A high-strength heat-resistant aluminum alloy containing zirconium and chromium and a method for manufacturing the same

Abstract

This invention discloses a high-strength, heat-resistant aluminum alloy containing Zr and Cr and its preparation method, belonging to the field of non-ferrous metal materials technology. Addressing the problem of high-temperature performance degradation caused by the coarsening of strengthening phases in traditional Al-Cu-Mg alloys above 200℃, this invention uses Al-5Cu-0.5Mg-0.1Ce as the matrix, first adding 0.1wt.% Zr, then compounding with 0.1wt.% Cr, followed by T6 heat treatment (solution at 530℃ for 10h + water quenching at 65℃ + aging at 170℃ for 6h) to obtain an Al-5Cu-0.5Mg-0.1Ce-0.1Zr-0.1Cr alloy. In this alloy, Zr forms an Al3Zr dispersed phase to refine the grains and promotes the dispersed precipitation of the θ′-Al2Cu phase. Cr and Zr synergistically form an Al3(Zr,Cr) phase to further refine the microstructure. After heat treatment, Al2.5Cu0.5Zr and Al... 20 The Cu2Cr3 dispersed phase effectively pins dislocations and grain boundaries. The alloy of this invention exhibits a room temperature tensile strength of 363.11 MPa and a high-temperature tensile strength of 185.41 MPa at 350°C, representing increases of 18.93% and 18.24% respectively compared to Zr alloys without Cr addition. Its high-temperature yield strength reaches 184.86 MPa. This alloy is suitable for load-bearing components in aerospace and automotive fields operating at temperatures above 300°C, offering significant advantages of being lightweight, high-strength, and heat-resistant.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal materials technology, specifically relating to a high-strength heat-resistant aluminum alloy containing Zr and Cr in the Al-Cu-Mg-Ce system and its preparation method, which is suitable for the manufacture of load-bearing components at high temperatures above 300℃ in the aerospace and automotive industries. Background Technology

[0002] Al-Cu-Mg heat-resistant aluminum alloys are widely used in key components such as aircraft skins and engine pistons due to their low density, high specific strength, and good machinability. However, when traditional alloys of this series are used for long-term service at temperatures above 200°C, the main strengthening phases θ′-Al2Cu and S-Al2CuMg rapidly coarsen and lose their coherent relationship, resulting in a sharp decline in high-temperature strength. The tensile strength at 350°C is generally below 130 MPa, which is insufficient to meet the instantaneous heat resistance requirements of hypersonic aircraft and new energy vehicle power systems for 300-400°C.

[0003] To improve high-temperature performance, researchers have attempted to add elements such as Sc and Zr to form thermally stable Al3Sc or Al3Zr phases. However, Sc is expensive (approximately 1000 times the price of Al), limiting its industrial applications. While rare-earth element Ce is inexpensive, adding Ce alone often reduces the age-hardening effect due to Cu consumption. Zr can form a dispersed Al3Zr phase that effectively pins dislocations, but the strengthening effect can still be improved when Zr is added alone. Currently, the synergistic mechanism between Zr and Cr in Ce-containing Al-Cu-Mg alloys is unclear, and there is a lack of component ratios and preparation processes for achieving low-cost, high-heat-resistant performance through composite microalloying. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a high-strength heat-resistant aluminum alloy containing Zr and Cr and its preparation method. The aim is to significantly improve the high-temperature tensile strength at 350℃ and the comprehensive mechanical properties at room temperature of the alloy by synergistic microalloying of Zr and Cr, while maintaining a low cost.

[0005] The technical solution is as follows: The alloy composition of the present invention, by mass percentage, is: Cu 5.0%, Mg 0.5%, Ce 0.1%, Zr 0.1%, Cr 0.1%, with the balance being Al and unavoidable impurities.

[0006] The preparation method includes the following steps: (1) Weigh pure aluminum ingots (99.9%), pure copper, pure magnesium granules (>99.9%), Al-10Ce master alloy, Al-10Zr master alloy and Al-10Cr master alloy according to the proportion; (2) Place the pure aluminum ingots in a medium frequency induction melting furnace and heat them at 750-760℃ until they are completely melted. Then add pure copper, Al-10Ce, Al-10Zr and Al-10Cr master alloy in sequence. After each element is added, stir thoroughly and remove the slag. After all the elements have melted, sprinkle a covering agent evenly. (3) The temperature of the melt is controlled at around 730°C. The melt is poured into a cast iron mold that has been preheated at 300°C for 30 minutes. The ingot is cooled and removed. (4) The ingot is subjected to T6 heat treatment: solution treatment at 530°C for 10 hours, followed by water quenching at 65°C, aging at 170°C for 6 hours, and air-cooled to room temperature. Attached Figure Description

[0007] Figure 1 This is a SEM image of the microstructure of alloy T6 in the heat-treated state of this invention. Figure 2 This is a SEM image of the fracture morphology of the alloy of the present invention under high temperature tensile stress at 350℃. Detailed Implementation

