Sc, Zr and Ag combined reinforced Al-Si-Cu-Mg alloy and preparation method thereof

Abstract

The invention belongs to the technical field of new material research and development and material strengthening, and relates to an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr and Ag and a preparation method of the Al-Si-Cu-Mg alloy. The alloy disclosed by the invention comprises the following main components in percentage by mass: 8.5%-9.5% of Si, 1.5%-2.0% of Cu, 0.45%-0.7% of Mg, 0.2%-0.4% of Mn, 0.08%-0.25% of Ti, 0.2%-0.4% of Sc, 0.1%-0.2% of Zr and 0.3%-0.5% of Ag. After the alloy is melted, when the temperature is raised to 710 DEG C, an AlZr4A intermediate alloy, an AlSc10 intermediate alloy and Ag which are weighed in proportion are added, and the alloy is refined by adopting a rotary spray head and a refining agent. The alloy is strengthened under the strict smelting process, the strength of the alloy can be improved to 375 MPa to 388 MPa, and the percentage elongation after fracture is improved to 5%.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new material research and development and material strengthening technology, and relates to a Sc, Zr and Ag combined strengthened Al-Si-Cu-Mg alloy and a preparation method thereof. BACKGROUND

[0002] With the development and research of aviation equipment, such as an aero-engine, the Mach number is higher and higher, and the load is larger and larger, which puts forward higher requirements on the reliability, strength and heat resistance of aluminum alloy components. Although the cast Al-Cu alloy has good performance, it is difficult to cast an integral complex thin-walled casting because of its poor castability and difficult control of casting defects. The Al-Si alloy is often used to cast integral complex castings with complex structure and medium load because of its excellent castability and easy control of casting defects such as porosity and cracks. However, with the increasing performance of aviation and aerospace and electronic equipment, the requirements on the mechanical properties and corrosion resistance of alloy materials are also increasing. For example, the service environment of Al-Si alloy in the fuel control system of an aviation aircraft is improved from 150℃ to 200℃, and the strength requirement is not less than 270MPa; the aluminum silicon alloy ZL114A alloy used in the transmission system of an engine accessory is pointed out to have insufficient strength performance at room temperature, and cannot meet the use requirements of a new model; at the same time, the cast Al-Si alloy is required to have a room temperature strength of 380MPa for the shell parts of a spacecraft. The conventional Al-Si-Mg series cast aluminum alloy such as ZL114A cannot meet the requirements. The development of Al-Si-Cu-Mg series cast aluminum alloy has started as early as the 1930s and 1940s of last century, and the typical ones are 354.0 and 355.0 alloys developed by the United States. Due to the Cu element, Al2Cu strengthening phase can be formed in the matrix, and the phase has higher room temperature / high temperature stability than the Mg2Si phase. Therefore, the room temperature / high temperature mechanical properties of the Al-Si-Cu-Mg series cast aluminum alloy are generally slightly higher than those of the Al-Si-Mg series cast aluminum alloy.

[0003] The main chemical components of the new Al-Si-Cu-Mg alloy are: Si: 8.5% to 9.5%, Cu: 1.5% to 2.0%, Mg: 0.45% to 0.7%, Mn: 0.2% to 0.4%, and Ti: 0.08 to 0.25%. Due to the high Si content of the alloy, the castability is excellent, and the casting defects such as porosity and cracks are easy to control. In addition, the alloy has good room temperature mechanical properties and high temperature mechanical properties, and can be used for components with complex structure and high load in aviation and spacecraft, such as aircraft framework and spacecraft shell. However, due to the high Si content of the alloy, the performance is relatively low (σ b about 320MPa to 340MPa) compared with the Al-Cu alloy, especially the elongation after fracture is low (δ5 is generally about 2%). SUMMARY

[0004] The present application is based on the requirement of aerospace equipment for cast aluminum-silicon alloy, and the current situation that the performance of ordinary cast aluminum-silicon alloy cannot meet the requirements, and a process method of Sc, Zr and Ag combined strengthening Al-Si-Cu-Mg alloy is developed.

