CN115961189A

CN115961189A - Al-Mg-Zn-Cu aluminum alloy test piece and preparation method and application thereof

Info

Publication number: CN115961189A
Application number: CN202111177565.3A
Authority: CN
Inventors: 徐鹏; 喻川; 胡中文; 李江山; 崔强; 西达思·苏哈斯·帕维尔
Original assignee: Guizhou Hansikai Intelligent Technology Co ltd
Current assignee: Guizhou Hansikai Intelligent Technology Co ltd
Priority date: 2021-10-09
Filing date: 2021-10-09
Publication date: 2023-04-14
Anticipated expiration: 2041-10-09
Also published as: CN115961189B

Abstract

The invention discloses an Al-Mg-Zn-Cu aluminum alloy test piece and a preparation method and application thereof, belonging to the technical field of aluminum alloys. The Al-Mg-Zn-Cu aluminum alloy test piece is obtained by depositing an Al-Mg-Zn-Cu aluminum alloy raw material on the surface of a base material in an arc fuse mode; the chemical composition of the Al-Mg-Zn-Cu aluminum alloy raw material comprises 5-6wt% of Zn, 2-3wt% of Mg, 1-2wt% of Cu, 0.1-0.3wt% of Cr, impurity elements not more than 0.9wt% and the balance of Al. The aluminum alloy test piece has higher hardness and wear resistance in the deposition direction, has higher self-corrosion potential, lower corrosion current density and higher mechanical tensile property on the whole, and can be used as a structural member in aerospace, transportation, automobile manufacturing, military equipment or tool fixtures.

Description

Al-Mg-Zn-Cu aluminum alloy test piece and preparation method and application thereof

Technical Field

The invention relates to the technical field of aluminum alloy, and particularly relates to an Al-Mg-Zn-Cu aluminum alloy test piece and a preparation method and application thereof.

Background

The Al-Zn-Mg-Cu alloy is widely applied to the fields of aerospace, transportation, automobile manufacturing, military and the like due to the characteristics of low density, high specific strength, good toughness, good corrosion resistance and the like, the traditional aluminum alloy processing technology mainly adopts the means of smelting, casting, forging and the like, and the aluminum alloy member prepared by adopting the traditional means of smelting, casting, forging and the like is increasingly difficult to meet the requirements of the aluminum alloy product with large size and complex structure in the aspects of organization structure and mechanical property.

The additive manufacturing technology is directly manufactured into a solid part from a three-dimensional digital model, so that the part has a light structure and composite performance, and has the advantages of material saving, short manufacturing period, low cost and the like. Therefore, the Al-Zn-Mg-Cu alloy manufactured by additive manufacturing has important research significance and good application prospect.

Currently, additive manufacturing mainly focuses on Selective Laser Melting (SLM), selective electron beam melting (EBSM), and arc fuse manufacturing (WAAM), depending on the heat source.

Among them, the SLM technique utilizes a high-energy laser beam to rapidly melt metal powder, obtaining a high-precision metal device of almost any size and shape. Its main advantages are high energy stability, near-net shape, high output and high utilization rate of raw materials. However, the forming efficiency is low, the temperature gradient caused by a local heat source is high, and large residual stress can be caused, so that the material is easy to deform and crack. In addition, due to the low deposition rate and the limited forming size, the SLM technology is difficult to meet the requirement of rapid manufacturing of large parts. The EBSM technology uses electron beams as a heat source to heat powder and stack the powder layer by layer to form a solid body. The power of the electron beam is high, heat input which cannot be achieved by laser can be provided, the production efficiency is improved to a certain degree, and the manufacturing of a structural member with a larger size is facilitated. However, the working conditions are harsh, the vacuum chamber is required to be in a vacuum environment, the equipment cost and the production cost are high, the precision is improved, and the size of a formed part is limited by the vacuum chamber. The WAAM takes the electric arc as a heat source, has the advantages of simple production equipment, high material utilization rate, capability of producing large-scale components, high efficiency and the like, but the Al-Mg-Zn-Cu aluminum alloy test piece manufactured by the existing electric arc fuse wire cannot give consideration to both mechanical property and corrosion resistance.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

One of the objectives of the present invention is to provide an Al-Mg-Zn-Cu aluminum alloy test piece having high mechanical properties and good corrosion resistance.

The second purpose of the invention is to provide a preparation method of the Al-Mg-Zn-Cu aluminum alloy test piece.

The invention also aims to provide application of the Al-Mg-Zn-Cu aluminum alloy test piece.

The application can be realized as follows:

in a first aspect, the application provides an Al-Mg-Zn-Cu aluminum alloy test piece, which is obtained by depositing an Al-Mg-Zn-Cu aluminum alloy raw material on the surface of a base material in an arc fuse manner; the Al-Mg-Zn-Cu aluminum alloy raw material comprises 5-6wt% of Zn, 2-3wt% of Mg, 1-2wt% of Cu, 0.1-0.3wt% of Cr, impurity elements not more than 0.9wt% and the balance of Al.

In a preferred embodiment, the Al-Mg-Zn-Cu aluminum alloy raw material has a chemical composition comprising 5.2 to 5.8wt% of Zn, 2.2 to 2.8wt% of Mg, 1.5 to 1.8wt% of Cu, 0.15 to 0.25wt% of Cr, and not more than 0.8wt% of impurity elements, with the balance being Al.

In a more preferred embodiment, the Al-Mg-Zn-Cu aluminum alloy feedstock has a chemical composition comprising 5.52 wt.% Zn, 2.56 wt.% Mg, 1.62 wt.% Cu, 0.20 wt.% Cr, and no more than 0.5 wt.% impurity elements, with the balance being Al.

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy raw material is 7075 aluminum alloy welding wire with the diameter of 0.8-1.5 mm; 7075 aluminum alloy welding wire with the diameter of 1.2mm is preferred.

In an alternative embodiment, the chemical composition of the substrate comprises 5-6wt% Zn, 2-3wt% Mg, 1-2wt% Cu, 0.15-0.35wt% Fe, 0.05-0.15wt% Si, 0.15-0.3wt% Cr, and no more than 0.5wt% of impurity elements, the balance being Al.

In a preferred embodiment, the chemical composition of the substrate comprises 5.5-5.8wt% Zn, 2.5-2.8wt% Mg, 1.2-1.8wt% Cu, 0.2-0.25wt% Cr, and no more than 0.4wt% of impurity elements, the balance being Al.

