High-strength heat-resistant aluminum alloy containing Ti / B refiner and preparation method thereof

Abstract

This invention discloses a high-strength, heat-resistant aluminum alloy containing Ti / B refining agents 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-Mn alloys above 300℃, this invention uses Al-6Cu-0.6Mn-0.3V as the matrix, adds 0.3wt.% Al-5Ti-B master alloy, and then performs T6 heat treatment (solution at 535℃ for 8 hours + water quenching + aging at 170℃ for 6 hours) to obtain an Al-6Cu-0.6Mn-0.3V-0.3(Al-5Ti-B) alloy. In this alloy, Ti / B forms Al3Ti and TiB2 heterogeneous nucleation cores, significantly refining α-Al grains and promoting the uniform dispersion and precipitation of θ′-Al2Cu nano-reinforcing phases. Simultaneously, Ti and B atoms solid-solution pin dislocations, inhibiting high-temperature recovery. The alloy of this invention exhibits a high-temperature tensile strength of 182.67 MPa at 350°C in the heat-treated state, representing a 68.4% increase compared to the matrix without added refining agents. Its room-temperature tensile strength reaches 386.18 MPa. This alloy is suitable for load-bearing components in the 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 an Al-Cu-Mn-V high-strength heat-resistant aluminum alloy containing Ti / B refining agent and its preparation method, which is suitable for the manufacture of high-temperature load-bearing components above 300℃ in the aerospace and automotive industries. Background Technology

[0002] Al-Cu 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 these alloys are used for long-term service at temperatures above 300°C, the main strengthening phase θ′-Al2Cu rapidly coarsens and loses its coherent relationship with the matrix, resulting in a sharp decline in high-temperature strength. At 350°C, the tensile strength is generally below 110 MPa, which is insufficient to meet the heat resistance requirements of high-power diesel engines and hypersonic aircraft operating under high-temperature and high-load conditions of 300-400°C.

[0003] To improve high-temperature performance, researchers have attempted to add transition elements such as V, Mn, and Ti to form a thermally stable second phase, or add rare earth elements to improve the thermal stability of the microstructure. Al-5Ti-B, as the most commonly used grain refiner in aluminum alloys, introduces TiB2 and Al3Ti particles that can act as heterogeneous nucleation cores for α-Al, significantly refining the grains. Simultaneously, Ti atoms dissolve in the matrix, inhibiting the coarsening of precipitated phases. However, for the Al-Cu-Mn-V system, the synergistic regulation mechanism of Al-5Ti-B addition amount and aging process on the precipitation behavior and high-temperature mechanical properties of nano-θ′-Al2Cu is still unclear, and a systematic process optimization scheme is lacking. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a high-strength heat-resistant aluminum alloy containing Ti / B refining agents and its preparation method. The aim is to introduce Ti and B elements into the Al-5Ti-B master alloy for composite microalloying, and combine this with an optimized aging process to significantly improve the alloy's high-temperature tensile strength at 350℃ and its comprehensive mechanical properties at room temperature.

[0005] The technical solution is as follows: The alloy composition of the present invention, by mass percentage, is: Cu 6.0%, Mn 0.6%, V 0.3%, Al-5Ti-B master alloy 0.3% (equivalent to approximately 0.015% Ti and approximately 0.003% B), with the balance being Al and unavoidable impurities.

[0006] The preparation method includes the following steps: (1) Weigh pure aluminum granules (99.9%), electrolytic copper sheets, Al-10Mn master alloy, Al-10V master alloy and Al-5Ti-B master alloy according to the proportion; (2) Place the pure aluminum granules in a medium frequency induction melting furnace and heat them at 780-800℃ until they are completely melted. Then add pure copper sheets, Al-10Mn and Al-10V master alloy in sequence. Stir thoroughly and remove slag after each element is added. After all the elements have melted, sprinkle a covering agent (a mixture of NaCl and KCl in equal mass ratio) evenly. After holding the heat for 10 minutes, remove the slag; cool down to 730-750℃, add hexachloroethane degassing agent twice for refining, with an interval of more than 2 minutes each time, and remove the slag after refining; then add Al-5Ti-B intermediate alloy, and stir and remove the slag after fully melting; (3) control the temperature of the melt at about 740℃, pour it into a cast iron mold preheated at 300℃, cool and demold to obtain the ingot; (4) perform T6 heat treatment on the ingot: solution treatment at 535℃ for 8 hours, then water quench at room temperature, then age at 170℃ for 6 hours, and air cool to room temperature. Attached Figure Description

[0007] Figure 1 This is a SEM image of the as-cast microstructure of the alloy of this invention. Figure 2 This is a SEM image of the microstructure of alloy T6 in the heat-treated state of this invention. Figure 3 This is a SEM image of the nano-θ′-Al2Cu phase distribution after heat treatment corrosion of the alloy of this invention. Figure 4 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-6Cu-0.6Mn-0.3V-0.3(Al-5Ti-B) (wt.%). Based on a total melt mass of 700g, and considering a burn-off rate of approximately 5%, approximately 650g of pure aluminum granules, 42g of electrolytic copper sheets, 42g of Al-10Mn master alloy, 21g of Al-10V master alloy, and 2.1g of Al-5Ti-B master alloy were actually weighed. The covering agent was a mixture of 4g NaCl and 4g KCl; the degassing agent was 6g hexachloroethane (divided into two 3g packets).