[0005] The purpose of the present application is realized by the following technical scheme: a Sc, Zr and Ag combined strengthening Al-Si-Cu-Mg alloy, characterized in that the main components of the alloy are as follows in mass percentage: Si: 8.5%-9.5%, Cu: 1.5%-2.0%, Mg: 0.45%-0.7%, Mn: 0.2%-0.4%, Ti: 0.08-0.25%, Sc: 0.2%-0.4%, Zr: 0.1-0.2%, and Ag: 0.3-0.5%. When the Al-Si-Cu-Mg alloy is prepared, high-purity Al, metal Mg, metal silver, Al-Si intermediate alloy, Al-Mn intermediate alloy, Al-Ti intermediate alloy, Al-Cu intermediate alloy, Al-Zr intermediate alloy, Al-Sc intermediate alloy and modifier Al-Sr intermediate alloy are used.

[0006] The Mg and Ag are in the form of magnesium ingot and silver ingot, and the Al is in the form of refined aluminum ingot; the content of Mg is more than 99.8%, the content of Ag is more than 99.9%, and the content of Al is 99.95%.

[0007] A preparation method of a Sc, Zr and Ag combined strengthening Al-Si-Cu-Mg alloy, comprising the following steps: 1) The amounts of each metal and intermediate alloy are calculated according to the chemical component content; the main alloy raw materials are high-purity Al, metal Mg, metal silver, Al-Si intermediate alloy, Al-Mn intermediate alloy, Al-Ti intermediate alloy, Al-Cu intermediate alloy, Al-Zr intermediate alloy, Al-Sc intermediate alloy and modifier Al-Sr intermediate alloy; and C2Cl6 refining agent is weighed according to 0.6% of the total amount of the alloy; 2) A crucible containing 100 Kg of aluminum alloy melt is placed in an electric resistance furnace, and the weighed high-purity Al, Al-Si intermediate alloy, Al-Mn intermediate alloy and Al-Ti intermediate alloy ingots are placed in the crucible; the electric resistance furnace is set at 850℃, and power is supplied for heating and melting; 3) After the alloy is melted into liquid, the temperature of the electric resistance furnace is set at 730℃, a handheld armored thermocouple is inserted into the alloy melt to measure the temperature of the alloy melt, and when the temperature reaches 700℃, the Al-Cu intermediate alloy is added and melted and stirred for 5 min; 4) Continue to supply power for heating, and when the temperature of the alloy melt reaches 710℃, the Al-Zr intermediate alloy, Al-Sc intermediate alloy and Ag are added into the melt, and melted and stirred for 5 min; 5) Set the temperature of the resistance furnace at 770℃, and send electricity to heat. A hand-held armored thermocouple is inserted into the alloy melt to measure the temperature of the alloy melt. When the temperature reaches 750℃, add the Al-Ti-B intermediate alloy. When it is melted and stirred for 5 minutes; 6) Set the temperature of the resistance furnace at 710℃, and insert a hand-held armored thermocouple into the alloy melt to measure the temperature of the alloy melt. When the temperature of the melt reaches 700℃, add the metal Mg into the melt, and melt and stir for 5 minutes; 7) Continue to send electricity to heat. When the temperature of the alloy melt reaches 710℃, refine the alloy melt with the refining agent C2Cl6. After the reaction is completed, stand for 15 minutes; 8) Raise the temperature of the resistance furnace to 730℃, send electricity to heat, and measure the temperature of the alloy melt. When it is raised to 720℃, add the Al-Sr intermediate alloy for modification. After it is completely melted, stir for 5 minutes; 9) Stabilize the alloy melt at 720℃, and pass argon through the rotating blowing device to refine for 10-15 minutes; 10) The temperature of the alloy melt is kept at 720-730℃. After refining is completed, remove the slag, and stand for 10-15 minutes; 11) Stabilize the alloy melt at 720℃, and pour the sample to test its mechanical properties.

[0008] The Al-Si intermediate alloy adopts an aluminum-silicon intermediate alloy ingot AlSi14A, and the silicon content is 14%.

[0009] The Al-Mn intermediate alloy adopts an aluminum-manganese intermediate alloy AlMn10A, and the manganese content is 10%.

[0010] The Al-Ti intermediate alloy adopts an aluminum-titanium intermediate alloy ingot AlTi5A, and the titanium content is 5%.

[0011] The Al-Cu intermediate alloy adopts an aluminum-copper intermediate alloy AlCu50A, and the copper content is 50%.

[0012] The Al-Zr intermediate alloy adopts an aluminum-zirconium intermediate alloy AlZr4A, and the zirconium content is 4%.

[0013] The Al-Sc intermediate alloy adopts an aluminum-scandium intermediate alloy AlSc10, and the scandium content is 10%.