In a more preferred embodiment, the chemical composition of the substrate comprises 5.65wt% Zn, 2.61wt% Mg, 1.46wt% Cu, 0.22wt% Cr, and no more than 0.3wt% impurity elements, with the balance being Al.

In an alternative embodiment, the substrate is a rolled sheet of 7075 aluminum alloy in the T6 temper.

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy test piece is a single-pass multi-layer Al-Mg-Zn-Cu aluminum alloy test piece.

In an alternative embodiment, the structure of the Al-Mg-Zn-Cu aluminum alloy test piece is layered and distributed with dendrites, equiaxial crystals and a small amount of columnar crystals in the horizontal direction, and the deposition direction is composed of equiaxial crystals and a small amount of slender columnar crystals.

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy test pieces contain a second phase consisting essentially of Mg ₂ Si phase and Mg (Zn, cu, al) ₂ And (4) phase(s).

In alternative embodiments, the hardness of the Al-Mg-Zn-Cu aluminum alloy test pieces in the horizontal direction is 70 to 75HV _0.1 The hardness in the deposition direction is 82-90HV _0.1 。

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy test piece has an average friction coefficient in the horizontal direction of not more than 0.511 and an average wear amountNot more than 1.093mm ³ The average abrasion coefficient in the deposition direction is not more than 0.356, and the average abrasion loss is not more than 0.8462mm ³ 。

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy test piece has a self-corrosion potential in the horizontal direction of not less than-0.9575V and a self-corrosion current of not more than-3.0794A/cm ² (ii) a The self-etching potential in the deposition direction is not lower than-0.9745V, and the self-etching current is not higher than-2.9362A/cm ² 。

In an alternative embodiment, the average tensile strength of the Al-Mg-Zn-Cu aluminum alloy test piece in the horizontal direction is not lower than 358.64MPa, the average yield strength is not lower than 196.15MPa, and the average elongation is not lower than 37.9%; the average tensile strength in the deposition direction is not less than 269.29MPa, the yield strength is not less than 140.65MPa, and the elongation is not less than 32.52%.

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy test piece has a ductile fracture mode.

In a second aspect, the present application provides a method of manufacturing an Al-Mg-Zn-Cu aluminum alloy test piece according to any one of the preceding embodiments, including the steps of: depositing Al-Mg-Zn-Cu aluminum alloy raw materials on the surface of a base material in an arc fuse mode.

In an alternative embodiment, the process conditions of the arc fuse include: the welding current is 80-120A, the welding voltage is 10-15V, the wire feeding speed is 7-10m/min, the advancing speed is 5-8m/min, and the air flow is 18-22L/min.

In a preferred embodiment, the process conditions of the arc fuse include: the welding current was 100A, the welding voltage was 12V, the wire feed speed was 8.5m/min, the travel speed was 6.5m/min, and the air flow rate was 20L/min.

In an alternative embodiment, before depositing the Al-Mg-Zn-Cu aluminum alloy raw material, the method also comprises the steps of removing oxide scales and organic matters on the surface of the base material, drying, and preheating to 75-85 ℃.

In a third aspect, the present application provides use of the Al-Mg-Zn-Cu aluminum alloy test piece according to any one of the preceding embodiments, for example, as a large-size aluminum alloy structural member.

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy test piece is used as a structural member in aerospace, transportation, automobile manufacturing, military equipment or tool fixtures.

In an alternative embodiment, al-Mg-Zn-Cu aluminum alloy test pieces are used as automotive chassis.

The beneficial effect of this application includes:

the method combines specific raw materials and manufacturing process parameters, so that the method for manufacturing the Al-Mg-Zn-Cu aluminum alloy test piece with higher mechanical property and corrosion resistance by adopting the arc fuse method becomes possible, the manufactured Al-Mg-Zn-Cu aluminum alloy test piece has higher hardness and wear resistance in the deposition direction, the whole test piece has higher self-corrosion potential, lower corrosion current density and higher mechanical tensile property, the high performance requirement of the aluminum alloy product with large size and complex structure at present is met, and the Al-Mg-Zn-Cu aluminum alloy test piece can be used as a structural member in aerospace, transportation, automobile manufacturing, military equipment or tool clamps.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

FIG. 1 is a schematic diagram of a macroscopic topography and a three-dimensional surface topography of surface roughness of a deposition sample in a macroscopic profiling topography analysis of a test example;

FIG. 2 is a microstructure morphology and a metallographic structure of a test piece in the microstructure analysis of the test example;

FIG. 3 is an EDS elemental distribution diagram of a test piece in the microstructure analysis of the test example;

FIG. 4 is a SEM EDS analysis result chart of a test piece in the microstructure analysis of the test example;

FIG. 5 is a diagram showing the results of XRD analysis of a test piece in phase structure analysis of the test examples;

FIG. 6 is a microhardness distribution diagram of a test piece in mechanical property analysis of a test example;

FIG. 7 is a graph showing the results of abrasion resistance of a test piece in mechanical property analysis of test examples;

FIG. 8 is a graph showing the tensile properties of test pieces in mechanical property analysis of test examples;

FIG. 9 is an SEM image of the fracture morphology of a test piece after a tensile test in the mechanical property analysis of the test example;

FIG. 10 is a graph showing the results of corrosion resistance of test pieces in corrosion resistance of test examples.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.

The Al-Mg-Zn-Cu aluminum alloy test piece provided by the application and the preparation method and the application thereof are specifically explained below.

The inventor proposes that the reason that the Al-Mg-Zn-Cu aluminum alloy test piece manufactured by the arc fuse at present cannot realize both the mechanical property and the corrosion resistance is probably mainly that: firstly, the hydrogen content is easy to exceed the surface in the aluminum alloy electric arc additive manufacturing process, and pores are generated; secondly, the residual stress is generated by remelting due to multiple deposition, and the segregation exists in the solidified structure, so that the mechanical strength of the sample is low.

In view of the above, the inventor creatively provides an effective and feasible additive manufacturing method for an Al-Mg-Zn-Cu aluminum alloy test piece, which effectively overcomes the problem that the Al-Mg-Zn-Cu aluminum alloy test piece manufactured by an arc fuse in the prior art cannot give consideration to both mechanical properties and corrosion resistance by adopting specific raw materials and combining manufacturing process parameters.

