High-strength cast aluminum-copper alloy and preparation method thereof

Abstract

The invention discloses a high-strength cast aluminum-copper alloy and a preparation method thereof, and belongs to the technical field of aluminum-copper alloys. According to the high-strength cast aluminum-copper alloy, through component adjustment, an Si element is added into an Al-Cu-Mn-Mg alloy to serve as an alloying element for adjusting the aluminum-copper alloy to form a secondary phase, and an Mg2Si eutectic phase is further formed at the grain boundary besides a net-shaped Al2Cu phase and a small amount of blocky Al20Cu2Mn3 phase at the grain boundary of the alloy. And after heat treatment, a nanoscale blocky Al5Mn12Si7 phase is formed at the theta ' / Al interface, so that the mechanical property of the alloy is obviously improved compared with that of the alloy without the Si element. The prepared cast aluminum-copper alloy material is good in casting process performance, excellent mechanical performance can be obtained after heat treatment, meanwhile, the alloy preparation method is simple, and good industrial application prospects and practical application value are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy material preparation, and particularly relates to a high-strength cast aluminum-copper alloy and a preparation method thereof. Background Art

[0002] As a widely used metallic material, cast aluminum alloy has the characteristics of low specific gravity, high specific strength, short preparation process flow, and low cost, and is widely used in manufacturing fields such as aviation, aerospace, and automobiles. In recent years, with the rapid development of new energy vehicles, intelligent vehicles, and autonomous driving technologies, the demand for lightweight in the automotive industry has been continuously increasing, and "replacing steel with aluminum" has become the main trend of automotive lightweight development, which poses more stringent requirements for aluminum alloy materials in terms of both high performance and low cost.

[0003] The Al-Cu series alloy is a typical high-strength and tough cast aluminum alloy. Due to its good comprehensive mechanical properties, such as high strength, good ductility and plasticity, good high-temperature performance, and cutting performance, this series of alloys is widely used in aerospace products. The ZL205A alloy is one of the typical representatives and is considered to be the currently highest-strength cast aluminum alloy material. However, due to the complex composition, high cost, poor fluidity during casting, and easy occurrence of defects such as hot cracks, segregation, and porosity in the ZL205A alloy, the yield rate of producing castings is low, which not only causes great economic losses but also becomes a bottleneck problem in production supporting. Although a series of patents such as CN 109136697 A, CN 111041304 A, and CN 111020321 A of Lanzhou Flight Control Co., Ltd. have been improved on the basis of ZL205A and achieved certain technical effects, the yield strength of such alloys is only 350 MPa, which cannot further meet the application requirements of high-performance castings. Introducing Ag element into the Al-Cu-Mg alloy is an effective way to improve the yield strength of the alloy. The published patent CN 114293077 A discloses a high-strength aluminum-copper alloy for aerospace structural parts and a preparation method thereof. This alloy adds 0.20 - 0.60 wt% of Ag element, the yield strength reaches above 430 MPa, the tensile strength reaches above 450 MPa, and the elongation rate reaches above 5%. However, due to the addition of the precious metal Ag element, the cost of the alloy has increased significantly, and it is only used in high-end products such as aerospace, which is not conducive to the application and promotion of the alloy. The patent with the publication number CN107267825 A discloses a high-strength aluminum-copper alloy containing Sc and Zr, aiming to replace the QT450-10 nodular iron material. However, on the one hand, the introduction of the precious metal Sc also significantly increases the cost of the alloy. On the other hand, the addition of Zr element will increase the viscosity of the aluminum melt, which is not conducive to controlling casting defects. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art, and to provide a high-strength cast aluminum-copper alloy and a preparation method thereof, so as to solve the problems of high melt viscosity, poor fluidity and high cost of high-strength aluminum-copper alloys in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A high-strength cast aluminum-copper alloy, by mass percentage, includes 4.2-6.0 wt.% of Cu, 0.2-1.2 wt.% of Mn, 0.10%-0.55 wt.% of Mg, 0.1%-0.35% of Si, 0.15-0.35 wt.% of Ti; the balance is aluminum and unavoidable impurities; The high-strength cast aluminum-copper alloy contains needle-like θ'(Al2Cu) phase, and there is Al5Mn 12 Si7 phase at the boundary of the θ'(Al2Cu) phase.

