A high-strength and tough cast Al-Cu alloy material and its preparation method

Abstract

The present invention provides a high-strength and toughness cast Al-Cu alloy material and a preparation method. The alloy material comprises the following components: Cu: 4.6-5.8%, Mn: 0.6-1.2%, Mg: 0.3-0.45%, Ti: 0.18-0.27%, Zr: 0.2-0.3%, and the remainder is aluminum, boron, and unavoidable impurities. The preparation method comprises the following steps: first, weighing an aluminum ingot and a master alloy according to a proportion; then, adding AlMn80, AlZr5, 2 / 3 of the weight of an aluminum-titanium-boron alloy, and pure aluminum; then, adding AlCu40, 1 / 3 of the weight of an aluminum-titanium-boron alloy, and a Mg block for smelting; and finally, subjecting the Al-Cu alloy material to a multi-stage heat treatment. The high-strength and toughness cast Al-Cu alloy material of the present invention contains few elements, has a simple preparation process and is low in cost. First, by adding materials in batches, the present invention can significantly improve the tensile strength of the alloy without reducing plasticity. Then, through a multi-stage heat treatment mechanism, the solid solubility of Cu in aluminum is adjusted, further improving the mechanical properties. The final tensile strength reaches 438 MPa and the elongation reaches 15%. It has broad application prospects in the field of plastic processing of high-performance aluminum alloys.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a high-strength and toughness cast Al-Cu alloy material and a preparation method thereof. Background Art

[0002] Cast aluminum alloys are currently a very widely used metal material. They feature low specific gravity, high specific strength, a short manufacturing process, and low cost, making them widely used in a wide range of fields, including aviation, aerospace, and automotive. The Cu content in Al-Cu alloys ranges from 3 to 11%. Heat treatment can be used to adjust the solid solubility of Cu in Al and the precipitation and distribution of the Al2Cu phase, resulting in precipitation strengthening and precipitation strengthening, significantly improving the room-temperature and high-temperature mechanical properties of the alloy. Typical domestic Al-Cu grades are ZL201A and ZL205A alloys, which outperform similar commercial alloys internationally and have made significant contributions to the rapid development of my country's aerospace, transportation, and machinery industries.

[0003] However, in actual production, it has been found that Al-Cu casting alloys have a wide crystallization temperature range and tend to form a mushy solid during solidification, resulting in poor alloy melt fluidity and a high incidence of casting defects such as cracks and shrinkage cavities. Furthermore, commercial aluminum-copper alloys such as ZL201A and ZL205A have complex ingredients, are prone to component segregation during the smelting process, and have a strong tendency to hot cracking. Therefore, it is difficult to produce castings with excellent comprehensive mechanical properties and complex shapes from Al-Cu casting alloys, especially in large quantities of cast bars / ingots that can be used in plastic processing fields such as forging, rolling, and stamping.

[0004] Application document CN 111041304 B discloses a thermal crack-resistant Al-Cu cast aluminum alloy and its preparation method. The alloy's composition is 4.0-6.0% Cu; 0.7-1.5% Mn; 0.1-0.4% Ti; 0.005-0.06% B; 0.005-0.030% V, with the balance being Al. The preparation process involves melting and casting weighed raw materials, followed by heat treatment. The base raw material is a cast aluminum-copper alloy, and the additional materials are an Al-Ti-B alloy and an Al-Mn alloy. The alloy is then solutionized at 525±5°C, held for 8-12 hours, and then rapidly cooled with water at 20-60°C. The alloy is then aged at 160-190°C, held for 6-12 hours, and air-cooled. The alloy undergoes a final hot-cold cycle: 135-145°C for 4-8 hours, followed by cooling to room temperature; -50-60°C for 2-8 hours, followed by cooling to room temperature; and 135-145°C for 4-8 hours, followed by cooling to room temperature. The alloy exhibits an elongation greater than 10% and a hot cracking factor less than 30, but its room-temperature tensile strength is not disclosed. Furthermore, the alloy requires the addition of the precious metal vanadium (1,500 yuan / kg), which complicates the heat treatment process and increases the manufacturing cost of the Al-Cu casting alloy.

