CN103225028A - Al-Er-Zr-Si heat-resistant aluminum alloy and its heat treatment technology - Google Patents

Abstract

The invention relates to an Al-Er-Zr-Si heat-resistant aluminum alloy and its heat treatment technology, and belongs to the technical field of alloys. 0.05-0.25wt% of Er, 0.2-0.3wt% of Zr, 0.01-0.2wt% of Si and other inevitable impurities are added to a pure aluminum matrix. The solid solution ageing heat treatment technology of the alloy comprises a step of solid solution at 630-650DEG C for 20-30h, a step of water quenching to room temperature, and a step of isothermal ageing at 350DEG C. The Al-Er-Zr-Si heat-resistant aluminum alloy has a very substantial ageing reinforcement effect because of the composite micro-alloying of Er, Zr and Si, has a higher ageing reinforcement speed and a higher peak value hardness than an Al-Er-Zr alloy, and has a good heat resistance.

Description

A kind of Al-Er-Zr-Si heat-resistant aluminum alloy and its heat treatment process

technical field

The invention relates to a micro-alloyed aluminum alloy material and a heat treatment process thereof, belonging to the technical field of metal alloys.

technical background

Heat-resistant aluminum alloy means that it has sufficient oxidation resistance at high temperature and has resistance to plastic deformation (creep) and damage, good thermal conductivity and low density under long-term action of temperature and load (dynamic and static). features. It is widely used in weapons, ships, aviation, aerospace, automobile and other industries, such as pistons, cylinder liners, connecting rods, boxes, cylinder heads of tank armored vehicle engines, missile shells, empennages, aeroengine cylinders, blades, aircraft covers leather etc.

The key to improving the heat resistance of aluminum alloys is to precipitate and form a large number of dispersed thermally stable precipitates in the alloy (it grows slowly and coarsens slowly under higher temperature conditions, and some structural transformations occur). In recent years, a large number of scholars at home and abroad have done a lot of research on the role of rare earth elements in the heat resistance of aluminum alloys. These studies mainly focus on the effects of La, Ce, Y, Sc, Zr and mixed rare earths on aluminum alloys, among which the rare earth element Sc is the most in-depth research, in Al-Si system, Al-Zn-Mg system and Al-Mg system, etc. The addition of Sc to aluminum alloys has achieved satisfactory research results. However, the addition of Sc greatly increases the production cost of aluminum alloys, which limits the industrial application of Sc-containing aluminum alloys. Adding Er to the aluminum alloy can generate the Al ₃ Er phase with the same L1 ₂ structure as Al ₃ Sc, which can increase the recrystallization temperature of the aluminum alloy, and can effectively play a positive role in fine grain strengthening and dispersion strengthening. , Improve the comprehensive performance of aluminum alloy. Moreover, the price of Er is relatively cheap. Adding a small amount of Er element in aluminum alloy will not greatly increase the production cost, and can be widely used in industrial production.

However, the solid solubility of Er in aluminum alloys is limited during the solidification process of conventional ingot metallurgy, which limits the further improvement of its effect. It is possible to increase the precipitation density by adding other alloying elements capable of forming L1 ₂ structure precipitates, thereby further exerting the effect of alloying. In addition to Sc, Zr is an alloying element that can form metastable L1 ₂ structure precipitates. After Zr and Er composite microalloying, it is possible to make the precipitates maintain a stable L12 structure under the induction of Al ₃ Er phase, and It can hinder the growth and coarsening of the Al ₃ Er phase, so good strengthening effect and thermal stability can be obtained. For example, an Al-Er-Zr alloy described in the invention patent ZL201010515843.7 has a significant aging strengthening effect. However, the precipitation process of Zr itself is very slow, especially when the composition is low, it takes thousands of hours to fully separate out. The addition of Si can promote the precipitation of Zr, so the combination of Er, Zr and Si may give full play to their respective effects , Play a better microalloying effect. The present invention designs the Al-Er-Zr-Si alloy based on the above considerations, and seeks its suitable composition range and corresponding heat treatment process.

Contents of the invention

The purpose of the present invention is to find out the law of Er, Zr and Si synergistically exerting strengthening effect through the method of composite microalloying, so as to improve the performance of aluminum alloy.

The Al-Er-Zr-Si heat-resistant aluminum alloy provided by the present invention is characterized in that 0.05-0.25% (weight percentage) of Er, 0.2-0.3% (weight percentage) of Zr, 0.01 ~0.2% (weight percent) of Si, and other unavoidable impurities.

It is further preferred that 0.15-0.25% (weight percent) of Er, 0.25-0.3 (weight percent) of Zr, and 0.05-0.15 (weight percent) of Si are added to the pure aluminum matrix.

The preparation method of the alloy is realized by adding AlEr and AlZr intermediate alloys in the process of smelting aluminum, or further adding aluminum-silicon alloys to adjust the elements of the alloys. The melting temperature is 780±10°C. Cast in iron molds.

The cast ingot is then subjected to solid solution aging heat treatment, and the process includes the following steps: firstly solid solution at 630±10°C for 20 to 30 hours, then water quenched to room temperature, and then isothermally aged at 350°C. Preferably, the holding time for isothermal aging at 350° C. is 10 minutes to 1000 hours, more preferably 1 to 100 hours.

