High-temperature high-strength heat-resistant aluminum alloy

Abstract

The invention discloses a high-temperature high-strength heat-resistant aluminum alloy which is characterized in that Al-6% of Cu-1. 5% of Zn-0. 5% of Mg is taken as a matrix, Mn and Cr elements are added, a target alloy is prepared by using a medium-frequency induction heating device, and after casting and machining, a JINDUN Jinton heat treatment device is adopted to carry out T6 process treatment on an aluminum alloy cast ingot.

Description

TECHNICAL FIELD

[0001] The present application relates to an aluminum alloy, a high-temperature high-strength heat-resistant aluminum alloy. BACKGROUND

[0002] Due to its high tensile strength, low density, high oxidation resistance and high creep resistance, Al-6%Cu-1.5%Zn-0.5%Mg-0.15%Mn-0.15%Cr alloy is the preferred material for manufacturing high-temperature parts in aerospace industry, top car companies and military manufacturing industry among other types of alloys. Due to the current research status, the commonly used series of alloys on the market cannot meet the high-temperature strength requirements of various industries. The use temperature of existing aluminum alloys is limited to below 250℃ due to the characteristics of the alloy itself, which cannot meet the performance requirements of heat-resistant parts in most industries, such as the skin material of hypersonic aircraft in the military industry and high-temperature engine heat-resistant parts in the automotive industry. Ultimately, the traditional heat-resistant aluminum alloy has a fatal defect of insufficient thermal stability of high-temperature strengthening phase, which directly leads to the coarsening of the high-temperature strengthening phase in the traditional aluminum alloy under long-term service conditions at high temperature, ultimately causing a significant decrease in the overall strength of the aluminum alloy. Based on the current situation, improvement of the high-temperature strengthening phase of traditional heat-resistant aluminum alloy is imminent, and the key improvement direction is the improvement method of the thermal stability of the high-temperature strengthening phase. Based on the improvement of the thermal stability of the strengthening phase at the micro level, the strength and stability of the base alloy at high temperature can be improved. SUMMARY

[0003] The present application found that the addition of Mn and Cr elements in Al-Cu-Zn-Mg alloy can significantly refine the grain size of the alloy, promote the uniform distribution of the strengthening phase, and effectively improve the thermal stability of the strengthening phase. In particular, the addition of Mn element can promote the transformation of the alloy cell from cellular to dendritic morphology, efficiently refining the as-cast grain; and the addition of Cr element can further optimize the microstructure of the alloy, inhibit the formation of harmful phases, and significantly improve the room temperature and high temperature mechanical properties of the alloy. Further, through specific heat treatment processes, including solid solution treatment and aging treatment, the microstructure of the alloy can be further optimized, and the strengthening phase is more finely and dispersedly distributed in the matrix, thereby significantly improving the strength and toughness of the alloy.

[0004] Especially when the adding amount of Mn and Cr is 0.15wt.% and 0.15wt.% respectively, the Al-Cu-Zn-Mg-0.15%Mn-0.15%Cr alloy after the optimized heat treatment process exhibits the best mechanical properties: the room temperature tensile strength is as high as 418.59 MPa, and the high temperature (350℃) tensile strength reaches 217.30 MPa, which is increased by 7.78% and 51.05% respectively compared with the alloy without adding Mn and Cr. This shows that the alloy composition design and preparation process of the present application can effectively improve the high temperature mechanical properties of heat-resistant aluminum alloy, and provide an alloy material with more excellent performance for related industrial fields. BRIEF DESCRIPTION OF DRAWINGS

[0005] Figure 1 is the high temperature mechanical tensile stress-strain curve of the alloy after secondary aging temperature; Figure 2 is the corrosion image. DETAILED DESCRIPTION

[0006] In the examples of the present application, a high-temperature high-strength heat-resistant aluminum alloy is characterized in that: the added metals are pure zinc particles, pure magnesium particles, pure aluminum ingots, Al-10Mn intermediate alloy and Al-10Cr intermediate alloy.