The application provides an Al-Mg-Zn-Cu aluminum alloy test piece which is obtained by depositing an Al-Mg-Zn-Cu aluminum alloy raw material on the surface of a base material in an arc fuse mode; the Al-Mg-Zn-Cu aluminum alloy raw material comprises 5-6wt% of Zn, 2-3wt% of Mg, 1-2wt% of Cu, 0.1-0.3wt% of Cr, impurity elements not more than 0.9wt% and the balance of Al.

The Zn content may be, by reference, 5wt%, 5.2wt%, 5.5wt%, 5.8wt%, or 6wt%, etc., and may be any other value within the range of 5 to 6 wt%.

The Mg content may be 2wt%, 2.2wt%, 2.5wt%, 2.8wt%, 3wt%, or the like, and may be any other value within the range of 2 to 3 wt%.

The Cu content may be 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, or the like, or may be any other value within the range of 1 to 2 wt%.

The Cr content may be 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, or the like, or may be any other value within the range of 0.1 to 0.3 wt%.

The impurity elements include Si, fe and the like, as follows.

It should be noted that the chemical compositions Zn, mg, cu and Cr of the Al-Mg-Zn-Cu aluminum alloy material in the present application can be freely combined in the above ranges, and the balance is Al.

In some preferred embodiments, the chemical composition of the Al-Mg-Zn-Cu aluminum alloy raw material may illustratively include 5.2 to 5.8wt% of Zn, 2.2 to 2.8wt% of Mg, 1.5 to 1.8wt% of Cu, 0.15 to 0.25wt% of Cr, and not more than 0.8wt% of impurity elements, with the balance being Al.

In some more preferred embodiments, the chemical composition of the Al-Mg-Zn-Cu aluminum alloy raw material illustratively may include 5.52wt% Zn, 2.56wt% Mg, 1.62wt% Cu, 0.20wt% Cr, and not more than 0.5wt% of impurity elements, with the balance being Al.

Of the above chemical components, mgZn formed by Zn in Mg ₂ Mainly plays a role of strengthening the second phase. When the Zn content is less than 4wt%, the strengthening effect tends to be insignificant, and when it is more than 7wt%, the stress corrosion cracking tendency tends to increase.

Mg mainly plays a role in increasing weldability and corrosion resistance, and simultaneously improves the strength of the alloy. When the Mg content is less than 1.5wt%, the solderability, corrosion resistance and strengthening effect are not remarkable, and when it is more than 3wt%, mg is easily formed ₂ The Si phase embrittles the alloy.

Cu mainly plays a role in solid solution strengtheningFruit, in addition to CuAl precipitating on aging ₂ Has obvious aging strengthening effect. When the Cu content is less than 1wt%, the strengthening effect tends to be insignificant, and when it exceeds 2.5wt%, the solid solution tends to be insufficient.

Cr forms intermetallic compound with other elements to block the nucleation and growth of re-crystallization and strengthen the crystal. When the Cr content is less than 0.1wt%, the strengthening effect tends to be insignificant, and when it is more than 0.3wt%, segregation tends to occur.

In an alternative embodiment, the Al-Mg-Zn-Cu aluminum alloy feedstock is 7075 aluminum alloy wire having a diameter of 0.8-1.5mm (e.g., 0.8mm, 1mm, 1.2mm, 1.5mm, etc.); 7075 aluminum alloy welding wire with the diameter of 1.2mm is preferred. The welding wire with the diameter size can obtain a better fuse wire effect under the arc fuse wire process condition adopted by the application, and further obtain better product performance.

In an alternative embodiment, the chemical composition of the substrate employed herein may illustratively include 5-6 wt.% Zn, 2-3 wt.% Mg, 1-2 wt.% Cu, 0.15-0.3 wt.% Cr, and no more than 0.5 wt.% of impurity elements, with the balance being Al.

The substrate may be, for example, a rolled plate of 7075 aluminum alloy in T6 temper, and the size may be, for example, 300mm × 100mm × 6mm (length × width × height).

In the application, the Al-Mg-Zn-Cu aluminum alloy test piece is preferably a single-pass multilayer Al-Mg-Zn-Cu aluminum alloy test piece.

Correspondingly, the application also provides a preparation method of the Al-Mg-Zn-Cu aluminum alloy test piece, which comprises the following steps: depositing Al-Mg-Zn-Cu aluminum alloy raw materials on the surface of a base material in an arc fuse mode.

In an alternative embodiment, the process conditions of the arc fuse may illustratively include: the welding current is 80-120A, the welding voltage is 10-15V, the wire feeding speed is 7-10m/min, the advancing speed is 5-8m/min, and the air flow is 18-22L/min.

The welding current may, by reference, be 80-120A, such as 80A, 85A, 90A, 95A, 100A, 105A, 110A, 115A or 120A, etc., or any other value within the range of 80-120A.

The welding voltage may be 10V, 11V, 12V, 13V, 14V, 15V, or the like, or may be any other value within a range of 10 to 15V.

The wire feed speed may be 7m/min, 7.5m/min, 8m/min, 8.5m/min, 9m/min, 9.5m/min, 10m/min, etc., or may be any other value within the range of 7-10 m/min.

The traveling speed may be 5m/min, 5.5m/min, 6m/min, 6.5m/min, 7m/min, 7.5m/min, 8m/min, or the like, or may be any other value within the range of 5 to 8 m/min.

The air flow can be 18L/min, 18.5L/min, 19L/min, 19.5L/min, 20L/min, 20.5L/min, 21L/min, 21.5L/min or 22L/min, etc., and can also be any other value within the range of 18-22L/min.

Among them, welding current is a major process parameter affecting the quality of a workpiece. When the welding current is lower than 80A, the electric arc is easy to be unstable, and defects such as air holes and inclusions are generated; defects such as undercut and flash are easily generated when the thickness is higher than 120A, and deformation of the workpiece is increased.

Welding voltage is also an important process parameter affecting the quality of the workpiece. When the welding voltage is lower than 10V, stick welding rods are easy to cause, and when the welding voltage is higher than 15V, the defects of unstable arc combustion, large splashing, undercut, air holes and the like are easy to cause.

The wire feed speed mainly affects the forming quality of the workpiece. When the wire feeding speed is lower than 7m/min, defects such as air holes, inclusion and the like are easy to generate, and when the wire feeding speed is higher than 10m/min, defects such as undercut, welding beading and the like are easy to generate.

The speed of travel also affects the quality of the workpiece being formed. When the moving speed is lower than 5m/min, the welding seam is easily widened, the residual height is increased, and the power is reduced; the weld seam is easy to narrow and uneven when the welding seam is higher than 8m/min, undercut is easy to generate, and the waveform of the weld seam is easy to sharpen.

