阅读说明：本技术 一种高强高耐热低钪银添加的Al-Cu-Mg系合金及其热处理工艺 (High-strength high-heat-resistance low-scandium-silver-added Al-Cu-Mg alloy and heat treatment process thereof ) 是由 刘刚 高一涵 孙军 杨冲 张金钰 于 2020-04-23 设计创作，主要内容包括：本发明公开了一种高强高耐热低钪银添加的Al-Cu-Mg系合金及其热处理工艺。合金中Cu、Mg为主合金化元素；Sc、Zr、Si、Ag、Ti、Mn、V为微合金化元素；杂质中Fe的质量百分含量适当放宽,对于包含Ni、Zn在内的其余杂质需要严格控制。对于Mg含量>0.3％的合金,在均匀化后前进行热变形以规避热裂倾向,再进行重新均匀化。本发明时效处理包含自然时效与人工时效的组合,通过团簇-析出行为的关联性改善微观组织,改善强度,在控制昂贵的钪、银元素用量小于0.2％的同时,可使目标合金在室温抗拉强度大于470MPa,在300℃和400℃的抗拉强度分别大于160MPa和100MPa。(The invention discloses an Al-Cu-Mg alloy with high strength, high heat resistance and low scandium and silver addition and a heat treatment process thereof. Cu and Mg in the alloy are main alloying elements; sc, Zr, Si, Ag, Ti, Mn and V are microalloying elements; the mass percentage of Fe in the impurities is properly relaxed, and the other impurities including Ni and Zn need to be strictly controlled. For alloys with Mg content > 0.3%, heat deformation is carried out after homogenization to avoid the tendency of heat cracking, and then homogenization is carried out again. The aging treatment comprises the combination of natural aging and artificial aging, the microstructure is improved through the association of cluster-precipitation behavior, the strength is improved, the tensile strength of the target alloy at room temperature is more than 470MPa, and the tensile strengths at 300 ℃ and 400 ℃ are respectively more than 160MPa and 100MPa while the use amount of expensive scandium and silver elements is controlled to be less than 0.2%.)

1. An Al-Cu-Mg series alloy with high strength, high heat resistance and low scandium and silver addition is characterized in that: 3.0-7.5% of Cu, 0.1-1.5% of Mg, 0.05-0.20% of Sc, 0.005-0.40% of Zr, 0.005-0.50% of Si, 0.005-0.20% of Ag, 0.005-0.30% of Ti, 0.1-1.0% of Mn and 0.005-0.15% of V, wherein the mass percentage of Fe can be properly broadened to 0.005-0.60%, the mass percentage of other impurities including Ni and Zn is strictly controlled to be less than 0.2%, and the balance is Al, the ingot is cast and formed by a conventional metal mold or sand mold, and for the alloy with the Mg content of more than 0.3%, the alloy is recommended to be subjected to thermal deformation to avoid the thermal cracking tendency after homogenization, and then subjected to re-aging and homogenization treatment.

2. The heat treatment process of the Al-Cu-Mg alloy with high strength, high heat resistance and low scandium and silver addition, which is disclosed by claim 1, comprises two parts of homogenization and aging treatment, and is characterized in that the homogenization process comprises the following steps: firstly, preserving heat for 0.5-72 hours at 400-500 ℃, then heating to 505-547 ℃ along with the furnace, wherein the heating rate is 0-20 ℃/hour, the temperature is not too fast, and the heat preservation is 0.5-Quenching in warm water or oil after 72 hours; the thermal deformation is carried out after the homogenization is finished, the temperature is 400-480 ℃, and the homogenization is carried out again after the thermal deformation is finished. For Mg content>The 0.3% alloy is more recommended to be used after hot deformation to prevent hot cracking during casting, and a homogenization temperature higher than 505 ℃ cannot be adopted for the alloy with the Mg content higher than 1.0% to prevent a large amount of S-Al₂When the CuMg is the same, the CuMg is melted to cause overburning; the aging process comprises the following steps: firstly, standing at room temperature for 5 minutes to 6 months after homogenization is completed, or adopting 50-125 ℃ pre-aging, and keeping the temperature for 5 minutes to 24 hours; and then, carrying out aging treatment on the alloy sample at 100-300 ℃, keeping the temperature for 5 minutes-2 days, taking out the sample, and then cooling in air to finish the process.