[0008] Example 1 The alloy was prepared according to the nominal composition Al-5Cu-0.5Mg-0.1Ce-0.1Zr-0.1Cr (wt.%). Based on a total melt mass of 700g, and considering a burn-off rate of approximately 5%, approximately 655g of pure aluminum ingots, 35g of pure copper, 3.5g of pure magnesium granules, 7g of Al-10Ce master alloy, 7g of Al-10Zr master alloy, and 7g of Al-10Cr master alloy were actually weighed. The covering agent was a mixture of 4g NaCl and 4g KCl; the degassing agent was 7g hexachloroethane (divided into two packets, 3.5g each).

[0009] Melting process: Place a graphite crucible in a medium-frequency induction furnace, add pure aluminum ingots, and heat until the ingots are completely melted. Remove surface slag, and use a type K thermocouple to measure the temperature and control the melt at 750-760℃. Add pure copper, Al-10Ce, Al-10Zr, and Al-10Cr master alloys sequentially, stirring for 2 minutes at each step. Sprinkle in a covering agent, maintain the temperature, and then remove slag. Cool to 720-730℃, wrap magnesium granules in aluminum foil and press them into the melt, let it stand after melting, and then remove slag. Raise the temperature to 730℃, wrap two bags of hexachloroethane in aluminum foil and press them into the bottom of the melt using a bell jar, stir to remove gas, let it stand, and then remove slag again. Pour the melt at 730℃ into a cast iron mold preheated to 300℃ for 30 minutes, and allow it to cool naturally before demolding.

[0010] After the ingot is cut, a tensile test bar is taken and subjected to T6 heat treatment: solution treatment at 530℃ for 10 hours (box-type resistance furnace), then quickly immersed in a 65℃ water bath for quenching; followed by aging at 170℃ for 6 hours and air cooling.

[0011] Test results of aluminum alloy

Claims

1. A high-strength, heat-resistant aluminum alloy containing Zr and Cr, characterized in that... It consists of the following components by weight percentage: Cu 4.0%-6.0%, Mg 0.3%-0.7%, Ce 0.05%-0.20%, Zr 0.05%-0.30%, Cr 0.05%-0.30%, with the balance being Al and unavoidable impurities.

2. The high-strength heat-resistant aluminum alloy containing Zr and Cr according to claim 1, characterized in that, The weight percentage of Cu is 4.5%-5.5%, the weight percentage of Mg is 0.4%-0.6%, the weight percentage of Ce is 0.08%-0.15%, the weight percentage of Zr is 0.08%-0.20%, and the weight percentage of Cr is 0.08%-0.20%.

3. The high-strength, heat-resistant aluminum alloy containing Zr and Cr according to any one of claims 1-2, characterized in that, The mass ratio of Zr to Cr is Zr / Cr, which is 0.8-1.

2.

4. The high-strength, heat-resistant aluminum alloy containing Zr and Cr according to any one of claims 1-3, characterized in that, The alloy, after being heat-treated with T6, has a tensile strength of over 180 MPa at 350°C.

5. A method for preparing a high-strength, heat-resistant aluminum alloy containing Zr and Cr as described in any one of claims 1 to 4, characterized in that, Includes the following steps: oS1: Weigh out pure aluminum ingots, pure copper, pure magnesium granules, Al-10Ce master alloy, Al-10Zr master alloy and Al-10Cr master alloy according to the proportions. oS2: Place pure aluminum ingots in a medium-frequency induction melting furnace and heat until completely melted. Then, add pure copper, Al-10Ce, Al-10Zr and Al-10Cr master alloy in sequence. After each element is added, stir thoroughly and skim off the slag. After all the aluminum ingots have melted, sprinkle a covering agent evenly, keep warm and then skim off the slag. oS3: Cool to 720-730℃, add pure magnesium granules, melt, let stand and remove slag; oS4: Heat to 730℃, press the degassing agent into the bottom of the melt and stir to degas, then let it stand and degas again; oS5: Control the melt temperature at 720-740℃, pour it into a mold preheated at 280-320℃, cool and demold to obtain an ingot; oS6: The ingot is solution treated at 520-540℃ for 9-11 hours, followed by water quenching at 60-80℃; oS7: Aging the ingot at 160-180℃ for 5-7 hours, followed by air cooling.

6. The method for preparing the high-strength heat-resistant aluminum alloy containing Zr and Cr according to claim 6, characterized in that, The solution treatment temperature in step S6 is 530℃, and the solution treatment time is 10h; the water quenching temperature is 65℃.

7. The method for preparing the high-strength, heat-resistant aluminum alloy containing Zr and Cr according to any one of claims 6-7, characterized in that, The aging treatment temperature in step S7 is 170℃, and the aging treatment time is 6 hours.

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