Scandium-containing lanthanum-zirconium high-strength aluminum alloy welding wire, preparation method and application thereof

Abstract

The application discloses a high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium as well as a preparation method and application thereof, and relates to the technical field of metal material processing. The components of the welding wire are as follows in percentage by mass: Zn is 7.5-8.0%, Mg is 2.0-2.5%, Cu is 1.6-2.0%, Mn is 0.4-0.5%, Zr is 0.15-0.20%, Sc is 0.20-0.25%, La is 0.08-0.12%, Fe is smaller than 0.08%, Si is smaller than 0.05%, Be is smaller than or equal to 0.0005%, and the balance is Al and impurities, and the total amount of the impurities is smaller than or equal to 0.15%. The diameter of the welding wire is 1.2+ / -0.05 mm. The application is suitable for repairing high-strength aluminum alloy, and realizes the synergistic improvement of strength and corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal material processing, in particular to a high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium as well as a preparation method and application thereof. BACKGROUND

[0002] Inadequate performance of conventional 7xxx series welding wires: the yield strength peak value of conventional Al-Zn-Mg-Cu welding wires after single-stage aging is only 420-460 MPa, which cannot meet the requirement of strength (>500 MPa) of aviation structural part repair.

[0003] Limitations of micro-alloying technology: in the prior art, Sc and Zr are often added alone to refine grains, but the cost increases dramatically when the addition amount of Sc is greater than 0.3%, and Al3Zr particles are prone to coarsening when Zr is added alone; although Sc can refine grains when added alone, the high-temperature stability is insufficient; La is often used in cast alloys, and the synergistic strengthening mechanism of La in the welding wire has not been clarified; the application of La in the welding wire is mostly limited to gas removal, and the synergistic strengthening mechanism of La with Sc and Zr has not been revealed; and the conventional T6 treatment (120 DEG C x 20h) is difficult to realize the gradient distribution of nanometer precipitates, resulting in a mismatch between strength and plasticity (elongation <5% at the strength peak value).

[0004] Therefore, the application provides a high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium and a preparation method thereof to solve the above problems. SUMMARY

[0005] To achieve the above object, the application provides the following technical scheme: a high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium, wherein the components of the welding wire are as follows in terms of mass percentage: Zn is 7.5-8.0%, Mg is 2.0-2.5%, Cu is 1.6-2.0%, Mn is 0.4-0.5%, Zr is 0.15-0.20%, Sc is 0.20-0.25%, La is 0.08-0.12%, Fe is <0.08%, Si is <0.05%, Be is <=0.0005%, and the balance is Al and impurities, and the total amount of impurities is <=0.15%; and the diameter of the welding wire is 1.2+ / -0.05 mm.

[0006] The application also provides a preparation method of the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium, which is used for preparing the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium and comprises the following steps:

[0007] Step 1, vacuum melting and continuous casting, the raw material is kept at 720 DEG C for 10 min, then stirred under the coupling of 0.5-1.0T static magnetic field and 10-20 kHz alternating electric field for 10 min, the continuous casting speed is 1.2-1.5 m / min, the argon atmosphere is rotated and sprayed for 30 min, the melt is heated to 740 DEG C, and then poured into a graphite mold preheated to 200 DEG C, and a casting ingot with a size of Φ120mm*300mm is obtained;

[0008] Step 2, after 5mm of the casting ingot car skin, the casting ingot is subjected to 350 DEG C, 8h and 470 DEG C, 12h step uniform treatment, the heating rate is controlled within 0.5 DEG C / min, after the treatment, the furnace is discharged and air cooled;

[0009] Step 3, after the casting ingot is turned to Φ100mm, first, hot extrusion is carried out at 450-500 DEG C, the extrusion ratio is 10:1, and a Φ9.5mm aluminum rod is extruded, then annealing is carried out, the heating rate is 1.6 DEG C / min, the temperature is kept at 375 DEG C for 3 hours, then the furnace is discharged and air cooled; the Φ9.5mm aluminum rod is processed to Φ2.7mm through three passes of rolling, the diameter reduction is 3.1, 1.7 and 2mm in turn, and finally drawing is carried out, and the welding wire is drawn to Φ1.2mm at one time;

[0010] Step 4, the finished welding wire is subjected to scraping treatment to remove surface microcracks and defects, then subjected to ultrasonic cleaning, drying, and finally wound.

[0011] The application further provides the application of the welding wire in arc additive manufacturing and aluminum alloy part repair.

