CN107964641B

CN107964641B - Heat treatment method for improving creep forming performance of aluminum-lithium alloy

Info

Publication number: CN107964641B
Application number: CN201710971395.3A
Authority: CN
Inventors: 郝敏; 何维维; 陈军洲; 张坤; 李超
Original assignee: AECC Beijing Institute of Aeronautical Materials
Current assignee: AECC Beijing Institute of Aeronautical Materials
Priority date: 2017-10-18
Filing date: 2017-10-18
Publication date: 2021-02-05
Anticipated expiration: 2037-10-18
Also published as: CN107964641A

Abstract

The invention provides a heat treatment method for improving creep forming performance of an aluminum lithium alloy, wherein the aluminum lithium alloy comprises the following components in percentage by weight: 1.8-2.8% of Cu1.8%, 0.30-0.90% of Li0.6-1.2% of Mg0.06-0.16% of microalloying elements Zr0.06-0.16%, 0.20-0.60% of Mn0.05% of Si, 0.06% or less of Fe, 0.15% or less of Ti, 0.05% or less of other impurities, 0.15% or less of total amount and the balance of Al. The improvement is that after the aluminum lithium alloy is subjected to solution quenching and pre-stretching, low-temperature long-time aging is carried out for 10-28 h at 80-120 ℃, creep aging forming is carried out to obtain a final precipitated phase, and a strengthening phase is subjected to secondary precipitation in the creep process of the underaged alloy, so that the creep resistance of the underaged alloy is greatly superior to that of the peak aged alloy.

Description

Heat treatment method for improving creep forming performance of aluminum-lithium alloy

Technical Field

The invention relates to an aluminum lithium alloy heat treatment process, in particular to a process for improving creep forming performance of an aluminum lithium alloy.

Background

The general use of materials with high comprehensive properties such as high specific strength, high specific modulus, excellent fracture toughness and the like in the fields of aviation and aerospace and the way of integrally manufacturing the materials with large specification are combined to meet the requirements of low cost, long service life and high reliability, and the current trend is achieved. Al-Cu-Li-X aluminum-lithium alloys having high strength, toughness and damage tolerance, and having good creep deformation capability suitable for age forming are favored. The aging forming process is one of important methods for improving the comprehensive performance of the alloy, the material can deform and organize to evolve under the environment of thermal-force coupling, and the aim of improving the comprehensive performance of the alloy is achieved by regulating and controlling the precipitated phase of the alloy in the creep forming process.

Disclosure of Invention

The invention provides a method for improving the comprehensive performance of an aluminum-lithium alloy by combining the low-temperature long-time treatment after quenching and pre-stretching and the subsequent aging forming process, aiming at the requirement of integral aging forming of the aluminum-lithium alloy product, so as to promote the uniform precipitation of a precipitated phase in the alloy and adjust the crystal boundary configuration.

The technical scheme for realizing the aim of the invention is as follows:

the technical scheme of the invention is as follows: a heat treatment process for improving creep forming performance of an aluminum-lithium alloy comprises the following applicable alloy components in percentage by weight: 1.8-2.8% of main alloying element Cu0.30-0.90%, 0.6-1.2% of Mg0.06-0.16% of microalloying element Zr0.06-0.16%, 0.20-0.60% of Mn0.05% of Si, 0.06% or less of Fe, 0.15% or less of Ti, 0.05% or less of other impurities, 0.15% or less of total amount and the balance of Al.

The method is characterized in that after the aluminum lithium alloy is subjected to solution quenching and pre-stretching, low-temperature long-term aging for 10-28 hours at 80-120 ℃, a large number of atom clusters which are uniformly and dispersedly distributed are formed in a crystal, an underaging effect is generated, then creep aging forming is carried out to obtain a final precipitated phase, and a strengthening phase is subjected to secondary precipitation in the creep process of the underaged alloy, so that the creep resistance of the underaged alloy is greatly superior to that of the peak aged alloy, the crystal boundary configuration is adjusted, and the comprehensive performance of the alloy can be greatly improved. The preparation method comprises the following steps:

