[0050] In some examples of the heat treatment process, the 300-400℃ is for 80-100h.

[0051] The application will be described in detail below with reference to examples, comparative examples and experimental data.

[0052] The alloy chemical composition in each example is as follows: Cu 5.5-6.6%, Mg 0.10-0.40%, Mn 0.20-0.50%, Ti 0.05-0.10%, Zr 0.10-0.25%, and Sc 0.30-0.60%. Pure Al and Mg ingots are selected as raw materials, and Al-50Cu, Al-10Mn, Al-4Ti, Al-3Sc and Al-5Zr intermediate alloys are used.

[0053] The multi-element refining agent and the degassing agent are common multi-element refining agents and degassing agents in the art (the mass ratio of the refining agent to the smelting ingredients is (1-3):100. The composition of the multi-element refining agent includes 20wt% NaCl, 20wt% KCl, 35wt% NaF and 25wt% LiF. The mass ratio of the degassing agent to the smelting ingredients is 1:100, and the degassing agent is hexachloroethane. When the purity of the raw materials is high, the multi-element refining agent and the degassing agent can not be added. The multi-element refining agent and the degassing agent have no substantial effect on the performance of the alloy.

[0054] For the convenience of comparison, the amount of unavoidable impurities in the following examples is not more than 0.3%.

[0055] Example 1

[0056] 1) Raw material smelting: Cu: 6.40wt%, Mg: 0.40wt%, Mn: 0.30wt%, Ti: 0.10wt%, Zr: 0.15wt%, Sc: 0.50wt% and the balance of Al are taken according to the weight percentage of the constituent elements; aluminum ingots, magnesium ingots, aluminum intermediate alloys and rare earth alloys are prepared, and alloy ingots are obtained by smelting at 720-760℃;

[0057] 2) Annealing treatment: the prepared alloy ingots are subjected to isothermal homogenization at 300℃ for 24h; non-isothermal homogenization treatment at 300-400℃ with a heating rate of 2℃ / 1min; isothermal homogenization at 400℃ for 48h; non-isothermal homogenization at 400-510℃ with a heating rate of 6℃ / 1min; isothermal homogenization at 510℃ for 24h; non-isothermal homogenization at 510-570℃ with a heating rate of 3℃ / 1min; isothermal homogenization at 570℃ for 16h, and the sample is then water-cooled;

[0058] 3) Aging treatment: the cast aluminum-copper alloy block is subjected to two-stage aging treatment (140℃, 1h, 180℃, 56h), and the sample is then water-cooled;

[0059] 4) Hot exposure treatment: the sample after the aging treatment is subjected to heat preservation at 300-400℃ for 100h, and the sample is then water-cooled;

[0060] 5) Mechanical property test of the peak-aged and heat-exposed alloys prepared in this example.

[0061] Example 2

[0062] 1) Raw material smelting: Cu: 6.20wt%, Mg: 0.30wt%, Mn: 0.30wt%, Ti: 0.10wt%, Zr: 0.15%, Sc: 0.40%, and the balance of Al according to the weight percentage of the constituent elements; prepare aluminum ingot, magnesium ingot, aluminum master alloy and rare earth alloy, and smelt at 720-760°C to obtain alloy ingot;

[0063] 2) Annealing treatment: the prepared alloy ingot is isothermally homogenized at 300°C for 12h; non-isothermally homogenized at 300-410°C with a heating rate of 2°C / 1min; isothermally homogenized at 410°C for 24h; non-isothermally homogenized at 410-510°C with a heating rate of 6°C / 1min; isothermally homogenized at 510°C for 12h; non-isothermally homogenized at 510-570°C with a heating rate of 3°C / 1min; isothermally homogenized at 570°C for 12h, and then water-cooled after taking out the sample;

[0064] 3) Aging treatment: the cast aluminum-copper alloy block is subjected to two-stage aging treatment (140°C, holding time 1h, 180°C, holding time 56h), and then water-cooled after taking out the sample;

[0065] 4) Heat exposure treatment: the sample after aging treatment is kept at 300-400°C for 100h, and then water-cooled after taking out the sample;

[0066] 5) Mechanical property test of the peak-aged and heat-exposed alloys prepared in this example.

