A particle-reinforced 7075 aluminum alloy seamless powder core wire for twin-wire electric arc additive

Abstract

A kind of granular reinforced 7075 aluminum alloy seamless powder core wire for double-wire electric arc additive belongs to the field of additive manufacturing, and the wire is composed of metal powder and seamless aluminum tube skin, wherein the alloy element composition in the powder core and its mass percentage are as follows: metal Mg powder 0.4%-1%, metal Zn powder 25%-35%, metal Cu powder 6%-8%, metal Cr powder 0.2%-0.4%, metal Ti powder 1%-3%, micro-nano particle powder 1%-5%, the micro-nano particle is at least one of TiB2, SiC, TiC and TiN, and the balance is metal Al powder;The outer cladding layer can be an aluminum-magnesium alloy seamless pipe, and the powder filling rate is 20-25%. The comprehensive mechanical properties of the additive component using the powder core wire of the application are significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of additive manufacturing, and particularly relates to a kind of granular reinforced 7075 aluminum alloy seamless powder core wire for double-wire electric arc additive manufacturing. BACKGROUND

[0002] 7xxx series aluminum alloy is Al-Zn-Mg-Cu series aluminum alloy, which has high specific strength, specific modulus and good fatigue resistance, and is widely used in the fields of aerospace, rail vehicles, automobile manufacturing, etc. Electric arc additive manufacturing technology uses electric arc as heat source and metal wire as raw material. The wire is melted to form a molten pool by electric arc heating. The molten pool is accumulated layer by layer according to the predetermined path to directly obtain a finished part. This technology has the advantages of high material utilization rate, short manufacturing cycle and low cost, and has broad application prospects in the manufacturing of large 7xxx series aluminum alloy components.

[0003] Due to the metallurgical characteristics of 7xxx series aluminum alloy (high alloying element content, wide crystallization temperature range) and the process characteristics of electric arc additive manufacturing technology (high heat input, high temperature gradient of molten pool, slow cooling speed), the electric arc additive manufacturing of 7xxx series aluminum alloy has the disadvantages of high crack sensitivity, non-uniform microstructure and element segregation, which leads to low performance of the formed sample, and becomes a bottleneck restricting its popularization and application. Adding micro and nano-sized reinforcing particles into the molten pool during additive manufacturing can promote heterogeneous nucleation effect and refine the crystalline structure. On the one hand, it promotes the release of local tensile stress in the micro area and inhibits the generation of cracks. On the other hand, the second phase particles interact with the dislocation movement in the aluminum alloy matrix to improve the strength of the additive component.

[0004] In the existing electric arc additive manufacturing of particle reinforced 7xxx series aluminum alloy, (1) Patent CN111266702A discloses a coaxial arc-in-wire + arc-out-powder TIG electric arc additive manufacturing device. Based on this device, second phase particle powder is fed into the molten pool to realize the electric arc additive manufacturing of 7xxx series aluminum alloy particle reinforcement. However, the repulsion of electric arc force to the second phase particles makes it impossible to feed all the second phase particles into the molten pool, resulting in uncontrollable content of second phase reinforcing particles, and the feeding of powder has safety hazards. (2) Patent CN115106620A proposes a method for obtaining 7xxx series aluminum alloy by double-wire electric arc additive manufacturing. The method alternately and reciprocally accumulates 5xxx series aluminum alloy welding wire and 7xxx series aluminum alloy welding wire layer by layer, and then performs heat treatment and post-processing such as rolling to obtain 7xxx series aluminum alloy material. However, the 7xxx series aluminum alloy material obtained by this method has the problem of uneven composition, and it is difficult to control the composition of trace alloying elements. Therefore, it is an urgent technical problem in the field to develop 7xxx series aluminum alloy particle reinforced wire suitable for additive manufacturing and improve the crack resistance and strength of electric arc additive manufactured 7xxx series aluminum alloy components. SUMMARY

[0005] The method of using aluminum alloy cored filling wire is easy to add micro-nano reinforcing particles and regulate alloy composition, which provides a new idea for reducing the crack sensitivity of arc additive aluminum alloy components and improving the mechanical properties.

