阅读说明：本技术 一种耐热稀土铝合金及其制备方法 (Heat-resistant rare earth aluminum alloy and preparation method thereof ) 是由 隋来智 程仁寨 隋信磊 马旭 张小刚 王兆斌 陈吉龙 郑卓阳 于 2019-09-23 设计创作，主要内容包括：本发明提供一种耐热稀土铝合金及其制备方法,主要涉及合金技术领域。一种耐热稀土铝合金,由以下质量百分比的组分组成：5~6%Zn；2~3%Mg；1~2%Cu；0.3~0.5%Gd；0.1~0.2%Nd；杂质元素总量小于0.1%,余量为Al。制备方法为各组分经过加热熔化,浇铸和热处理。本发明的有益效果在于：本发明的稀土铝合金Al-Zn-Mg-Cu-Gd-Nd具有良好的综合力学性能,经固溶处理和时效处理后具有强度高、塑性好,各项性能相对稳定的特点,能够满足其在航空航天、军工、汽车及其它行业中的要求。(The invention provides a heat-resistant rare earth aluminum alloy and a preparation method thereof, and mainly relates to the technical field of alloys, wherein the heat-resistant rare earth aluminum alloy comprises the following components, by mass, 5 ~ 6% of Zn, 2 ~ 3% of Mg, 1 ~ 2% of Cu, 0.3 ~ 0.5.5% of Gd, 0.1 ~ 0.2.2% of Nd, less than 0.1% of impurity elements, and the balance Al..)

1. The heat-resistant rare earth aluminum alloy is characterized by comprising, by mass, 5 ~ 6% of Zn, 2 ~ 3% of Mg, 1 ~ 2% of Cu, 0.3 ~ 0.5.5% of Gd, 0.1 ~ 0.2.2% of Nd, less than 0.1% of impurity elements and the balance of Al.

2. The heat-resistant rare earth aluminum alloy according to claim 1, wherein the sum of the mass percentages of Nd and Gd in the composition is 0.4 ~ 0.7.7%.

3. The heat-resistant rare earth aluminum alloy as set forth in claim 1, wherein the metallographic structure of the heat-resistant rare earth aluminum alloy is mainly composed of an α -Al matrix and eutectic (α -Al + β -Al)₂Mg₃Zn₃+β-Al₂Cu).

4. The preparation method of the heat-resistant rare earth aluminum alloy is characterized by comprising the following steps of:

① mixing pure Al, pure Zn, pure Cu and intermediate alloys Mg-30Gd and Mg-25Nd as raw materials according to the proportion and preheating;

② heating and melting aluminum, zinc, copper and magnesium, adding intermediate alloys Mg-30Gd and Mg-25Nd at 700 ~ 720 ℃, and keeping the temperature;

③ when the materials are completely melted, heating to 750 ~ 770 deg.C and stopping heating;

④, when the temperature is reduced to 680 ~ 710 ℃, casting to obtain as-cast aluminum alloy;

⑤ the heat-resistant rare earth aluminum alloy is obtained after the heat treatment of the as-cast aluminum alloy.

5. The method of claim 4, wherein the preheating temperature of step ① is 120 ~ 150 ℃ C.

6. The method according to claim 4, wherein the casting step ④ is further performed by preheating the mold to 200 ~ 250 ℃.

7. The method of claim 4, wherein the heat treatment of step ⑤ is performed by subjecting the obtained as-cast aluminum alloy to solution treatment and aging treatment in this order.

8. The method of claim 7, wherein the solution treatment temperature is 450 ~ 550 ℃, the treatment time is 6 ~ 16 hours, and the aging treatment temperature is 150 ~ 250 ℃, the treatment time is 12 ~ 24 hours.

9. The aluminum alloy produced by the method according to any one of claims 4 to 8, which comprises, in mass%, 5 ~ 6% Zn, 2 ~ 3% Mg, 1 ~ 2% Cu, 0.3 ~ 0.5.5% Gd, 0.1 ~ 0.2.2% Nd, less than 0.1% of impurity elements, and the balance Al.

Technical Field

The invention mainly relates to the technical field of alloys, in particular to a heat-resistant rare earth aluminum alloy and a preparation method thereof.

Background

Aluminum is a light metal structure material and is increasingly applied in the fields of aerospace, war industry, automobiles and the like, but the application of aluminum alloy in the fields of aerospace, war industry, automobiles and other industries is seriously influenced due to poor strength and heat resistance of the aluminum alloy, so that the improvement of the strength and the heat resistance of the aluminum alloy is an important subject for developing the aluminum alloy material.

The existing heat-resistant aluminum alloy is developed mainly by starting from limiting dislocation movement and strengthening grain boundaries, and improving the strength and heat resistance of the aluminum alloy by means of introducing a second phase with high heat stability, reducing the diffusion rate of elements in an aluminum matrix, improving the structure state and the structure form of the grain boundaries and the like through proper alloying.