[0007] Example 1 A high-temperature high-strength heat-resistant aluminum alloy has a preparation process as follows: S1: Put the graphite crucible coated with a protective layer on the surface and dried at 120℃ into a medium-frequency induction furnace, start the cooling water circulation system, and then power on to heat up, add high-purity aluminum particles (≥99.9%) in batches until completely melted, and then perform the first melt stirring (30r / min) and surface slag removal; S2: When the melt temperature reaches 780-800℃ measured by the thermocouple, add pure copper plates (≥99.95%) in batches, continue to add Al-10Mn and Al-10Cr intermediate alloy particles (10-15mm) after cooling to 780℃, immediately cover 8g of NaCl-KCl mixed molten salt (0.5-1mm) and keep for 10 minutes; S3: After the end of the heat preservation, perform secondary slag removal and temperature detection in turn, when the melt is cooled to 730℃, press in a total of 6g of hexachloroethane tablets for deep refining in two times (interval 2 minutes), and keep standing for 2 minutes after each refining and thoroughly remove the slag; S4: After the end of the heat preservation, perform secondary slag removal and temperature detection in turn, when the melt is cooled to 730℃, press in a total of 6g of hexachloroethane tablets for deep refining in two times (interval 2 minutes), and keep standing for 2 minutes after each refining and thoroughly remove the slag; S4: After the end of the heat preservation, perform secondary slag removal and temperature detection in turn, when the melt is cooled to 730℃, press in a total of 6g of hexachloroethane tablets for deep refining in two times (interval 2 minutes), and keep standing for 2 minutes after each refining and thoroughly remove the slag; S5: finally pouring the 750℃ alloy melt into a 250℃ preheated cast iron mold (pouring speed 100g / s), demolding after natural cooling to 150℃, obtaining Φ80x120mm standard ingot.

[0008] Compared with the prior art, the beneficial effects of the present application are: (1) In the Al-6%Cu-1.5%Zn-0.5%Mg series alloy heat treated alloy sample, Mn element is added, and the strengthening mechanism of Mn element on the micro level is analyzed. The essence is that through the addition of Mn element, the unit cell of Al-Cu-Zn-Mg alloy will undergo a change process based on cellular to dendritic morphology. The maximum feature of such change is the high-efficiency refinement of as-cast grains in the alloy. The principle is that the manganese-rich compounds are formed in the alloy, which are enriched in the grain boundary during the overall alloy crystallization. When the addition amount of Mn element is floating within a certain reasonable range, the manganese-containing compounds will be enriched in the grain boundary, preventing the growth of coarse phase grains such as , and the solidified grains will play the same hindering effect, contributing to the overall organization refinement. After adding 0.3wt.% Mn element to the as-cast room temperature Al-Cu-Zn-Mg alloy, the maximum overall tensile strength is 205.74 MPa, which is 23.01% higher than that of the Al-Cu-Zn-Mg alloy substrate. After adding 0.3wt.% Mn element to the as-cast high-temperature Al-Cu-Zn-Mg alloy, the maximum overall tensile strength is 99.53 MPa, which is 13.31% higher than that of the Al-Cu-Zn-Mg alloy substrate. After T heat treatment process, after adding 0.3wt.% Mn element to the heat treated room temperature Al-Cu-Zn-Mg alloy, the maximum overall tensile strength is 406.40 MPa, which is 7.78% higher than that of the Al-Cu-Zn-Mg alloy substrate. After adding 0.15wt.% Mn element to the heat treated high-temperature Al-Cu-Zn-Mg alloy, the maximum overall tensile strength is 161.56 MPa, which is 2.21% higher than that of the Al-Cu-Zn-Mg alloy substrate.