[0005] Chinese patent CN 114293077 B discloses a high-strength aluminum-copper alloy for aerospace structural components and its preparation method. The alloy's composition is Cu: 4.5-5.5%; Mn: 0.25-0.60%; Ti: 0.12-0.30%; Mg: <0.30%; Si: <0.25%; Fe: <0.20%; Ag: 0.20-0.60% or Sn: 0.15-0.30%, with the balance being Al. This alloy has a yield strength of >430 MPa and a tensile strength of >450 MPa, but its low elongation makes it unsuitable for plastic working.

[0006] Chinese patent application CN 115786786 A discloses a cast aluminum-copper alloy, its preparation method, and its application. Its composition is 4.8-5.3% Cu; 0.3-0.5% Mn; 0.1-0.2% Ti; 0.1-0.2% V; 0.1-0.2% Zr; 0.1-0.15% Cd; 0.03-0.1% B; 0.08-0.5% TiB2; 0-0.15% FeO, with the balance being Al. By introducing submicron TiB2 ceramic particles and combining them with a heat treatment process, the alloy achieves a tensile strength of 450-500 MPa, a yield strength of 350-400 MPa, and an elongation of >9%. However, the alloy has a complex composition ratio and contains the toxic element Cd. The alloy also contains the precious metal V, which has a high manufacturing cost. In addition, if the submicron TiB2 ceramic particles are unevenly distributed in the matrix, it can easily act as a component defect and cause a significant decrease in mechanical properties. How to achieve uniform dispersion of submicron Ti B2 ceramic particles in a macroscopic matrix in industrial production is a common problem in the industry.

[0007] In summary, how to reduce the production cost of Al-Cu casting alloys, improve the comprehensive mechanical properties of the alloys, and expand their application areas are bottleneck issues faced in the research and development of high-performance Al-Cu alloys. Summary of the Invention

[0008] The present invention addresses the difficulties that traditional Al-Cu based casting alloys cannot have their strength and plasticity improved simultaneously, cannot be mass-produced, and have high manufacturing costs. A high-strength and toughness casting Al-Cu based alloy material and a preparation method thereof are proposed.

[0009] To achieve the purpose of the present invention, the present invention provides a high-strength and toughness cast Al-Cu alloy material, the components of which are as follows, calculated by mass percentage:

[0010] Cu: 4.6-5.8%

[0011] Mn: 0.6~1.2%

[0012] Mg: 0.30~0.45%

[0013] Ti: 0.18~0.27%

[0014] Zr: 0.2~0.3%

[0015] The rest are aluminum, boron and inevitable impurities.

[0016] The method for preparing a high-strength and toughness cast Al-Cu alloy material according to the present invention comprises the following steps:

[0017] Step 1: Weigh the aluminum ingot and the master alloy according to the designed composition ratio;

[0018] Step 2: Add AlMn80 master alloy, AlZr5 master alloy, most of the aluminum-titanium-boron alloy and pure aluminum in a crucible preheated to 300-500°C in sequence until the crucible is full.

[0019] Step 3: Melting:

[0020] 1. Heat up to melt the charge, add the second charge when the temperature reaches 730-750℃, add the baked AlCu40 master alloy, keep warm for 10-20 minutes, add the Mg block wrapped in aluminum foil, let it stand for 5-10 minutes, and then stir it electrically;

[0021] 2. After all the raw materials are melted, when the charge temperature drops to 720-740℃, start heat preservation and conduct composition detection before the furnace to control the Fe content;

[0022] 3. Raise the temperature to 740-760℃, add the remaining aluminum-titanium-boron alloy, let it stand for 5-10 minutes, and then stir the charge electrically.

[0023] 4. The measured temperature is 740°C and poured into a mold to obtain an Al Cu alloy material;

[0024] Step 4: Perform multi-stage heat treatment on the Al-Cu alloy material.