[0006] The present application aims to solve the problem that the composition of the filling wire cannot be controlled or micro-nano reinforcing particles cannot be added in the existing arc additive manufacturing technology, and combines the characteristics that the aluminum alloy powder core wire is easy to regulate alloy composition and micro-nano reinforcing particles promote heterogeneous nucleation effect, and designs a seamless powder core filling wire for double-wire arc additive manufacturing of micro-nano particle reinforced 7075 aluminum alloy. Using the existing 7075 aluminum alloy filling wire, the arc additive component is prone to alloy element burning and thermal crack defects, and the microstructure inside the component is coarse and the strength is low. Using the filling wire and the application method thereof, the characteristics of the powder core wire that the alloy composition is easy to regulate and the reinforcing particles promote heterogeneous nucleation can be used to refine the grain structure, reduce the crack sensitivity, and improve the mechanical properties, thereby promoting the application process of the arc additive manufacturing technology in the production and manufacturing of 7xxx aluminum alloy components.

[0007] The present application realizes the following technical scheme: a particle reinforced 7075 aluminum alloy seamless powder core wire for double-wire arc additive manufacturing, characterized in that the powder core wire is composed of a seamless aluminum tube skin and a powder core. The aluminum magnesium alloy seamless pipe with an outer diameter of 23-30 mm and an inner diameter of 13-20 mm is selected as the skin of the filling wire.

[0008] The powder core composition and its mass percentage are as follows: Mg: 0.2-1wt%;Zn: 25-40wt%;Cu: 4-12wt%;Micro-nano reinforcing particles: 1-8wt%;Cr: 0.1-0.4wt%;Ti: 1-5wt%;Al: balance.

[0009] Further, the above-mentioned micro-nano reinforcing particles include at least one of TiB2, SiC, TiC, TiN, etc., which can be mixed in any mass ratio.

[0010] Further, after a large number of experiments, the above-mentioned alloy powder particle size is 75μm-300μm, preferably 150μm-200μm, and the particle shape is spherical or near-spherical.

[0011] Further, the diameter of the seamless powder core wire is 1.0-2.0mm, and the powder core filling rate is 20-25%.

[0012] The design and selection of the element composition of the cored powder of the present application are based on the following:

[0013] The addition of Ti powder can generate Al3Ti strengthening particles in-situ during the additive manufacturing process, which can limit the grain boundary movement, hinder the grain growth, refine the grain size, limit the growth of columnar crystals and inhibit the expansion of thermal cracks, in cooperation with the in-situ added micro-nano particles.

[0014] Zn: the main strengthening element of the 7075 alloy, which is used to transition zinc element to the molten pool.

[0015] Mg: the main strengthening element of the 7075 alloy, which is used to transition magnesium element to the weld metal, form MgZn2 phase with Zn element, improve the heat treatment effect, improve the tensile strength and corrosion resistance.

[0016] Cu: the strengthening element of the 7075 alloy, and the content of Cu exceeding 1.25% can obviously increase the strength and hardness of the alloy.

[0017] Cr: Cr can form (CrFe)Al7 and (CrMn)Al 12 intermetallic compounds in aluminum, which can hinder the nucleation and growth process of recrystallization, have a certain strengthening effect on the alloy, and can also improve the toughness of the alloy and reduce the stress corrosion cracking sensitivity.

[0018] The micro-nano particles added in the application have the following effects: ① promoting heterogeneous nucleation effect and refining the crystalline structure; ② interacting with the dislocation movement in the aluminum alloy matrix, pinning the grain boundary and hindering the dislocation movement, reducing the thermal cracking tendency and improving the strength of the additive component.