[0009] In the case of the Al-6%Cu-1.5%Zn-0.5%Mg-0.15%Mn series alloy with the best performance obtained by adding 0.15% Mn, Cr was added for further experiments. The Al-6%Cu-1.5%Zn-0.5%Mg series alloy in the heat-treated state mainly contains an α-Al matrix, Al2Cu phase, and a small amount of Al2CuMg phase and Al7Cr phase. The morphology and size of the α-Al matrix and Al2Cu phase are different from those in the as-cast state. The amount of Al7Cr phase is so small that it cannot be detected by XRD. However, SEM-EDS detection shows that the Al7Cr phase is formed in the alloy. The Al7Cr phase is fine and has excellent heat resistance, and is in a coherent relationship with the matrix, which can strongly pin dislocations and prevent grain boundary migration. The presence of the Al2CuMg phase inhibits the precipitation of the Ω phase, which negatively affects the mechanical properties of the obtained alloy. A small amount of Al2CuMg phase is only found in the alloy without Cr, while this phase is not found in other Cr-containing alloys, which strongly proves that the addition of Cr inhibits the formation of the Al2CuMg phase. With the increase of Cr content, the room temperature mechanical properties of the alloy first increase and then decrease, and the plasticity decreases. After adding 0.15wt.% Cr to the as-cast Al-Cu-Zn-Mg-0.15%Mn alloy, the maximum overall tensile strength is 238.42 MPa, which is 7.98% higher than that of the Al-Cu-Zn-Mg-0.15%Mn alloy. After adding 0.3wt.% Cr to the as-cast Al-Cu-Zn-Mg-0.15%Mn alloy, the maximum overall tensile strength is 124.90 MPa, which is 16.03% higher than that of the Al-Cu-Zn-Mg-0.15%Mn alloy. After T heat treatment, after adding 0.15wt.% Cr to the heat-treated Al-Cu-Zn-Mg-0.15%Mn alloy, the maximum overall tensile strength is 418.59 MPa, which is 2.02% higher than that of the Al-Cu-Zn-Mg-0.15%Mn alloy. After adding 0.15wt.% Cr to the heat-treated Al-Cu-Zn-Mg-0.15%Mn alloy, the maximum overall tensile strength is 217.30 MPa, which is 51.05% higher than that of the Al-Cu-Zn-Mg-0.15%Mn alloy. The stress-strain curve of the warm mechanical tensile properties of the alloy is shown in Figure 1 , and the SEM image after corrosion is shown in Figure 2 .

Claims

1. A high temperature high strength heat resistant aluminum alloy characterized by: Al-6%Cu-1.5%Zn-0.5%Mg as the base, adding Mn and Cr elements, using the intermediate frequency induction heating device to prepare the target alloy, and after casting and machining, using JINDUN heat treatment equipment to treat the aluminum alloy ingot with T6 process.

2. The high-temperature, high-strength, heat-resistant aluminum alloy according to claim 1, characterized in that: The composition of the aluminum copper alloy is Al-xCu-yZn-zMg-mMn-nCr, wherein x=5.5%-6.5%, y=1%-2%, z=0.3%-0.8%, m=0.1%-0.5%, and n=0.1%-0.5%.

3. The high-temperature, high-strength, heat-resistant aluminum alloy according to claim 1, characterized in that: The added metals are pure zinc particles, pure magnesium particles, pure aluminum ingots, Al-10Mn intermediate alloy, and Al-10Cr intermediate alloy.

4. The high-temperature, high-strength, heat-resistant aluminum alloy according to claim 1, characterized by: The preparation process is as follows: a graphite crucible coated with a Na2O·SiO2-ZnO2 protective layer and dried at 120 DEG C is placed in a medium-frequency induction furnace, the cooling water circulation system is started, and power is turned on to heat up, high-purity aluminum particles (≥99.9%) are added in batches until complete melting, and then the first melt stirring (30 r / min) and surface slag removal are performed; when the melt temperature reaches 780-800 DEG C measured by a thermocouple, pure copper plates (≥99.95%) are added in batches, and after cooling to 780 DEG C, Al-10Mn and Al-10Cr intermediate alloy particles (10-15 mm) are continuously added, and then 8 g of NaCl-KCl mixed molten salt (0.5-1 mm) is immediately covered and kept for 10 minutes; after the heat preservation is completed, secondary slag removal and temperature detection are performed in sequence, when the melt is cooled to 730 DEG C, a total of 6 g of hexachloroethane tablets is pressed in two times (2 minutes apart) for deep refining, and 2 minutes of standing and complete slag removal are required after each refining; finally, the alloy melt at 750 DEG C is poured into a preheated cast iron mold (pouring speed 100 g / s) at 250 DEG C, and after natural cooling to 150 DEG C, the mold is demolded to obtain a standard ingot with a diameter of Φ80*120 mm.

5. The high temperature, high strength heat resistant aluminum alloy of claim 1, wherein: The surface of high-temperature contact parts such as graphite crucibles and casting molds needs to be uniformly coated with a water-based coating agent with a Na2O·SiO2:ZnO2 ratio of 1:3, and needs to be dried at 120 DEG C.

6. The alloy production process of claim 4, wherein: The degassing refining agent is hexachloroethane, 3.5 g per package, a total of two packages, and the alloy melt covering agent is KCl and NaCl, uniformly mixed at a ratio of 1:1, each 3 g.

7. The T6 process treatment of claim 1 wherein: Solution 515 DEG C X 6 h + water quenching + aging 170 DEG C X 12 h.

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