China has abundant rare earth resources, and the research on rare earth aluminum alloys is increasing and deepening in recent years. So far, a plurality of defects still exist in the design, preparation and application processes of the rare earth aluminum alloy: firstly, the content of rare earth elements has a great influence on various properties of the final rare earth aluminum alloy and is difficult to control. The rare earth with too little amount is not enough to improve the heat resistance of the alloy, and the rare earth with too high amount can generate impurities due to the reaction of the rare earth with oxygen and hydrogen, and is easy to generate heat crack in the casting process. Secondly, there are many rare earth elements to choose from, and the interaction between many rare earth elements is complicated. At present, the types of the heat-resistant rare earth aluminum alloy which can be selected for practical application are few, and the high-temperature performance of the heat-resistant rare earth aluminum alloy can not completely meet the requirements of the heat-resistant rare earth aluminum alloy in aerospace, military industry, automobiles and other industries.

Disclosure of Invention

The rare earth aluminum alloy Al-Zn-Mg-Cu-Gd-Nd has good comprehensive mechanical properties, has the characteristics of high strength, good plasticity and relatively stable performance after solution treatment and aging treatment, and can meet the requirements of the rare earth aluminum alloy in aerospace, military industry, automobiles and other industries.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a heat-resistant rare earth aluminum alloy comprises, by mass, 5 ~ 6% of Zn, 2 ~ 3% of Mg, 1 ~ 2% of Cu, 0.3 ~ 0.5.5% of Gd, 0.1 ~ 0.2.2% of Nd, less than 0.1% of impurity elements, and the balance of Al.

Preferably, the sum of the mass percentages of Nd and Gd in the heat-resistant rare earth aluminum alloy is 0.4 ~ 0.7.7%.

Preferably, the metallographic structure of the heat-resistant rare earth aluminum alloy mainly comprises an alpha-Al matrix and eutectic (alpha-Al + beta-Al)₂Mg₃Zn₃+β-Al₂Cu).

A preparation method of heat-resistant rare earth aluminum alloy comprises the following steps:

① mixing pure Al, pure Zn, pure Cu and intermediate alloys Mg-30Gd and Mg-25Nd as raw materials according to the proportion and preheating;

② heating and melting aluminum, zinc, copper and magnesium, adding intermediate alloys Mg-30Gd and Mg-25Nd at 700 ~ 720 ℃, and keeping the temperature;

③ when the materials are completely melted, heating to 750 ~ 770 deg.C and stopping heating;

④, when the temperature is reduced to 680 ~ 710 ℃, casting to obtain as-cast aluminum alloy;

⑤ the heat-resistant rare earth aluminum alloy is obtained after the heat treatment of the as-cast aluminum alloy.

Preferably, the pre-heating temperature of step ① is 120 ~ 150 ℃.

Preferably, the casting described in step ④ further requires preheating the mold to 200 ~ 250 ℃.

Preferably, the heat treatment method of step ⑤ is to subject the obtained as-cast aluminum alloy to solution treatment and aging treatment in sequence.

Preferably, the treatment temperature of the solution treatment is 450 ~ 550 ℃, the treatment time is 6 ~ 16 hours, and the treatment temperature of the aging treatment is 150 ~ 250 ℃, and the treatment time is 12 ~ 24 hours.

Preferably, the aluminum alloy prepared by the preparation method of the heat-resistant rare earth aluminum alloy comprises, by mass, 5 ~ 6% of Zn, 2 ~ 3% of Mg, 1 ~ 2% of Cu, 0.3 ~ 0.5.5% of Gd, 0.1 ~ 0.2.2% of Nd, less than 0.1% of the total amount of impurity elements, and the balance of Al.

Compared with the prior art, the invention has the following substantial effects:

the rare earth aluminum alloy comprises the components of Al-Zn-Mg-Cu-Gd-Nd. At present, rare earth elements are the most effective alloy elements for improving the heat resistance of aluminum alloy, besides the effects of degassing, removing impurities, improving casting fluidity and corrosion resistance, most of the rare earth elements have higher solid solubility in aluminum, and the solid solubility is sharply reduced along with the reduction of temperature, so that supersaturated aluminum alloy solid solution can be obtained, and dispersed high-melting-point rare earth phases are precipitated in the artificial aging process. The rare earth elements can also refine crystal grains and improve the room temperature strength, and the dispersed high-melting point rare earth compounds which are distributed in the crystal interior and in the crystal boundary are mainly the crystal boundary can pin the crystal interior dislocation and the crystal boundary slippage at high temperature, thereby improving the high temperature strength of the aluminum alloy. Meanwhile, the diffusion rate of the rare earth element in the aluminum matrix is slow, so that the rare earth aluminum alloy is suitable for long-term operation in a high-temperature environment. The maximum solid solubility of heavy rare earth Gd adopted by the invention in aluminum is 0.82%, which is an element with larger solid solubility in rare earth elements. In the aluminum-rare earth binary alloy, the high-temperature strength and creep property of the Al-Gd alloy are most obvious, and the precipitation equilibrium phase in the alloy is Al₂Gd has higher melting point and generates better strengthening effect on the room-temperature and high-temperature mechanical properties of the aluminum alloy; the Nd element added into the aluminum alloy can generate a synergistic effect with the main strengthening element Gd, so that the main strengthening element can generate a better strengthening effect on the room-temperature and high-temperature mechanical properties of the aluminum alloy.

