CN114574735A - Cu-containing high-strength corrosion-resistant Al-Mg-Si alloy and preparation method thereof - Google Patents

Abstract

A Cu-containing high-strength corrosion-resistant Al-Mg-Si alloy and a preparation method thereof, belonging to the technical field of non-ferrous metal alloys. The chemical element component of the alloy is Mg, and the weight percentage is 0.8 to 1.2 percent; 1.2 to 1.6 weight percent of Si; 0.05-0.6 wt% of Cu; 0.2 to 0.6 weight percent of Mn; 0.01-0.2 wt% of Er; 0.01 to 0.2 weight percent of Zr and the balance of Al. Obtaining an ingot by a casting method, carrying out two-stage homogenization heat treatment on the ingot, and keeping the temperature of the first stage at 300 +/-10 ℃ for 10 hours; the second stage is hot rolled at 535 +/-20 ℃ for 12h, and the deformation is 85%. Then solid solution aging treatment is carried out, and the aged alloy is subjected to a tensile test and a spalling corrosion test. The alloy obtained by the invention has higher strength and excellent corrosion resistance.

Description

A kind of Cu-containing high-strength corrosion-resistant Al-Mg-Si alloy and preparation method thereof

technical field

The invention relates to a Cu-containing high-strength corrosion-resistant Al-Mg-Si alloy and a preparation method thereof, belonging to the technical field of non-ferrous metal alloys.

Background technique

6XXX series aluminum alloys have low density, medium strength, good corrosion resistance and formability, and are widely used in aerospace, rail transit, automobile manufacturing and building materials industries. Mg and Si are the main alloying elements of this series of aluminum alloys, and the mass fractions of Mg and Si are generally lower than 1.5% and 1.8%, respectively. The sum of the two is lower than the maximum solid solubility of Mg ₂ Si of 1.85%. This type of aluminum alloy has good forging and extrusion deformation properties, and is a deformed aluminum alloy that can be strengthened by heat treatment. Precipitation strengthening is the main strengthening method of 6XXX series aluminum alloys, and Mg ₂ Si is the main strengthening phase of the alloy. Since the solubility of the Mg ₂ Si phase in the aluminum matrix decreases with the decrease of the temperature, the alloy has good age hardening ability. Therefore, the second phase dispersed and precipitated in the alloy can be controlled by heat treatment, so as to obtain a relatively high temperature. high strength. About 80% of the extrusion parts in the world are made of 6XXX series aluminum alloys.

The equilibrium atomic ratio of Mg and Si elements is 1.73:1. According to the research, each increase of 0.1% Mg ₂ Si can increase the peak strength of the alloy about 5MPa, and the elongation increases a little; for each increase of 0.1% primary Si, the peak aging tensile strength of the alloy increases by 10-15MPa. The greater the excess amount of Si, the higher the strength of the alloy. The presence of excess Si may lead to changes in the composition of the metastable phase, and the reduction of Mg/Si in local regions and clusters will increase the precipitation phase and strengthen the alloy. However, when 6XXX series aluminum alloys are solidified and crystallized, Si atoms are easily segregated on the grain boundaries to form a non-equilibrium eutectic structure, which affects the properties of the alloy. Therefore, rationally increasing the Si content and reducing Mg/Si can improve the strength and formability of the alloy. When the content of Si is excessive, the strength of the alloy is high, and it is easy to combine with the impurity element Fe to form an insoluble phase, which reduces the adverse effect of Fe on the properties of the alloy; when the content of Mg is excessive, although the corrosion resistance of the alloy is good, it will affect its strengthening effect. Therefore, in general, the Si content should be kept slightly higher than the Mg content.

Cu element is an important alloying element in this series of alloys, which has a certain solid solution strengthening effect on the alloy. In addition, Cu will accelerate the ageing hardening rate of the Al-Mg-Si-Cu alloy, increase the ageing hardness of the alloy, and reduce the over-aging softening process. This is because Cu will promote the nucleation of the GP region during the aging process, and change the types of precipitates during the aging process, making the precipitates more finely dispersed and more numerous. However, the presence of Cu is generally detrimental to the corrosion resistance of Al-Mg-Si alloys because the grain boundary chemistry is sensitive to the addition of Cu. It is generally believed that the intergranular corrosion of Al-Mg-Si alloys forms a potential difference with the β' phase, Q phase and other Mg, Si (or Cu)-rich grain boundary precipitation phases and the aluminum matrix to form a micro-couple, which leads to corrosion. The solute-depleted zone also forms a potential difference with the aluminum matrix, which leads to grain boundary corrosion.

