阅读说明：本技术 一种Al-Cu-Mg合金及消除有害含铁相的方法 (Al-Cu-Mg alloy and method for eliminating harmful iron-containing phase ) 是由 戴菡 余鑫祥 于 2021-08-20 设计创作，主要内容包括：本发明涉及有色金属合金技术领域,尤其涉及一种Al-Cu-Mg合金及消除有害含铁相的方法。利用固溶在铝基体中的Sn的强空位结合能力显著抑制Al-Cu-Mg合金有害含铁相的形成。同时利用先共析Mg-(2)Sn相细化合金的晶粒组织,进一步细化和球化有害含铁相。该方法为Al-Cu-Mg合金结构材料后续热加工提供了有效技术手段,为相关高综合性能铝合金结构材料开发及产业化应用提供了新思路。由于微合金化和常规热处理方法设备要求简单、操作容易、大范围、可控性好,具有很好的重现性,而且相对于传统的方法成本大大降低。本发明利用的手段,无特殊条件要求、工艺条件成熟,因此特别适合商业化大规模生产。(The invention relates to the technical field of non-ferrous metal alloys, in particular to an Al-Cu-Mg alloy and a method for eliminating harmful iron-containing phases. The formation of harmful iron-containing phases of the Al-Cu-Mg alloy is remarkably inhibited by utilizing the strong vacancy bonding capability of Sn which is dissolved in an aluminum matrix in a solid mode. Simultaneously using the first eutectoid Mg 2 The Sn phase refines the grain structure of the alloy, and further refines and spheroidizes the harmful iron-containing phase. The method provides an effective technical means for the subsequent hot working of the Al-Cu-Mg alloy structural material, and provides a new idea for the development and industrial application of the related high-comprehensive-performance aluminum alloy structural material. The microalloying and conventional heat treatment method has the advantages of simple equipment requirement, easy operation, large range, good controllability and good reproducibilityAnd the cost is greatly reduced compared with the traditional method. The method of the invention has no special condition requirement and mature process condition, thus being particularly suitable for commercial large-scale production.)

1. An Al-Cu-Mg alloy comprises the following alloy components in percentage by mass: cu: 4.10-5.50, Mg: 0.30-1.60, Fe: 0.03-0.1, Si: 0.03-0.06 wt%, and Al for the rest, and is characterized by also containing 0.04-1.0 wt% of Sn.

2. A method of eliminating harmful ferrous phases in an Al-Cu-Mg alloy according to claim 1, characterized by the steps of:

smelting and casting: alloy smelting is carried out in a resistance wire furnace, pure Al and intermediate alloy Al-Cu are put into a high-purity graphite crucible, the temperature of the crucible is raised to 780 ℃ along with the furnace, and a refining covering agent is added into the crucible for the first time; after the raw materials are completely melted in 6-12min, putting hexachloroethane in a bell jar, pressing the hexachloroethane into the melt, removing slag after degassing is finished, and adding a refining covering agent for the second time; adding Sn into the crucible by using a clamp, stirring for 3-5 minutes, adding Mg into the crucible by using a bell jar after the Sn is completely melted, standing for a period of time, performing secondary degassing and slagging off, and adding a third refining covering agent; standing for 3-5min, and casting at 720 deg.C;

homogenizing and annealing: carrying out homogenizing annealing on the cast ingot in a vacuum atmosphere furnace, and strictly controlling the temperature error to be +/-3 ℃; adopting a two-stage homogenizing annealing process, annealing at 490 +/-3 ℃ for 3-5h, annealing at 510 +/-3 ℃ for 2-24h, taking out and quenching in room temperature water.

3. The Al-Cu-Mg alloy according to claim 1 or the method for eliminating harmful iron-containing phases in an Al-Cu-Mg alloy according to claim 2, wherein: the Sn element functions to suppress the generation of a solidified phase by utilizing a strong vacancy bonding effect.

4. The method of eliminating harmful ferrous phases in an Al-Cu-Mg alloy according to claim 2, characterized in that: in the step a, the purity of pure Al is 99.90wt%, the purity of pure Mg is 99.92 wt%, the purity of pure Sn is 99.9 wt%, and the purity of Cu in the intermediate alloy Al-Cu is 21.51 wt%.

5. The method of eliminating harmful ferrous phases in an Al-Cu-Mg alloy according to claim 2, characterized in that: the refining covering agent is a mixture of sodium chloride, potassium chloride and sodium fluoroaluminate =2:2:1 in mass ratio.

6. The method of eliminating harmful ferrous phases in an Al-Cu-Mg alloy according to claim 2, characterized in that: the addition amount of the refining covering agent for the first time and the second time is 8-14g, and the addition amount for the third time is 1-3 g; the addition amount of hexachloroethane is 2-4g each time, and degassing time is 1-2 min.

7. The method of eliminating harmful ferrous phases in an Al-Cu-Mg alloy according to claim 2, characterized in that: the pressure of the vacuum atmosphere furnace is 100-140 Pa.

