A method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength

Abstract

This invention relates to a method for designing the composition of arc-additive aluminum alloys that balances hot cracking susceptibility and strength. The method involves: calculating a baseline value E0 for the hot cracking susceptibility index of a standard high-strength aluminum alloy composition; using the elemental contents of Cu+Cd+Sc and Cu+Ag+Mg+Sc as variables, employing orthogonal experimental design to design different composition ratios, calculating the hot cracking susceptibility index E1 for each ratio, and selecting composition ratios where E1 is less than 1.1E0; conducting circumferential weld tests under restraint conditions on each selected high-strength aluminum alloy composition ratio to screen for low hot cracking susceptibility ratios; calculating the change in yield strength with aging temperature and time to further screen for composition ratios that meet the yield strength requirements; and testing the mechanical properties of the high-strength aluminum alloy using single-wall specimens produced by arc additive manufacturing, selecting the composition ratio that meets the mechanical property requirements as the final high-strength aluminum alloy composition. This invention solves the problem that traditional Al-Cu-Mn high-strength aluminum alloy arc additive manufacturing cannot simultaneously achieve low hot cracking susceptibility and high strength.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology and relates to a method for designing the composition of arc-additive aluminum alloys that takes into account both thermal cracking sensitivity and strength. Background Technology

[0002] Currently, the yield strength of 2219 aluminum alloy formed by arc additive manufacturing (WAAM) is relatively low, which cannot meet the manufacturing requirements of large, lightweight, high-strength aluminum alloy critical load-bearing components. WAAM-formed 2219 aluminum alloy shells typically have features such as ring ribs and reinforcing ribs, making integral cold deformation difficult; generally, only T6 heat treatment can be used. Through optimization of the forming process and heat treatment regime, the highest yield strength of currently produced 2219 aluminum alloy products reaches 300 MPa, which is still significantly lower than the 350 MPa yield strength required for critical load-bearing components. This issue has become a bottleneck restricting the application of WAAM technology in aerospace high-strength aluminum alloy critical load-bearing components.

[0003] Developing Al-Cu alloys for WAAM (Waam-Assembled Aluminum) using alloying and micro-alloying methods to improve the strength of WAAM components is one of the most promising technical approaches to overcome the aforementioned bottlenecks. However, it faces challenges in designing high-strength, high-toughness aluminum alloys with low crack sensitivity. The WAAM process is characterized by non-uniform rapid heating and cooling, and multiple thermal cycles. Under the influence of forming energy / mass input and structural shape, it can cause varying degrees of macro- and micro-segregation, hot cracking, and inhomogeneous microstructure and properties. High-strength aluminum alloys for WAAM designed to address these problems are currently lacking.

[0004] To address this challenge, it is necessary to research a composition design method for high-strength aluminum alloys produced by arc additive manufacturing that balances thermal cracking sensitivity and strength. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a method for designing the composition of aluminum alloys for arc additive manufacturing that takes into account both hot cracking sensitivity and strength, thereby solving the problem that traditional Al-Cu-Mn high-strength aluminum alloy arc additive manufacturing cannot simultaneously achieve low hot cracking sensitivity and high strength.

[0006] The solution to the technical problem of this invention is: to propose a method for designing the composition of arc-additive aluminum alloys that takes into account both hot cracking sensitivity and strength, comprising the following steps:

[0007] (1) Calculate the baseline value E0 of the hot cracking sensitivity index of the standard composition of Al-Cu-Mn high-strength aluminum alloy.

[0008] (2) Using the elemental contents of Cu+Cd+Sc and Cu+Ag+Mg+Sc as variables, the orthogonal experimental design method was adopted to design different component ratios, calculate the hot cracking sensitivity index E1 under each component ratio, and take the component ratio with E1 less than 1.1E0 as the preferred component ratio of high strength aluminum alloy.

[0009] (3) For each high-strength aluminum alloy composition selected in step (2): prepare wire, arc additive forming single wall test plate, and process into flat circumferential weld test piece, and conduct circumferential weld welding test under restraint conditions; count the proportion of solidification crack length of circumferential weld to the total weld length, verify the hot cracking sensitivity of high-strength aluminum alloys with different compositions, and then screen out the composition with low hot cracking sensitivity.

[0010] (4) Based on the molar fraction ratio of main and microalloying elements in the composition ratio selected in step (3), establish an aging precipitation kinetic model of Al-Cu-Mn-X alloy considering the effect of microalloying elements, calculate the changes in Cu mass fraction and the radius, quantity and volume fraction of nano-strengthening phase during aging; establish a yield strength prediction model considering solid solution strengthening and second phase precipitation strengthening, use the calculation results of the aging precipitation kinetic model as input, calculate the change in yield strength with aging temperature and time, and then select the composition ratio that meets the yield strength condition, where X represents one of Cd+Sc or Ag+Mg+Sc;

[0011] (5) Based on the results of the calculation of hot cracking sensitivity and yield strength, the mechanical properties of high-strength aluminum alloy are tested by electric arc additive single wall specimens. The component ratio that meets the mechanical properties requirements in step (4) is selected as the Al-Cu-Mn high-strength aluminum alloy composition for electric arc additive manufacturing that takes into account both hot cracking sensitivity and strength.