[0006] A further improvement of the present invention lies in: Preferably, the yield strength of the high-strength cast aluminum-copper alloy is greater than 420 MPa, and the tensile strength is greater than 470 MPa.

[0007] Preferably, by mass percentage, it includes 4.6-5.3 wt.% of Cu, 0.4-1.0 wt% of Mn, 0.15-0.45 wt.% of Mg, 0.15-0.30 wt.% of Si, 0.15-0.30 wt.% of Ti, and the balance is Al.

[0008] Preferably, it further includes Al 20 Cu2Mn3 phase.

[0009] A preparation method of a high-strength cast aluminum-copper alloy includes the following steps: Step 1: After all the pure Al is melted, add red copper or Al-Cu alloy, electrolytic Mn or Al-Mn alloy, Al-Si alloy and pure Mg, melt them, and then add Al-Ti-B alloy to pour into an ingot; Step 2: Perform solution treatment and aging treatment on the ingot.

[0010] Preferably, in Step 1, heat the aluminum ingot to 730-750 °C, wait for all the aluminum ingot to melt to obtain aluminum liquid; add red copper or Al-Cu master alloy, electrolytic Mn or Al-Mn master alloy, Al-Si master alloy into the aluminum liquid; after all the metals are melted, adjust the temperature of the aluminum liquid to 690-710 °C, and add pure Mg; after all the pure Mg is melted, adjust the temperature of the aluminum liquid to rise to 740-750 °C, add Al-Ti-B alloy, after all the metals are melted, stir to make the components mix evenly, and adjust the temperature of the aluminum liquid to 730-740 °C for heat preservation and then casting.

[0011] Preferably, in step 2, the solutionizing process is as follows: heat the casting to 475 - 505 °C and hold for 1 - 6 h, then raise the furnace temperature to 515 - 535 °C, hold for 9 - 16 h, and perform quenching after holding.

[0012] Preferably, in step 2, the solutionizing process is as follows: heat the casting to 480 - 500 °C and hold for 2 - 4 h, then raise the furnace temperature to 520 - 530 °C, hold for 10 - 15 h, and perform quenching after holding.

[0013] Preferably, in step 2, the aging treatment process is as follows: perform aging treatment on the solution-treated casting at 165 - 195 °C for 4 - 10 h.

[0014] Preferably, in step 2, the aging treatment process is as follows: perform aging treatment on the solution-treated casting at 170 - 190 °C for 5 - 9 h.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a high-strength cast aluminum-copper alloy. Through the adjustment of the composition, Si element is added as an alloying element for adjusting the formation of secondary phases in the Al-Cu-Mn-Mg alloy. Besides the network-shaped Al2Cu and a small amount of massive Al 20 Cu2Mn3 phases at the grain boundaries of the alloy, a eutectic structure Al + Al2Cu + Mg2Si with a low melting point is also formed at the grain boundaries during the solidification process. This eutectic structure and the Al2Cu eutectic phase dissolve during the solutionizing process, and the Al 20 Cu2Mn3 phase at the grain boundaries does not change during the heat treatment process and remains at the grain boundaries after heat treatment. The introduction of Si element in the alloy, on the one hand, accelerates the diffusion of Cu atoms, changes the precipitation kinetic conditions of the θ' phase, and a double-peak phenomenon appears in the aging hardening curve of the alloy, and the first aging hardness peak appears significantly earlier than that without Si; on the other hand, during the heat treatment process, a large number of nano-scale massive Al5Mn 12 Si7 phases are formed at the interface between the θ' phase and the Al matrix, significantly improving the mechanical properties of the alloy compared with that without Si element. The cast aluminum-copper alloy material prepared by the present invention has good casting process performance, can obtain excellent mechanical properties after heat treatment, and at the same time, the alloy preparation method is simple, having good industrial application prospects and practical application value. The alloy of the present invention can improve the mechanical properties and casting process performance of the cast aluminum-copper alloy as much as possible without using precious metal elements such as Ag and Sc.