Zinc, magnesium and copper are important alloy elements in the aluminum alloy, the zinc and the magnesium have larger solid solution capacity in an aluminum matrix, the solid solution capacity is respectively 12.7wt% and 8.3wt%, and the beta-Al is formed after the zinc and the magnesium are added into the aluminum matrix₂Mg₃Zn₃、β-Al₂Cu phase in the form of dissimilarity eutectic, and Zn, Mg and Cu are used for strengthening in Al alloyThe effect is mainly embodied in two aspects, namely, the beta-Al is formed₂Mg₃Zn₃、β-Al₂The second phase of the Cu phase is strengthened, and the second phase is the solid solution strengthening of zinc and magnesium atoms in an aluminum matrix. But too high a content of beta-Al₂Mg₃Zn₃、β-Al₂The Cu phase affects the heat resistance of the aluminum alloy, so the content of zinc and magnesium in the aluminum alloy is controlled below 6wt%, while the content of zinc and magnesium which are too low can damage the casting performance of the aluminum alloy, and the content of zinc and magnesium should not be lower than 5 wt%.

Based on this, the beneficial effects of the invention are as follows:

the rare earth aluminum alloy Al-Zn-Mg-Cu-Gd-Nd has good comprehensive mechanical property, has the characteristics of high strength, good plasticity and relatively stable various properties after solution treatment and aging treatment, and has the tensile strength at room temperature of more than 600MPa, the elongation of more than 10 percent, the tensile strength at 150 ℃ of more than 560MPa, the elongation of more than 16 percent, the tensile strength at 200 ℃ of more than 530MPa, the elongation of more than 18 percent, the tensile strength at 250 ℃ of more than 460MPa and the elongation of more than 22 percent, thereby meeting the requirements of the rare earth aluminum alloy in aerospace, war industry, automobile and other industries.

Drawings

FIG. 1 is a picture of an aged sample of a rare earth aluminum alloy in example 1 of the present invention;

FIG. 2 is a photograph of an aged sample of a rare earth aluminum alloy of comparative example 1 of the present invention;

FIG. 3 is a photograph of an aged sample of a rare earth aluminum alloy of comparative example 2 of the present invention.

Detailed Description

The invention is further described with reference to the accompanying drawings and specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and these equivalents also fall within the scope of the present application.

As shown in figures 1-3, the heat-resistant rare earth aluminum alloy comprises, by mass, 5 ~ 6% of Zn, 2 ~ 3% of Mg, 1 ~ 2% of Cu, 0.3 ~ 0.5.5% of Gd, 0.1 ~ 0.2.2% of Nd, less than 0.1% of impurity elements, and the balance of Al.

Preferably, the sum of the mass percentages of Nd and Gd in the heat-resistant rare earth aluminum alloy is 0.4 ~ 0.7.7%.

Preferably, the metallographic structure of the heat-resistant rare earth aluminum alloy mainly comprises an alpha-Al matrix and eutectic (alpha-Al + beta-Al)₂Mg₃Zn₃+β-Al₂Cu) and the average grain size of the alloy is 40-50 μm.

A preparation method of heat-resistant rare earth aluminum alloy comprises the following steps:

① mixing pure Al, pure Zn, pure Cu and intermediate alloys Mg-30Gd, Mg-25Nd as raw materials according to the proportion and preheating, wherein the purity of pure Al, pure Zn, pure Cu is 99.9%, and the purity of intermediate alloys Mg-30Gd, Mg-25Nd is 99.5%;

② heating and melting aluminum, zinc, copper and magnesium, adding intermediate alloys Mg-30Gd and Mg-25Nd at 700 ~ 720 ℃, and keeping the temperature;

③ when the materials are completely melted, heating to 750 ~ 770 deg.C and stopping heating;

④, when the temperature is reduced to 680 ~ 710 ℃, casting to obtain as-cast aluminum alloy;

⑤ the heat-resistant rare earth aluminum alloy is obtained after the heat treatment of the as-cast aluminum alloy.

Preferably, the pre-heating temperature of step ① is 120 ~ 150 ℃.

Preferably, the casting described in step ④ further requires preheating the mold to 200 ~ 250 ℃.

Preferably, the heat treatment method of step ⑤ is to subject the obtained as-cast aluminum alloy to solution treatment and aging treatment in sequence.

Preferably, the treatment temperature of the solution treatment is 450 ~ 550 ℃, the treatment time is 6 ~ 16 hours, and the treatment temperature of the aging treatment is 150 ~ 250 ℃, and the treatment time is 12 ~ 24 hours.

Preferably, the aluminum alloy prepared by the preparation method of the heat-resistant rare earth aluminum alloy comprises, by mass, 5 ~ 6% of Zn, 2 ~ 3% of Mg, 1 ~ 2% of Cu, 0.3 ~ 0.5.5% of Gd, 0.1 ~ 0.2.2% of Nd, less than 0.1% of the total amount of impurity elements, and the balance of Al.