The gas flow mainly plays a role in protecting the electric arc and liquid metal in the welding pool from being polluted by oxygen, nitrogen, hydrogen and the like in the atmosphere, so as to achieve the purpose of improving the welding quality. When the gas flow rate is less than 18L/min, the isolation effect of air from the molten metal in the welding area is not obvious, and when the gas flow rate is more than 22L/min, the gas is wasted, and the production cost is increased.

In some preferred embodiments, the process conditions of the arc fuse exemplarily comprise: the welding current was 100A, the welding voltage was 12V, the wire feed speed was 8.5m/min, the travel speed was 6.5m/min, and the air flow rate was 20L/min.

Preferably, before depositing the Al-Mg-Zn-Cu aluminum alloy material, the method further comprises removing the scale (e.g. polishing) and organic matter (e.g. cleaning with acetone) on the surface of the substrate, drying, and preheating to 75-85 ℃ (preferably 80 ℃).

After the base material is pretreated, the surface of the base material is subjected to unidirectional movement to deposit the Al-Mg-Zn-Cu aluminum alloy raw material.

The cooling rate of the arc fuse process is lower than that of the laser additive manufacturing method, and solidification cracks can be avoided to a great extent. In the structure of the Al-Mg-Zn-Cu aluminum alloy test piece prepared by the method, dendrites, equiaxed crystals and a small amount of columnar crystals are distributed in a layered mode in the horizontal direction, the deposition direction is composed of equiaxed crystals and a small amount of slender columnar crystals, and the characteristic of epitaxial growth is shown. The second phase contained in the Al-Mg-Zn-Cu aluminum alloy test piece mainly comprises Mg ₂ Si phase and Mg (Zn, cu, al) ₂ And (4) phase.

The hardness of the Al-Mg-Zn-Cu aluminum alloy test piece in the horizontal direction is 70-75HV _0.1 The hardness in the deposition direction is 82-90HV _0.1 (ii) a The average friction coefficient in horizontal direction is not more than 0.511, and the average abrasion loss is not more than 1.093mm ³ (ii) a The average abrasion coefficient in the deposition direction is not more than 0.356, and the average abrasion loss is not more than 0.8462mm ³ (ii) a The self-corrosion potential in the horizontal direction is not lower than-0.9575V, and the self-corrosion current is not higher than-3.0794A/cm ² (ii) a The self-etching potential in the deposition direction is not lower than-0.9745V, and the self-etching current is not higher than-2.9362A/cm ² (ii) a In the horizontal directionThe average tensile strength is not lower than 358.64MPa, the average yield strength is not lower than 196.15MPa, and the average elongation is not lower than 37.9%; the average tensile strength in the deposition direction is not lower than 269.29MPa, the yield strength is not lower than 140.65MPa, and the elongation is not lower than 32.52 percent; the fracture mode of the Al-Mg-Zn-Cu aluminum alloy test piece is ductile fracture.

It is emphasized that the preparation process of the present application may further include adding auxiliary fields (such as ultrasonic field and magnetic field) to the preparation process for composite preparation, and further performing appropriate subsequent treatments (such as heat treatment) on the obtained product to further improve the performance.

In addition, the application also provides the application of the Al-Mg-Zn-Cu aluminum alloy test piece, such as large-size aluminum alloy members. In addition, the Al-Mg-Zn-Cu aluminum alloy test piece can be used as a structural member in aerospace, transportation, automobile manufacturing, military equipment or tool fixtures, for example, as an automobile chassis (such as an unmanned automobile aluminum alloy chassis).

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

This example provides an Al-Mg-Zn-Cu aluminum alloy test piece, which is prepared by depositing Al-Mg-Zn-Cu aluminum alloy raw material on the surface of a base material in the manner of arc fuse.

Wherein the chemical composition of the Al-Mg-Zn-Cu aluminum alloy raw material comprises 5.52wt% of Zn, 2.56wt% of Mg, 1.62wt% of Cu, 0.20wt% of Cr and 0.57wt% of impurity elements, and the balance of Al.

The chemical composition of the substrate comprises 5.65wt% of Zn, 2.61wt% of Mg, 1.46wt% of Cu, 0.22wt% of Cr and 0.36wt% of impurity elements, and the balance of Al.

The Al-Mg-Zn-Cu aluminum alloy raw material is 7075 aluminum alloy welding wire with the diameter of 1.2 mm. The base material was a rolled 7075 aluminum alloy sheet in the T6 state having dimensions of 300 mm. Times.100 mm. Times.6 mm.

The preparation method of the Al-Mg-Zn-Cu aluminum alloy test piece comprises the following steps:

pretreating a base material: the surface of the base material is polished by a polisher to remove oxide skin, then acetone is used for cleaning to remove organic matters, the base material is preheated to 80 ℃ by using flame after being dried, and then unidirectional movement deposition is carried out.

Depositing Al-Mg-Zn-Cu aluminum alloy raw materials on the surface of the base material, wherein the process conditions of arc fuse deposition comprise: the welding current is 100A, the welding voltage is 12V, the wire feeding speed is 8.5m/min, the advancing speed is 6.5m/min, and the air flow is 20L/min.

The deposition system used in the process consists of a Fronius CMT Advanced 4000R arc power supply with a wire feeding device, a CMT welding gun arranged on a KR 150R2700KUKA robot, an argon gas conveying system and a working platform. Before deposition, a standard reference coordinate system was established using Rhino3D NURBS software, where the X-axis is defined as the travel direction of the torch, the Z-axis is defined as the thin wall forming direction, and the Y-axis is defined as the transverse direction.

Example 2

This example differs from example 1 in that: the Al-Mg-Zn-Cu aluminum alloy raw material comprises 5.2wt% of Zn, 2.8wt% of Mg, 1.5wt% of Cu, 0.25wt% of Cr and 0.6wt% of impurity elements, and the balance of Al.

Example 3

This example differs from example 1 in that: the chemical composition of the Al-Mg-Zn-Cu aluminum alloy raw material comprises 5.8wt% of Zn, 2.2wt% of Mg, 1.8wt% of Cu and 0.15wt% of Cr, and the balance of Al.

Example 4

This example differs from example 1 in that: the chemical composition of the Al-Mg-Zn-Cu aluminum alloy raw material comprises 5wt% of Zn, 2wt% of Mg, 1wt% of Cu, 0.1wt% of Cr and 0.4wt% of impurity elements, and the balance is Al.