[0014] The Al-Sr intermediate alloy adopts an aluminum-strontium intermediate alloy AlSr3A, and the strontium content is 3%.

[0015] The present application has the following beneficial effects: The application provides a Sc+Zr+Ag element combined strengthening Al-Si-Cu-Mg alloy process, and the proportion of Sc, Zr and Ag elements is as follows: Sc: 0.2%-0.4%, Zr: 0.1-0.2% and Ag: 0.3-0.5%.

[0016] A typical Al-Si-Cu-Mg alloy, such as ZL111 alloy in China, has the chemical composition as follows: Si: 8.0%-10.0%, Cu: 1.3%-1.8%, Mg: 0.4%-0.6%, Mn: 0.1%-0.35% and Ti: 0.1-0.35%, and the typical room temperature tensile strength σb is 320 MPa-340 MPa, and the elongation δ5 after fracture is generally about 2%, which cannot meet the requirements of modern aerospace equipment. The application optimizes the alloy composition on the basis of the alloy, and adopts a Sc+Zr+Ag combined strengthening process (the adding amount is as follows: Sc: 0.2%-0.4%, Zr: 0.1-0.2% and Ag: 0.3-0.5%): after the alloy is melted, the AlZr4A intermediate alloy, the AlSc10 intermediate alloy and Ag are added in proportion at 710 DEG C, and the alloy is refined by adopting a rotary nozzle+refining agent. The alloy is strengthened under a strict melting process, so that the alloy strength is increased to 375 MPa-388 MPa, and the elongation after fracture is increased to 5%. Specific implementation method The application is further described below in combination with specific embodiments. In order to ensure stable performance, the Al-Si-Cu-Mg alloy is first optimized in composition on the basis of ZL111 alloy: Si: reduced from 8.0%-10.0% to 8.5%-9.5%; Cu: adjusted from 1.3%-1.8% to 1.5%-2.0%; Mg: adjusted from 0.4%-0.6% to 0.45%-0.7%; Mn: adjusted from 0.1%-0.35% to 0.2%-0.4%; Ti: adjusted from 0.1-0.35% to 0.08-0.25%.

[0017] The effect of the fine-tuned chemical composition is that the Sc element and the Zr element have more obvious strengthening effect (such as the Ti element content is slightly reduced), and the alloy performance is more stable and has small fluctuation (such as the Si element adding range is reduced).

[0018] Secondly, alloying strengthening elements Zr, Sc, and Ag are added in the following proportions: Sc: 0.2%–0.4%, Zr: 0.1–0.2%, Ag: 0.3–0.5%. The amounts of AlZr4A master alloy, AlSc10A master alloy, and Ag are calculated according to these proportions. The alloy melt is then added at 710℃ for strengthening.

[0019] Example 1: The total amount of alloy is 100 kg, and the content of each element is as follows: Si: 8.5%, Cu: 1.5%, Mg: 0.45%, Mn: 0.2%, Ti: 0.08%, Sc: 0.2%, Zr: 0.1%, Ag: 0.3%.

[0020] The main smelting process of the alloy is as follows: ①. Prepare the alloy materials according to the predetermined chemical composition: 26.7 kg of high-purity Al, 0.45 kg of metallic Mg, 0.3 kg of metallic Ag, 60.71 kg of Al-Si master alloy, 2 kg of Al-Mn master alloy, 1.6 kg of Al-Ti master alloy, 3.03 kg of Al-Cu master alloy, 2.5 kg of Al-Zr master alloy, 2 kg of Al-Sc master alloy, and 0.5 kg of Al-Sr master alloy modifier; weigh out 0.6% of refining agent.