Technical Field

The invention relates to the technical field of nonferrous metals, in particular to a high-strength high-heat-resistance low-scandium-silver Al-Cu-Mg alloy and a heat treatment process thereof.

Background

2 xxx-series (Al-Cu) alloys, which are representative of age-hardenable aluminum alloys, have excellent overall mechanical properties and are generally considered to be the better heat resistant series of aluminum-based alloys. In general, different Mg contents are required to be added to the 2xxx series alloys to improve the time hardening performance of the alloys. Taking the classic 2024 alloy as an example, the main alloying elements include Cu: 3.8% -4.9%, Mg: 1.2% -1.8%, and other elements such as Mn, Si, etc. The main function of Mg in the alloy is to combine with Cu to form Cu-Mg co-cluster so as to enable the alloy to be rapidly hardened during natural aging, or to guide the precipitation sequence of supersaturated Solid Solution (SS) -GPB zones-theta ' -theta-Al 2Cu of an Al-Cu binary system into the precipitation sequence of SS-Cu-Mg co-clusters (GPB) -S ' (GPB2) -S ' -S-Al 2CuMg of an Al-Cu-Mg ternary system, so that the peak aging strength of the alloy is greatly improved.

The classic idea of heat resistance research on Al-Cu-Mg-based aging-strengthenable alloy is to improve strengthening effect by increasing Cu/Mg ratio and performing Mg-Ag composite microalloying, and the microscopic mechanism thereof is to transform the theta '-Al2Cu precipitated phase with the conventional plane {100} α into the omega phase with the conventional plane {111} α, thereby ensuring that the theta' -Al2 precipitated phase can bear a large stress of 200MPa or more at around 200 ℃, and has extremely excellent creep resistance performance.

Disclosure of Invention

The Al-Cu-Mg series alloy added with high strength, high heat resistance and low scandium and silver and the heat treatment process thereof aim to control the contents of expensive elements Sc and Ag to be lower than 0.2 percent, simultaneously utilize trace (impurity) elements such as Zr, Si, Ti, Mn and the like which are usually present or added in the aluminum alloy to realize the precipitation process of atom clustering and subsequent artificial aging in the combined regulation and control natural aging, obviously reduce the preparation cost of the alloy and simultaneously realize excellent mechanical properties under the room temperature and 300-400 ℃ high-temperature service environment. The main strengthening phases of the Al-Cu-Mg alloy are G.P.B region/S ' phase and S ' phase, and are not theta ' phase in the traditional Al-Cu alloy.

The invention provides an Al-Cu-Mg alloy with high strength, high heat resistance and low scandium and silver addition, which is characterized in that: 3.0 to 7.5 percent of Cu, 0.1 to 1.5 percent of Mg, 0.05 to 0.20 percent of Sc, 0.005 to 0.40 percent of Zr, 0.005 to 0.50 percent of Si, 0.005 to 0.20 percent of Ag, 0.005 to 0.30 percent of Ti, 0.1 to 1.0 percent of Mn, 0.005 to 0.15 percent of V, properly widened Fe content to 0.005 to 0.60 percent, and strictly controlled content of less than 0.2 percent of other impurities including Ni and Zn, and the balance of Al. The cast ingot is formed by conventional metal mold casting or sand mold casting. For alloys with Mg content > 0.3%, hot deformation is recommended after homogenization to avoid hot tearing tendency, followed by re-homogenization and aging

The invention provides a heat treatment system matched with Al-Cu-Mg series alloy with high strength, high heat resistance and low scandium and silver addition, which comprises two parts of homogenization and aging treatment. The corresponding homogenization process is characterized in that: firstly, preserving heat at 400-500 ℃ for 0.5-72 hours, then heating to 505-547 ℃ along with a furnace, wherein the heating rate is 0-20 ℃/hour, the heating rate is not too fast, and after preserving heat for 0.5-72 hours, quenching in warm water or oil quenching; the thermal deformation is carried out after the homogenization is complete and the temperature is 400-480 ℃. After the thermal deformation is finished, homogenization should be carried out again, and the heat preservation time can be properly shortened. Alloys with Mg contents > 0.3% are more recommended for use after hot deformation to prevent hot cracking during casting. Homogenization temperatures above 505 ℃ cannot be used for alloys with Mg contents > 1.0%, preventing overburning caused by melting of large amounts of S-Al2CuMg at the same time.