Example 5

This example differs from example 1 in that: the chemical composition of the Al-Mg-Zn-Cu aluminum alloy raw material comprises 6wt% of Zn, 3wt% of Mg, 2wt% of Cu, 0.3wt% of Cr and no more than 0.8wt% of impurity elements, and the balance of Al.

Example 6

The present example differs from example 1 in that: the process conditions of the arc fuse include: the welding current was 80A, the welding voltage was 10V, the wire feed speed was 7m/min, the traveling speed was 5m/min, and the air flow rate was 18L/min.

Example 7

This example differs from example 1 in that: the process conditions of the arc fuse include: the welding current was 120A, the welding voltage was 15V, the wire feed speed was 10m/min, the travel speed was 8m/min, and the air flow rate was 22L/min.

Comparative example 1

The comparative example differs from example 1 in that the Al-Mg-Zn-Cu aluminum alloy starting material used had a chemical composition of: 8wt% Zn, 5wt% Mg, 1wt% Cu, 0.35wt% Fe, 0.03wt% Si, and 0.1wt% Cr, the balance being Al. The horizontal hardness of the obtained aluminum alloy electric arc additive manufactured part is 68HV _0.1 Hardness in the deposition direction of 79HV _0.1 (ii) a The average tensile strength in the horizontal direction is 326MPa, the average yield strength is 168MPa, and the average elongation is 28%; the average tensile strength in the deposition direction is 230MPa, the yield strength is 116MPa, and the elongation is 26%; the self-corrosion potential in the horizontal direction is lower than-0.9575V, and the self-corrosion current exceeds-3.0794A/cm ² (ii) a The self-etching potential in the deposition direction is lower than-0.9745V, and the self-etching current exceeds-2.9362A/cm ² The corrosion resistance was lower than that of example 1.

Comparative example 2

The comparative example differs from example 1 in that the process conditions of the arc fuse are: the welding current was 50A, the welding voltage was 8V, the wire feed speed was 6m/min, the traveling speed was 4m/min, and the air flow rate was 15L/min. The horizontal hardness of the obtained aluminum alloy electric arc additive manufactured part is 51HV _0.1 Hardness in the deposition direction of 65HV _0.1 (ii) a The average tensile strength in the horizontal direction is 280MPa, the average yield strength is 140MPa, and the average elongation is 18 percent; the average tensile strength in the deposition direction is 198MPa, the yield strength is 96MPa, and the elongation is 16%; the self-corrosion potential in the horizontal direction is lower than-0.9575V, and the self-corrosion current exceeds-3.0794A/cm ² (ii) a The self-etching potential in the deposition direction is lower than-0.9745V, and the self-etching current exceeds-2.9362A/cm ² The corrosion resistance was lower than that of example 1.

Comparative example 3

The comparative example differs from example 1 in that the process conditions of the arc fuse are: the welding current was 150A, the welding voltage was 18V, the wire feed speed was 12m/min, the travel speed was 10m/min, and the air flow rate was 25L/min. The horizontal hardness of the obtained aluminum alloy electric arc additive manufactured part is 63HV _0.1 Hardness in the deposition direction of 75HV _0.1 (ii) a The average tensile strength in the horizontal direction is 310MPa, the average yield strength is 160MPa, and the average elongation is 26%; the average tensile strength in the deposition direction is 225MPa, the yield strength is 112MPa, and the elongation is 24 percent; the self-corrosion potential in the horizontal direction is lower than-0.9575V, and the self-corrosion current exceeds-3.0794A/cm ² (ii) a The self-etching potential in the deposition direction is lower than-0.9745V, and the self-etching current exceeds-2.9362A/cm ² The corrosion resistance was lower than that of example 1.

Test examples

The Al-Mg-Zn-Cu aluminum alloy test piece obtained in the above example 1 was subjected to macro morphology analysis, microstructure analysis, phase analysis, mechanical property analysis (microhardness, wear resistance, tensile properties) and corrosion resistance analysis.

The analysis and test methods and results are as follows:

(1) macro-topographic analysis

The surface roughness is an important characteristic parameter for measuring the surface forming quality of parts, and directly influences the service performance and the service life of a formed part.

In this test, a surface roughness test was performed on the molded sample using a olympus LEXT OLS5000 type LASER confocal scanning MICROSCOPE (3 d measurement LASER olsf 5000).

The results are as follows:

the macroscopic morphology of the Al-Mg-Zn-Cu aluminum alloy test piece (hereinafter, may be referred to as "deposit sample") obtained in example 1 is as shown in fig. 1 (a) of fig. 1, and when viewed from the front, the surface of the deposit sample is smooth and bright overall, and exhibits periodic concave-convex lines, and each independent deposit layer can be distinguished, and the lap joint region between the weld beads is flat and compact, and has no offset phenomenon along the forming direction, and has no defects such as undercut, welding beading and the like. FIG. 1 (b) shows the surface roughness three-dimensional surface topography of a small sample of the deposit, FIG. 1 (c) shows the scan line, FIG. 1 (d) shows the corresponding coordinate curve, from which it can be derived: the maximum height Rz of the profile of this sample was 112.567 μm, and the arithmetic mean deviation of the Ra profile was 5.95. Mu.m.

The side surface of the multilayer single-channel deposition sample has no obvious fluctuation, and the multilayer single-channel deposition sample has good interlayer interface lapping characteristics, and the main reason for good forming characteristics can be as follows: the former layer is deposited under the action of the subsequent electric arc, the upper area is melted for the second time, but the remelting process is uniform and stable, so that the molten drop is stably transited to a molten pool.

(2) Microstructural analysis

The method comprises the following steps: the microstructure and elemental composition distribution of the powder and the deposit were analyzed by a JEOLJSM-7500 field Scanning Electron Microscope (SEM).

The results are shown in FIG. 2:

FIGS. 2 (a) and 2 (b) show the horizontal microstructure of the deposited samples, the former being at 100-fold magnification and the latter at 500-fold magnification. FIGS. 2 (c) and 2 (d) show the microstructure of the deposit sample in the deposition direction, the former being at a magnification of 100 times and the latter being at a magnification of 500 times.