[0025] Furthermore, during the above-mentioned addition, the aluminum-titanium-boron alloy is added at 2 / 3 of its weight for the first addition and at 1 / 3 of its weight for the second addition.

[0026] Furthermore, the specific steps of the above step 4 are:

[0027] First stage heat treatment: keep at 500-530℃ for 20-48h, then air cool or water quench;

[0028] Second stage heat treatment: keep at 535-545℃ for 8-18 hours, then water quench at 40-60℃;

[0029] The third stage heat treatment: aging at 160-180℃ for 4-8 hours.

[0030] The Al-Cu alloy material is prepared by the above preparation method.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] 1. Calculations based on the Panda phase diagram show that the Ti and Zr elements added to the technical solution of the present invention significantly influence the order of phase precipitation during alloy solidification. When the Ti content in the alloy is less than 0.093%, only a very small amount of Al3Ti appears during solidification. When the Ti content is greater than 0.093%, the alloy acts as heterogeneous nuclei to refine the Al3Ti grains, forming dispersed, small-sized Al3Ti particles. The significant refinement of the α(Al) matrix grains becomes increasingly pronounced with increasing Ti content. The addition of Zr is fully coherent with the Al3Ti phase, enhancing the grain-refining effect of Ti. Furthermore, Zr can inhibit recrystallization in the alloy. Al3Zr particles are small and highly dispersed, making them less likely to grow at high temperatures. They also exhibit greater thermal stability and better coherence with α-Al, providing a stronger pinning effect on dislocations and grain boundary motion, effectively suppressing recrystallization after forging. Due to the segregation effect of Zr, the solute distribution and composition supercooling at the α(Al) crystallization front are affected, hindering the growth of dendrites and the formation of secondary crystals, thereby refining the microstructure and grain size. During the smelting process, the present invention adds the aluminum-titanium-boron alloy to the crucible in two batches: the first addition of 2 / 3 of the weight of the aluminum-titanium-boron alloy is intended to generate a large amount of Al3Ti phase as a heterogeneous nucleation core at a lower melting temperature to inhibit the nucleation and growth of the α(Al) matrix; the second addition of 1 / 3 of the weight of the aluminum-titanium-boron alloy is intended to precipitate strengthening phases at the fine grain boundaries of the α(Al) matrix to achieve grain boundary strengthening. Therefore, the present invention can significantly improve the tensile strength of the alloy without reducing plasticity.

[0033] 2. The present invention utilizes AlCu40 and AlMn80 master alloys. Generally, aluminum alloys are smelted using AlCu50 and AlMn10 master alloys. The equilibrium microstructure of the AlCu50 master alloy at room temperature is primarily composed of a primary θ-Al2Cu phase, an (α-Al + θ-Al2Cu) eutectic, and a small amount of a θ-Al2Cu secondary phase. The θ-Al2Cu secondary phase is a brittle phase that degrades the alloy's performance. The equilibrium microstructure of the AlCu40 master alloy at room temperature is primarily composed of a primary θ-Al2Cu phase and an (α-Al + θ-Al2Cu) eutectic, with minimal θ-Al2Cu secondary phase content. Therefore, the addition of the AlCu40 master alloy results in even fewer brittle phases. The equilibrium microstructure of the AlMn10 master alloy at room temperature is composed of an α-Al + θ-Al12Mn phase (the Al12Mn phase then decomposes into Al6Mn). Dispersed Al6Mn exhibits solid solution strengthening and readily combines with Fe in the matrix to form stable Al6(Mn, Fe), reducing the harmful effects of impurities. The equilibrium microstructure of the Mn-rich AlMn80 master alloy at room temperature consists solely of the β-Mn phase. This β-Mn phase (AlMn3) is a stable DO3-type body-centered cubic phase with a larger lattice constant than Al. It not only exhibits the same dispersion strengthening effect as Al6Mn but also possesses the same number of slip systems as Al, ensuring the matrix's plastic deformation capacity. Furthermore, excess Mn accumulates near grain boundaries, strongly inhibiting grain boundary diffusion and refining the grains, thereby improving the alloy's overall mechanical properties.