8. The method of eliminating harmful ferrous phases in an Al-Cu-Mg alloy according to claim 2, characterized in that: the standard for melting is clockwise stirring with a molybdenum rod, with no apparent resistance indicating complete melting.

9. The method of eliminating harmful ferrous phases in an Al-Cu-Mg alloy according to claim 2, characterized in that: the transfer time of taking out the ingot to water quenching at room temperature is within 4 s.

Technical Field

The invention relates to the technical field of non-ferrous metal alloys, in particular to an Al-Cu-Mg alloy and a method for eliminating harmful iron-containing phases.

Background

Al-Cu-Mg alloys are the most common aerospace alloys due to their excellent mechanicsThe performance and the corrosion resistance are widely applied in the fields of aircraft skins, rivets, aviation structural materials and the like. In Al-Cu-Mg alloys, Fe, the most prevalent impurity, has a significant adverse effect on ductility and toughness because of the tendency to precipitate a microscopic-sized brittle, sharp iron-rich phase (e.g., Al) along the grain boundaries of the alloy₇Cu₂Fe). These Fe-rich phases are often considered crack sources in Al-Cu-Mg alloys, and tend to cause significant stress concentrations and crack initiation. Therefore, in the industrial production of aerospace Al-Cu-Mg alloy, the content level of Fe is strictly controlled.

In general, it is costly to strictly control the iron element in the raw aluminum. To solve this problem, one strategy is to modify the structure of the iron-rich phase by microalloying (e.g., Mn, Cr, Be, Co, Mo, Ni, V, W, Sr, and rare earth elements) to attenuate the effects of the sharpness and brittleness of the iron-rich phase and thereby improve the properties of the alloy. And secondly, the formation of a coarse iron-rich phase is inhibited by methods of promoting liquid phase dispersion such as rapid solidification. However, for large-sized ingots in industrial production, the above strategies may cause new problems, for example, by conventional microalloying metallic elements, which often lead to new harmful precipitates and/or harmful segregated elements, while rapid cooling, etc., often lead to large internal stresses. Thus, despite the high refining costs, it is almost a single way of industrial production of aerospace Al-Cu-Mg alloys. Therefore, there is a need to develop a feasible method for eliminating the harmful iron-containing phase in Al-Cu-Mg alloy in industrial production.

Disclosure of Invention

The invention aims to provide a novel Al-Cu-Mg alloy and a method for eliminating harmful iron-containing phases in the Al-Cu-Mg alloy, wherein the harmful iron-containing phases in the Al-Cu-Mg alloy are refined and spheroidized by adding Sn, so that the toughness and plasticity of the Al-Cu-Mg alloy are obviously improved, and the subsequent hot working performance of the alloy is improved.

The Al-Cu-Mg alloy comprises the following alloy components in percentage by mass: cu: 4.10-5.50, Mg: 0.30-1.60, Fe: 0.03-0.1, Si: 0.03-0.06, the rest is Al, and different from the prior art, the alloy also contains 0.04-1.0 mass percent of Sn.

The method for eliminating the harmful iron-containing phase in the Al-Cu-Mg alloy comprises the following steps:

a) smelting and casting: alloy smelting is carried out in a resistance wire furnace, pure Al and intermediate alloy Al-Cu are put into a high-purity graphite crucible, the temperature of the crucible is raised to 780 ℃ along with the furnace, and a refining covering agent is added into the crucible for the first time; after the raw materials are completely melted in 6-12min, putting hexachloroethane in a bell jar, pressing the hexachloroethane into the melt, removing slag after degassing is finished, and adding a refining covering agent for the second time; adding Sn into the crucible by using a clamp, stirring for 3-5 minutes, adding Mg into the crucible by using a bell jar after the Sn is completely melted, standing for a period of time, performing secondary degassing and slagging off, and adding a third refining covering agent; standing for 3-5min, and casting at 720 deg.C;

b) homogenizing and annealing: carrying out homogenizing annealing on the cast ingot in a vacuum atmosphere furnace, and strictly controlling the temperature error to be +/-3 ℃; adopting a two-stage homogenizing annealing process, annealing at 490 +/-3 ℃ for 3-5h, annealing at 510 +/-3 ℃ for 2-24h, taking out and quenching in room temperature water.

Further, the Sn element functions to suppress the generation of a solidified phase by utilizing a strong vacancy bonding effect.

Further, in step a, the purity of pure Al is 99.90wt%, the purity of pure Mg is 99.92 wt%, the purity of pure Sn is 99.9 wt%, and the purity of Cu in the master alloy Al-Cu is 21.51 wt%.

Further, the refining covering agent is a mixture of sodium chloride, potassium chloride and sodium fluoroaluminate =2:2:1 by mass ratio.

Further, the addition amount of the refining covering agent for the first time and the second time is 8-14g, and the addition amount for the third time is 1-3 g; the addition amount of hexachloroethane is 2-4g each time, and degassing time is 1-2 min.