[0012] The application has the following beneficial effects:

[0013] The application adopts Sc, La and Zr ternary synergy: Sc, Zr composite particles (≤20nm) refine the grain, and La is segregated at the grain boundary to inhibit cracks;

[0014] The two-stage aging system of the application: through GP zone-η' phase gradient precipitation, the single aging strength limit is broken through;

[0015] Through the synergy of Sc, Zr and La multiple elements and the combination of two-stage aging, the yield strength 510MPa bottleneck can be broken through; the Be content is controlled to be below 0.0005%, the oxidation resistance and safety are considered; the application is suitable for high-strength aluminum alloy repair, and the strength and corrosion resistance are synergistically improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1SEM images of different regions of the additive manufacturing component after heat treatment in the present application; wherein (a) is the SEM image of the bottom region of the additive manufacturing component after heat treatment; (b) is the SEM image of the middle region of the additive manufacturing component after heat treatment; (c) is the SEM image of the top region of the additive manufacturing component after heat treatment;

[0017] Figure 2 Element distribution map of the additive manufacturing component after heat treatment in the present application; wherein (a) is the element distribution map; (b) is the scanning electron microscope image of the scanning region; (c) is the Zn element distribution map; (d) is the Al element distribution map; (e) is the Mg element distribution map; (f) is the Cu element distribution map; (g) is the Mn element distribution map; (h) is the Sc element distribution map; (i) is the Fe element distribution map;

[0018] Figure 3 Mechanical property comparison chart of the component before and after heat treatment in the present application;

[0019] Figure 4 Preparation process schematic diagram of the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium in the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] The present application will be further described in detail below according to the drawings and embodiments.

[0022] Embodiment one: the present embodiment provides a high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium, and the components of the welding wire are as follows in terms of mass percentage: Zn is 7.5-8.0%, Mg is 2.0-2.5%, Cu is 1.6-2.0%, Mn is 0.4-0.5%, Zr is 0.15-0.20%, Sc is 0.20-0.25%, La is 0.08-0.12%, Fe is <0.08%, Si is <0.05%, Be is ≤0.0005%, and the balance is Al and impurities, and the total amount of impurities is ≤0.15%; the diameter of the welding wire is 1.2±0.05mm;

[0023] The component design of the welding wire is as follows:

[0024] (1) main strengthening system (mass percentage)

[0025] Zn (7.5-8.0%) + Mg (2.0-2.5%) + Cu (1.6-2.0%)

[0026] Forming η-MgZn2, S-Al2CuMg, etc. strengthening phase, the design is based on the precipitation strengthening formula:

[0027] ;

[0028] ;

[0029] Wherein is the contribution of the precipitate phase to the strength, k is the process constant, f is the volume fraction of the precipitate phase, r is the average radius of the particles, m and n are material constants related to the properties of the matrix and precipitate phase, usually positive, is the concentration of Zn element, is the concentration of Mg element, and the coherent strain energy is optimized by adjusting the Zn / Mg / Cu ratio.

[0030] (2) Synergistic effect of micro-alloying elements

[0031] Sc (0.20-0.25%) + Zr (0.15-0.20%) + La (0.1%)

[0032] Sc / Zr forms Al3(Sc, Zr) composite particles, pinning dislocations and subgrain boundaries (Zener pinning force model):

[0033] ;

[0034] Wherein p is the pinning pressure, is the grain boundary energy, f is the volume fraction of the precipitate phase, r is the average radius of the particles, and the recrystallization during deposition is inhibited. The strengthening increment brought by micro-alloying particles According to the Orowan mechanism:

[0035] ;

[0036] Wherein G is the shear modulus, b is the Burgers vector, is the interparticle distance, is the particle diameter.

[0037] The addition of La is used to modify the structure of the oxide film, reduce the porosity (La / O adsorption energy calculation verification), and at the same time, it is segregated at the grain boundary to reduce the crack sensitivity.

[0038] (3) Impurity control

[0039] Fe <0.08%, Si <0.05%: Avoid forming coarse Al7Cu2Fe, Mg2Si phase, determine the critical solubility according to the phase diagram calculation. Be≤0.0005%: Trace Be adsorbed on the surface of the molten pool to reduce oxidation and improve arc stability.