In fig. 2 (a) and 2 (b), the microstructure of the sample region mainly contains a small amount of fine columnar crystal structure and a large amount of equiaxed crystal structure having irregular characteristics, which may be caused by the fact that fine crystal grains are easily obtained by a high cooling rate at the center of the molten pool to form a fine crystal region. The cooling speed of the edge of the molten pool is low, and the edge area is secondarily melted when the second layer is welded after the previous layer is completely deposited, so that the edge of the molten pool bears a large amount of welding heat input, partial remelting occurs, crystal grains are coarsened, and a coarse crystal area is formed. The remelting process is uniform and stable, so that molten drops are stably transited to a molten pool, and an equiaxed crystal structure with irregular characteristics appears in the horizontal direction.

In fig. 2 (c) and 2 (d), most grains in the in-layer region exhibit coarse equiaxed features, while a small number of elongated columnar grain structures are distributed along the boundary lines between layers, with more heat accumulation in the top layer in the deposition direction, which means that the temperature gradient of the top molten pool is smaller, leading to an early change in the direction of the temperature gradient. The solidification process is carried out from the bottom to the top of the bath, depending on the heat transfer characteristics of the bath, during which the liquid metal is kept in contact with the solid substrate. The extent of nucleation undercooling at the melt pool-solid matrix interface is typically the lowest compared to nucleation within the melt pool, which means that a good nucleation point is provided. Consequently, the subsequent solidification of the melt pool exhibits typical epitaxial growth characteristics.

Compared with the metallographic structure of an as-cast 7075 aluminum alloy (fig. 2 (f)), the metallographic structure of the Al-Mg-Zn-Cu aluminum alloy test piece (fig. 2 (e)) provided in example 1 of the present application has a finer grain size and a more uniform distribution. The main reason is that the solidification speed of the liquid metal of the arc fuse wire is high, the electric arc has a stirring effect on a molten pool, the solidification process is dynamic solidification, and a large amount of precipitated phases are not as long as being aggregated and are in dispersed distribution.

In order to characterize the microstructure of the Al-Mg-Zn-Cu aluminum alloy test piece of example 1 and the distribution of elements in the aluminum alloy in dendrites, scanning electron microscopy and energy spectrum analysis were performed, as shown in FIG. 3, in which FIG. 3 (a) shows the EDS element distribution in the horizontal direction, FIG. 3 (b) shows the EDS element distribution in the deposition direction, and the results of FIG. 3 show that: the distribution of the main alloying elements has a certain segregation. During non-equilibrium crystallization, they become enriched at grain boundaries and dendritic boundaries, forming a precipitated second phase.

TABLE 1 EDS energy Spectroscopy (At.%) in the different regions

These second phases are continuously distributed on the grain boundaries to form a complex lattice, as shown in fig. 4, fig. 4 (a) shows a horizontal SEM EDS analysis result, fig. 4 (b) shows a deposition direction SEM EDS analysis result, and fig. 4 shows: a small amount of grey phase is wrapped by the white phase. The chemical composition was determined by performing energy spectrum analysis on 4 points of the alloy, and the results are shown in Table 1, in which the white phases have similar chemical compositions, a higher aluminum content, a higher magnesium content relative to other alloying elements, and a lower copper proportion. The zinc content is obviously reduced. In the arc manufacturing process, the repeated heating of the next layer to the previous layer causes partial melting of the previous layer, and because Zn is a volatile metal with a low melting point and boiling point, the high temperature reached in the molten pool causes vaporization of Zn, so that a small amount of air holes are caused by burning loss of Zn element. In addition, the melting point of the alloy elements such as Fe, si and the like is high, so that the formed second phase can not be dissolved in the repeated heating process, when the alloy elements are dissolved in the non-equilibrium solidification process, if the evidence of a crystal structure does not exist, the phase type which is difficult to determine from the tested chemical composition can be preliminarily judged to be the precipitated second phase which is distributed along the grain boundary and is dispersed at the grain boundary or in the crystal.

(3) Phase structure

Cutting into blocks with the size of 10 × 10 × 6mm along the deposition advancing direction by using a linear cutting machine, polishing with sand paper to be flat and smooth, analyzing the phase composition by using a Dutch Pasnake X-ray diffractometer (XRD), and analyzing the phase composition by using a Cu target with the wavelength of 1.54060 at the scanning speed (2 theta) of 5deg/min within a scanning range; 20deg to 90deg, step length 0.02deg.

The phase structure test results are as follows:

XRD analysis results of the horizontal direction and the deposition direction of the Al-Mg-Zn-Cu aluminum alloy test piece of example 1 and an as-cast 7075 aluminum alloy (provided by Shenzhen Shenhui Metal materials Co., ltd., the same applies hereinafter) are shown in FIG. 5. The matrix phase of the 7075 aluminum alloy was α -Al, the major alloying elements were Zn, mg and Cu, and the Al-Mg-Zn-Cu aluminum alloy test pieces of example 1 had the phases mainly consisting of α -Al and a small amount of Al in the horizontal and deposition directions ₉ Si and Mg (Fe, mn, al). Due to the high cooling rate, a small amount of liquid phase is eutectic and eutectic phases (alpha-Al and Mg (Fe, mn, al) are formed ₉ Si phase) is retained because there is not enough time to transition at high cooling rate. The formation of the second phase particles in the ultrahigh strength aluminum alloy belongs to diffusion type phase change, and the size of the atomic diffusion rate is mainly controlled by the temperature, so that the size of the second phase particles is sensitive to the temperature. After the cast 7075 aluminum alloy is subjected to solution treatment and artificial aging, coarse second phases are dissolved, and then crystal grains are re-nucleated and grow into fine isometric crystals, so that the main peak is higher than the peak of additive manufacturing, and the second phases are obviously reduced.

(4) Analysis of mechanical Properties

A. Microhardness

The method comprises the following steps: and (3) carrying out microhardness analysis on the sample by adopting an HV-50 type small-load Vickers hardness tester, wherein the loading force is 1.98N, and the distance between measuring points is 5mm. Each hardness value was tested in triplicate and averaged.

As a result: as shown in FIG. 6, which is a graph showing the microhardness distribution in the horizontal direction and the deposition direction of the Al-Mg-Zn-Cu aluminum alloy test pieces of example 1. As is clear from the figure, the average hardness in the horizontal direction of the Al-Mg-Zn-Cu aluminum alloy test pieces was 73.15HV _0.1 The average hardness in the deposition direction was 86.06HV _0.1 Under the action of arc circulating heat, grains in a heat affected zone grow, and according to a Hall-Petch equation, the larger the grain size is, the smaller the microhardness value is; the structure in the horizontal direction is coarser than the grains in the deposition direction, the equiaxed structure with irregular characteristic is more, the structure layering is more obvious, and meanwhile, the precipitated second phase is coarser, so the hardness is slightly lower.