[0067] Example 3

[0068] 1) Raw material smelting: Cu: 5.80wt%, Mg: 0.34wt%, Mn: 0.27wt%, Ti: 0.09wt%, Zr: 0.20%, Sc: 0.35%, and the balance of Al according to the weight percentage of the constituent elements; prepare aluminum ingot, magnesium ingot, aluminum master alloy and rare earth alloy, and smelt at 720-760°C to obtain alloy ingot;

[0069] 2) Annealing treatment: the prepared alloy ingot is isothermally homogenized at 320°C for 20h; non-isothermally homogenized at 320-400°C with a heating rate of 2°C / 1min; isothermally homogenized at 400°C for 36h; non-isothermally homogenized at 400-510°C with a heating rate of 6°C / 1min; isothermally homogenized at 510°C for 20h; non-isothermally homogenized at 510-570°C with a heating rate of 3°C / 1min; isothermally homogenized at 570°C for 14h, and then water-cooled after taking out the sample;

[0070] 3) aging treatment: the cast aluminum-copper alloy bulk is subjected to two-stage aging treatment (140 °C, holding time 1 h, 180 °C, holding time 56 h), and the sample is water-cooled after being taken out;

[0071] 4) thermal exposure treatment: the sample after aging treatment is kept at 300-400 °C for 100 h, and the sample is water-cooled after being taken out;

[0072] 5) the peak-aged and thermal-exposed alloy prepared in the embodiment is subjected to mechanical property test.

[0073] Example 4

[0074] 1) raw material smelting: Cu: 5.40wt%, Mg: 0.31wt%, Mn: 0.21wt%, Ti: 0.07wt%, Zr: 0.23%, Sc: 0.52%, and the balance is Al according to the weight percentage of the constituent elements; aluminum ingot, magnesium ingot, aluminum master alloy and rare earth alloy are prepared, and alloy ingot is obtained by smelting at 720-760 °C;

[0075] 2) annealing treatment: the prepared alloy ingot is subjected to isothermal homogenization at 390 °C for 24 h; non-isothermal homogenization at 400-510 °C with a heating rate of 6 °C / 1 min; isothermal homogenization at 510 °C for 12 h; non-isothermal homogenization at 510-570 °C with a heating rate of 3 °C / 1 min; isothermal homogenization at 570 °C for 12 h, and the sample is water-cooled after being taken out;

[0076] 3) aging treatment: the cast aluminum-copper alloy bulk is subjected to two-stage aging treatment (140 °C, holding time 1 h, 180 °C, holding time 56 h), and the sample is water-cooled after being taken out;

[0077] 4) thermal exposure treatment: the sample after aging treatment is kept at 300-400 °C for 100 h, and the sample is water-cooled after being taken out;

[0078] 5) the peak-aged and thermal-exposed alloy prepared in the embodiment is subjected to mechanical property test.

[0079] Example 5

[0080] 1) raw material smelting: Cu: 6.10wt%, Mg: 0.28wt%, Mn: 0.41wt%, Ti: 0.09wt%, Zr: 0.16%, Sc: 0.55%, and the balance is Al according to the weight percentage of the constituent elements; aluminum ingot, magnesium ingot, aluminum master alloy and rare earth alloy are prepared, and alloy ingot is obtained by smelting at 720-760 °C;

[0081] 2) annealing treatment: the prepared alloy ingot was isothermally homogenized at 410 ℃ for 48 h; non-isothermally homogenized at 400-510 ℃, the heating rate was 6 ℃ / 1 min; isothermally homogenized at 500 ℃ for 24 h; non-isothermally homogenized at 500-570 ℃, the heating rate was 3 ℃ / 1 min; isothermally homogenized at 560 ℃ for 24 h, and the sample was water-cooled after being taken out;

[0082] 3) aging treatment: the cast aluminum-copper alloy block was subjected to two-stage aging treatment (140 ℃, the holding time was 1 h, 180 ℃, the holding time was 56 h), and the sample was water-cooled after being taken out;

[0083] 4) heat exposure treatment: the sample after aging treatment was kept at 300-400 ℃ for 100 h, and the sample was water-cooled after being taken out;

[0084] 5) the mechanical properties of the peak-aged and heat-exposed alloy prepared in the embodiment were tested.

[0085] Example 6

[0086] 1) raw material smelting: Cu: 5.90wt%, Mg: 0.32wt%, Mn: 0.45wt%, Ti: 0.08wt%, Zr: 0.21%, Sc: 0.45%, and the balance was Al according to the weight percentage of the constituent elements; aluminum ingot, magnesium ingot, aluminum master alloy and rare earth alloy were prepared, and the alloy ingot was obtained by smelting at 720-760 ℃;

[0087] 2) annealing treatment: the prepared alloy ingot was isothermally homogenized at 300 ℃ for 24 h; non-isothermally homogenized at 300-400 ℃, the heating rate was 2 ℃ / 1 min; non-isothermally homogenized at 400-510 ℃, the heating rate was 6 ℃ / 1 min; isothermally homogenized at 510 ℃ for 24 h; non-isothermally homogenized at 510-570 ℃, the heating rate was 3 ℃ / 1 min; isothermally homogenized at 570 ℃ for 16 h, and the sample was water-cooled after being taken out;

[0088] 3) aging treatment: the cast aluminum-copper alloy block was subjected to two-stage aging treatment (140 ℃, the holding time was 1 h, 180 ℃, the holding time was 56 h), and the sample was water-cooled after being taken out;

[0089] 4) heat exposure treatment: the sample after aging treatment was kept at 300-400 ℃ for 100 h, and the sample was water-cooled after being taken out;

[0090] 5) the mechanical properties of the peak-aged and heat-exposed alloy prepared in the embodiment were tested.