[0012] Furthermore, the baseline value E0 for calculating the hot cracking susceptibility index of the standard composition of Al-Cu-Mn high-strength aluminum alloy is specifically included:

[0013] The solidification path of Al-Cu-Mn alloy under standard composition was calculated using Thermal-Calc thermodynamic software, i.e., the temperature-solid mass fraction (T-fs) curve. The square root curve (T-fs) of temperature-solid mass fraction was extracted when the solid mass fraction at the end of solidification was 0.9-0.99. 0.5 The maximum absolute value of the slope |dT / d(fs) 0.5 )|max, which is the solidification hot crack index, serves as the benchmark value E0 for the hot crack sensitivity index of this standard composition.

[0014] Furthermore, the cooling rate was calculated to be 100 K / s and the secondary dendrite spacing was 10 μm when calculating the solidification path.

[0015] Furthermore, the hot cracking susceptibility index E1 is calculated for each component ratio, under the following conditions:

[0016] When the solid mass fraction at the end of solidification is 0.9-0.99, E1=|dT / d(fs) 0.5 )|max.

[0017] Furthermore, the selection of low thermal cracking susceptibility components is specifically as follows:

[0018] Let f1 be the measured value of the ratio of the solidification crack length of the circumferential weld to the total weld length corresponding to the high-strength aluminum alloy composition selected in step (2), and f0 be the ratio of the solidification crack length of the circumferential weld to the total weld length corresponding to the standard composition of the high-strength aluminum alloy. Select composition ratios with f1 less than 1.1f0.

[0019] Furthermore, the nano-reinforcing phase includes: Cd segregation at the interface, {100} α-Al Al2Cu transition phase θ' precipitated at the habit surface; Ag-Mg binary segregation at the interface, {111} α-Al The Al2Cu-like transition phase Ω is precipitated on the habitual surface.

[0020] Furthermore, an aging precipitation kinetic model for Al-Cu-Mn-X alloys considering the effects of microalloying elements is established, specifically including:

[0021] Cluster incubation time: t0 = f(C0), where C0 is the initial molar concentration of solute atoms;

[0022] Enhanced phase nucleation rate: J = f(Cm, Ce(TM), TM), where TM is the aging temperature, Cm is the average molar concentration of solute atoms, Ce is the average molar concentration of solute atoms in equilibrium, and Ce(TM) is the average molar concentration of solute atoms in equilibrium at the aging temperature TM.

[0023] Strengthening phase radius: R = f(t, t0, Cm, Cr(R(t-Δt), Ce(TM)), Ce(TM), D(Cm)), where t is the aging time, D(Cm) is the diffusion coefficient related to the solute atom concentration, Cr is the equilibrium concentration of solute atoms at the precipitated phase interface, Δt is the small time interval, and R(t-Δt) is the strengthening phase radius calculated before time Δt.

[0024] When Cm ≤ Cr, the strengthening phase begins to coarsen, then R = f(t, t0, t) pa Ce(TM), TM, D(Cm), R(t) pa )), where t pa The peak efficiency time is the moment when Cm≤Cr first appears.

[0025] Furthermore, a yield strength prediction model considering solid solution strengthening and second-phase precipitation strengthening is established, specifically including:

[0026] σ y =σ0+σ ss (Cm)+σ ppt (t, t0, J, f) v (t,t0,t pa J, R))

[0027] Where σ0 is the inherent strength of the alloy (MPa), σ ss Contribution to solid solution strengthening of solute atoms (MPa), σ ppt For the second-phase enhancement contribution (MPa), f v This represents the volume fraction of the precipitated phase.

[0028] Furthermore, the component ratios that satisfy the yield strength condition are selected, specifically:

[0029] The component ratios with a room temperature yield strength greater than or equal to 350 MPa were selected.

[0030] Furthermore, the mechanical performance indicators to be tested in step (5) and the corresponding indicator requirements include:

[0031] At room temperature, parallel and perpendicular to the deposition direction: tensile strength greater than or equal to 430 MPa, yield strength greater than or equal to 350 MPa, and elongation after fracture greater than or equal to 6%.

[0032] Under high temperature conditions of 220℃, parallel to and perpendicular to the deposition direction: tensile strength greater than or equal to 350MPa, yield strength greater than or equal to 330MPa, and elongation after fracture greater than or equal to 6%.