[0016] The present invention also discloses a preparation method of a high-strength cast aluminum-copper alloy. Based on the Al-Cu-Mn-Mg alloy, Si is introduced as an alloying element, which well improves the fluidity and casting performance of the cast aluminum-copper alloy. After T6 heat treatment, not only a large number of needle-like θ' (Al2Cu) phases precipitate in the alloy matrix, but also a large number of nano-scale massive Al5Mn 12 Si7 phases precipitate. The defect tendency of the cast aluminum-copper alloy significantly decreases, and the yield rate is greatly improved. Under the synergistic strengthening effect of a variety of second-phase particles, a high-strength cast aluminum-copper alloy with a room-temperature yield strength greater than 420 MPa, a tensile strength greater than 470 MPa, and an elongation greater than 8% can be obtained. The yield strength is increased by more than 80 MPa compared with that without Si, and it is suitable for the casting of complex components in the aerospace field. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the as-cast microstructure of the alloy in Example 1; Figure 2 is the precipitated phase in the matrix of the alloy in Example 2 after solution treatment; Figure 3 is the precipitated phase in the matrix of the alloy in Example 2 after solution + aging treatment; Figure 4 is the stress-strain curve of the alloy in Example 2 and the alloy without Si element. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following further describes the present invention in detail with reference to the accompanying drawings: To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0019] In this article, unless otherwise specified, the terms "comprising", "including", "containing", "having" or similar terms cover the meanings of "consisting of" and "mainly consisting of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0020] The following further elaborates the present invention with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0021] In the following examples, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following examples, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. In the following examples, various raw materials are used. Unless otherwise specified, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0022] In the first aspect of the present invention, a low-cost and high-strength cast Al-Cu alloy is provided. The Al-Cu alloy is composed of the following components by mass percentage: the Cu content is 4.2 - 6.0 wt.%; the Mn content is 0.2 - 1.2 wt.%, the Mg content is 0.10% - 0.55 wt.%; the Si is 0.1% - 0.35%; the Ti is 0.15 - 0.35 wt.%; the balance is aluminum and unavoidable impurities. Among them, the content of unavoidable impurity elements is less than 0.15 wt.%.

[0023] Preferably, the mass percentages of the components in the aluminum-copper alloy are as follows: the Cu content is 4.6 - 5.3 wt.%; the Mn content is 0.4 - 1.0 wt%, the Mg content is 0.15 - 0.45 wt%; the Si content is 0.15 - 0.30 wt%; the Ti content is 0.15 - 0.30 wt%; the balance is Al.

[0024] In the second aspect of the present invention, a method for preparing the above-mentioned high-strength cast Al-Cu alloy is provided. The method includes: S1. Alloy melting and casting: After all the high-purity Al is melted, preheated electrolytic copper or Al-Cu master alloy, electrolytic Mn or Al-Mn master alloy, Al-Si master alloy and industrial pure Mg are added thereto. After the alloy is melted and mixed evenly, it is refined to remove slag and cast into ingots; S2. Heat treatment of the alloy: The cast ingots formed by casting are subjected to solution treatment and aging treatment; Preferably, in the step S1, put the high-purity aluminum ingot into the preheated crucible, heat it up to 730 - 750 °C. After the aluminum ingot is completely melted, add the prepared electrolytic manganese or Al-Mn master alloy, Al-Si master alloy into the aluminum liquid. After all the metals are melted, adjust the temperature of the aluminum liquid to 690 - 710 °C, and add the prepared Mg ingot. After all the pure Mg is melted, raise the temperature of the aluminum liquid to 740 - 750 °C, and add the prepared Al-Ti-B master alloy. After all the metals are melted, stir to make the components evenly mixed, adjust the temperature of the aluminum liquid to 730 - 740 °C for heat preservation. Press the preheated refining agent into the melt by using a bell jar and stir well. When no bubbles are generated, sprinkle the preheated drossing agent and stir up and down sufficiently. Let it stand for 5 - 10 minutes and then skim the dross. Then pour the melted metal liquid into the preheated metal mold, cool and demold to prepare the high-strength aluminum-copper alloy ingot.

[0025] Preferably, in the step S2, the solution treatment process parameters of the alloy are as follows: first, heat the casting to 475 - 505 °C and hold for 1 - 6 h to dissolve the eutectic structure with low melting point in the alloy and avoid overburning the alloy by directly heating to a high temperature. Then raise the furnace temperature to 515 - 535 °C and hold for 9 - 16 h, and control the temperature difference of the furnace temperature within ±3 °C. This stage is mainly to ensure the full solution of Al2Cu at the grain boundary and form the Al 20 Cu2Mn3 phase with a micron scale in the aluminum matrix. After the heat preservation is completed, quench with room temperature water, and the quenching transfer time is less than 15 s. The aging temperature is 165 - 195 °C, the heat preservation time is 4 - 10 h, and the temperature difference of the furnace temperature is controlled within ±3 °C. After the heat preservation is completed, take it out and cool it in the air.