1, standing at room temperature for 5 minutes to 6 months after homogenization is finished, or pre-aging at 50-125 ℃ for 5 minutes to 24 hours; 2. and then, carrying out aging treatment on the alloy sample at 100-300 ℃, keeping the temperature for 5 minutes-2 days, taking out the sample, and then cooling in air to finish the process.

The invention proposes to carry out thermal deformation after homogenization before the homogenization of the alloy with the Mg content of more than 0.3 percent to avoid the hot cracking tendency, and then carry out re-homogenization. The aging treatment mainly comprises the combination of natural aging and artificial aging, and is used for improving the microstructure and improving the strength through the association of cluster-precipitation behaviors. The invention can control the dosage of expensive scandium and silver element to be less than 0.2 percent, and simultaneously can lead the tensile strength of the target alloy to be more than 470MPa at room temperature, and the tensile strength to be more than 160MPa and 100MPa at 300 ℃ and 400 ℃ respectively.

Drawings

FIG. 1 is a graph of room temperature tensile engineering stress-engineering strain curves for examples 1-3 and comparative examples 4-5 provided herein;

FIG. 2 is a graph of engineering stress versus engineering strain for examples 1-3 and comparative example 5, according to the present invention, at high temperature of 300 deg.C;

FIG. 3 is a graph of engineering stress versus engineering strain for examples 1-3 and comparative examples 4-5, according to the present invention, at a high temperature of 400 deg.C;

Detailed Description

The following examples are intended to illustrate the invention but not to further limit it.

As shown in fig. 1, example alloys 1-3 have a better room temperature strength-ductility match than comparative example alloys 4-5. The deformed example alloy 2 had better ductility but decreased strength compared to the as-cast example alloys 1 and 3.

FIG. 2 compares the 300 ℃ high temperature tensile properties of some alloy materials provided by the present invention. It can be seen from the figure that the high temperature tensile strength of the example alloys 1-3 is significantly improved over the comparative example alloy 5.

FIG. 3 compares the 400 ℃ high temperature tensile properties of some alloy materials provided by the present invention. As can be seen, alloy 1 of the example has the best tensile strength at high temperature, and the tensile strength reaches to be close to 125MPa, and is obviously improved compared with other alloys.

Examples 1

An Al-Cu-Mg series alloy with high strength, high heat resistance and low scandium and silver addition comprises the following steps: (1) casting with a conventional metal mold to obtain an Al-4.2Cu-1.5Mg-0.15Sc-0.10Zr-0.12Si-0.09Ti-0.79Mn-0.3Fe (in mass percent) alloy ingot, then keeping the temperature of the ingot at 480 ℃ for 24 hours, then gradually heating to 495 ℃ along with the furnace, wherein the heating rate is 5 ℃/hour, and keeping the temperature for 12 hours. (2) The treated samples were left at room temperature for 2 weeks, followed by 12 hours aging at 175 ℃, and the samples were removed and allowed to air cool.

EXAMPLES example 2

An Al-Cu-Mg series alloy with high strength, high heat resistance and low scandium and silver addition comprises the following steps: (1) casting with a conventional metal mold to obtain an Al-3.8Cu-1.0Mg-0.16Sc-0.13Zr-0.02Si-0.02Ti-0.34Mn-0.05Fe (in mass percent) alloy ingot, then keeping the temperature of the ingot at 480 ℃ for 24 hours, then gradually heating to 485 ℃ along with the furnace, wherein the heating rate is 5 ℃/hour, and keeping the temperature for 12 hours. Taking out the sample, immediately carrying out hot extrusion to obtain a 10mm bar, and then carrying out air cooling; (3) homogenizing the bar material obtained in the step (2) for the second time at 515 ℃, preserving the heat for 12 hours, and then quenching the bar material in warm water. (4) The treated samples were left at room temperature for 2 weeks, followed by 12 hours aging at 175 ℃, and the samples were removed and allowed to air cool.

