CN113930644B - A kind of heat-resistant Al-Fe-Si aluminum alloy and preparation method thereof - Google Patents

Abstract

The invention provides a heat-resistant Al-Fe-Si aluminum alloy and a preparation method thereof. The Al-Fe-Si aluminum alloy comprises the following components in terms of mass percentage: 4.5-5.5% of iron, 2.8-3.5% of silicon %, the balance is Al and unavoidable impurities, and the total amount of impurities is less than or equal to 0.06%. The preparation method is to cast an Al-Fe-Si alloy ingot, remelt it at 750-820°C in a vacuum environment, and then quench it to obtain a heat-resistant Al-Fe-Si aluminum alloy. The quenching speed is ≧300℃/s. The present invention obtains an Al-Fe-Si aluminum alloy in which 100% of the iron-containing phase is eutectic ɑ-AlFeSi through composition control and cooperative remelting chilling treatment. The eutectic ɑ-AlFeSi has an extremely excellent strengthening effect, so that the Al ‑Fe‑Si aluminum alloy has the characteristics of high structural thermal stability and excellent strength and toughness. It can be used in components that serve at higher temperatures, such as engine housings, pistons, etc.

Description

A kind of heat-resistant Al-Fe-Si aluminum alloy and preparation method thereof

technical field

The invention relates to a heat-resistant Al-Fe-Si aluminum alloy, belonging to the technical field of aluminum alloy preparation.

Background technique

Al-Si alloy is a commonly used material for automobile engines. Pure Al-Si alloy has low strength, so a small amount of Cu and Mg elements are usually added to the alloy to improve the strength of the alloy. The main strengthening mechanism is aging precipitation strengthening, and the aging heat treatment temperature is generally below 200 °C. These Mg-containing and Cu-containing precipitates will coarsen after being kept for a long time (above 100h) at a temperature of 200°C and above, and the size will become larger, the number density will decrease, and the ability to hinder dislocation movement will decrease, thereby making the strength of the alloy reduce. However, the operating temperature of an automobile engine is about 200°C, which is detrimental to the strength of the Al-Si alloy. Therefore, it is necessary to develop an aluminum alloy that can serve at a higher temperature to make up for the shortcomings of the existing Al-Si alloys.

At present, the common new heat-resistant aluminum alloys mainly include Al-Ni, Al-Ce and other alloy systems. The alloy mainly relies on Al ₃ Ni and Al ₁₁ Ce ₃ phases which are stable at high temperature as the strengthening phase of the alloy. The size of these phases is generally below 200nm and the distribution is uniform, which makes the alloy have higher strength and elongation. However, the cost of strengthening elements of the above-mentioned heat-resistant aluminum alloy is relatively high.

Patent CN113416870A discloses an Al-Ce series high-strength heat-resistant aluminum alloy, wherein the amount of Ce added reaches 12-16%, and 0.3-0.8% Sc and 0.15-0.32% Zr are also added. The addition of these alloying elements greatly increases the cost of the alloy. Among them, the unit price of Ce is more than 5 times that of Fe, and the unit price of Sc per kilogram (32,000 yuan/kg) is even higher. The addition of 0.3-0.8% increases the cost of the alloy by 100,000-250,000 per ton, which is not conducive to commercialization.

The formation temperature of ɑ-AlFeSi phase is above 600 °C, and the diffusion rate of Fe element in the aluminum matrix is also slow, so the stability of ɑ-AlFeSi is high at high temperature. And the required elements Fe and Si are low-cost additive elements, so the study of fine ɑ-AlFeSi eutectic alloys as strengthening phases will be a direction to obtain low-cost heat-resistant aluminum alloys. However, the Al-Fe-Si system involves three elements, and a wide variety of iron-containing phases are formed. Under normal conditions, it is impossible to obtain an alloy whose iron-containing phase is completely ɑ-AlFeSi, and it is inevitable to produce flaky Al ₁₃ Fe ₄ And β-AlFeSi harmful phase. At present, there is no alloy whose microstructure containing iron phase is all ɑ-AlFeSi eutectic.

Contents of the invention

Aiming at the deficiencies of the prior art, the object of the present invention is to provide an Al-Fe-Si heat-resistant aluminum alloy whose iron-containing phases are all ɑ-AlFeSi and a preparation method thereof.