[0026] Preferably, the solution treatment process parameters are as follows: first, heat the casting to 480 - 500 °C and hold for 2 - 4 h, then raise the furnace temperature to 520 - 530 °C, the heat preservation time is 10 - 15 h, and the temperature difference of the furnace temperature is controlled within ±3 °C. After the heat preservation is completed, quench with room temperature water, and the quenching transfer time is less than 15 s. The artificial aging temperature is 170 - 190 °C, the heat preservation time is 5 - 9 h, and the temperature difference of the furnace temperature is controlled within ±3 °C. After the heat preservation is completed, take it out and cool it in the air.

[0027] In the embodiments of the present invention, the components in the alloy are all in mass percentage.

[0028] In the second aspect of the present invention, a high-strength cast aluminum-copper alloy is disclosed. By mass percentage, it includes Cu 4.2-6.0 wt.%, Mn 0.2-1.2 wt.%, Mg 0.10%-0.55 wt.%, Si 0.1%-0.35%, Ti 0.15-0.35 wt.%; the balance is aluminum and inevitable impurities.

[0029] The high-strength cast aluminum-copper alloy contains needle-like θ'(Al2Cu) phase, and there is Al5Mn at the boundary of the θ'(Al2Cu) phase. 12 Si7 phase.

[0030] The yield strength of the high-strength cast aluminum-copper alloy is greater than 420 MPa, and the tensile strength is greater than 470 MPa. Due to the existence of the Al5Mn 12 Si7 phase, the mechanical properties of the alloy are significantly improved.

[0031] In a preferred embodiment, the aluminum-copper alloy, by mass percentage, includes Cu 4.6-5.3 wt.%, Mn 0.4-1.0 wt%, Mg 0.15-0.45 wt%, Si 0.15-0.30 wt%, Ti 0.15-0.30 wt%, and the balance is Al. The mechanical properties of the alloy are better within this composition range.

[0032] In a preferred embodiment, the finally formed aluminum-copper alloy further includes Al 20 Cu2Mn3 phase.

[0033] The following is further illustrated with specific examples.

[0034] Example 1 A preparation method of a high-strength cast aluminum-copper alloy includes the following steps: Step 1, using high-purity Al (99.99%), Al-50Cu master alloy, Al-10Mn master alloy, pure magnesium (99.9%), Al-20Si master alloy, and Al-5Ti-1B master alloy as raw materials, preparing according to the weight percentage of Al-4.8%Cu-0.6%Mn-0.35%Mg-0.3%Ti-0.2%Si. Before charging into the furnace, remove the oxide film, oil and other impurities on the surface of the raw materials, and preheat at 200 °C to remove the moisture on the surface of the raw materials.

[0035] Step 2: First, place the preheated high-purity aluminum block in a graphite-clay crucible and put it into a pit-type resistance furnace. Adjust the furnace temperature to rise to 750 °C. After the high-purity aluminum block is completely melted, add Al-50Cu master alloy, Al-10Mn master alloy, and Al-20Si master alloy. After the alloys are melted, stir for 5 min to make the composition of the aluminum liquid uniform, and adjust the temperature of the aluminum liquid to 700 °C. Press pure magnesium into the melt with a bell jar and stir evenly. Then adjust the temperature to 750 °C, add the preheated Al-5Ti-1B master alloy. After the master alloy is completely melted, stir for 5 min, and adjust the temperature of the aluminum liquid to 740 °C for heat preservation. Press the refining agent into the melt with a bell jar and stir up and down sufficiently. When no more bubbles are generated, sprinkle the preheated slag cleaning agent on the surface of the melt and stir well. Let it stand for 10 minutes and then skim the slag.

[0036] Step 3: Pour the alloy liquid smelted in Step 2 into a metal mold preheated to 250 °C, cool and demold to prepare an alloy ingot.