[0019] The inner and outer diameters of the aluminum-magnesium alloy pipe and the size of the filling wire of the finished product

[0020] Aluminum magnesium alloy outer diameter (mm) 23 25 28 30 Aluminum magnesium alloy inner diameter (mm) 13 15 17 20 Filler wire diameter (mm) 1.0 1.2 1.6 2.0

[0021] The process for carrying out double-wire arc additive manufacturing of an ultra-high strength aluminum alloy single-wall wall by using the obtained particle-reinforced 7075 aluminum alloy seamless powder core wire and the commercial ER7075 solid core wire as a heat source of a TIG arc is as follows: the same angle of off-axis wire feeding is adopted, the arc current is 100-250 A, the solid core wire feeding speed is 1.3-2.0 m / min, the powder core wire feeding speed is 1.3-2.0 m / min, the scanning speed is 80-100 mm / min, the protective gas flow is 15 L / min, the interlayer temperature is controlled to be 70℃, and the protective gas is high-purity argon with a purity higher than 99.99%.

[0022] The obtained particle reinforced 7075 aluminum alloy seamless powder core wire and the commercial ER7075 solid core wire are used to additively manufacture the ultra-high strength aluminum alloy single-wall wall by taking the TIG arc as a heat source, the feeding speed of the solid core filling wire and the seamless powder core filling wire is changed, so that the trace alloying elements are controlled and the second phase particles are transitioned to the deposited layer, and finally the solid core filling wire and the seamless powder core filling wire are co-pool additive manufactured 7075 aluminum alloy, so that the composition of the wire is controlled, the strength of the as-deposited sample is improved, and the purpose of reducing pores and cracks is achieved. DETAILED DESCRIPTION

[0023] In order to further clarify the purpose, inventive idea and technical scheme of the present application, the present application will be further described in detail below in combination with examples, but the protection scope of the present application is not limited to the following examples.

[0024] Example 1

[0025] The seamless powder core wire for TIG arc double-wire additive manufacturing of 7075 ultra-high strength aluminum alloy with added micro-nano particles adopts a 5052 aluminum magnesium alloy pipe skin with an outer diameter of 23 mm and an inner diameter of 13 mm, a filling rate of 15%, and a final product wire diameter of 1.0 mm after drawing and reducing. The composition of the powder core is as follows: Mg: 0.4wt%; Zn: 35wt%; Cu: 8wt%; micro-nano TiB2 particles: 3.5wt%; Cr: 0.4wt%; Ti: 2.7wt%; Al: balance. The powder core filling wire is additively manufactured together with the ER7075 solid core filling wire, the powder core filling wire feeding speed is 2m / min, the solid core filling wire feeding speed is 1.3m / min, the scanning speed is 100mm / min, the protective gas is high-purity argon with a purity of more than 99.99%, the gas flow is 15L / min, the forming current is 100A, the interlayer temperature is controlled at 70℃, and 50 layers are cladded.

[0026] In this example, the arc is stable and burns, both types of filling wires are fully melted, the additive manufacturing process is continuous and stable, the obtained additive single-wall wall is well formed, the obtained additive single-wall wall does not have obvious pores and cracks, the internal organization is uniformly distributed, and presents the microstructure characteristics of arc wire metal additive manufacturing. The tensile strength is 436MPa and the microhardness is 156HV after room temperature uniaxial tension.

[0027] Example 2

[0028] The seamless powder core wire for 7075 ultra-high strength aluminum alloy TIG arc double wire additive manufacturing adopts 5052 aluminum magnesium alloy pipe skin size of outer diameter 25 mm, inner diameter 15 mm, filling rate of 20%, and the filling wire is drawn and reduced to the final product wire diameter of 1.2 mm. The mass ratio of the composition of the powder core is Mg: 0.4wt%; Zn: 35wt%; Cu: 7wt%; micro-nano TiC particles: 2.6wt%; Cr: 0.34wt%; Ti: 2.5wt%; Al: balance; and the TIG arc additive is carried out together with the ER7075 solid core filling wire, the powder core filling wire feeding speed is 1.8m / min, the solid core filling wire feeding speed is 1.4m / min, the scanning speed is 90mm / min, the protective gas is high-purity argon with purity higher than 99.99%, the gas flow is 15L / min, the forming current is 120A, the interlayer temperature is controlled at 70℃, and 50 layers are cladded.