1.1, solution treatment: carrying out solution treatment in an air furnace or a salt bath furnace, wherein the heating temperature is 470-530 ℃, and the heat preservation time is the maximum section thickness (t) mmX (3.0-10.0) min/mm. Then carrying out water quenching on the alloy at room temperature;

1.2, pre-stretching: prestretching the quenched alloy on a prestretching machine, wherein the prestretching deformation is 2.5-7%;

1.3, low-temperature long-term treatment: carrying out low-temperature long-term treatment on the quenched alloy in a heat treatment furnace at the temperature of 80-120 ℃ for 10-28 h;

1.4, creep age forming treatment: processing the plate into parts, fixing the parts in modes of mechanical loading or vacuum adsorption and the like, and carrying out aging forming on the plate at 140-180 ℃, wherein the heat preservation time is as follows: 10 to 20 hours.

Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:

1. the technical scheme provided by the invention has the advantages of simple process and strong industrialized feasibility;

2. the aging forming process provided by the invention has obvious comprehensive effect. The method of the invention greatly improves the comprehensive performance of the aluminum lithium alloy after creep forming.

Drawings

FIG. 1 is HAADF-STEM images of the plate microstructure after treatment according to the first embodiment and the plate microstructure without deep cooling treatment;

wherein (a) is a sample of example 1 of the present invention and (b) is an aluminum alloy sample which has not been subjected to long-term low-temperature treatment.

Detailed description of the preferred embodiments

The technical solutions provided by the present invention will be further described in detail with reference to the following specific examples, but the present invention is not limited to the following examples.

Example one

The paint comprises the following components in percentage by weight: 2.8 percent of Cu2, 0.9 percent of Li0, 0.45 percent of Mg0, 0.40 percent of Mn0, 0.12 percent of Zr0, 0.06 percent of Ti0.06 percent of Si0.05 percent of Fe0.05 percent of Al, the balance of Al, and the hot rolled aluminum-lithium alloy plate with the thickness of 80mm is subjected to solution treatment at 535 ℃ for 5 hours, and is sprayed and quenched by room temperature water. Pre-stretching the quenched plate by 4.5%, and then preserving the heat at 80 ℃ for 20h for long time aging at low temperature; and then processing the aluminum alloy plate subjected to the aging treatment into a part, fixing the obtained aluminum lithium alloy plate by using a mechanical loading or vacuum adsorption mode, and preserving the heat for 10 hours at 180 ℃ for creep aging.

The tensile strength, fracture properties, fatigue crack growth rate properties, and microstructure of the above-treated samples were measured, and the results are shown in Table 1, FIG. 1, in which (a) is a sample of example 1 of the present invention, and (b) is an aluminum alloy sample which was not subjected to low-temperature long-term treatment, as compared with an aluminum lithium alloy plate which was not subjected to low-temperature long-term treatment.

The comparison of the measured results shows that after the treatment by the method, the strength, the fracture toughness property and the fatigue crack propagation rate property of the alloy after aging forming are respectively improved, the precipitated phases in the crystal are uniformly dispersed, and the tissues after low-temperature long-term aging are more uniform and fine.

TABLE 1 comparison of Performance before and after treatment according to the method of example 1 of the present invention

Example two

The alloy comprises the following components in percentage by weight: 2.6 percent of Cu2, 0.85 percent of Li0, 0.41 percent of Mg0.38 percent of Mn0.38 percent of Zr0.12 percent of Ti0.06 percent of Si0.05 percent of Fe0.05 percent of Al, the balance of Al, and an aluminum-lithium alloy plate with the thickness of 80mm is hot-rolled for solution treatment at the temperature of 535 ℃, the heat preservation time of 5 hours, and room temperature water is sprayed for quenching. Pre-stretching the quenched plate by 4.5%, and performing long-term aging at a low temperature of 100 ℃ and keeping the temperature for 16 h; then processing the plate into a part, fixing the part in a mechanical loading or vacuum adsorption mode and the like, creep aging forming the plate at 160 ℃, and keeping the temperature for: 16 hours: the properties after age forming were measured and compared with those without low temperature long term treatment as shown in table 2.