[0037] Step 4: Put the alloy ingot prepared in Step 3 into a box-type resistance furnace for T6 heat treatment to obtain a high-strength cast aluminum-copper alloy with excellent properties. The T6 heat treatment process is as follows: First, heat the casting to 495 °C and hold for 2 h, then raise the furnace temperature to 525 °C and hold for 10 h. The temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, quench with room temperature water, and the quenching transfer time is less than 15 s. The artificial aging temperature is 175 °C, hold for 7 h, the temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, take it out and cool in the air.

[0038] Example 2 A preparation method of a high-strength cast aluminum-copper alloy, comprising the following steps: Step 1: Using high-purity Al (99.99%), Al-50Cu master alloy, Al-10Mn master alloy, pure magnesium (99.9%), Al-20Si master alloy, and Al-5Ti-1B master alloy as raw materials, prepare according to the weight percentage of Al-5.2%Cu-0.7%Mn-0.45%Mg-0.30%Ti-0.30%Si. Before charging into the furnace, remove impurities such as oxide films and oil stains on the surface of the raw materials, and preheat at 200 °C to remove the water on the surface of the raw materials.

[0039] Step 2: First, place the preheated high-purity aluminum block in a graphite-clay crucible and put it into a pit-type resistance furnace. Adjust the furnace temperature to rise to 750 °C. After the high-purity aluminum block is completely melted, add Al-50Cu master alloy, Al-10Mn master alloy, and Al-20Si master alloy. After the alloy is melted, stir for 5 min to make the composition of the aluminum liquid uniform. Adjust the temperature to 700 °C, press pure magnesium into the melt with a bell jar, and stir evenly. Then adjust the temperature to 740 °C, add the preheated Al-5Ti-1B master alloy. After all the metal is melted, stir for 3 min, and adjust the temperature of the aluminum liquid to 740 °C for heat preservation. Press the refining agent into the melt with a bell jar, stir up and down sufficiently. When no more bubbles are generated, sprinkle the preheated slag cleaning agent on the surface of the melt, and stir well. After standing for 10 minutes, skim the slag.

[0040] Step 3: Pour the alloy liquid smelted in Step 2 into a metal mold preheated to 260 °C, cool and demold to prepare an alloy ingot.

[0041] Step 4: Put the alloy ingot prepared in Step 3 into a box-type resistance furnace for T6 heat treatment to obtain a high-strength aluminum-copper alloy with excellent properties. The T6 heat treatment process is as follows: First, heat the casting to 485 °C and hold for 2 h, then raise the furnace temperature to 525 °C and hold for 12 h. The temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, quench with room temperature water, and the quenching transfer time is less than 15 s. The artificial aging temperature is 175 °C and the holding time is 8 h. The temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, take it out and cool in the air.

[0042] Example 3 Step 1: Using high-purity Al (99.99%), Al-50Cu master alloy, Al-10Mn master alloy, pure magnesium (99.9%), Al-20Si master alloy, and Al-5Ti-1B master alloy as raw materials, prepare according to the weight percentage of Al-5.0%Cu-0.8%Mn-0.45%Mg-0.30%Ti-0.25%Si. Before putting into the furnace, remove impurities such as oxide films and oil stains on the surface of the raw materials, and preheat at 200 °C to remove the water on the surface of the raw materials.

[0043] Step 2: First, place the preheated high-purity aluminum block in a graphite-clay crucible and put it into a pit-type resistance furnace. Adjust the furnace temperature to rise to 740 °C. After the high-purity aluminum block is completely melted, add Al-50Cu master alloy, Al-10Mn master alloy, and Al-20Si master alloy in sequence. After the alloy is melted, stir for 6 min to make the composition of the aluminum liquid uniform, and adjust the temperature to 700 °C. Press pure magnesium into the melt with a bell jar, stir evenly, then adjust the temperature to 750 °C, add the preheated Al-5Ti-1B master alloy. After all the metal is melted, stir for 5 min, and adjust the temperature of the aluminum liquid to 740 °C for heat preservation. Press the refining agent into the melt with a bell jar, stir up and down sufficiently. When no more bubbles are generated, sprinkle the preheated slag cleaning agent on the surface of the melt and stir it sufficiently. Skim the slag after standing for 10 minutes.

[0044] Step 3: Pour the alloy liquid smelted in Step 2 into a metal mold preheated at 260 °C, cool and demold to prepare an alloy ingot.