B. Wear resistance

The method comprises the following steps: an HSR-2M high-speed reciprocating friction tester is adopted to detect the wear resistance, the material of the grinding ball is GCr15, the load is 50N, the reciprocating stroke is 6mm, and the testing time is 15min.

As a result: as shown in FIG. 7, it shows the wear resistance in the horizontal direction and the deposition direction of the Al-Mg-Zn-Cu aluminum alloy test pieces of example 1. As can be seen from FIG. 7 (a), the average friction coefficients in the horizontal direction and the deposition direction of the Al-Mg-Zn-Cu aluminum alloy test pieces of example 1 were 0.511 and 0.356, respectively, as can be seen from FIG. 7 (b), the average wear amounts in the horizontal direction and the deposition direction of the Al-Mg-Zn-Cu aluminum alloy test pieces of example 1 were 1.093mm, respectively ³ And 0.8462mm ³ . Fig. 7 (c) shows the three-dimensional profile of the wear scar for two samples, the results of which show: the width of the grinding mark becomes narrow, the depth becomes shallow, and the groove becomes smoother.

C. Tensile Properties

The method comprises the following steps: the microcomputer controlled electronic universal tester model selected was MTS810 (250 KN) with a laser extensometer used to measure strain (elongation). The initial strain rate of stretching was set at 1mm/min and the pulling force was 50N.

As a result: as shown in fig. 8, tensile tests in the deposition direction and the horizontal direction were performed on the Al-Mg-Zn-Cu aluminum alloy test pieces of example 1 and the 7075 aluminum alloy casting to evaluate their macro-mechanical properties. Fig. 8 (a) shows the tensile curve of the sample, and fig. 8 (b) shows the strength and elongation obtained from the tensile curve. The Al-Mg-Zn-Cu aluminum alloy test piece of example 1 had an average tensile strength of 358.64MPa in the horizontal direction, an average yield strength of 196.15MPa, and an average elongation of 37.9%; the Al-Mg-Zn-Cu aluminum alloy test piece of example 1 had an average tensile strength of 269.29MPa in the deposition direction, a yield strength of 140.65MPa, and an elongation of 32.52%. The average yield strength and ultimate strength in the horizontal direction are 24.91% and 26.03% higher than in the deposition direction, respectively, and the anisotropy of mechanical properties can be attributed to the change in microstructure. Referring to fig. 2, the sample has dendrites that are strongly elongated upward. Compared to the vertical samples, the horizontal samples have more dendrite boundaries or interdendritic regions in the loading direction, so that crack nucleation in this region can accommodate more dislocations as the load increases before fracture occurs.

Further, the fracture analysis was performed on the above deposition sample using a JEOLJSM-7500 type field Scanning Electron Microscope (SEM), and fig. 9 shows the fracture morphology of the tensile sample, in which fig. 9 (a) and 9 (b) are horizontal directions, and fig. 9 (c) and 9 (d) are deposition directions. A small amount of air holes are formed on the surface of the fracture, zn air holes mainly come from evaporation of Zn caused by high arc temperature in an arc fuse process, but steam can be left to form the air holes in the solidification process of aluminum liquid. A large number of dimples are arranged in the horizontal direction and the deposition direction of the fracture of the sample, which shows that the 7075 aluminum alloy prepared by the arc fuse process has good plasticity, and the fracture mode is represented as typical ductile fracture. Compared with the sample in the deposition direction, the sample in the horizontal direction has more dendritic boundaries or interdendritic regions, can accommodate more dislocations in the crack nucleation process, and therefore has better plasticity.

(5) Corrosion resistance

The method comprises the following steps: the polarization curves were collected using an electrochemical corrosion experiment performed with an IM-6 type electrochemical workstation. The three-electrode method is adopted, the sample electrode is used as a working electrode, the saturated calomel electrode and the platinum electrode are respectively used as a reference electrode and an auxiliary electrode, and the corrosion environment is 3.5 percent of NaCl solution.

The results are shown in FIG. 10, and FIG. 10 (a) shows polarization curves of the cast 7075 aluminum alloy and the Al-Mg-Zn-Cu aluminum alloy test pieces of example 1 in the horizontal direction and the deposition direction. Table 2 shows the main electrochemical parameters obtained by Tafel extrapolation.

TABLE 2 electrochemical corrosion results of the deposited samples in the bulk, horizontal and cast 7075 aluminum alloys

The results show that the cast 7075 aluminum alloy has a self-corrosion potential of-1.0076V and a self-corrosion current of-2.6876A/cm ² . The Al-Mg-Zn-Cu aluminum alloy test piece of example 1 had a self-corrosion potential of-0.9575V in the horizontal direction and a self-corrosion current of-3.0794A/cm ² . The self-etching potential in the deposition direction is-0.9745V, and the self-etching current is-2.9362A/cm ² . The corrosion current density is gradually reduced along with the change of the potential from negative to positive; during the cathodic polarization, mainly hydrogen evolution reactions occur. When reaching the self-etching potential, the self-etching current density is minimum, the charge transfer resistance is larger, and the polarization reaction rate is lowest. When the potential is further increased, the corrosion current density is gradually reduced from negative to positive with the potential.

Compared with an as-cast 7075 aluminum alloy, the deposited sample provided by the application has higher self-corrosion potential, smaller self-corrosion current and wider passivation area in the horizontal direction and the deposition direction, so that the deposited sample has better corrosion resistance. In addition, the difference in corrosion resistance between the horizontal direction and the deposition direction is not large. This is because the corrosion resistance is related to the grain size and the precipitated phase. The grain size produced by additive manufacturing is smaller, the distribution is more uniform, and because the solidification speed is higher, the precipitated phase can not be aggregated later, and the corrosion resistance is better.

Fig. 10 (b) shows the 3D profile of the erosion profile of the three samples. As can be seen from this figure, the cast 7075 aluminum alloy has a greater surface roughness and a greater degree of corrosion after corrosion. The more concentrated the surface pitting is, the larger the pitting pits are.