In order to achieve the above object, the present invention adopts the following technical solutions:

The present invention is a heat-resistant Al-Fe-Si aluminum alloy. In the Al-Fe-Si aluminum alloy, 100% of the iron-containing phase is eutectic ɑ-AlFeSi, and the Al-Fe-Si aluminum alloy is calculated by mass percentage , including the following components: 4.5%-5.5% of iron, 2.8%-3.5% of silicon, the balance being Al and unavoidable impurities, and the total impurity content is less than or equal to 0.06%.

The present invention is the first to provide an Al-Fe-Si aluminum alloy in which all iron-containing phases are eutectic ɑ-AlFeSi. Since there is no flaky Al ₁₃ Fe ₄ and β-AlFeSi, the Al-Fe provided by the present invention -Si aluminum alloy has excellent strength and elongation, and the microstructure has excellent heat resistance.

In the present invention, the mass percentage content of Al-Fe-Si aluminum alloy is very important, if the content is not within the scope of the present invention, it is impossible to make all the iron-containing phases be eutectic ɑ-AlFeSi. When the iron content is too high or the silicon content is too low, coarse flake-like or flower-like Al ₁₃ Fe ₄ phases will be produced in the alloy, which will damage the strength and elongation of the alloy. When the iron content is too low or the silicon content is too high, coarse flaky β-AlFeSi will be precipitated, resulting in stress concentration and damage to the strength and elongation of the alloy.

Preferably, the Al-Fe-Si aluminum alloy contains the following components in terms of mass percentage: 4.8%-5.5% of iron, 3.0%-3.5% of silicon, the balance is Al and unavoidable impurities, the total amount of impurities is The content is less than or equal to 0.06%.

Preferably, the grains of the ɑ-AlFeSi are ≤200nm.

In the Al-Fe-Si aluminum alloy provided by the present invention, the iron-containing phases are all ɑ-AlFeSi with crystal grains ≤ 200nm, and the morphology of ɑ-AlFeSi is maze-like or Chinese character-like. The inventors found that this morphology is similar to that of Al- The Al ₁₁ Ce ₃ morphology of the reinforcement phase in the Ce eutectic alloy is very similar, and the reinforcement effect is remarkable.

Preferably, the microstructure of the Al-Fe-Si aluminum alloy is an Al/ɑ-AlFeSi eutectic cluster, and the diameter of the Al/ɑ-AlFeSi eutectic cluster is 20-40 μm.

Preferably, the tensile strength of the Al-Fe-Si aluminum alloy is 240-260 MPa, and the elongation is 15-20%.

A kind of preparation method of heat-resistant Al-Fe-Si aluminum alloy of the present invention comprises the following steps:

Cast Al-Fe-Si alloy ingots, remelt them at 750-820°C in a vacuum environment, and then quench to obtain heat-resistant Al-Fe-Si aluminum alloys. The quenching speed is ≧300°C/s, Preferably it is 400°C/s.

The inventors found that after remelting the Al-Fe-Si alloy ingot with the composition ratio of the designed formula, then chilling it, it is possible to control the iron-containing phases to be ɑ-AlFeSi.

In the present invention, as long as the cooling rate can meet the requirements, the quenching means is not limited, but if the cooling rate is too small, Al ₁₃ Fe ₄ and β-AlFeSi phases will be generated, which will damage the strength and elongation of the alloy.

Preferably, the remelting temperature is 780-800° C., and the holding time is 20-40 minutes.

A kind of preparation method of heat-resistant Al-Fe-Si aluminum alloy of the present invention comprises the following steps:

Al-Fe-Si alloy ingot is cast, and Al-Fe-Si alloy short rod is obtained by machining, and Al-Fe-Si alloy short rod is packaged in a vacuum quartz tube, at 750-820°C, preferably 780-800°C Remelt and hold for 20-40 minutes to obtain remelted Al-Fe-Si alloy, then clamp the quartz tube, drop the remelted Al-Fe-Si alloy directly into cooling water, and chill to obtain Al-Fe-Si aluminum alloy, the temperature of the cooling water is ≤20°C.

In the above process, the remelted Al-Fe-Si alloy is directly dropped into the cooling water, and the Al-Fe-Si aluminum alloy cooled to room temperature is obtained in about 2 seconds, and the cooling rate is ≧300°C/s. The inventors found that the final performance of the Al-Fe-Si aluminum alloy obtained by the above preparation process is the best.