[0045] Step 4: Put the alloy ingot prepared in Step 3 into a box-type resistance furnace for T6 heat treatment to obtain a high-strength aluminum-copper alloy with excellent properties. The T6 heat treatment process is as follows: First, heat the casting to 495 °C and hold for 2 h, then raise the furnace temperature to 525 °C and hold for 12 h. The temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, quench with room temperature water, and the quenching transfer time is less than 15 s. The artificial aging temperature is 175 °C and the holding time is 7 h. The temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, take it out and cool in the air.

[0046] Example 4 Step 1: Using high-purity Al (99.99%), Al-50Cu master alloy, Al-10Mn master alloy, pure magnesium (99.9%), Al-20Si master alloy, and Al-5Ti-1B master alloy as raw materials, prepare according to the weight percentage of Al-5.0%Cu-0.9%Mn-0.45%Mg-0.3%Ti-0.20%Si. Before putting into the furnace, remove impurities such as oxide films and oil stains on the surface of the raw materials, and preheat at 200 °C to remove the water on the surface of the raw materials.

[0047] Step 2: First, place the preheated high-purity aluminum block in a graphite-clay crucible and put it into a pit-type resistance furnace. Adjust the furnace temperature to rise to 750 °C. After the high-purity aluminum block is completely melted, add Al-50Cu master alloy, Al-10Mn master alloy, and Al-20Si master alloy in sequence. After the alloys are melted, stir for 6 min to make the composition of the aluminum liquid uniform, and then adjust the temperature to 690 °C. Press pure magnesium into the melt with a bell jar, stir evenly, then adjust the temperature to 750 °C, add the preheated Al-5Ti-1B master alloy. After all the metals are melted, stir for 5 min, adjust the temperature of the aluminum liquid to 730 °C for heat preservation, press the refining agent into the melt with a bell jar, stir up and down sufficiently. When no more bubbles are generated, sprinkle the preheated slag cleaning agent on the surface of the melt and stir well. Skim the slag after standing for 10 minutes.

[0048] Step 3: Pour the alloy liquid smelted in Step 2 into a metal mold preheated to 250 °C, cool and demold to prepare an alloy ingot.

[0049] Step 4: Put the alloy ingot prepared in Step 3 into a box-type resistance furnace for T6 heat treatment to obtain a high-strength aluminum-copper alloy with excellent properties. The T6 heat treatment process is as follows: First, heat the casting to 495 °C and keep it warm for 3 h, then raise the furnace temperature to 525 °C, with a holding time of 10 h. The temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, quench it with room-temperature water, and the quenching transfer time is less than 15 s. The artificial aging temperature is 185 °C, with a holding time of 8 h. The temperature difference of the furnace temperature is controlled within ±3 °C. After heat preservation, take it out and cool it in the air.

[0050] Example 5 Step 1: Use high-purity Al (99.99%), Al-50Cu master alloy, Al-10Mn master alloy, pure magnesium (99.9%), Al-20Si master alloy, and Al-5Ti-1B master alloy as raw materials, and prepare according to the weight percentage of Al-4.2%Cu-1.2%Mn-0.55%Mg-0.1%Ti-0.15%Si. Before putting them into the furnace, remove impurities such as oxide films and oil stains on the surface of the raw materials, and preheat them at 200 °C to remove the water on the surface of the raw materials.

[0051] Step 2, first place the preheated high-purity aluminum block in a graphite clay crucible and put it into a pit-type resistance furnace, adjust the furnace temperature to 730 ° C, and add Al-50Cu master alloy, Al-10Mn master alloy and Al-20Si master alloy in sequence after the high-purity aluminum block is completely melted. After the alloy is melted, stir for 5 minutes to make the aluminum liquid composition uniform, and adjust the temperature to 710 ° C. Use a bell jar to press pure magnesium into the melt, stir evenly, then adjust the temperature to 740 ° C, add the preheated Al-5Ti-1B master alloy, and after all the metals are melted, stir for 5 minutes, adjust the aluminum liquid temperature to 735 ° C for insulation, press the refining agent into the melt with a bell jar, stir up and down sufficiently, and when no bubbles are generated, sprinkle the preheated slag removal agent on the surface of the melt and stir sufficiently, and skim the slag after standing for 10 minutes.