[0034] 3. The present invention utilizes a multi-stage heat treatment process. Compared to existing technologies, the added first-stage heat treatment process homogenizes and dissolves the Al2Cu phase, which forms a network at the grain boundaries, into the matrix phase while maintaining a stable grain size. This process is followed by conventional solution and aging treatments: solution treatment at 535-545°C for 8-18 hours, followed by water quenching at 40-60°C. Due to the previous homogenization treatment, the alloy phases are macroscopically uniform, resulting in fine grains. This allows for rapid dissolution of coarse primary phases during the solution stage, forming a supersaturated solid solution after quenching. Aging at 160-180°C for 4-8 hours causes the Al2Cu phase to reprecipitate in large quantities and form a dispersed distribution. This results in a uniform and stable microstructure at room temperature for the Al2Cu alloy. The present invention utilizes a multi-stage heat treatment process to create an effective synergistic effect between the heat treatments, resulting in excellent comprehensive mechanical properties. The material exhibits excellent high strength and toughness, achieving a room-temperature tensile strength of 438 MPa at an elongation of 15%.

[0035] 4. The process of the present invention is simple and easy to implement; the raw materials used are low in cost, the energy consumption in the preparation process is low, the raw materials are non-toxic, there is no safety hazard to the operators, no special protective measures are required, and the entire preparation process cost is low: the present invention realizes the preparation of large-size Al-Cu alloy casting rods with a diameter of 200 mm, providing good supporting conditions for the application and development of integrated casting and forging preparation of aluminum alloys in the fields of aerospace, automotive industry, and mechanical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 and Figure 3 The stress-strain curves of Example 1 and Example 2, respectively;

[0037] Figure 2 and Figure 4 The metallographic structures of Example 1 and Example 2 respectively;

[0038] Figure 5 and Figure 6 Phase diagrams of Al-Cu binary alloy and Al-Mn binary alloy respectively. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0040] Example 1, a method for preparing a high-strength and toughness cast Al-Cu alloy material, comprising the following steps:

[0041] Step 1: Weigh aluminum ingots and master alloys according to the designed composition ratio, including Cu: 5.0%, Mn: 0.7%, Mg: 0.38%, Ti: 0.24%, Zr: 0.28%, and the rest being aluminum and inevitable impurities.

[0042] Step 2: Add the materials at one time: AlMn80 master alloy, AlV5 master alloy, AlZr5 master alloy, 2 / 3 of the weight of aluminum-titanium-boron alloy, and pure aluminum in sequence to a crucible preheated to 350° C. until the crucible is full.

[0043] Step 3: Melting:

[0044] 1. Heat up to melt the charge. When the temperature reaches 735℃, add the baked AlCu40 master alloy. Keep warm for 10 minutes, then add the Mg block wrapped in aluminum foil. Let it stand for 5 minutes and then stir it electrically for 2 minutes.

[0045] 2. After all the raw materials are melted, when the charge temperature reaches 728℃, start heat preservation and conduct composition detection before the furnace to control the Fe content.

[0046] 3. Raise the temperature to 747°C, add the remaining 1 / 3 weight of aluminum-titanium-boron alloy, let it stand for 5 minutes, and then stir the charge electrically for 1 minute.

[0047] 4. The measured temperature is 740°C and the Al-Cu alloy material is poured into a mold.

[0048] Step 4: Perform multi-stage heat treatment on the Al-Cu alloy material:

[0049] First stage heat treatment: keep at 500℃ for 48h, then water quench;

[0050] Second stage heat treatment: solution treatment at 545°C for 10 hours, followed by water quenching at 40-60°C;

[0051] The third stage heat treatment: aging at 175℃ for 4 hours, then air cooling.

[0052] The experimental results show that the room temperature tensile strength of the cast Al-Cu alloy obtained in this embodiment is 436 MPa and the elongation is 13.0%. Figure 1 As shown, the metallographic Figure 2 shown.

