Heat treatment method of magnesium-containing cast aluminum lithium alloy

A heat treatment method and technology for casting aluminum, applied in the field of aluminum alloy heat treatment, can solve the problems of difficult heat treatment and low plasticity, and achieve the effect of solving the problem of grain size growth, improving elongation, and solving low plasticity problems

Active Publication Date: 2017-09-22
SHANGHAI JIAO TONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0010] The purpose of the present invention is to overcome the shortcomings of difficult heat treatment and low plasticity of magnesium-containing cast aluminum-lithium alloys,

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  • Heat treatment method of magnesium-containing cast aluminum lithium alloy
  • Heat treatment method of magnesium-containing cast aluminum lithium alloy
  • Heat treatment method of magnesium-containing cast aluminum lithium alloy

Examples

Experimental program
Comparison scheme
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Embodiment 1

[0036] The magnesium-containing cast aluminum-lithium alloy used in this example is self-smelted and obtained by gravity casting of a metal mold. The nominal chemical composition is: Li 2.0%, Cu 2.0%, Zr 0.20%, 0.4% Mg, and the rest is Al, denoted as alloy B, in order to show the beneficial effect of Mg element in casting aluminum-lithium alloy, the same process was used to smelt aluminum-lithium alloy without magnesium as a comparison group, denoted as alloy A, the actual composition of alloy A and alloy B As shown in Table 1. The as-cast structure is composed of dendrites, and the continuous second phase is enriched on the grain boundaries. figure 1 Among them, a and b are metallographic photographs of the as-cast structure of alloy A and alloy B in this embodiment respectively, and through XRD and EDS analysis, the second phase is mainly composed of Al 2 Cu、Al 2 CuLi and Al 3 Composition of Li, there is also a small amount of Al in magnesium-containing alloys 2 CuMg pha...

Embodiment 2

[0055] The magnesium-containing cast aluminum-lithium alloy used in this example is self-smelted and obtained by gravity casting of a metal mold. The nominal chemical composition is: Li 2.0%, Cu 2.0%, Zr 0.20%, 2.5% Mg, and the rest is Al. When a higher content of Mg is added, the as-cast structure of the alloy is composed of dendrites, more continuous second phases are enriched on the grain boundaries, and the grains are slightly refined compared with the control group without adding Mg. The reason is that the supercooling of the components caused by the segregation of Mg elements has a certain refining effect on the as-cast structure, such as Figure 5 As shown, the as-cast alloy containing 2.5Mg has a certain degree of grain refinement than the as-cast alloy without Mg (0Mg). According to XRD and EDS analysis, the second phase enriched near the grain boundary is mainly Al 2 Cu、Al 2 CuLi, Al 3 Li and Al 2 CuMg phase. The tensile strength of the alloy containing 2.5Mg i...

Embodiment 3

[0068]The magnesium-containing cast aluminum-lithium alloy used in this example is self-smelted and obtained by gravity casting of a metal mold. The nominal chemical composition is: Li 2.0%, Cu 2.0%, Zr 0.20%, 1.0% Mg, 0.11% by mass percentage Sc, the rest is Al. Sc element is a very effective refiner in Al alloy. Compared with alloy B in Example 1, the grain size is greatly reduced, and the comparison with the grain size before adding Sc is as Image 6 As shown in a and 6b, the as-cast structure transforms from dendrites to fine equiaxed grains. The continuous network non-equilibrium second phase is still enriched near the grain boundary. Significantly refined grains will not only increase the strength of the alloy, but also further improve the plasticity.

[0069] The magnesium-containing cast aluminum-lithium alloy prepared in this example was used for heat treatment, and only the time of the first-stage solid solution treatment was controlled to obtain 3 samples. Among t...

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Abstract

The invention provides a heat treatment method of magnesium-containing cast aluminum lithium alloy. The heat treatment method comprises a ternary solution treatment step and a slow heating ageing treatment step which are carried out in sequence. By a reasonable optimized ageing treatment process and a method for slowly heating the alloy to the ageing temperature, the volume fraction, the size and the distribution of main strengthening phases (Al3Li, Al2CuLi and Al2Cu) of the alloy are controlled. Compared with the traditional ageing treatment process, the heat treatment method of the magnesium-containing cast aluminum lithium alloy has the characteristics that uniform growing of Al3Li and separation of an Al2Cu (theta') can be promoted, and heterogeneous nucleation and growing of a S(Al2CuMg) phase and a T1(Al2CuLi) phase are promoted; and by the slow heating ageing process, the plasticity of the magnesium-containing cast aluminum lithium alloy is greatly improved while the strength of the cast aluminum lithium alloy is improved.

Description

technical field [0001] The invention relates to a heat treatment method for magnesium-containing cast aluminum-lithium alloy, which belongs to the technical field of aluminum alloy heat treatment. Background technique [0002] Aluminum-lithium alloy material is an advanced lightweight structural material. It has developed rapidly in aerospace materials in recent years. It has low density, high specific strength and specific stiffness, high elastic modulus, low fatigue crack growth rate, and low temperature performance. Good, good corrosion resistance and excellent superplastic forming performance and many other excellent comprehensive properties. Using it instead of conventional high-strength aluminum alloy can reduce the structural mass by 10-20%, and increase the rigidity by 15-20%. [0003] Lithium (Li) is the lightest metal element in nature, with a density of only 0.534g / cm 3 , studies have shown that: every addition of 1% Li in the aluminum alloy can reduce the alloy...

Claims

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Application Information

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IPC IPC(8): C22F1/04C22F1/057
Inventor 张小龙张亮吴国华史春昌陈安涛陶佳申
Owner SHANGHAI JIAO TONG UNIV
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