[0091] Example 7

[0092] 1) Raw material smelting: Cu: 6.50wt%, Mg: 0.27wt%, Mn: 0.39wt%, Ti: 0.10wt%, Zr: 0.25%, Sc: 0.24%, and the balance of Al according to the weight percentage of the constituent elements; prepare aluminum ingots, magnesium ingots, aluminum master alloys, and rare earth alloys, and smelt at 720-760°C to obtain alloy ingots;

[0093] 2) Annealing treatment: homogenize the prepared alloy ingots at 300°C for 24h; non-isothermal homogenization treatment at 300-400°C with a heating rate of 2°C / 1min; isothermal homogenization at 400°C for 48h; non-isothermal homogenization at 400-510°C with a heating rate of 6°C / 1min; non-isothermal homogenization at 510-570°C with a heating rate of 3°C / 1min; isothermal homogenization at 570°C for 16h, and water cooling after taking out the sample;

[0094] 3) Aging treatment: two-stage aging treatment (140°C, holding time 1h, 180°C, holding time 56h) is performed on the cast aluminum-copper alloy block, and water cooling is performed after taking out the sample;

[0095] 4) Heat exposure treatment: the sample after aging treatment is kept at 300-400°C for 100h, and water cooling is performed after taking out the sample;

[0096] 5) Mechanical property test is performed on the peak-aged and heat-exposed alloy prepared in this embodiment.

[0097] Example 8

[0098] 1) Raw material smelting: Cu: 5.20wt%, Mg: 0.16wt%, Mn: 0.48wt%, Ti: 0.06wt%, Zr: 0.19%, Sc: 0.36%, and the balance of Al according to the weight percentage of the constituent elements; prepare aluminum ingots, magnesium ingots, aluminum master alloys, and rare earth alloys, and smelt at 720-760°C to obtain alloy ingots;

[0099] 2) Annealing treatment: homogenize the prepared alloy ingots at 300°C for 24h; non-isothermal homogenization treatment at 300-400°C with a heating rate of 2°C / 1min; isothermal homogenization at 400°C for 48h; non-isothermal homogenization at 400-510°C with a heating rate of 6°C / 1min; isothermal homogenization at 510°C for 24h, and water cooling after taking out the sample;

[0100] 3) Aging treatment: two-stage aging treatment (140°C, holding time 1h, 180°C, holding time 56h) is performed on the cast aluminum-copper alloy block, and water cooling is performed after taking out the sample;

[0101] 4) Heat exposure treatment: the sample after aging treatment is kept at 300-400°C for 100h, and water cooling is performed after taking out the sample;

[0102] 5) Mechanical properties test of the peak-aged and heat-exposed alloys prepared in this example.

[0103] Comparative Example 1

[0104] 1) Raw material smelting: Cu: 5.80wt%, Mg: 0.32wt%, Mn: 0.35wt%, Ti: 0.08wt%, Zr: 0.11%, Sc: 0.54%, and the balance of Al according to the weight percentage of the constituent elements; prepare aluminum ingot, magnesium ingot, aluminum master alloy and rare earth alloy, and smelt at 720-760℃ to obtain alloy ingot;

[0105] 2) Annealing treatment: the prepared alloy ingot is homogenized at 510℃ for 24h; non-isothermal homogenization at 510-570℃ with a heating rate of 3℃ / 1min; isothermal homogenization at 570℃ for 16h, and water cooling after taking out the sample;

[0106] 3) Aging treatment: the cast aluminum-copper alloy block is subjected to two-stage aging treatment (140℃, holding time 1h, 180℃, holding time 56h), and water cooling after taking out the sample;

[0107] 4) Heat exposure treatment: the sample after aging treatment is kept at 300-400℃ for 100h, and water cooling after taking out the sample;

[0108] 5) Mechanical properties test of the peak-aged and heat-exposed alloys prepared in this example.