Further, the pressure of the vacuum atmosphere furnace is 100-140 Pa.

Further, the standard for melting is clockwise stirring with a molybdenum rod, with no significant resistance indicating complete melting.

Further, the time for taking out the ingot to room temperature water for quenching is 1-4 s.

The invention has the beneficial effects that:

in the conventional Al-Cu-Mg alloyThe addition of Sn in the Al-Cu-Mg alloy is more likely to cause Cu and Fe to have similar diffusion inhibition effect because the solidification process of the Al-Cu-Mg alloy is non-equilibrium solidification. Meanwhile, Sn enhances the adhesion of a liquid phase along dendritic crystals, is beneficial to dispersing the liquid phase, and further inhibits the formation of a coarse-grain solidification phase in the Al-Cu-Mg alloy, especially the formation of a Fe-rich phase. Although some Mg is formed during the solidification of the alloy₂Sn phase, but these new phases are mainly dispersed, and have no harmful effect on the mechanical properties of the Al-Cu-Mg alloy. Therefore, the addition of Sn can solve the influence of the coarse iron-rich phase in the Al-Cu-Mg alloy on the material performance.

Drawings

FIG. 1 is a morphological feature of a harmful iron-containing phase of an Al-Cu-Mg alloy after solid solution;

FIG. 2 is a morphological feature of a harmful iron-containing phase of the Al-Cu-Mg-0.04Sn alloy after solid solution;

FIG. 3 is a morphological feature of a harmful iron-containing phase of the Al-Cu-Mg-0.15Sn alloy after solid solution;

FIG. 4 is a morphological feature of a harmful iron-containing phase of the Al-Cu-Mg-1.0Sn alloy after solid solution;

FIG. 5 is an alloy XRD analysis curve;

FIG. 6 is a graph of tensile properties of the alloy.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

a. Smelting and casting: alloy smelting is carried out in a resistance wire furnace, pure Al (99.90 wt%) and intermediate alloy Al-Cu (21.51 wt%) are put into a high-purity graphite crucible, and the temperature is raised to 780 ℃ along with the furnace. 9g of refining covering agent (a mixture of sodium chloride, potassium chloride and sodium fluoroaluminate mixed in a ratio of 2:2: 1) was placed in the crucible. 6-12min after the alloy is completely melted (clockwise stirring with molybdenum rod without obvious resistanceOptionally), 3g of hexachloroethane (C) are employed₂Cl₆) Placing the mixture in a bell jar, pressing the mixture into the melt, removing slag after degassing for 2min, and adding 9g of refining covering agent for the second time. Then pure Sn (99.9 wt%) is added into the crucible by a clamp, stirred for 3-5 minutes, Mg (99.92 wt%) is added by a bell jar after the Sn is completely melted, and the crucible is kept stand for a period of time and then degassed for the second time (3 g hexachloroethane (C)₂Cl₆) Degassing for 1 min), skimming slag, and adding 2g of refining covering agent. Standing for 2-3min, and casting at 720 deg.C. And a cast iron square mould is adopted during casting. The size of the finished ingot is about 400 mm multiplied by 40 mm. The alloy components except Al are as follows (all in percentage by mass): 4.28Cu, 1.23Mg, 0.09Fe, 0.03Si, and the addition of Sn is 0.00, 0.04, 0.15, 1.0, respectively.

b. Homogenizing and annealing: carrying out homogenizing annealing on the cast ingot in a vacuum atmosphere furnace, and strictly controlling the temperature error to be +/-3 ℃; adopting a two-stage homogenization annealing process, annealing at 490 +/-3 ℃ for 3h, annealing at 510 +/-3 ℃ for 24h, and taking out a sample to be uniformly quenched in room-temperature water. The transfer time is within 4 s.

FIGS. 1-4 are phase diagrams of alloys with Sn additions of 0.00, 0.04, 0.15, and 1.0 mass percent, respectively, showing that the harmful iron-containing phase is significantly reduced and decreased when Sn is added as compared with the alloy without Sn; this is because the strong vacancy-bonding ability of Sn solid-dissolved in the aluminum matrix significantly suppresses the formation of the harmful iron-containing phase of Al-Cu-Mg alloy while utilizing the pre-eutectoid phase Mg₂Sn refines the grain structure of the alloy, and further refines and spheroidizes harmful iron-containing phases.

Fig. 5 and 6 show that the tensile property of the alloy is remarkably improved by adding Sn compared with the alloy without adding Sn.

The invention provides an effective technical means for the subsequent hot working of the Al-Cu-Mg alloy structural material and provides a new idea for the development and industrial application of the related high-comprehensive-performance aluminum alloy structural material. The microalloying and conventional heat treatment methods have the advantages of simple equipment requirement, easy operation, large range, good controllability and good reproducibility, and the cost is greatly reduced compared with the conventional method. The method of the invention has no special condition requirement and mature process condition, thus being particularly suitable for commercial large-scale production.

The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.