[0052] Step 3, pouring the alloy liquid melted in step 2 into a metal mold preheated at 250°C, cooling and demoulding, and preparing an alloy ingot.

[0053] Step 4, placing the alloy ingot prepared in step 3 into a box-type resistance furnace for T6 heat treatment to obtain a high-strength aluminum-copper alloy with excellent performance. The T6 heat treatment process is: first heat the casting to 475°C for 6 hours, then raise the furnace temperature to 515°C, keep it for 16 hours, control the temperature difference of the furnace temperature at ±3°C, quench with room temperature water after the insulation, and the quenching transfer time is less than 15 s. The artificial aging temperature is 165°C, the insulation time is 10 hours, the temperature difference of the furnace temperature is controlled at ±3°C, and after the insulation is completed, take it out and cool it in the air.

[0054] Example 6 Step 1, using high-purity Al (99.99%), Al-50Cu master alloy, Al-10Mn master alloy, pure magnesium (99.9%) Al-20Si master alloy and Al-5Ti-1B master alloy as raw materials, Al-6.0%Cu-0.2%Mn-0.1%Mg-0.35%Ti-0.35%Si is prepared according to weight percentage, and the oxide film, oil stain and other impurities on the surface of the raw materials are removed before entering the furnace, and the raw materials are preheated at 200 °C to remove water from the surface.

[0055] Step 2, first place the preheated high-purity aluminum block in a graphite clay crucible and put it into a pit-type resistance furnace, adjust the furnace temperature to 740 ° C, and add Al-50Cu master alloy, Al-10Mn master alloy and Al-20Si master alloy in sequence after the high-purity aluminum block is completely melted. After the alloy is melted, stir for 8 minutes to make the aluminum liquid composition uniform, and adjust the temperature to 690 ° C. Use a bell jar to press pure magnesium into the melt, stir evenly, and then adjust the temperature to 745 ° C. Add the preheated Al-5Ti-1B master alloy. After all the metals are melted, stir for 5 minutes, adjust the aluminum liquid temperature to 730 ° C for insulation, press the refining agent into the melt with a bell jar, stir up and down sufficiently, and when no bubbles are generated, sprinkle the preheated slag removal agent on the surface of the melt and stir sufficiently, and skim the slag after standing for 10 minutes.

[0056] Step 3, pouring the alloy liquid melted in step 2 into a metal mold preheated at 250°C, cooling and demoulding, and preparing an alloy ingot.

[0057] Step 4, placing the alloy ingot prepared in step 3 into a box-type resistance furnace for T6 heat treatment to obtain a high-strength aluminum-copper alloy with excellent performance. The T6 heat treatment process is: first heat the casting to 505°C for 1 hour, then raise the furnace temperature to 535°C, keep it for 9 hours, control the temperature difference of the furnace temperature at ±3°C, quench with room temperature water after the insulation, and the quenching transfer time is less than 15 s. The artificial aging temperature is 195°C, the insulation time is 4 hours, the temperature difference of the furnace temperature is controlled at ±3°C, and after the insulation is completed, take it out and cool it in the air.

[0058] The chemical composition comparison of the aluminum alloys of Examples 1-6 is shown in Table 1.

[0059] Table 1 Chemical composition of aluminum alloy in Examples 1-6 (wt.%)

[0060] The mechanical properties comparison of the aluminum alloys of Examples 1-6 is shown in Table 2.

[0061] Table 2 Mechanical properties of aluminum alloys of Examples 1-6.

[0062]

[0063] like Figure 1 , Figure 2 As shown in Table 1 and Table 2, the above-mentioned high-strength Al-Cu alloy contains strengthening elements such as Cu, Mn, Mg and Si. In the cast alloy, in addition to Al2Cu and Al 20In addition to the Cu2Mn3 eutectic phase, a reticular Mg2Si eutectic phase is also formed. In the as-cast heat-treated alloy, due to the relatively high content of Mn element in the alloy, on the one hand, a dispersed T phase is formed in the Al matrix during the solution process. On the other hand, the Mn atoms dissolved in the matrix combine with the Si atoms in the matrix during the aging process to form a dispersed Al5Mn 12 Si7, which is beneficial to improving the yield strength of the alloy. In addition, the introduction of Si element can increase the fluidity of the aluminum liquid and improve the casting performance of the alloy. Therefore, the aluminum-copper alloy material of the present invention not only has good casting performance, but also has the advantages of low cost and high strength.