[0021] ②. Prepare a temperature-controlled alloy melting resistance furnace and a crucible containing 100 kg of molten aluminum alloy. Place the crucible into the resistance furnace. After completing the batching and aluminum alloy melting preparation, place the weighed alloy ingots of high-purity Al, Al-Si master alloy, Al-Mn master alloy, and Al-Ti master alloy into the crucible. Set the resistance furnace to 850℃ and heat it to melt. ③. After the alloy melts into a liquid, set the resistance furnace temperature to 730℃. Use a handheld armored thermocouple to probe the alloy melt and measure its temperature. When the temperature reaches 700℃, add the Al-Cu master alloy, allow it to melt, and stir for 5 minutes. ④. Continue heating with electricity until the alloy melt temperature reaches 710℃. Then add the Al-Zr master alloy, Al-Sc master alloy and Ag to the melt, and stir for 5 minutes after they melt. ⑤. Set the resistance furnace temperature to 770℃, turn on the power to heat, use a hand-held armored thermocouple to probe into the alloy melt to measure the temperature of the alloy melt, and add Al-Ti-B master alloy when the temperature reaches 750℃, wait for it to melt and stir for 5 minutes. ⑥. Set the resistance furnace temperature to 710℃, use a handheld armored thermocouple to probe the alloy melt to measure the temperature of the alloy melt, and when the melt temperature drops to 700℃, add metallic Mg to the melt, wait for it to melt and stir for 5 minutes.

[0022] ⑦. Continue heating with electricity until the alloy melt temperature reaches 710℃. Then refine the alloy melt with C2Cl6. After the reaction is complete, let it stand for 15 minutes. ⑧. Heat the resistance furnace to 730℃, turn on the power to heat, measure the temperature of the alloy melt, and when it reaches 720℃, add the Al-Sr master alloy for modification. After it is completely melted, stir for 5 minutes.

[0023] 9. Stabilize the alloy melt at 720℃ and refine it with argon gas using a rotary jetting device for 10-15 minutes; ⑩. Maintain the temperature of the molten aluminum at 720-730℃; after refining, remove the slag and let it stand for 10-15 minutes. (11) The alloy melt was stabilized at 720℃, and a sample was poured to test its mechanical properties.

[0024] Example 2: The total amount of alloy is 100 kg, and the content of each element is as follows: Si: 9%, Cu: 1.8%, Mg: 0.6%, Mn: 0.3%, Ti: 0.17%, Sc: 0.3%, Zr: 0.15%, Ag: 0.4%.

[0025] The main smelting process of the alloy is as follows: ①. Prepare the alloy materials according to the predetermined chemical composition: 18 kg of high-purity Al, 0.6 kg of metallic Mg, 0.4 kg of metallic Ag, 64.3 kg of Al-Si master alloy, 3 kg of Al-Mn master alloy, 3.4 kg of Al-Ti master alloy, 3.64 kg of Al-Cu master alloy, 3.75 kg of Al-Zr master alloy, 3 kg of Al-Sc master alloy, and 0.5 kg of Al-Sr master alloy modifier; weigh out 0.6% of refining agent.

[0026] The remaining smelting process is the same as in Example 1.

[0027] Example 3: The total amount of alloy is 100 kg, and the content of each element is as follows: Si: 9.5%, Cu: 2.0%, Mg: 0.7%, Mn: 0.4%, Ti: 0.25%, Sc: 0.4%, Zr: 0.2%, Ag: 0.5%.

[0028] The main smelting process of the alloy is as follows: ①. Prepare the alloy materials according to the predetermined chemical composition: 8.9 kg of high-purity Al, 0.7 kg of metallic Mg, 0.5 kg of metallic Ag, 67.86 kg of Al-Si master alloy, 4 kg of Al-Mn master alloy, 5 kg of Al-Ti master alloy, 4.04 kg of Al-Cu master alloy, 5 kg of Al-Zr master alloy, 4 kg of Al-Sc master alloy, and 0.5 kg of Al-Sr master alloy modifier; weigh out 0.6% of refining agent.

[0029] The remaining smelting process is the same as in Example 1.

[0030] After the alloy was smelted, samples were taken and heat-treated to test its mechanical properties. The results are shown in Appendix 1 and Appendix 2. As can be seen from Appendix 1 and Appendix 2, the strength of the Al-Si-Cu-Mg alloy increased to 375MPa~388MPa and the elongation after fracture increased to 5% after strengthening with Sc, Zr and Ag.

[0031] Table 1 Properties of Al-Si-Cu-Mg alloys before combined strengthening with Sc, Zr, and Ag

[0032] Table 2 Properties of Al-Si-Cu-Mg alloys after combined strengthening with Sc, Zr, and Ag (Example 1)

[0033] Table 3 Properties of Al-Si-Cu-Mg alloys after combined strengthening with Sc, Zr, and Ag (Example 2)

[0034] Table 4 Properties of Al-Si-Cu-Mg alloys after combined strengthening with Sc, Zr, and Ag (Example 3)

Claims

1. A Sc, Zr, Ag co-strengthened Al-Si-Cu-Mg alloy, characterized in that, The main components of the alloy are as follows (by mass percentage): Si: 8.5%–9.5%, Cu: 1.5%–2.0%, Mg: 0.45%–0.7%, Mn: 0.2%–0.4%, Ti: 0.08%–0.25%, Sc: 0.2%–0.4%, Zr: 0.1%–0.2%, Ag: 0.3%–0.5%.