In summary, the method combines specific raw materials and manufacturing process parameters, so that the method for manufacturing the Al-Mg-Zn-Cu aluminum alloy test piece with higher mechanical property and corrosion resistance by adopting the arc fuse method becomes possible, the manufactured Al-Mg-Zn-Cu aluminum alloy test piece has higher hardness and wear resistance in the deposition direction, the whole test piece has higher self-corrosion potential, lower corrosion current density and higher mechanical tensile property, the high-performance requirement of the current aluminum alloy product with large size and complex structure is met, and the aluminum alloy test piece can be used as a structural member in aerospace, transportation, automobile manufacturing, military equipment or tool fixtures.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An Al-Mg-Zn-Cu aluminum alloy test piece is characterized in that the Al-Mg-Zn-Cu aluminum alloy test piece is obtained by depositing an Al-Mg-Zn-Cu aluminum alloy raw material on the surface of a base material in an arc fuse mode; the chemical components of the Al-Mg-Zn-Cu aluminum alloy raw material comprise 5-6wt% of Zn, 2-3wt% of Mg, 1-2wt% of Cu, 0.1-0.3wt% of Cr, impurity elements not more than 0.9wt% and the balance of Al.

2. The Al-Mg-Zn-Cu aluminum alloy test piece according to claim 1, wherein the Al-Mg-Zn-Cu aluminum alloy raw material has a chemical composition including 5.2 to 5.8wt% of Zn, 2.2 to 2.8wt% of Mg, 1.5 to 1.8wt% of Cu, 0.15 to 0.25wt% of Cr, and not more than 0.8wt% of impurity elements, and the balance being Al.

3. The Al-Mg-Zn-Cu aluminum alloy test piece according to claim 2, wherein the Al-Mg-Zn-Cu aluminum alloy raw material has a chemical composition including 5.52wt% Zn, 2.56wt% Mg, 1.62wt% Cu, 0.20wt% Cr, and not more than 0.5wt% of impurity elements, with the balance being Al.

4. An Al-Mg-Zn-Cu aluminum alloy test piece according to any one of claims 1 to 3, wherein the Al-Mg-Zn-Cu aluminum alloy raw material is 7075 aluminum alloy welding wire having a diameter of 0.8 to 1.5 mm;

preferably, the Al-Mg-Zn-Cu aluminum alloy raw material is 7075 aluminum alloy welding wire with the diameter of 1.2 mm.

5. An Al-Mg-Zn-Cu aluminum alloy test piece according to any one of claims 1 to 3, characterized in that the chemical composition of the base material comprises 5 to 6 wt.% Zn, 2 to 3 wt.% Mg, 1 to 2 wt.% Cu, 0.15 to 0.3 wt.% Cr, and not more than 0.5 wt.% of impurity elements, the balance being Al;

preferably, the chemical composition of the base material comprises 5.5-5.8wt% of Zn, 2.5-2.8wt% of Mg, 1.2-1.8wt% of Cu, 0.2-0.25wt% of Cr, and not more than 0.4wt% of impurity elements, and the balance of Al;

more preferably, the chemical composition of the base material comprises 5.65wt% of Zn, 2.61wt% of Mg, 1.46wt% of Cu, 0.22wt% of Cr and no more than 0.3wt% of impurity elements, and the balance of Al;

preferably, the substrate is a rolled plate of 7075 aluminum alloy in the T6 temper.

6. The Al-Mg-Zn-Cu aluminum alloy test piece according to claim 5, wherein the Al-Mg-Zn-Cu aluminum alloy test piece is a single-pass multilayer Al-Mg-Zn-Cu aluminum alloy test piece;

preferably, in the structure of the Al-Mg-Zn-Cu aluminum alloy test piece, dendritic crystals, equiaxial crystals and a small amount of columnar crystals are distributed in a layered manner in the horizontal direction, and the deposition direction consists of equiaxial crystals and a small amount of slender columnar crystals;

preferably, the second phase contained in the Al-Mg-Zn-Cu aluminum alloy test piece mainly comprises Mg ₂ Si phase and Mg (Zn, cu, al) ₂ Phase (1);

preferably, the hardness of the Al-Mg-Zn-Cu aluminum alloy test piece in the horizontal direction is 70-75HV _0.1 The hardness in the deposition direction is 82-90HV _0.1 ；

Preferably, the Al-Mg-Zn-CuThe average friction coefficient of the aluminum alloy test piece in the horizontal direction is not more than 0.511, and the average abrasion loss is not more than 1.093mm ³ Average abrasion coefficient in the deposition direction is not more than 0.356, and average abrasion loss is not more than 0.8462mm ³ ；

Preferably, the self-corrosion potential of the Al-Mg-Zn-Cu aluminum alloy test piece in the horizontal direction is not lower than-0.9575V, and the self-corrosion current is not more than-3.0794A/cm ² (ii) a The self-etching potential in the deposition direction is not lower than-0.9745V, and the self-etching current is not higher than-2.9362A/cm ² ；

Preferably, the average tensile strength of the Al-Mg-Zn-Cu aluminum alloy test piece in the horizontal direction is not lower than 358.64MPa, the average yield strength is not lower than 196.15MPa, and the average elongation is not lower than 37.9%; the average tensile strength in the deposition direction is not lower than 269.29MPa, the yield strength is not lower than 140.65MPa, and the elongation is not lower than 32.52 percent;

preferably, the fracture mode of the Al-Mg-Zn-Cu aluminum alloy test piece is ductile fracture.

7. Method for producing an Al-Mg-Zn-Cu aluminum alloy test piece according to any one of claims 1 to 6, characterized by comprising the steps of: depositing Al-Mg-Zn-Cu aluminum alloy raw materials on the surface of a base material in an arc fuse mode.

8. The method of claim 7, wherein the process conditions of the arc fuse include: the welding current is 80-120A, the welding voltage is 10-15V, the wire feeding speed is 7-10m/min, the advancing speed is 5-8m/min, and the air flow is 18-22L/min;

preferably, the process conditions of the arc fuse include: the welding current was 100A, the welding voltage was 12V, the wire feed speed was 8.5m/min, the travel speed was 6.5m/min, and the air flow rate was 20L/min.

9. The preparation method of claim 8, wherein before depositing the Al-Mg-Zn-Cu aluminum alloy raw material, the method further comprises removing oxide scales and organic matters on the surface of the base material, drying and preheating to 75-85 ℃.

10. Use of the Al-Mg-Zn-Cu aluminum alloy test piece according to any one of claims 1 to 6, wherein the Al-Mg-Zn-Cu aluminum alloy test piece is used as a large-sized aluminum alloy structural member;

preferably, the Al-Mg-Zn-Cu aluminum alloy test piece is used as a structural member in aerospace, transportation, automobile manufacturing, military equipment or tool fixtures;

preferably, the Al-Mg-Zn-Cu aluminum alloy test piece is used for manufacturing an automobile chassis.