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Heat treatment method for high-lithium-content cast aluminum-lithium alloy

A heat treatment method and casting aluminum technology, applied in the heat treatment of cast aluminum-lithium alloys with high lithium content, and in the field of heat treatment process of cast aluminum-lithium alloys with high lithium content, can solve the problem that aluminum-lithium alloys cannot obtain plasticity, cannot eliminate metal compounds, and alloy plasticity Poor toughness and other problems, to avoid excessive growth, solve low plasticity problems, and improve strength

Active Publication Date: 2016-09-21
SHANGHAI JIAO TONG UNIV
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  • Summary
  • Abstract
  • Description
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  • Application Information

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Problems solved by technology

In the Chinese patent document CN201410674805.4, the heat treatment process used for the cast aluminum-lithium alloy with a lithium content of about 2wt% is a two-stage solid solution (first stage: 400~450°C×8~10h, second stage: 510~ 540℃×20~28h) plus single-stage aging treatment (120~190℃×30~48h), the heat treatment process involved has been greatly changed compared with the traditional process. Plasticity
However, for cast aluminum-lithium alloys with high lithium content, the traditional heat treatment process cannot eliminate the metal compounds enriched on the grain boundaries, resulting in poor plasticity and toughness of the alloy
Raising the solid solution temperature or holding time alone can reduce the number of metal compounds, but it will also cause the grains to grow excessively and even the structure to be overheated, resulting in a decrease in the strength of the alloy

Method used

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  • Heat treatment method for high-lithium-content cast aluminum-lithium alloy
  • Heat treatment method for high-lithium-content cast aluminum-lithium alloy
  • Heat treatment method for high-lithium-content cast aluminum-lithium alloy

Examples

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Effect test

Embodiment 1

[0031] The cast aluminum-lithium alloy with high lithium content used in this example is a self-made rectangular parallelepiped slab, and its chemical composition is: Li 2.8%, Cu 1.41%, Zr 0.17%, and the rest is Al. The tensile strength in the as-cast state is 130Mpa, and the elongation is 0.6%. Such as figure 1 , the as-cast structure is composed of equiaxed grains, and continuous intermetallic compounds are enriched on the grain boundaries. According to XRD and EDS analysis, it is mainly Al 2 Cu、Al 2 CuLi and Al 3 Li.

[0032] Step 1: First, put the fine sand in a container to dry and heat up in a heat treatment furnace. After the furnace temperature is stabilized at the set first-stage solid solution temperature, the prepared cast aluminum-lithium alloy with high lithium content is buried in dry fine sand. After 10 hours of heat preservation, the temperature was raised to 560°C for 30 hours of heat preservation, and after the heat preservation was completed, it was tra...

Embodiment 2

[0044] The cast aluminum-lithium alloy with high lithium content used in the embodiment of the present invention is a self-made cuboid flat ingot, and its chemical composition is: Li 3.1%, Cu 1.52%, Zr 0.18%, Ag 0.31%, Mn 0.4%, and the rest is Al. Previous research by our research group found that manganese (Mn) was added to aluminum-lithium alloys to form Al 6 Mn, Al 6 (FeMn), Al 20 mn 3 Cu 2 phase, can effectively reduce the grain size of the alloy in the as-cast state and after heat treatment, and has a significant effect on improving the plasticity of the aluminum-lithium alloy. In this example, the tensile strength of the alloy in the as-cast state is 145Mpa, and the elongation is 0.3%. Such as Figure 4 , the as-cast structure of the alloy in this example is also composed of equiaxed grains, and continuous intermetallic compounds are enriched on the grain boundaries. According to XRD and EDS analysis, it is mainly Al 2 Cu、Al 2 CuLi and Al 3 Li. Compared with Ex...

Embodiment 3

[0057] The cast aluminum-lithium alloy with high lithium content used in the embodiment of the present invention is a self-made cuboid flat ingot, and its chemical composition is: Li 2.93%, Cu 1.46%, Zr 0.18%, Ag 0.44%, Mn 0.48%, and the rest is Al. In this example, the tensile strength of the alloy in the as-cast state is 149Mpa, and the elongation is 0.4%. The as-cast structure of the alloy in this example is also composed of equiaxed grains, and continuous intermetallic compounds are enriched on the grain boundaries. According to XRD and EDS analysis, they are mainly Al2Cu, Al2CuLi and Al3Li.

[0058] Step 1: First, put the fine sand in a container to dry and heat up in a heat treatment furnace. After the furnace temperature is stabilized at the set first-stage solid solution temperature, the prepared cast aluminum-lithium alloy with high lithium content is buried in dry fine sand. After 20 hours of heat preservation, the temperature was raised to 560°C for 30 hours of he...

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Abstract

The invention provides a heat treatment method for a high-lithium-content cast aluminum-lithium alloy, and belongs to the technical field of aluminum alloy heat treatment. The heat treatment method comprises the step of two-stage solid solution treatment conducted on the high-lithium-content cast aluminum-lithium alloy and the step of two-stage ageing treatment conducted on the high-lithium-content cast aluminum-lithium alloy. In the step of two-stage solid solution treatment, the high-lithium-content cast aluminum-lithium alloy is subjected to solid solution heat preservation for 5-20 h at the temperature ranging from 500 DEG C to 540 DEG C, then, the temperature is increased to 560 DEG C, and solid solution heat preservation is conducted for 20-40 h. In the step of two-stage ageing treatment, the alloy subjected to two-stage solid solution treatment is subjected to ageing heat preservation for 8-24 h at the temperature ranging from 125 DEG C to 150 DEG C, and then ageing heat preservation is conducted for 8-24 h when the temperature is increased to 175 DEG C-190 DEG C. According to the high-temperature two-stage solid solution and two-stage ageing heat treatment technology, the number of massive unbalanced intercrystalline compounds caused by the high lithium content is greatly reduced, the separated-out strengthening phase in the ageing process is greatly refined, the high-lithium-content cast aluminum-lithium alloy has low density and high strength, meanwhile, the plasticity of the alloy is greatly improved, and accordingly the application range of the aluminum-lithium alloy is enlarged.

Description

technical field [0001] The invention belongs to the technical field of heat treatment of aluminum alloys, and relates to a heat treatment method for casting aluminum-lithium alloys with high lithium content, in particular to a high-temperature double-stage solid solution treatment plus double-stage aging as process conditions to obtain high-quality alloys with excellent comprehensive mechanical properties. Heat treatment process for cast Al-Li alloys with lithium content. While the heat treatment process improves the strength of the alloy, it also enables the cast aluminum-lithium alloy with high lithium content to obtain better plasticity. Background technique [0002] With the development of high-performance aerospace vehicles, higher requirements are put forward for the lightweight of internal components. The main structural materials of the C919 large aircraft manufactured by China Commercial Aircraft Co., Ltd. use a large number of ultra-light and high-strength aluminum...

Claims

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Application Information

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IPC IPC(8): C22F1/04C22F1/057C22C21/00C22C21/12
CPCC22C21/00C22C21/12C22F1/04C22F1/057
Inventor 彭雨张亮吴国华陈安涛刘文才史春昌张小龙
Owner SHANGHAI JIAO TONG UNIV
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