2. The Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 1, characterized in that, The Al-Si-Cu-Mg alloy is prepared using high-purity Al, metallic Mg, metallic silver, Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy, and the modifier Al-Sr master alloy.

3. The Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 2, characterized in that, The Mg and Ag are obtained from magnesium ingots and silver ingots, and the Al is obtained from refined aluminum ingots; the magnesium content is above 99.8%, the silver content is above 99.9%, and the aluminum content is 99.95%.

4. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 2 or 3, characterized in that, Includes the following steps: 1) Calculate the amount of each metal and master alloy according to the above chemical composition content; the main alloy raw materials are high-purity Al, metallic Mg, metallic silver, Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy and modifier Al-Sr master alloy; weigh C2Cl6 refining agent at 0.6% of the total alloy amount; 2) Place the crucible containing 100 kg of molten aluminum alloy into the resistance furnace, place the weighed alloy ingots of high-purity Al, Al-Si master alloy, Al-Mn master alloy and Al-Ti master alloy into the crucible, set the resistance furnace to 850℃, and heat it to melt. 3) After the alloy melts into a liquid, set the temperature of the resistance furnace to 730℃, use a hand-held armored thermocouple to probe into the alloy melt to measure the temperature of the alloy melt, and when the temperature reaches 700℃, add the Al-Cu master alloy, wait for it to melt and stir for 5 minutes. 4) Continue heating with electricity. When the temperature of the alloy melt reaches 710℃, add the Al-Zr master alloy, Al-Sc master alloy and Ag into the melt, wait for them to melt and stir for 5 minutes. 5) Set the resistance furnace temperature to 770℃, turn on the power to heat, use a hand-held armored thermocouple to probe into the alloy melt to measure the temperature of the alloy melt, and add Al-Ti-B master alloy when the temperature reaches 750℃, wait for it to melt and stir for 5 minutes. 6) Set the resistance furnace temperature to 710℃, use a handheld armored thermocouple to probe the alloy melt to measure the temperature of the alloy melt, and when the melt temperature drops to 700℃, add the Mg metal to the melt, wait for it to melt and stir for 5 minutes. 7) Continue heating with electricity. When the temperature of the alloy melt reaches 710℃, refine the alloy melt with refining agent C2Cl6. After the reaction is complete, let it stand for 15 minutes. 8) Heat the resistance furnace to 730℃, turn on the power to heat, measure the temperature of the alloy melt, and when it reaches 720℃, add the Al-Sr master alloy for modification. After it is completely melted, stir for 5 minutes. 9) Stabilize the alloy melt at 720℃ and refine it with argon gas using a rotary jetting device for 10-15 minutes; 10) Maintain the alloy melt temperature at 720–730℃; after refining, remove the slag and let it stand for 10–15 minutes. 11) The alloy melt is stabilized at 720℃, and a sample is poured to test its mechanical properties.

5. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 4, characterized in that, The Al-Si master alloy is made of aluminum-silicon master alloy ingot AlSi14A with a silicon content of 14%.

6. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 4, characterized in that, The Al-Mn master alloy used is the aluminum-manganese master alloy AlMn10A, with a manganese content of 10%.

7. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 4, characterized in that, The Al-Ti master alloy is made of aluminum-titanium master alloy ingot AlTi5A with a titanium content of 5%.

8. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 4, characterized in that, The Al-Cu master alloy used is AlCu50A, an aluminum-copper master alloy with a copper content of 50%.

9. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 4, characterized in that, The Al-Zr master alloy used is AlZr4A, an aluminum-zirconium master alloy with a zirconium content of 4%.

10. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 4, characterized in that, The Al-Sc master alloy is an aluminum-scandium master alloy AlSc10 with a scandium content of 10%.

11. The method for preparing an Al-Si-Cu-Mg alloy jointly strengthened by Sc, Zr, and Ag according to claim 4, characterized in that, The Al-Sr master alloy is an aluminum-strontium master alloy AlSr3A with a strontium content of 3%.

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