Considering that adding excess Si and appropriate amount of Cu can improve the strength of 6XXX series aluminum alloys, and appropriate heat treatment process can further improve the comprehensive properties of alloys such as strength, corrosion resistance and formability. In the present invention, an appropriate amount of Cu element is added to the Al-Mg-Si alloy with excess Si, and a high-strength corrosion-resistant Al-Mg-Si aluminum alloy containing Cu is obtained through a suitable heat treatment process.

SUMMARY OF THE INVENTION

The invention relates to a high-strength, corrosion-resistant Al-Mg-Si alloy containing Cu and a preparation method thereof. By adjusting the addition amount of Cu and main alloy elements, optimizing the heat treatment process parameters, improving the mechanical properties of the alloy and improving the corrosion resistance of the alloy, In order to obtain an Al-Mg-Si aluminum alloy material containing Cu with high strength and good corrosion resistance.

The technical scheme of the present invention is:

A high-strength and corrosion-resistant Al-Mg-Si alloy containing Cu, characterized in that: Cu element is added to the Al-Mg-Si alloy with excess Si, and the chemical element composition of the alloy is Mg 0.8wt%-1.2wt%, Si 1.2wt% %-1.6wt%, Cu 0.05wt%-0.6wt%, Mn 0.2wt%-0.6wt%, Er 0.01wt%-0.2wt%, Zr 0.01wt%-0.2wt%, the balance is Al.

More preferably, the Cu element content is 0.2 wt % to 0.4 wt %, and more preferably, the Cu element content is 0.4 wt %.

The above-mentioned alloy preparation method comprises the following operation steps:

1) Smelting and casting: design alloys with different Cu contents, carry out ingredients according to the design components, obtain aluminum alloy ingots by melting and casting, and then perform cutting and milling on the aluminum alloy ingots;

2) Homogenization heat treatment: The homogenization heat treatment of aluminum alloy ingots includes two methods; the first method, single-stage homogenization heat treatment: 535 ℃ ± 20 ℃ for 6-24 hours; the second method, double-stage homogenization heat treatment : The first-level homogenization process is 300℃±20℃ for 8-12h, and the second-level homogenization process is 535℃±20℃ for 6-24h;

3) Hot rolling deformation: After the alloy undergoes homogenization heat treatment, the alloy is subjected to hot rolling deformation with 85% of the total deformation at a homogenization temperature of 535 ° C, and air-cooled to room temperature;

4) Solution and aging heat treatment: The hot-rolled alloy is subjected to solution treatment at 545°C ± 10°C for 20-120 minutes and then water quenched immediately, and then the alloy is immediately aged at 150°C-185°C for 0-48h.

Step 4) It is further preferred to perform water quenching immediately after solution treatment at 545°C for 30 minutes, and then the alloy is immediately aged at 155°C for 8-12 hours.

Under this condition, the tensile strength of the alloy at room temperature is not less than 380MPa, the yield strength is not less than 285MPa, the elongation is not less than 16%, and the exfoliation corrosion rating is above PC. The tensile strength of the optimal Cu content alloy at room temperature can reach 387MPa, the yield strength can reach 302MPa, the elongation can reach 19%, and the exfoliation corrosion rating is PC.

The beneficial effects of the present invention are:

1. The present invention makes full use of adding excess Si to increase the strength of the 6XXX series aluminum alloy, reasonably increase the Si content in the alloy, and improve the mechanical properties of the alloy.

2. Adding Cu element to the Al-Mg-Si alloy containing excess Si can accelerate the ageing hardening rate of the alloy, change the types of precipitates during the aging process, make the precipitates more fine and dispersed, and increase the number, and improve the mechanical properties of the alloy. . At the same time, the heat treatment parameters of the alloy are optimized to further improve the comprehensive properties of the alloy such as strength, corrosion resistance and formability.

3. The high-strength and corrosion-resistant Al-Mg-Si alloy containing Cu of the present invention has good deformation properties at high temperatures above 500 ° C, and the alloy is subjected to hot rolling deformation immediately after the homogenization heat treatment, which helps to further shorten the alloy production process. process, improve production efficiency, reduce production costs, and are conducive to the industrial application of alloys.

Detailed ways:

The present invention will be further described below with specific examples, and the following implementations are all implemented on the premise of the technical solutions of the present invention, but the protection scope of the present invention is not limited to the following examples and comparative examples.

Example 1

A low-content Cu alloy ingot was prepared. The mass fraction of each alloy element was Mg, 0.9%; Si, 1.5%; Cu, 0.2%; Mn, 0.4%; Er, 0.15%; Aluminum alloy ingots are cut and milled. The ingot is subjected to two-stage homogenization heat treatment. The two-stage homogenization process is: the first stage is kept at 300 °C for 8-12 hours; the second stage is kept at 535 °C for 12 hours. After the ingot undergoes homogenization heat treatment, it is then subjected to hot rolling deformation with 85% of the total deformation at a homogenization temperature of 535° C., and air-cooled to room temperature. The hot-deformed alloy was solution treated at 545°C for 30 minutes, water quenched, and aged at 155°C for 10 hours. Further preferably, the solution treatment at 545 °C for 30 min is immediately followed by water quenching, and then the alloy is immediately aged at 155 °C for 10 h.