Preferably, the method for obtaining the Al-Fe-Si alloy ingot is: matching the Al source, Fe source, and Si source according to the designed ratio, melting and obtaining a melt, and casting the melt to obtain Al-Fe-Si Alloy ingots.

Further preferably, the Al source is selected from at least one of pure aluminum, aluminum-iron alloy, and aluminum-silicon alloy, the iron source is selected from at least one of pure iron, aluminum-iron alloy, and the silicon source is selected from pure silicon , at least one of aluminum-silicon alloys.

In actual operation, after the Al-Fe-Si alloy ingot is processed into a short rod, the surface processing traces are removed by sandpaper grinding, alcohol cleaning, and the processed short rod is put into a cylindrical corundum crucible, and then the crucible and the sample Sealed together in a vacuum quartz tube.

The outstanding substantive features and remarkable progress of the present invention are mainly reflected in:

(1) The present invention obtains an Al-ɑ-AlFeSi eutectic aluminum alloy by rationally adjusting the composition and controlling the cooling rate, and explores a new heat-resistant aluminum alloy system. In the Al-Fe-Si aluminum alloy obtained in the present invention, 100% of the iron-containing phase is eutectic ɑ-AlFeSi, and the effect of ɑ-AlFeSi on the Al-Fe-Si aluminum alloy is equivalent to the eutectic Al in the Al-Ce eutectic alloy ₁₁ Ce ₃ , or the eutectic Al ₃ Ni in the Al-Ni eutectic alloy, which has a labyrinth-like lamellar structure similar to the eutectic Al ₁₁ Ce ₃ alloy, and the width of the sheet is below 200nm, which has great influence on the mechanical properties of the alloy. Great enhancement.

(2) The alloy obtained in the present invention can realize the excellent properties of tensile strength of 247 MPa and elongation of 19% without adding other precipitation strengthening elements.

(3) The alloy obtained in the present invention has the characteristics of high structural thermal stability and excellent strength and toughness. It can be used in components that serve at higher temperatures, such as engine housings, pistons, etc.

(4) The Fe and Si elements contained in the alloy have obvious price advantages over Ce and Ni, and are more suitable for commercialization.

Description of drawings

Figure 1 Schematic diagram of vacuum sealing tube.

2 is an SEM image of the microstructure of the Al-Fe-Si aluminum alloy of Example 1.

Fig. 3 is the microstructure of the Al-Fe-Si aluminum alloy sheet in Example 1 after heat treatment at 520°C for 0, 2, 4 and 8 hours.

4 is an SEM image of the microstructure of the Al-Fe-Si aluminum alloy of Example 2.

5 is an SEM image of the microstructure of the Al-Fe-Si aluminum alloy of Example 3.

6 is an SEM image of the microstructure of the Al-Fe-Si aluminum alloy of Comparative Example 1.

7 is an SEM image of the microstructure of the Al-Fe-Si aluminum alloy of Comparative Example 2.

Fig. 8 is the tensile stress-strain curve of Al-Fe-Si aluminum alloy in Example 1 and Comparative Examples 1 and 2.

Detailed ways

The invention relates to a heat-resistant Al-Fe-Si aluminum alloy and a preparation method thereof, the composition of which comprises, by mass percentage, 4.5-5.5% of iron, 2.8-3.5% of silicon, the balance being Al and unavoidable impurities, and the total amount of impurities Less than or equal to 0.06%. Preferably, the alloy composition is: iron 4.8-5.5%, silicon 3-3.5%, the balance is Al and unavoidable impurities, and the total amount of impurities is less than or equal to 0.06%.

The present invention also provides a kind of corresponding processing technique:

(1) Alloy smelting and casting: mix pure aluminum and intermediate alloy according to the mass fraction of 4.8-5.5% iron, 3-3.5% silicon, the balance is Al and unavoidable impurities, and then put the alloy into the graphite crucible Among them, aluminum rods are melted and cast, and the induction current is 260A during the alloy melting and casting process. After the melting and casting is completed, it is poured into a copper mold to obtain an alloy ingot.

(2) Machining: The alloy ingot is cut into a short rod with a diameter of 12 mm and a height of 20 mm by wire electric discharge cutting, polished with sandpaper to remove surface processing traces, and cleaned with alcohol for later use.