EXAMPLE 3

An Al-Cu-Mg series alloy with high strength, high heat resistance and low scandium and silver addition comprises the following steps: (1) casting with a conventional metal mold to obtain an Al-6.8Cu-0.89Mg-0.05Sc-0.20Zr-0.06Si-0.05Ti-0.88Mn-0.30Fe-0.18Ag (in mass percent) alloy ingot, then keeping the temperature of the ingot at 485 ℃ for 24 hours, then gradually heating to 515 ℃ along with the furnace, wherein the heating rate is 5 ℃/hour, and keeping the temperature for 24 hours. Taking out the sample and immediately quenching in warm water; (2) the treated sample of step (1) was left at room temperature for 2 weeks, followed by aging at 175 ℃ for 8 hours, and the sample was taken out and air-cooled.

Comparative example 4

A high-strength high-temperature-resistant high-scandium composite microalloyed Al-Cu-Mg series alloy comprises the following steps: (1) casting with a conventional metal mold to obtain an Al-4.0Cu-0.4Mg-0.25Sc-0.25Zr-0.09Ti (the content of other impurities is less than 0.05 percent in mass percent) alloy ingot, then preserving heat of the ingot at 485 ℃ for 24 hours, then gradually increasing the temperature to 535 ℃ along with the furnace, wherein the heating rate is 5 ℃/hour, and preserving heat for 12 hours. Taking out the sample and immediately quenching in warm water; (2) the treated sample of step (1) was left at room temperature for 2 weeks, followed by aging at 250 ℃ for 8 hours, and the sample was taken out and air-cooled.

Comparative example 5

A high scandium microalloyed Al-Cu series alloy comprises the following steps: (1) casting an Al-4.5Cu-0.31Sc alloy ingot (the content of other impurities is lower than 0.05 percent in mass percent) by using a conventional metal mold, then keeping the temperature of the ingot at 485 ℃ for 24 hours, then gradually heating to 535 ℃ along with a furnace, wherein the heating rate is 5 ℃/hour, and keeping the temperature for 12 hours. Taking out the sample and immediately quenching in warm water; (2) the treated sample of step (1) was left at room temperature for 2 weeks, followed by aging at 250 ℃ for 8 hours, and the sample was taken out and air-cooled.

The room temperature tensile mechanical properties of the aluminum alloy materials of practical examples 1-3 and comparative examples 4-5 were measured using national standards GB/T1173-1995. The results of the experiments are summarized in table 1. It can be seen that the embodiments 1-2 designed according to the present invention all have more excellent room temperature yield and tensile strength than the comparative example 3.

The tensile creep mechanical properties at 300 ℃ and 400 ℃ were measured for the aluminum alloy materials of examples 1 to 3 and comparative examples 4 to 5 using the national standard GB/T2039-2012. The results of the experiments are summarized in table 1. It can be seen that examples 1-2 of the inventive design have several times higher temperature yield, tensile strength relative to comparative example 3.

TABLE 1 comparison of the Room temperature Performance of high-strength, high-temperature resistant, high-scandium composite microalloyed Al-Cu-Mg alloys of examples 1-3 to comparative examples 4-5 according to the present invention

Alloy code	Yield strength/MPa	Tensile strength/MPa	Elongation/percent
				Examples 1	357	480	9
EXAMPLES example 2	231	340	14
				EXAMPLE 3	420	500	5
Comparative example 4	264	340	10
				Comparative example 5	161	257	10

TABLE 2 comparison of the high temperature mechanical properties of the high scandium composite microalloyed Al-Cu-Mg alloys of examples 1-3 with comparative examples 4-5, which are high in strength and high in temperature resistance, according to the present invention