The sheet of Example 1 was processed into a tensile specimen along the rolling direction, and the tensile test was carried out. The test temperature was 298K (room temperature), the temperature error was ±5K, and the tensile rate was 2 mm/min. The tensile test results are listed in 1. At the same time, the exfoliation corrosion test was carried out for Example 1 according to the GB/T 22639-2008 standard.

Example 2

A medium-content Cu alloy ingot was prepared. The mass fraction of each alloy element was Mg, 0.9%; Si, 1.5%; Cu, 0.4%; Mn, 0.4%; Er, 0.15%; Zr, 0.15%, and the balance was Al, which The steps are the same as in Example 1, and the tensile test results are listed in 1.

Example 3

A high-content Cu alloy ingot was prepared. The mass fraction of each alloy element was Mg, 0.9%; Si, 1.5%; Cu, 0.6%; Mn, 0.4%; Er, 0.15%; The steps are the same as in Example 1, and the tensile test results are listed in 1.

Comparative Example 1

Preparation of Cu-free alloy ingots, the mass fraction of each alloy element is Mg, 0.9%; Si, 1.5%; Mn, 0.4%; Er, 0.15%; , the tensile test results are listed in 1.

Table 1 Tensile properties and exfoliation corrosion ratings of Al-Mg-Si alloys with different Cu contents at room temperature

The above is a specific description of the preferred embodiments of the present invention, but the present invention is not limited to the embodiments, and those skilled in the art can make various equivalents without departing from the spirit of the present invention. Modifications or substitutions of these equivalent modifications or substitutions are all included within the scope defined by the claims of the present application.

Claims (6)

1. A high-strength and corrosion-resistant Al-Mg-Si alloy containing Cu, characterized in that: adding Cu element in the Al-Mg-Si alloy of excess Si, the alloy chemical element composition is Mg 0.8wt%-1.2wt%, Si 1.2wt%-1.6wt%, Cu 0.05wt%-0.6wt%, Mn 0.2wt%-0.6wt%, Er 0.01wt%-0.2wt%, Zr 0.01wt%-0.2wt%, and the balance is Al. 2 . The high-strength and corrosion-resistant Al-Mg-Si alloy containing Cu according to claim 1 , wherein the Cu element content is 0.2wt% to 0.4wt%. 3 . 3 . The high-strength and corrosion-resistant Al-Mg-Si alloy containing Cu according to claim 1 , wherein the Cu element content is 0.4 wt %. 4 . 4. the preparation method of the Cu-containing high-strength corrosion-resistant Al-Mg-Si alloy described in any one of claims 1-3, is characterized in that: comprises the following operation steps: 1) Smelting and casting: design alloys with different Cu contents, carry out ingredients according to the design components, obtain aluminum alloy ingots by melting and casting, and then perform cutting and milling on the aluminum alloy ingots; 2) Homogenization heat treatment: The homogenization heat treatment of aluminum alloy ingots includes two methods; the first method, single-stage homogenization heat treatment: 535 ℃ ± 20 ℃ for 6-24 hours; the second method, double-stage homogenization heat treatment : The first-level homogenization process is 300℃±20℃ for 8-12h, and the second-level homogenization process is 535℃±20℃ for 6-24h; 3) Hot rolling deformation: After the alloy undergoes homogenization heat treatment, the alloy is subjected to hot rolling deformation with 85% of the total deformation at a homogenization temperature of 535 ° C, and air-cooled to room temperature; 4) Solution and aging heat treatment: The hot-rolled alloy is subjected to solution treatment at 545°C ± 10°C for 20-120 minutes and then water quenched immediately, and then the alloy is immediately aged at 150°C-185°C for 0-48h. 5. The method according to claim 4, characterized in that, in step 4), water quenching is performed immediately by solution treatment at 545° C. for 30 minutes, and then the alloy is immediately aged at 155° C. for 8-12 hours. 6. The method according to claim 4 or 5, characterized in that the tensile strength of the alloy at room temperature is not less than 380MPa, the yield strength is not less than 285MPa, the elongation is not less than 16%, and the exfoliation corrosion rating is in PC above. The tensile strength of the optimal Cu content alloy at room temperature can reach 387MPa, the yield strength can reach 302MPa, the elongation can reach 19%, and the exfoliation corrosion rating is PC.