[0029] In the double wire additive process, the arc is stable and burns, the two types of filling wires are fully melted, the additive process is continuous and stable, the obtained additive single-wall wall is well formed, the obtained additive single-wall wall does not have obvious pores and cracks, the internal organization is uniformly distributed, and the microstructure characteristics of the arc wire metal additive manufacturing are presented. The tensile strength is 453MPa, and the microhardness is 161HV after room temperature uniaxial tension.

[0030] Example 3

[0031] The seamless powder core wire for 7075 ultra-high strength aluminum alloy TIG arc double wire additive manufacturing adopts 5052 aluminum magnesium alloy pipe skin size of outer diameter 25 mm, inner diameter 15 mm, filling rate of 20%, and the filling wire is drawn and reduced to the final product wire diameter of 1.2 mm. The mass ratio of the composition of the powder core is Mg: 0.4wt%; Zn: 35wt%; Cu: 7wt%; micro-nano TiC particles: 2.6wt%; Cr: 0.34wt%; Ti: 2.5wt%; Al: balance; and the TIG arc additive is carried out together with the ER7075 solid core filling wire, the powder core filling wire feeding speed is 1.8m / min, the solid core filling wire feeding speed is 1.4m / min, the scanning speed is 90mm / min, the protective gas is high-purity argon with purity higher than 99.99%, the gas flow is 15L / min, the forming current is 120A, the interlayer temperature is controlled at 70℃, and 50 layers are cladded.

[0032] In the double-wire additive process, the electric arc is stable and burns, both types of filler wires are fully melted, the additive process is continuous and stable, the obtained additive single-wall wall is well formed, the obtained additive single-wall wall does not have obvious pores and cracks, the internal structure is uniformly distributed, and presents the microstructure characteristics of the electric arc wire metal additive manufacturing. The tensile strength is 427 MPa and the microhardness is 159 HV after room temperature uniaxial stretching.

[0033] Example 4

[0034] The seamless powder core wire for 7075 ultra-high strength aluminum alloy TIG electric arc double-wire additive manufacturing adopts a 5052 aluminum magnesium alloy pipe skin with an outer diameter of 30 mm and an inner diameter of 20 mm, and a filling rate of 30%. The filler wire is drawn and reduced in size, and the final product wire diameter is 2.0 mm. The mass ratio of the composition of the powder core is Mg: 0.4wt%; Zn: 26wt%; Cu: 4.7wt%; micro-nano SiC particles: 1.7wt%; Cr: 0.3wt%; Ti: 2.3wt%; Al: balance. The TIG electric arc additive manufacturing is carried out together with the ER7075 solid core filler wire. The powder core filler wire feeding speed is 1.3 m / min, the solid core filler wire feeding speed is 2.0 m / min, the scanning speed is 80 mm / min, the protective gas is high-purity argon with a purity of more than 99.99%, the gas flow is 15 L / min, the forming current is 160 A, the interlayer temperature is controlled at 70°C, and 50 layers are cladded.

[0035] In the double-wire additive process, the electric arc is stable and burns, both types of filler wires are fully melted, the additive process is continuous and stable, the obtained additive single-wall wall is well formed, the obtained additive single-wall wall does not have obvious pores and cracks, the internal structure is uniformly distributed, and presents the microstructure characteristics of the electric arc wire metal additive manufacturing. The tensile strength is 427 MPa and the microhardness is 159 HV after room temperature uniaxial stretching.

