CN112501482B - Si microalloyed AlZnMgCu alloy and preparation method thereof - Google Patents

Abstract

A Si microalloyed AlZnMgCu alloy and a preparation method thereof belong to the field of high-strength Al-Zn-Mg-Cu alloys, and contain the following alloy components: 4.0wt%-5.0wt% of zinc, 1.0wt%-2.0wt% of zinc Magnesium, 0.5%-1.5wt% copper, 0.15wt%-0.5wt% silicon, no more than 0.2wt% unavoidable inclusions, and the rest are aluminum. The invention adopts Si micro-alloying and aging treatment (two methods of single-stage aging treatment or double-stage aging treatment), which has significant aging strengthening effect, improves the corrosion resistance of the alloy, and the alloy strength after hot rolling has further improvement. The purpose of this patent is to improve the strength and corrosion resistance of Al-Zn-Mg-Cu alloy.

Description

A kind of Si microalloyed AlZnMgCu alloy and preparation method thereof

technical field

The invention belongs to the technical field of metal alloys, and relates to a microalloyed aluminum alloy material and a preparation process thereof.

technical background

Al-Zn-Mg-Cu alloy (7xxx series) high-strength aluminum alloy is a heat-treatable strengthened aluminum alloy, which has the advantages of low density, high strength and good processing performance, and is widely used in aviation and civil industries. However, the balance of its strength and corrosion performance has not been well resolved. Therefore, the present invention aims at this problem and optimizes the alloy composition to produce a new high-strength aluminum alloy with both high strength and good corrosion resistance.

The strength and corrosion resistance of Al-Zn-Mg-Cu alloy are mainly affected by the three microstructures of matrix precipitation, grain boundary precipitation and no precipitation zone near grain boundary. The small and dense matrix precipitates (MPt) in the alloy can significantly strengthen the alloy, but the continuous grain boundary phase formed at the same time leads to high corrosion susceptibility. In order to improve the strength and corrosion resistance of the alloy, it is necessary to make the matrix precipitate phase (MPt) of the alloy fine and dispersed, and at the same time make the grain boundary precipitate phase (GBP) coarse and discontinuous distribution. The present invention attempts to add Si to 7xxx aluminum alloys, hoping that Si can stabilize the intragranular precipitation phase under high temperature or long-term heat treatment conditions, maintain a higher strength of the alloy, and at the same time make the grain boundary precipitation phase (GBP) discontinuous to improve Alloy corrosion resistance.

Based on the above considerations, the present invention designs an Al-Zn-Mg-Cu-Si alloy, and determines the suitable composition range and corresponding preparation process of the alloy.

SUMMARY OF THE INVENTION

The purpose of the present invention is to invent a kind of Si microalloyed AlZnMgCu alloy and its preparation method. The preparation method of the alloy is to add cheap Si element to the AlZnMgCu alloy, and through a special aging process, the intragranular precipitation phase of the alloy is stabilized under high temperature or long-term heat treatment conditions, maintaining the high strength of the alloy, while making the crystal The boundary precipitation phase is discontinuous to improve the corrosion resistance of the alloy.

In the alloy of the present invention, the mass percentages of Zn, Mg and Cu in the alloy are preferably: Zn: 4.0wt%-5.0wt%; Mg: 1.0wt%-2.0wt%; Cu: 0.5wt%-1.5wt%; Si : 0.15wt%-0.5wt%, the balance is Al.

The present invention is realized by the following technical solutions: a preparation method of Si microalloyed AlZnMgCu alloy, the method comprises the following steps: (1) adopting graphite crucible smelting and iron mold casting to prepare AlZnMgCuSi alloy ingot; (2) preparing the alloy for 450℃～500℃, 13h～15h homogenization annealing treatment; (3) hot rolling the alloy after homogenization annealing; (4) hot rolling the alloy after 500℃～550℃, 0.5h～1.5h Solution treatment followed by artificial aging. There are two artificial aging processes. The first is to age the alloy at 125°C for 12h to 48h, and then perform the second-stage aging at 175°C for 3h to 12h; the second is to age the alloy at 125°C to 225°C. Grade aging 0.5h ~ 120h.

