CN-122013076-A - High-strength 7xxx aluminum alloy and preparation method thereof

Abstract

The invention relates to the technical field of additive manufacturing, in particular to a 7xxx aluminum alloy with high strength and plasticity and a preparation method thereof, comprising the following steps of S1, cleaning the surfaces of 7A52 aluminum alloy bars and aluminum alloy substrates, S2, taking the cleaned 7A52 aluminum alloy bars as a deposition raw material, carrying out layer-by-layer deposition on the cleaned aluminum alloy substrates by adopting a friction stir deposition additive manner to obtain 7A52 aluminum alloy additive bodies, and S3, sequentially carrying out solution treatment and two-stage aging treatment on the 7A52 aluminum alloy additive bodies to obtain finished high strength and plasticity 7A52 aluminum alloy. According to the invention, on the premise of not changing alloy components, cooperative promotion of the strength and plasticity of the additive body is realized through solute homogenization in a solid solution stage and staged precipitation regulation and control in a two-stage aging stage, and the performance difference of different deposition layers is obviously reduced.

Inventors

• WANG WEN
• FANG MO
• LV TIANYANG
• ZHANG XU
• Huo Keyue
• ZHANG YUYE
• DENG JINGYU
• ZHANG JIANGYUN
• LIU JIANG
• LIU JIAHAO
• YAN BAOHONG

Assignees

• 西安建筑科技大学

Dates

Publication Date

20260512

Application Date

20260318

Claims (10)

1. 1.A method for preparing a high-strength plastic 7xxx series aluminum alloy, which is characterized by comprising the following steps: s1, cleaning surfaces of 7A52 aluminum alloy bars and aluminum alloy substrates; s2, taking the cleaned 7A52 aluminum alloy bar as a deposition raw material, and performing layer-by-layer deposition on the cleaned aluminum alloy substrate by adopting a friction stir deposition material adding mode to obtain a 7A52 aluminum alloy material adding body; And S3, sequentially carrying out solution treatment and double-stage aging treatment on the 7A52 aluminum alloy additive body to obtain the finished product high-strength plastic 7A52 aluminum alloy.
2. 2. The method for preparing the high-strength plastic 7xxx aluminum alloy according to claim 1, wherein in S1, the chemical components of the 7A52 aluminum alloy bar are, by mass, 4.0% -5.0% of Zn, 1.8% -2.5% of Mg, 0.1% -0.4% of Cu, 0.2% -0.5% of Mn, 0.1% -0.3% of Cr, 91.0% -93% of Al, and the balance of impurities.
3. 3. The method for preparing the high-strength and high-plasticity 7xxx aluminum alloy according to claim 1, wherein in S2, parameters in layer-by-layer deposition meet that an axial load is 20-40 kN, a main shaft rotating speed is 800-1200 rpm, a traveling speed is 10-40 mm/min, a feeding speed is 3-8 mm/min, and a shaft shoulder diameter of a stirring head is 55-65 mm.
4. 4. A method of producing a 7xxx series aluminum alloy having high strength and plasticity as defined in claim 3, wherein in S2, the deposit structure of the 7a52 aluminum alloy additive body is a fine equiaxed grain structure having an average grain size of 7 μm or less.
5. 5. The method for manufacturing a high-strength and high-plasticity 7 xxx-series aluminum alloy according to claim 1, wherein in the step of S3, the 7A52 aluminum alloy additive is heated to 450-490 ℃ and is kept for 1-3 hours during solution treatment, and then quenched in water at 10-40 ℃ to obtain the intermediate aluminum alloy.
6. 6. The method for producing a 7xxx series aluminum alloy having high strength and plasticity according to claim 5, wherein a Fe/Mn enriched dispersed phase is retained in the intermediate aluminum alloy, the dispersed phase including an Al 6 (Fe/Mn) phase in an amount of 2.31% to 3.36%.
7. 7. The method for manufacturing a high-strength and high-plasticity 7 xxx-series aluminum alloy according to claim 1, wherein in S3, the two-stage aging treatment is that the 7a52 aluminum alloy additive body after solid solution is sequentially subjected to the first-stage aging treatment and the second-stage aging treatment; Wherein, during primary aging treatment, the temperature is 90-115 ℃, and the temperature is kept for 4-10 hours to obtain crude aluminum alloy; And (3) in the secondary aging treatment, the temperature is 120-150 ℃, and the heat preservation is carried out for 10-20 hours, so that the finished product high-strength plastic 7A52 aluminum alloy with eta' precipitated phase is obtained.
8. 8. The method for producing a 7 xxx-series aluminum alloy having high strength and plasticity according to claim 7, wherein in S3, an equivalent size of an η' precipitated phase is 15 to 30 nm.
9. 9. The method for manufacturing a 7xxx series aluminum alloy having high strength and plasticity according to claim 7, wherein the Al 18 Mg 3 Cr 2 phase of the finished 7a52 aluminum alloy having high strength and plasticity contains a nano twin structure.
10. 10. A high-strength plastic aluminum alloy obtained by the method for preparing a high-strength plastic 7xxx series aluminum alloy according to any one of claims 1 to 9, wherein the difference of ultimate tensile strengths of different deposited layers of the high-strength plastic aluminum alloy along the deposition height direction is less than or equal to 30 MPa, and the difference of elongation is less than or equal to 6%.