[0009] Melting process: Place the graphite crucible in a medium-frequency induction furnace, add pure aluminum granules, and heat until the aluminum granules are completely melted. Remove surface slag, and use a K-type thermocouple to measure the temperature and control the melt at 780-800℃. Add pure copper sheets, Al-10Mn, and Al-10V master alloys sequentially, stirring for 2 minutes at each step. Sprinkle in a covering agent, hold for 10 minutes, and then remove slag. Cool to 730-750℃, wrap two bags of hexachloroethane in aluminum foil, press them into the bottom of the melt with a bell jar, stir to remove gas, repeating at 2-minute intervals, and then remove slag after refining. Add Al-5Ti-B master alloy, melt thoroughly, stir, and remove slag. Pour the melt at 740℃ 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 535℃ for 8 hours (box-type resistance furnace), then quickly immersed in a room temperature water bath for quenching; followed by aging at 170℃ for 6 hours and air cooling.

[0011] Tensile specimens (gauge length 30 mm) were prepared according to standard procedures. Tensile tests were conducted at room temperature and 350°C on a universal testing machine. At 350°C, the specimens were held at this temperature for 20 minutes before being loaded at a rate of 0.5 mm / min. The results showed: room temperature tensile strength 386.18 MPa, yield strength 323.13 MPa, elongation after fracture 8.9%; 350°C tensile strength 182.67 MPa, yield strength 179.61 MPa, elongation after fracture 14.53%.

[0012] Performance test results of aluminum alloy

Claims

1. A high-strength, heat-resistant aluminum alloy containing Ti / B refining agents, characterized in that... Composed of the following components by weight percentage Composition: Cu 5.5%-6.5%, Mn 0.5%-0.8%, V 0.25%-0.35%, Al-5Ti-B master alloy 0.25%-0.35%, balance Al and unavoidable impurities.

2. The high-strength heat-resistant aluminum alloy containing Ti / B refining agent according to claim 1, characterized in that, The weight percentage of Cu is 5.8%-6.2%, the weight percentage of Mn is 0.55%-0.65%, the weight percentage of V is 0.28%-0.32%, and the weight percentage of Al-5Ti-B master alloy is 0.28%-0.32%.

3. The high-strength, heat-resistant aluminum alloy containing Ti / B refining agent according to any one of claims 1-2, characterized in that, The mass ratio of Ti to B in the Al-5Ti-B master alloy is 5:

1.

4. The high-strength, heat-resistant aluminum alloy containing Ti / B refining agent 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 heat-resistant aluminum alloy refining agent, characterized in that, The refining agent is an Al-5Ti-B master alloy, and its mass percentage is 0.25%-0.35% of the total alloy.

6. A method for preparing a high-strength, heat-resistant aluminum alloy containing a Ti / B refining agent as described in any one of claims 1 to 5, characterized in that, Includes the following steps: oS1: Weigh out pure aluminum granules, electrolytic copper sheets, Al-10Mn master alloy, Al-10V master alloy and Al-5Ti-B master alloy according to the proportions; oS2: Place pure aluminum granules in a medium-frequency induction melting furnace and heat them to 780-800℃ until completely melted. Then, add pure copper sheets, Al-10Mn, and Al-10V master alloy in sequence. After each element is added, stir thoroughly and skim off the slag. After all the aluminum granules have melted, sprinkle a covering agent evenly, keep warm, and then skim off the slag. oS3: Cool to 730-750℃, add degassing agent in two batches for refining, with an interval of more than 2 minutes between each batch, and remove slag after refining; oS4: Add Al-5Ti-B master alloy, melt it completely, and then stir and remove the slag; oS5: Control the melt temperature at 730-750℃, pour it into a mold preheated at 280-320℃, cool and demold to obtain an ingot; oS6: The ingot is solution treated at 525-545℃ for 6-10 hours, followed by water quenching at room temperature; oS7: Aging the ingot at 160-180℃ for 4-8 hours, followed by air cooling.

7. The method for preparing the high-strength heat-resistant aluminum alloy containing Ti / B refining agent according to claim 6, characterized in that, The solution treatment temperature in step S6 is 535℃, and the solution treatment time is 8h.

8. The method for preparing a high-strength, heat-resistant aluminum alloy containing a Ti / B refining agent 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 6h.

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