[0109] Performance comparison of Al-Cu-Mg cast alloys with different heat treatment processes

[0110] The high-copper high-scandium Al-Cu-Mg cast alloys obtained in the examples and comparative examples are subjected to performance test, wherein the melting point of the alloy is determined by using differential scanning calorimeter (DSC); the test method for strength and elongation is determined according to GB / T 228.1-2010 "Metallic materials-tensile testing-Part 1: Method of test at room temperature". The test results are shown in Table 1.

[0111] Table 1, Performance comparison of Al-Cu-Mg cast alloys with different heat treatment processes

[0112] No. Room temperature tensile strength / MPa Elongation / % Heat exposed tensile strength / MPa Elongation / % Example 1 512.5 6.2 431.3 7.2 Example 2 491.1 8.1 403.6 9.5 Example 3 501.2 7.4 416.3 8.6 Example 4 475.6 9.9 384.2 11.2 Example 5 462.2 10.9 367.2 12.0 Example 6 460.2 11.4 371.3 11.8 Example 7 443.8 9.4 342.5 10.5 Example 8 487.3 8.3 392.1 10.1 Comparative Example 1 458.9 11.9 364.3 11.2

[0113] Figure 1 is the microstructure diagram of the high-copper high-scandium Al-Cu-Mg cast alloy prepared in Example 1. From Figure 1 It can be seen that the obtained W phase is more fine and dispersed, and the distribution is uniform, and the number is less. At the same time, the multi-phase structure of the enhanced Sc atomic interface segregation θ'-Al2Cu and Al3(Sc, Zr) / Al3Sc complex precipitated phase is obtained.

[0114] The above is a further detailed description of the present application, which cannot be considered as a limitation of the specific implementation of the present application. For those skilled in the art to which the present application belongs, simple deductions or replacements without departing from the concept of the present application are within the protection scope of the present application.

Claims

1. A high-copper, high-scandium Al-Cu-Mg casting alloy, with the following mass composition: Cu 5.5–6.6%, Mg 0.10–0.40%, Mn 0.20–0.50%, Ti 0.05–0.10%, Zr 0.10–0.25%, Sc 0.30–0.55%, unavoidable impurities, and the remainder being Al. Its heat treatment process includes the following steps: Raw material smelting: Based on the composition of the high-copper, high-scandium Al-Cu-Mg casting alloy, weigh the raw materials and smelt them to obtain ingots; Annealing treatment: The ingot is subjected to isothermal and non-isothermal multi-stage homogenization annealing at 300-570℃. The annealing treatment is as follows: isothermal homogenization at 300-320℃ for 12-24h → non-isothermal homogenization at 300-400℃ with a heating rate of 2-4℃ / min → isothermal homogenization at 390-410℃ for 24-48h → non-isothermal homogenization at 400-510℃ with a heating rate of 4-6℃ / min → isothermal homogenization at 500-510℃ for 12-24h → non-isothermal homogenization at 510-570℃ with a heating rate of 1-3℃ / min → isothermal homogenization at 560-570℃ for 12-16h. After annealing, the ingot is water-cooled. Aging treatment: The annealed ingots are subjected to a two-stage aging treatment, which is to hold at 120-150℃ for 0.5-3h and at 160-185℃ for 0.5-56h respectively. After the samples are removed, they are water-cooled. Heat exposure treatment: The aged ingots are subjected to long-term heat exposure treatment, specifically: heat treatment at 300-400℃ for 80-100h, and the sample is removed and water-cooled to obtain a high-copper and high-scandium Al-Cu-Mg casting alloy.

2. The high-copper, high-scandium Al-Cu-Mg casting alloy according to claim 1, characterized in that, The unavoidable impurities do not exceed 1%.

3. The high-copper, high-scandium Al-Cu-Mg casting alloy according to claim 1, characterized in that, The annealing treatments were performed sequentially as follows: isothermal homogenization at 300–320℃ for 12–24 h → non-isothermal homogenization at 300–400℃ with a heating rate of 2℃ / min → isothermal homogenization at 390–410℃ for 24–48 h → non-isothermal homogenization at 400–510℃ with a heating rate of 6℃ / min → isothermal homogenization at 500–510℃ for 12–24 h → non-isothermal homogenization at 510–570℃ with a heating rate of 3℃ / min → isothermal homogenization at 560–570℃ for 12–16 h.

4. The high-copper, high-scandium Al-Cu-Mg casting alloy according to claim 1, characterized in that, The aging treatment consisted of holding at 120–150℃ for 0.5–2 hours, holding at 160–185℃ for 1–40 hours, and then water cooling.

5. A profile made of the high-copper, high-scandium Al-Cu-Mg casting alloy as described in any one of claims 1 to 4.

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