[0040] The embodiment also provides a preparation method of the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium, for preparing the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium as described above, which specifically comprises the following steps: Figure 4

[0041] Step 1, vacuum (50 Pa) smelting and continuous casting, raw materials (containing Zn, Mg, Cu, Mn, Zr, Sc, La, Fe, Si, Be, Al and the like) are kept at 720 ℃ for 10 min, then stirred under the coupling of a 0.5-1.0 T static magnetic field and a 10-20 kHz alternating electric field for 10 min, the continuous casting speed is 1.2-1.5 m / min, and the melt is refined by rotating and spraying under a high-purity argon atmosphere for 30 min, the melt is heated to 740 ℃, and then poured into a graphite mold preheated to 200 ℃, a casting ingot with a size of Φ120 mm*300 mm is obtained, the cooling rate is >100 ℃ / s, and segregation is inhibited.

[0042] Step 2, after 5 mm of the casting ingot, the casting ingot is subjected to 350 ℃, 8 h and 470 ℃, 12 h step uniformization treatment, the heating rate is controlled to be less than or equal to 0.5 ℃ / min, and after the treatment is completed, the furnace is discharged and air-cooled.

[0043] Step 3, hot extrusion and cold drawing, after the casting ingot is turned to Φ100 mm, the casting ingot is first subjected to hot extrusion at 450-500 ℃, the extrusion ratio is 10:1, and a Φ9.5 mm aluminum rod is extruded, then annealing is performed, the heating rate is 1.6 ℃ / min, the temperature is kept at 375 ℃ for 3 hours, then the furnace is discharged and air-cooled, the Φ9.5 mm aluminum rod is processed to Φ2.7 mm through three passes of rolling, the diameter reduction is 3.1, 1.7 and 2 mm in turn, and finally drawing is performed, and a welding wire with a diameter of 1.2 mm (ellipticity ≤0.03 mm) is obtained through one-time drawing.

[0044] Step 4, the finished welding wire is subjected to scraping treatment to remove surface microcracks and defects, then subjected to ultrasonic cleaning, drying, and finally wound.

[0045] The high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium prepared by the above method is applied to arc additive manufacturing (cold metal transition (CMT) additive manufacturing), and the process and parameters are as follows:

[0046] Current: 130-150 A (pulse peak value); voltage: 16-20 V; wire feeding speed: 6-8 m / min; deposition speed: 0.3-0.5 m / min; deposition path: the adjacent layer scanning direction is rotated by 67° (golden section angle), and anisotropy is reduced. Interlayer temperature: ≤80 ℃ (water-cooled copper substrate temperature control, infrared temperature feedback), to avoid overheating area coarsening, and the surface oxide layer is removed after each layer deposition is completed.

[0047] ​The high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium prepared by the above method is applied to the repair of aluminum alloy parts (repair of aerospace load-bearing components), and the process and parameters are as follows:

[0048] Before repair, polish the repair area to remove impurities and oxide layers. Before arc additive repair, preheat the repaired parts to 150-200℃. Deposit the above additive manufacturing process single layer or multiple layers for repair. After repair, remove the excess material and perform non-destructive testing on the parts. If the defects are not eliminated, repeat the above steps until the defects are completely repaired.

[0049] The above arc additive manufacturing and heat treatment process after repair include:

[0050] (1) Solution treatment (430℃×3h+470℃×3h, water cooling)

[0051] According to the TTT curve of AlZnMgCu alloy, 430℃×3h+470℃×3h is selected to completely dissolve η' phase and avoid overburning (DSC detection determines that the liquidus is 485℃).

[0052] (2) Two-stage aging (120℃×12h+150℃×6h)

[0053] Primary aging: High-density GP zones are formed at 120℃, providing nucleation sites for subsequent precipitation.

[0054] Secondary aging: 150℃ promotes the transformation of GP zones into η' transition phase and controls the Ostwald mechanism to achieve strength and toughness balance.

[0055] Precipitation kinetics model:

[0056] ;

[0057] Where t is the time required to complete the precipitation stage, A is the pre-exponential factor, related to the atomic vibration frequency and nucleation site density of the material itself, is the activation energy for precipitation, representing the energy barrier that needs to be overcome for atomic diffusion, mainly controlled by the Zn, Mg vacancy diffusion energy, R is the ideal gas constant (8.314 J·mol -1 ·K -1 ), T is the absolute temperature (unit K).

[0058] By adjusting the T1 / T2 combination (T1 is primary aging 120℃ / 12h, T2 is secondary aging 150℃ / 6h), the peak value of the precipitate size distribution is located at 25nm.

[0059] Example 2: The welding wire is prepared by the preparation method of the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium described in Example 1.