It can be found that the strength, fracture toughness and fatigue crack propagation rate of the alloy after aging forming are improved after the alloy is treated by the method of the invention.

Table 2 comparison of performance before and after treatment according to the method of example 2 of the present invention

EXAMPLE III

The method for improving the comprehensive performance of the aluminum-lithium alloy comprises the following steps: cu2.8 percent, Li0.90 percent, Mg0.45 percent, Mn0.35 percent, Zr0.12 percent, Ti0.06 percent, Si0.05 percent, Fe0.05 percent and the balance of Al, and hot rolled plates with the thickness of 80mm are subjected to solution treatment, the temperature is 535 ℃, the heat preservation time is 5 hours, and room temperature water is sprayed and quenched. Pre-stretching the quenched plate by 5.5%, and performing long-term aging at a low temperature of 120 ℃ and keeping the temperature for 10 hours; then processing the plate into a part, fixing the part in a mechanical loading or vacuum adsorption mode and the like, creep aging forming the plate at 170 ℃, and preserving heat for a period of time: 12 hours: the properties after age forming were measured and compared with those without low temperature long term treatment as shown in table 3.

TABLE 3 comparison of Performance before and after treatment according to the method of example 3 of the present invention

Claims

1. A heat treatment method for improving creep forming performance of an aluminum lithium alloy comprises the following components in percentage by weight:

2.8 percent of Cu2, 0.9 percent of Li0, 0.45 percent of Mg0, 0.40 percent of Mn0, 0.12 percent of Zr0, 0.06 percent of Ti0.06 percent of Si0.05 percent of Fe0.05 percent of Al, the balance of Al, and the hot rolled aluminum-lithium alloy plate with the thickness of 80mm is subjected to solution treatment at the temperature of 535 ℃, the heat preservation time of 5 hours, and room temperature water is sprayed and quenched;

pre-stretching the quenched plate by 4.5%, and then preserving the heat at 80 ℃ for 20h for long time aging at low temperature; and then processing the aluminum alloy plate subjected to the aging treatment into a part, fixing the obtained aluminum lithium alloy plate by using a mechanical loading or vacuum adsorption mode, and preserving the heat for 10 hours at 180 ℃ for creep aging.

2. A heat treatment method for improving creep forming performance of an aluminum lithium alloy comprises the following components in percentage by weight:

2.6 percent of Cu2, 0.85 percent of Li0, 0.41 percent of Mg0.38 percent of Mn0.38 percent of Zr0.12 percent of Ti0.06 percent of Si0.05 percent of Fe0.05 percent of Al, the balance of Al, and an aluminum-lithium alloy plate with the thickness of 80mm is hot-rolled for solution treatment at the temperature of 535 ℃, the heat preservation time is 5 hours, and room temperature water is sprayed for quenching;

pre-stretching the quenched plate by 4.5%, and performing long-term aging at a low temperature of 100 ℃ and keeping the temperature for 16 h; then processing the plate into a part, fixing the part in a mechanical loading or vacuum adsorption mode, creep aging forming the plate at 160 ℃, and preserving heat for: for 16 hours.

3. A heat treatment method for improving creep forming performance of an aluminum lithium alloy comprises the following components in percentage by weight: 2.8 percent of Cu2, 0.90 percent of Li0, 0.45 percent of Mg0, 0.35 percent of Mn0, 0.12 percent of Zr0, 0.06 percent of Ti0.06 percent of Si0.05 percent of Fe0.05 percent of Al, the balance of Al, hot rolled plates with the thickness of 80mm are subjected to solution treatment, the temperature is 535 ℃, the heat preservation time is 5 hours, and room temperature water is sprayed and quenched; pre-stretching the quenched plate by 5.5%, and performing long-term aging at a low temperature of 120 ℃ and keeping the temperature for 10 hours; then processing the plate into a part, fixing the part in a mechanical loading or vacuum adsorption mode, creep aging forming the plate at 170 ℃, and preserving heat for: for 12 hours.