Step (1) The raw material is placed in a smelting furnace, and the smelting temperature is 770 ℃～790 ℃, after reaching the temperature, the temperature is kept for standing, so that the components of each element in the melt are evenly distributed, and then casting is performed to obtain the desired alloy ingot.

Step (3) Process parameters of hot rolling: the alloy after homogenization and annealing is first kept at 450±10° C., and then rolled, with a deformation amount of 75% to 95%.

The single-stage aging of artificial aging is: single-stage aging treatment between 175 ℃ ~ 225 ℃ for 1h ~ 10h.

In the present invention, Si element is compounded in the AlZnMgCu alloy, and under a special aging process, the intragranular precipitation phase of the alloy is stabilized under high temperature or long-term heat treatment conditions, the alloy has a high strength, and at the same time, the grain boundary precipitation phase is not affected. Continuously thereby improving the corrosion resistance of the alloy. The problem of unbalanced strength and corrosion resistance of AlZnMgCu alloy is solved.

In the method of the present invention, the price of Si element is relatively cheap, and the adopted aging process is simple, which is suitable for industrial production.

Description of drawings:

Figure 1: Microhardness curves of alloys artificially aged at 125°C.

Figure 2: Microhardness curves obtained from alloys artificially aged at 175°C.

Figure 3: Microhardness curves of alloys artificially aged at 225°C.

Fig. 4: Microhardness curves obtained by artificial ageing at 175°C after the alloy was artificially aged at 125°C for 24h.

Figure 5a: Photo of intergranular corrosion of Al-4.5Zn-1.5Mg-1.0Cu alloy after hot rolling in 540 solution, 1h at 125°C for 24h and 24h at 175°C.

Fig. 5b: Photo of intergranular corrosion of Al-4.5Zn-1.5Mg-1.0Cu-0.35Si alloy after hot rolling in 540 solution, 1h, 125℃ and 24h, 175℃ and 24h aging.

Detailed ways:

The following examples are set to further illustrate the present invention, but the present invention is not limited to the following examples.

Example 1 (i.e. comparative example):

The alloy ingots were prepared by graphite crucible melting and iron mold casting. The raw materials used were pure aluminum, pure zinc, pure magnesium and Al-50Cu, Al-24Si master alloys, and the melting temperature was 780±10℃. After reaching the smelting temperature, it is held for 30 minutes and then cast in an iron mold. The alloys Al4.5Zn1.5Mg1.0Cu and Al4.5Zn1.5Mg1.0Cu0.35Si were prepared and their actual compositions were determined by XRF (refer to Table 1). The two alloys were annealed at 500℃/15h for homogenization and then water quenched to room temperature, then heated to 450℃ for rolling (deformation 90%). Solution was carried out at 540 °C for 1 hour, water quenched to room temperature, and then single-stage aging was carried out at 125 °C to obtain the aging hardness curves of the two alloys (refer to Figure 1). There is no obvious strengthening effect on the age hardening of the alloy.

Table 1: Composition table of alloys measured by XRF

Example 2: Al4.5Zn1.5Mg1.0Cu, Al4.5Zn1.5Mg1.0Cu0.15Si and Al4.5Zn1.5Mg1.0Cu0.35Si were prepared by the same method as in Example 1 (refer to Table 1 for the actual composition). The three alloys were annealed at 500℃/15h for homogenization, then water quenched to room temperature, and then heated to 450℃ for rolling (deformation 90%). The solution was carried out at 540 °C for 1 hour, water quenched to room temperature, and then single-stage aging was carried out at 175 °C to obtain the aging hardness curves of the three alloys (refer to Figure 2). From Figure 2, it can be seen that with the increase of Si content , the age hardening peak value of the alloy is getting higher and higher, and the peak value is getting slower and slower (the hardness peaks of alloys without Si, 0.15Si, and 0.35Si are 117.7HV, 129.6HV, 148.9HV respectively), and the hardness after reaching the peak value The decline is getting faster and faster. It shows that the strengthening effect of Si element becomes obvious after aging at a medium temperature of 175 ℃.