[0060] The welding wire prepared in the embodiment is applied to arc additive manufacturing:

[0061] The CMT process is adopted for deposition, the current is 144 A, the voltage is 16.5 V, and the wire feeding speed is 6 m / min. The interlayer temperature is controlled within 80 DEG C, and the oxide layer is removed between layers. After deposition, solid solution treatment (430 DEG C * 3h + 470 DEG C * 3h, water cooling for 30s) and two-stage aging (120 DEG C * 12h + 150 DEG C * 6h) are carried out, and the scanning electron microscope (SEM) image after heat treatment is as shown in Figure 1 The energy spectrum after heat treatment is as shown in Figure 2 The unsolidified residual elements after heat treatment are Mg and Cu elements, and the remaining elements are uniformly distributed, which indicates that sufficient solid solution is obtained, and the heat treatment process and the material are well matched. The tensile strength is 581 MPa, the yield strength is 510 MPa (ultra-high strength aluminum alloy standard), the elongation is 7.9%, and the stress-strain curve is as shown in Figure 3 .

[0062] In summary, the welding wire realizes the comprehensive performance of yield strength ≥ 510 MPa and elongation > 5% after aging through composition optimization and heat treatment process synergistic regulation, and is suitable for laser, arc additive repair manufacturing in multiple scenes.

[0063] The application adopts Sc, La and Zr ternary synergy: Sc, Zr composite particles (≤20 nm) refine the grain, and La segregates the grain boundary to inhibit cracks;

[0064] The two-stage aging system of the application: through GP zone and η' phase gradient precipitation, the single aging strength limit is broken through;

[0065] Through the synergy of Sc, Zr and La multiple elements, combined with two-stage aging, the bottleneck of 570 MPa ultimate tensile strength limit can be broken through, the yield strength is 510 MPa (ultra-high strength aluminum alloy standard), the elongation is 7.9%, the Be content is controlled to be less than 0.0005%, the oxidation resistance and safety are considered, and the application is suitable for high-strength aluminum alloy repair, and the strength and elongation are synergistically improved.

[0066] Although the embodiments of the application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the application, and the scope of the application is defined by the appended claims and their equivalents.

Claims

1. A high-strength aluminum alloy welding wire containing scandium lanthanum zirconium, characterized by, The components of the welding wire are as follows in percentage by mass: Zn is 7.5-8.0%, Mg is 2.0-2.5%, Cu is 1.6-2.0%, Mn is 0.4-0.5%, Zr is 0.15-0.20%, Sc is 0.20-0.25%, La is 0.08-0.12%, Fe is less than 0.08%, Si is less than 0.05%, Be is less than or equal to 0.0005%, and the balance is Al and impurities, and the total amount of impurities is less than or equal to 0.15%; the diameter of the welding wire is 1.2±0.05 mm.

2. A method of producing a high-strength aluminum alloy wire containing scandium lanthanum zirconium, characterized by, The method for preparing the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium as claimed in claim 1 comprises the following steps: Step 1, vacuum melting and continuous casting, the raw material is kept at 720℃ for 10 min, then stirred under the coupling of 0.5-1.0T static magnetic field and 10-20kHz alternating electric field for 10 min, the continuous casting speed is 1.2-1.5m / min, and the melt is refined by rotating blowing for 30 min in argon atmosphere, the melt is heated to 740℃, and then poured into a graphite mold preheated to 200℃, and the pouring size is a Φ120mm×300mm ingot; Step 2, after 5mm of the ingot car skin, the ingot is subjected to 350℃, 8h and 470℃, 12h step uniformization treatment, the heating rate is controlled within 0.5℃ / min, and after the treatment, the furnace is discharged and air cooled; Step 3, after the ingot is turned to Φ100mm, it is first subjected to hot extrusion at 450-500℃, the extrusion ratio is 10:1, and a Φ9.5mm aluminum rod is extruded, then annealing is carried out, the heating rate is 1.6℃ / min, and the temperature is kept at 375℃ for 3 hours, then the furnace is discharged and air cooled; the Φ9.5mm aluminum rod is processed to Φ2.7mm by three passes of rolling, the diameter reduction is 3.1, 1.7 and 2mm in turn, and finally drawn to Φ1.2mm welding wire; Step 4, the finished welding wire is subjected to scraping treatment to remove surface microcracks and defects, then subjected to ultrasonic cleaning, drying, and finally wound.

3. The application of the high-strength aluminum alloy welding wire containing scandium, lanthanum and zirconium as claimed in claim 1 or the welding wire prepared by the preparation method as claimed in claim 2 in arc additive manufacturing and aluminum alloy part repair.

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