[0036] Comparative Example 1

[0037] Two identical commercially available ER7075 solid core filler wires are used for double-wire TIG electric arc additive manufacturing. The wire feeding speed is 1.6 m / min, the protective gas is high-purity argon with a purity of more than 99.99%, the gas flow is 15 L / min, the scanning speed is 90 mm / min, the forming current is 120 A, the interlayer temperature is controlled at 70°C, and 50 layers are cladded.

[0038] The electric arc is stable in the double wire additive process, both of the ER7075 filler wires are fully melted, the additive process is continuous and stable, the obtained additive single-wall wall is well formed, the obtained additive single-wall wall has a small amount of pores, no obvious cracks are seen, the internal structure is uniformly distributed, and the microstructure characteristics of the arc wire metal additive manufacturing are presented. The tensile strength is 301 MPa and the microhardness is 124 HV after room temperature uniaxial stretching.

[0039] Comparative Example 2

[0040] Two identical commercially available ER7075 solid core filler wires are used for double wire TIG arc additive, the wire feeding speed is 1.8 m / min, the protective gas is high-purity argon with a purity of more than 99.99%, the gas flow is 15 L / min, the scanning speed is 90 mm / min, the forming current is 140 A, the interlayer temperature is controlled at 70 DEG C, and 50 layers are cladded.

[0041] The electric arc is stable in the double wire additive process, both of the ER7075 filler wires are fully melted, the additive process is continuous and stable, the obtained additive single-wall wall is well formed, the obtained additive single-wall wall has a small amount of pores, no obvious cracks are seen, the internal structure is uniformly distributed, and the microstructure characteristics of the arc wire metal additive manufacturing are presented. The tensile strength is 301 MPa and the microhardness is 124 HV after room temperature uniaxial stretching.

[0042] Table 1: Additive process parameters of each example and comparative example

[0043]

[0044] Table 2: Chemical composition content and mechanical property comparison of deposited layers of each example and comparative example

[0045]

Claims

1. A dual wire electric arc additive granule-reinforced 7075 aluminum alloy seamless powder core wire, characterized in that, The additive manufacturing method adopts a particle-reinforced 7075 aluminum alloy seamless powder core wire and an ER7075 solid core wire, takes a TIG arc as a heat source, adopts a side-shaft wire feeding, a forming current is 100-250 A, a solid core wire feeding speed is 1.3-2.0 m / min, a seamless powder core wire feeding speed is 1.3-2.0 m / min, an additive speed is 80-100 mm / min, a protective gas flow is 15 L / min, an interlayer temperature is controlled to be 70 DEG C, and the protective gas is argon; the TIG arc is taken as the heat source, The particle-reinforced 7075 aluminum alloy seamless powder core wire is composed of metal powder and an outer skin, and an aluminum magnesium alloy seamless pipe is taken as the outer skin; the mass percentage of each alloy component in the powder core is as follows: metal Mg powder 0.4%-1%, metal Zn powder 25%-35%, metal Cu powder 6%-8%, metal Cr powder 0.2%-0.4%, metal Ti powder 1%-3%, micro-nano particle powder 1%-5%, the micro-nano particle is TiC, and the balance is metal Al powder.

2. A dual wire electric arc augmented, particulate-reinforced 7075 aluminum alloy seamless powder core wire according to claim 1, wherein, The powder filling rate of the powder core wire is 20-25%, and the diameter is 1.0-2.0 mm.

3. A dual wire electric arc augmented particulate reinforced 7075 aluminum alloy seamless powder core wire as claimed in claim 1, wherein, The alloy powder particle size is 75-300 microns, and the particle shape is spherical or near-spherical.

4. A dual wire electric arc augmented, particulate-reinforced 7075 aluminum alloy seamless powder core wire according to claim 1, wherein, The Cr powder, Ti powder, Mg powder, Zn powder and Cu powder are added in the form of metal powder with a purity greater than 99.9%.

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