[0053] Example 2, a method for preparing a high-strength and toughness cast Al-Cu alloy material, comprising the following steps:

[0054] Step 1: Weigh aluminum ingots and master alloys according to the designed composition ratio, including Cu: 5.2%, Mn: 0.62%, Mg: 0.38%, Ti: 0.22%, Zr: 0.26%, and the rest being aluminum and inevitable impurities.

[0055] Step 2: Add the materials at one time: AlMn80 master alloy, AlV5 master alloy, AlZr5 master alloy, 2 / 3 of the weight of aluminum-titanium-boron alloy, and pure aluminum in sequence into a crucible preheated to 400° C. until the crucible is full.

[0056] Step 3: Melting:

[0057] 1. Heat up to melt the charge. When the temperature reaches 744℃, add the baked AlCu40 master alloy. Keep warm for 10 minutes, then add the Mg block wrapped in aluminum foil. Let it stand for 10 minutes and then stir it electrically for 1 minute.

[0058] 2. After all the raw materials are melted, when the charge temperature reaches 735℃, start heat preservation and conduct composition detection before the furnace to control the Fe content.

[0059] 3. Raise the temperature to 756℃, add the remaining 1 / 3 weight of aluminum-titanium-boron alloy, let it stand for 10 minutes, and then stir the charge electrically for 2 minutes.

[0060] 4. The measured temperature is 740°C and the Al-Cu alloy material is poured into a mold.

[0061] Step 4: Perform multi-stage heat treatment on the Al-Cu alloy material:

[0062] First stage heat treatment: keep at 520℃ for 24h, then water quench;

[0063] Second stage heat treatment: solution treatment at 535°C for 14 hours, followed by water quenching at 40-60°C;

[0064] The third stage heat treatment: aging at 165℃ for 5 hours, then air cooling.

[0065] According to the test results, the room temperature tensile strength of the cast Al-Cu alloy material obtained in this embodiment is 438MPa and the elongation is 15.0%. Figure 3 As shown, the metallographic Figure 4 shown.

[0066] After comprehensive analysis, the above embodiment 2 is the best embodiment.

[0067] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength and tough cast Al-Cu alloy material, characterized in that: High strength and toughness cast Al-Cu alloy material, calculated by mass percentage, has the following composition: Cu: 4.6~5.8% Mn: 0.6~1.2% Mg: 0.30~0.45% Ti: 0.18~0.27% Zr：0.2~0.3% The rest are aluminum, boron and inevitable impurities; The following steps are involved: Step 1: Weigh the aluminum ingot and the master alloy according to the designed composition ratio; Step 2: Add AlMn80 master alloy, AlZr5 master alloy, most of the aluminum-titanium-boron alloy, and pure aluminum to a crucible preheated to 300-500°C, in sequence, until the crucible is full. Step 3: Melting: 1) Heat the furnace to melt the charge, add the baked AlCu40 master alloy when the temperature reaches 730-750°C, keep the mixture warm for 10-20 minutes, add the Mg block wrapped in aluminum foil, let it stand for 5-10 minutes, and then stir it electrically; 2) After all the raw materials are melted, when the charge temperature drops to 720-740°C, start heat preservation and conduct composition detection before the furnace to control the Fe content; 3) Heat to 740-760°C, add the remaining aluminum-titanium-boron alloy, let it stand for 5-10 minutes, and then stir the charge electrically; 4) The temperature was measured to be 740°C, and the Al-Cu alloy material was poured into a mold; Step 4: Perform multi-stage heat treatment on the Al-Cu alloy material. The specific steps are: First stage heat treatment: keep at 500~530℃ for 20~48h, then air cool or water quench; Second stage heat treatment: keep at 535~545℃ for 8~18 hours, then water quench at 40~60℃; The third stage heat treatment: aging at 160~180℃ for 4~8 hours When adding the materials, the aluminum-titanium-boron alloy is added in an amount of 2 / 3 of its weight for the first time and in an amount of 1 / 3 of its weight for the second time.

2. The Al-Cu alloy material obtained by the preparation method according to claim 1.

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