Description

High-strength 7xxx aluminum alloy and preparation method thereof Technical Field The invention relates to the technical field of additive manufacturing, in particular to a high-strength 7xxx aluminum alloy and a preparation method thereof. Background The 7A52 aluminum alloy serving as the Al-Zn-Mg-Cu series high-strength aluminum alloy has the characteristics of low density, high specific strength and the like, and has good application prospect in lightweight bearing members. The existing 7A52 aluminum alloy component is prepared by combining casting with thermo-mechanical processing, and generally has the problems of long manufacturing flow, low material utilization rate, high energy consumption and the like, is limited by a mold and a deformation path, is difficult to realize near-net forming and rapid iterative manufacturing of a complex component, and is difficult to meet the requirements of high-end equipment on rapid manufacturing and green low-carbon production. To improve the manufacturing efficiency and reduce the material waste, additive manufacturing technology is considered as a potential effective way to prepare 7A52 aluminum alloy components due to the advantages of rapid forming, high material utilization rate and the like. However, 7xxx aluminum alloys such as 7a52 have the characteristics of high crack sensitivity, poor weldability and the like, and in the traditional melting additive manufacturing process (such as laser powder bed melting, electric arc additive and the like), metallurgical defects such as air holes, thermal cracks and the like are easily generated due to solidification shrinkage of a molten pool and thermal stress action, so that the strength and plasticity of an additive member are difficult to be compatible, and the mechanical property is often difficult to reach the level of similar thermal mechanical processing state materials. In order to avoid the liquid-solid phase transition defects in the process of melting the additive, the prior art discloses a solid additive manufacturing method, wherein the additive friction stir deposition (Additive Friction Stir Deposition, AFSD) enables the materials to generate viscoplastic flow and deposit layer by layer through friction heat generation and extrusion shearing action, so that the risks of defects such as air holes, hot cracks and the like can be reduced to a certain extent, and a new process route is provided for 7xxx series aluminum alloy additive manufacturing. Despite the advantages of solid state deposition, the prior art shows that AFSD molding quality and tissue performance are relatively sensitive to heat input and that the molding process window is relatively narrow. Particularly, in the multilayer layer-by-layer deposition process, repeated heat-force cyclic superposition makes the heat accumulation effect difficult to avoid, and heat Shi Chayi along the deposition height/thickness direction easily causes the difference of morphology and size of a precipitated phase in different deposition layers, and possibly causes no tissue characteristics such as a precipitated band and the like, so that interlayer gradient is caused to appear in performance indexes such as hardness, ultimate tensile strength, elongation and the like, and the defects of tissue and performance uniformity are expressed. Aiming at the problems, the prior art generally realizes heat input matching by adjusting the process parameters such as the rotation speed, the advancing speed, the axial load, the lap joint mode and the like of the main shaft so as to simultaneously meet the requirements of plastic flow, dynamic recrystallization, local overheating avoidance and the like, and also has the technology of reducing deposition temperature rise or optimizing a deposition path to relieve interlayer difference. However, due to the inherent heat accumulation effect and the thermodynamic and kinetic characteristics of coarsening of the precipitated phases, on the premise of not changing alloy components, the problems of coarsening of the precipitated phases and non-uniformity between layers are difficult to fundamentally solve only through AFSD (fast Fourier transform) process parameter optimization, so that the integral strength and plasticity of the additive are still difficult to realize collaborative improvement. In order to improve the characteristics and mechanical properties of precipitated phases, the prior art also discloses a traditional T6 heat treatment mode of solid solution and artificial aging for the 7xxx aluminum alloy, so that the strength of the alloy is improved by solid solution and re-dissolution of coarse eta phases and formation of nano eta' phases in the aging stage. However, for fine grain structures obtained by friction stir processing or solid-state additive, the conventional T6 heat treatment can cause a significant increase in the migration driving force of grain boundaries under the condition of solid solution heat exposure