[0064] As Figure 3 shown, it can be seen from the microstructure of Example 2 that in the sample after solution + aging treatment, a large amount of Al5Mn 12 Si7 phase is formed at the interface between θ′ and the Al matrix. The mechanical property test results of Example 2 and the mechanical property test results without Si are as Figure 4 shown. The cast Al-Cu alloy of the present invention has lower cost, better casting performance and good comprehensive mechanical properties compared with the traditional cast Al-Cu alloy.

[0065] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-strength cast aluminum-copper alloy, characterized in that, By mass percentage, it includes 4.2 - 6.0 wt.% of Cu, 0.2 - 1.2 wt.% of Mn, 0.10% - 0.55 wt.% of Mg, 0.1% - 0.35% of Si, 0.15 - 0.35 wt.% of Ti; the balance is aluminum and inevitable impurities; The high-strength cast aluminum-copper alloy contains needle-like θ'(Al2Cu) phase, and there is Al5Mn 12 Si7 phase at the boundary of the θ'(Al2Cu) phase.

2. The high-strength cast aluminum-copper alloy according to claim 1, wherein, The yield strength of the high-strength cast aluminum-copper alloy is greater than 420 MPa, and the tensile strength is greater than 470 MPa.

3. A high-strength cast aluminum-copper alloy according to claim 1, characterized in that, By mass percentage, it includes 4.6 - 5.3 wt.% of Cu, 0.4 - 1.0 wt% of Mn, 0.15 - 0.45 wt% of Mg, 0.15 - 0.30 wt% of Si, 0.15 - 0.30 wt% of Ti, and the balance is Al.

4. A high-strength cast aluminum-copper alloy according to claim 1, characterized in that It also includes Al 20 Cu2Mn3 phase 5. The preparation method of the high-strength cast aluminum-copper alloy according to claim 1, characterized in that, It includes the following steps: Step 1: After melting all the pure Al, add electrolytic copper or Al-Cu alloy, electrolytic Mn or Al-Mn alloy, Al-Si alloy and pure Mg. After melting, add Al-Ti-B alloy and pour it into an ingot. Step 2: Perform solution treatment and aging treatment on the ingot.

6. The preparation method of a high-strength cast aluminum-copper alloy according to claim 5, characterized in that, In Step 1, heat the aluminum ingot to 730 - 750 °C until all the aluminum ingot is melted to obtain aluminum liquid; add electrolytic copper or Al-Cu master alloy, electrolytic Mn or Al-Mn master alloy, Al-Si master alloy to the aluminum liquid; after all the metals are melted, adjust the temperature of the aluminum liquid to 690 - 710 °C, and add pure Mg; after all the pure Mg is melted, adjust the temperature of the aluminum liquid to 740 - 750 °C, add Al-Ti-B alloy, after all the metals are melted, stir to make the components mix evenly, and adjust the temperature of the aluminum liquid to 730 - 740 °C for heat preservation and then cast.

7. The preparation method of a high-strength cast aluminum-copper alloy according to claim 5, characterized in that, In Step 2, the process of the solution treatment is: heat the casting to 475 - 505 °C for heat preservation for 1 - 6 h, then raise the furnace temperature to 515 - 535 °C, keep the temperature for 9 - 16 h, and perform quenching after heat preservation.

8. The preparation method of a high-strength cast aluminum-copper alloy according to claim 5, characterized in that, In Step 2, the process of the solution treatment is: heat the casting to 480 - 500 °C for heat preservation for 2 - 4 h, then raise the furnace temperature to 520 - 530 °C, keep the temperature for 10 - 15 h, and perform quenching after heat preservation.

9. The preparation method of a high-strength cast aluminum-copper alloy according to claim 5, characterized in that, In Step 2, the process of the aging treatment is: perform aging treatment on the casting after solution treatment at 165 - 195 °C, and the aging time is 4 - 10 h.

10. The preparation method of a high-strength cast aluminum-copper alloy according to claim 5, characterized in that, In Step 2, the process of the aging treatment is: perform aging treatment on the casting after solution treatment at 170 - 190 °C, and the aging time is 5 - 9 h.

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