(3) Vacuum tube sealing: Put the processed short rod into a cylindrical corundum crucible with an inner diameter of 13 mm, and then seal the crucible into a vacuum quartz tube; pump the inside of the tube to below 50 Pa on a vacuum tube sealing machine, and place it 2 cm above the crucible Burn the quartz tube out of the ring neck; then take it out and put it into the quartz plug, and then pump the inside of the tube to below 50Pa on the sealing machine, and then sinter the quartz tube and the quartz plug together to form a vacuum closed space in the tube.

(4) Remelting chilling: From room temperature to 750-820°C at a rate of less than 10°C/min, keep it warm for 20 minutes, then take out the sample, quickly move the sample to the water surface with pliers, and break the quartz tube. The sample is dropped directly into the water to obtain a chilled sample.

Example 1

The composition of the heat-resistant Al-Fe-Si aluminum alloy in Example 1 is calculated by mass percentage: 5% iron, 3% silicon, and the rest is Al and unavoidable impurities. According to the design ratio, pure aluminum, Al-10Fe, Al-20Si master alloys are melted and cast through the above process, vacuum sealed, and remelted at 800°C. After remelting, the quartz tube is clamped, and the samples are directly dropped into about 20°C. The water is chilled, and the alloy is cooled to room temperature in about 2s. After that, the water-cooled sample is obtained, which is Al-Fe-Si aluminum alloy. Afterwards, the mechanical properties of the Al-Fe-Si aluminum alloy were tested, and the tensile strength of the obtained alloy was 247MPa, and the elongation was 19%.

The Al-Fe-Si aluminum alloy was processed into thin slices with a thickness of 1mm by wire electric discharge, and three slices were taken and placed in a box furnace at 520°C, and heat-treated for 2 hours, 4 hours, and 8 hours respectively.

Figure 2 is an SEM picture of the microstructure of the Al-Fe-Si aluminum alloy prepared in Example 1. It can be seen from the figure that the microstructure of the alloy is all fine Al/ɑ-AlFeSi eutectic clusters, and ɑ-AlFeSi It is distributed in a maze shape, with a thickness below 200nm.

Figure 3 is the microstructure of the Al-Fe-Si aluminum alloy sheet obtained in Example 1 after heat treatment at 520°C for 0 hour, 2 hours, 4 hours, and 8 hours. It can be seen from the figure that the alloy The evenly distributed ɑ-AlFeSi phase in the alloy can still be kept below 0.5 μm, and the alloy exhibits high thermal stability of the structure.

Example 2

The composition of the heat-resistant Al-Fe-Si aluminum alloy in Example 2 is calculated by mass percentage: 4.8% iron, 3% silicon, and the rest are Al and unavoidable impurities. According to the design ratio, pure aluminum, Al-10Fe, Al-20Si master alloys are melted and cast through the above process, vacuum sealed, and remelted at 800°C. After remelting, the quartz tube is clamped, and the samples are directly dropped into about 20°C. The water is chilled, and the alloy is cooled to room temperature in about 2s.

After chilling, the water-cooled sample is Al-Fe-Si aluminum alloy, and then the mechanical properties of the alloy are tested. The tensile strength of the obtained alloy is 244MPa, and the elongation is 16%.

Figure 4 is the SEM picture of the microstructure of Example 2, from which it can be seen that the iron-containing phases in the alloy are all fine eutectic ɑ-AlFeSi.

Example 3

The composition of the heat-resistant Al-Fe-Si aluminum alloy in Example 3 is calculated by mass percentage: 5% iron, 3.5% silicon, and the rest are Al and unavoidable impurities. Melt and cast pure aluminum, Al-10Fe, Al-20Si master alloys through the above process, vacuum seal the tube, and remelt at 800°C. , about 2s alloy is cooled to room temperature. After chilling, the water-cooled sample is Al-Fe-Si aluminum alloy. Afterwards, the mechanical properties of the Al-Fe-Si aluminum alloy were tested, and the tensile strength of the obtained alloy was 252MPa, and the elongation was 15%.

Figure 5 is the SEM picture of the microstructure of Example 3, from which it can be seen that the iron-containing phases in the alloy are all fine eutectic ɑ-AlFeSi.

Comparative example 1

The composition is 5% iron, 3% silicon, and the rest is Al and unavoidable impurities. Pure aluminum, Al-10Fe, and Al-20Si master alloys are smelted and cast through the above process to obtain as-cast samples, and the cooling rate of casting is ≦1°C/s. Afterwards, the mechanical properties of the alloy were tested, and the tensile strength of the obtained alloy was 126MPa, and the elongation was 1.6%.