Example 3: Al4.5Zn1.5Mg1.0Cu and Al4.5Zn1.5Mg1.0Cu0.35Si were prepared by the same method as in Example 1 (refer to Table 1 for the actual composition), and the two alloys were homogenized at 500°C/15h After annealing, water quenched to room temperature, and then heated to 450 ℃ for rolling (deformation 90%). The solid solution was carried out at 540 °C for 1 hour, water quenched to room temperature, and then single-stage aging was carried out at 225 °C to obtain the aging hardness curves of the two alloys (refer to Figure 3). From Figure 3, we can see the aging hardening of Si to the alloy. effect is more obvious. And with the increase of Si content, the age hardening peak value of the alloy increases, and the hardness decreases slowly after reaching the peak value. Two alloys, Al4.5Zn1.5Mg1.0Cu and Al4.5Zn1.5Mg1.0Cu0.35Si, were tested for intergranular corrosion and exfoliation corrosion at the peak state of single-stage aging hardness at 225℃ (1h and 3h, respectively). The intergranular corrosion performance of the alloy is better than that of the alloy without Si. It shows that the strengthening effect of Si can make the hardness and corrosion resistance of Al4.5Zn1.5Mg1.0Cu alloy reach a better balance only under high temperature single-stage aging.

Example 4: Al4.5Zn1.5Mg1.0Cu and Al4.5Zn1.5Mg1.0Cu0.35Si alloys were prepared by the same method as in Example 1 (refer to Table 1 for the actual composition), and the two alloys were homogenized at 500°C/15h After annealing, water quenched to room temperature, and then heated to 450 ℃ for rolling (deformation 90%). Carry out solid solution at 540 °C for 1 hour, quench with water to room temperature, and then first age at 125 °C to obtain the aging hardness curves of the two alloys. Aging hardness curve (refer to Figure 4). It can be seen that the hardness of the alloy without Si shows a decreasing trend during the second-stage aging, while the hardness of the alloy containing Si shows a trend of first increasing and then decreasing, indicating that the addition of Si can make the alloy further increase in hardness after double-aging. promote. The intergranular corrosion and exfoliation corrosion performance tests of the two alloys were carried out in the 24h aging state of secondary aging, and it was found that the Si-containing alloy had better intergranular corrosion performance (refer to Figure 5a and Figure 5b) and exfoliation corrosion performance than the Si-free alloy. . It shows that Si can make the hardness and corrosion resistance of Al4.5Zn1.5Mg1.0Cu alloy reach a good balance under double-stage aging.

Claims (3)

1. a Si microalloyed aluminum-zinc-magnesium-copper alloy, characterized in that it contains the following alloy components: 4.0wt%-5.0wt% zinc, 1.0wt%-2.0wt% magnesium, 0.5%-1.5wt% % copper, 0.15wt%-0.5wt% silicon, the balance is Al; The preparation method includes the following steps: (1) using graphite crucible smelting and iron mold casting to prepare an AlZnMgCuSi alloy ingot; (2) performing homogenization annealing treatment on the alloy at 450° C. to 500° C. for 13 h to 15 h; (3) uniformly annealing the alloy The alloy after chemical annealing is subjected to hot rolling; (4) the alloy after hot rolling is subjected to solution treatment at 500 ℃ ~ 550 ℃ for 0.5h ~ 1.5h, and then artificial aging; there are two artificial aging processes, the first one The alloy is aged at 125°C for 12h~48h, and then the second stage is aged at 175°C for 3h~12h; the second is the single-stage aging at 125°C~225°C for 0.5h~120h; Step (3) Process parameters of hot rolling: the alloy after homogenization annealing is firstly kept at 450±10° C., and then rolled, with a deformation amount of 75% to 95%. 2. The aluminum-zinc-magnesium-copper alloy of a kind of Si microalloying according to claim 1, it is characterized in that, (1) ingot preparation process is as follows: raw material is placed in melting furnace, melting temperature is 770 ℃～790 ℃ ℃, after reaching the temperature, keep the temperature and let it stand, so that the components of each element in the melt are evenly distributed, and then cast to obtain the desired alloy ingot. 3. A kind of Si microalloyed aluminum-zinc-magnesium-copper alloy according to claim 1, characterized in that, the single-stage aging temperature range is between 175 ~ 225 ℃, and the aging is 1h ~ 10h in this temperature interval.

Images