Because the present invention has adopted Er, Si and Zr composite micro-alloying, there is very remarkable and faster aging strengthening effect, as shown in accompanying drawing 1, Al-0.2Er-0.28Zr-0.1Si (S3 sample) and Al Compared with Al-Er-Zr (S1, S2) alloy, -0.2Er-0.28Zr-0.2Si (S4 sample) improves the speed of aging strengthening effect and peak hardness, and the alloy has good heat resistance.

Description of drawings

Figure 1: 350°C isothermal aging curve;

Figure 2: Short-term (1h) heat resistance curve of S4 alloy;

Figure 3: High-temperature compressive strength of S4 alloy in solid solution state and aging state.

Detailed ways

Example 1: The alloy ingot is prepared by melting in a graphite crucible and casting in an iron mold. The raw materials used are pure aluminum and Al-6Er, Al-4Zr, Al-20Si master alloy, and the melting temperature is 780±10°C. After reaching the melting temperature, keep it warm for 30 minutes, and then cast it with an iron mold. Five alloys with different design compositions were prepared, and their actual compositions were tested by XRF, as shown in Table 1 below.

Table 1 Experimental alloy composition

sample Design composition (wt.%) Er actual composition The actual composition of Zr Si actual composition

(wt.%) (wt.%) (wt.%) S1 Al-0.2Er-0.15Zr 0.18 0.20 0.01 S2 Al-0.2Er-0.28Zr 0.21 0.30 0.01 S3 Al-0.2Er-0.28Zr-0.1Si 0.25 0.29 0.11 S4 Al-0.2Er-0.28Zr-0.2Si 0.19 0.28 0.15 S5 Al-0.1Er-0.28Zr-0.2Si 0.05 0.30 0.20

Example 2: The alloy in Example 1 was solid-dissolved at 640±10°C for 20 hours, water quenched to room temperature, and then aged at 350°C. Figure 1 shows the hardness change curve of isothermal aging. It can be seen from the figure that the maximum hardness values of samples S3 and S4 are higher than those of sample S2, and the time to reach the peak hardness is faster than that of sample S2. Although the Er and Zr components of S2, S3, and S4 are relatively close, Si is added to S3 and S4 relative to S2, and 0.01% of Si in S2 is an impurity in pure aluminum. This shows that the compound addition of Er, Zr and Si can accelerate the formation process of precipitates, and can increase the density of precipitates so as to improve the hardness of the alloy.

Example 3: Homogenize alloy S4 in Example 1 at 635±10°C for 20 hours, water quench to room temperature, and then age at 350°C for 100 hours, and then use cold rolling to roll with a deformation of 70%; rolling After annealing at 200-600°C for 1 hour, the change in hardness is shown in Figure 2. It can be seen that within the temperature range of 200-375°C, the hardness of the alloy hardly decreases significantly, and the hardness of the alloy decreases significantly at temperatures above 375°C. It shows that the recrystallization temperature of the alloy is about 400℃, and it has good heat resistance.

Example 4: Homogenize alloy S4 in Example 1 at 635±10°C for 20 hours, water quench to room temperature, and then age at 350°C for 100 hours. ), the test temperature is 300°C, the strain rate strain rate range is 10 ^-3 -50s ^-1 , the sample is heated up to the test temperature at a heating rate of 5°C/s, kept for 3 minutes, and then begins to deform, the total compression strain is 0.6 . Its high-temperature compressive strength in solid solution state and aging state is shown in Figure 3. It can be seen that at 300 °C and at the same strain rate, the flow stress of the S4 aging state alloy is higher than that of the S4 solid solution state alloy, that is, the high temperature strength of the S4 aging state alloy is higher than that of the S4 aging state alloy. S4 solid solution alloy.

Claims (6)

1. Al-Er-Zr-Si heat-resisting aluminium alloy, it is characterized in that, added the 0.05-0.25%(weight percent in the pure aluminum substrate) Er, the 0.2-0.3%(weight percent) Zr, the 0.01-0.2%(weight percent) Si, and other unavoidable impurities.

2. a kind of Al-Er-Zr-Si heat-resisting aluminium alloy of claim 1 is characterized in that, has added 0.15～0.25%(weight percent in the pure aluminum substrate) Er, 0.25～0.3%(weight percent) Zr, 0.05～0.15%(weight percent) Si.

3. the method for preparing the described aluminium alloy of claim 1, it is characterized in that, adding AlEr and AlZr master alloy are realized in the process of melting aluminium, or further add aluminum silicon alloy, regulate the element of alloy, smelting temperature is 780 ± 10 ℃, arrives behind the smelting temperature insulation 30 minutes, then with the swage casting and carry out solid-solution and aging heat treatment.

4. claim 1 Al-Er-Zr-Si heat-resisting aluminium alloy solid-solution and aging heat treatment method is characterized in that: at first at 630 ± 10 ℃ of solid solution 20-30 hours, shrend subsequently is to room temperature, then at 350 ℃ of isothermal agings.

5. according to the method for claim 4, it is characterized in that the soaking time of 350 ℃ of isothermal agings 10 minutes-1000 hours.

6. according to the method for claim 4, it is characterized in that the soaking time 1-100 of 350 ℃ of isothermal agings hour.

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