Figure 6 shows the SEM picture of the microstructure of this comparative example. It can be seen from the figure that the alloy contains a large number of coarse flower-like/flaky Al ₁₃ Fe ₄ phases, which will cause stress concentration and damage the strength and Elongation. It can be seen from this comparative example that the cooling rate is important for the preparation of Al-ɑ-AlFeSi eutectic heat-resistant alloy.

Comparative example 2

The composition is 5% iron, 5% silicon, and the rest is Al and unavoidable impurities. Pure aluminum, Al-10Fe, Al-20Si master alloys were smelted and cast, vacuum-sealed, remelted and quenched according to the conditions of Example 1 to obtain water-cooled samples. Afterwards, the mechanical properties of the alloy were tested, and the tensile strength of the obtained alloy was 184MPa, and the elongation was 2%.

Figure 7 shows the SEM picture of the microstructure of the comparative example. It can be seen from the figure that the alloy with a higher silicon content contains a large amount of coarse flaky β-AlFeSi, which is a recognized harmful phase. The mechanical properties of the alloy are greatly damaged. This comparative example shows that in order to obtain the Al-ɑ-AlFeSi eutectic heat-resistant alloy, the composition should also be within a certain range, which is the best within the range required by this patent.

It should be pointed out that this patent aims to protect the composition that can obtain a complete Al-ɑ-AlFeSi eutectic alloy. The key to the preparation method is a high cooling rate, and the means to achieve rapid cooling include the use of water-cooled molds, die-casting, selective laser melting (3D printing, additive manufacturing), etc. As long as it is under the composition, it should be considered within the scope of protection of this patent.

Claims (5)

1. A preparation method of heat-resistant Al-Fe-Si aluminum alloy is characterized by comprising the following steps: the method comprises the following steps: the method comprises the following steps of (1) carrying out machining on an Al-Fe-Si alloy ingot to obtain an Al-Fe-Si alloy short rod, packaging the Al-Fe-Si alloy short rod in a vacuum quartz tube, remelting at 750-820 ℃, carrying out heat preservation for 20-40min to obtain a remelted Al-Fe-Si alloy, then clamping the quartz tube, directly dropping the remelted Al-Fe-Si alloy into cooling water, and carrying out chilling to obtain the Al-Fe-Si aluminum alloy, wherein the temperature of the cooling water is less than or equal to 20 ℃, and the chilling speed is greater than or equal to 300 ℃/s; in the Al-Fe-Si aluminum alloy, 100% of an iron-containing phase is eutectic alpha-AlFeSi, and the Al-Fe-Si aluminum alloy comprises the following components in percentage by mass: 4.5 to 5.5 percent of iron, 2.8 to 3.5 percent of silicon, and the balance of Al and inevitable impurities, wherein the total content of the impurities is less than or equal to 0.06 percent;

the microstructure of the Al-Fe-Si aluminum alloy is Al/alpha-AlFeSi eutectic cluster, and the diameter of the Al/alpha-AlFeSi eutectic cluster is 20-40 mu m;

the crystal grain of the eutectic alpha-AlFeSi is less than or equal to 200nm.

2. The method for preparing a heat-resistant Al-Fe-Si aluminum alloy according to claim 1, wherein: the remelting temperature is 780-800 ℃, and the heat preservation time is 20-40min.

3. The method for preparing the heat-resistant Al-Fe-Si aluminum alloy according to claim 1, comprising the following steps: the method for obtaining the Al-Fe-Si alloy cast ingot comprises the following steps: and (2) preparing an Al source, an Fe source and an Si source according to a designed proportion, smelting to obtain a melt, and casting and molding the melt to obtain the Al-Fe-Si alloy ingot.

4. The method for preparing a heat-resistant Al-Fe-Si aluminum alloy according to claim 1, wherein: the Al-Fe-Si aluminum alloy comprises the following components in percentage by mass: 4.8 to 5.5 percent of iron, 3.0 to 3.5 percent of silicon, and the balance of Al and inevitable impurities, wherein the total content of the impurities is less than or equal to 0.06 percent.

5. The method for preparing a heat-resistant Al-Fe-Si aluminum alloy according to claim 1, wherein: the tensile strength of the Al-Fe-Si aluminum alloy is 240-260MPa, and the elongation is 15-20%.

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