[0033] The advantages of this invention compared to the prior art are:

[0034] (1) The Al-Cu-Mn alloy obtained by the composition design method of the present invention has a hot cracking sensitivity that is no more than 10% higher than that of conventional 2219 aluminum alloy;

[0035] (2) The Al-Cu-Mn alloy obtained by the composition design method of the present invention has a 20% higher yield strength than the conventional 2219 aluminum alloy. Attached Figure Description

[0036] Figure 1 This is a flowchart of the arc additive aluminum alloy composition design method of the present invention, which takes into account both hot cracking sensitivity and strength.

[0037] Figure 2 Typical T-fs of the present invention 0.5 curve;

[0038] Figure 3 This is a specimen sensitive to hot cracking of the fixed restraint circumferential seam, as described in an embodiment of the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] Based on the characteristics of aluminum alloy arc additive manufacturing, this invention proposes a method for designing the composition of high-strength aluminum alloys for arc additive manufacturing that comprehensively considers both hot cracking sensitivity and strength. Figure 1 The specific steps are as follows:

[0041] (1) Calculate the hot cracking sensitivity index of the standard composition of Al-Cu-Mn high-strength aluminum alloy.

[0042] The solidification path (i.e., temperature-solid mass fraction T-fs curve) of Al-Cu-Mn alloys with standard compositions (such as 2219 aluminum alloy) was calculated using thermodynamic software such as Thermal-Calc. Based on the characteristics of WAAM, the cooling rate during solidification path calculation was 100 K / s, and the secondary dendrite spacing was 10 μm. The square root curve of temperature-solid mass fraction (T-fs) at the end of solidification (fs = 0.9-0.99) was extracted. 0.5 The maximum absolute value of the slope |dT / d(fs) 0.5 )|max (solidification hot crack index), which serves as the benchmark value E0 for the hot crack sensitivity index of this standard composition.

[0043] (2) Based on |dT / d(fs) 0.5 The composition was optimized based on the maximum thermal cracking sensitivity index.

[0044] Based on the Al-Cu-Mn standard composition, and using the contents of elements such as Cu+Cd+Sc and Cu+Ag+Mg+Sc as variables, an orthogonal experimental design method was used to design different component ratios. The thermal cracking susceptibility index E1 for each component ratio was calculated using thermodynamic software such as Thermal-Calc. The calculation condition was E1=|dT / d(fs) 0.5 The preferred composition ratio for high-strength aluminum alloys is one where E1 is less than 1.1E0.

[0045] (3) Screening of high-strength aluminum alloy composition for low thermal cracking sensitivity arc additive manufacturing.

[0046] For each high-strength aluminum alloy composition selected in step (2): prepare it into wire, arc additive forming single wall test plate, process it into flat circumferential weld test piece, and then conduct circumferential weld welding test under restraint conditions; count the proportion of solidification crack length of circumferential weld to the total weld length, verify the hot cracking sensitivity of high-strength aluminum alloys with different compositions, and further screen out composition with low hot cracking sensitivity.

[0047] Preferred: Let f1 be the measured value of the ratio of the solidification crack length of the circumferential weld to the total weld length corresponding to the high-strength aluminum alloy composition selected in step (2), and f0 be the ratio of the solidification crack length of the circumferential weld to the total weld length corresponding to the standard composition of the high-strength aluminum alloy. Select composition ratios with f1 less than 1.1f0.

[0048] (4) Predict the yield strength of high-strength aluminum alloy produced by electric arc additive manufacturing.

[0049] Based on the molar fraction ratio of main and microalloying elements in the composition ratio selected in step (3), an aging precipitation kinetic model of Al-Cu-Mn-X alloy considering the role of microalloying elements is established to calculate the changes in Cu mass fraction and the radius, quantity, and volume fraction of nano-reinforcing phases during the aging process; wherein, X represents either Cd+Sc or Ag+Mg+Sc, and the nano-reinforcing phase includes: Cd segregation at the interface, {100} α-Al Al2Cu transition phase θ' precipitated at the habit surface; Ag-Mg binary segregation at the interface, {111} α-Al The Al2Cu-like transition phase Ω is precipitated on the habitual surface. Then, a yield strength prediction model considering solid solution strengthening and second-phase precipitation strengthening is established. Using the calculation results of the aging precipitation kinetic model as input, the change of yield strength with aging temperature and time is calculated, and then the composition ratio with a room temperature yield strength greater than or equal to 350 MPa is screened.

[0050] The establishment of the aging precipitation kinetics model for Al-Cu-Mn-X alloys considering the effects of microalloying elements specifically includes:

[0051] Cluster incubation time: t0 = f(C0), where C0 is the initial molar concentration of solute atoms (Cu) (at.%);

[0052] Enhanced phase nucleation rate: J = f(Cm, Ce(TM), TM), where TM is the aging temperature (K), Cm is the average molar concentration of solute atoms (at.%), Ce is the average molar concentration of solute atoms in equilibrium (at.%), and Ce(TM) is the average molar concentration of solute atoms in equilibrium (at.%) at the aging temperature TM.

[0053] Strengthening phase radius: R = f(t, t0, Cm, Cr(R(t-Δt), Ce(TM)), Ce(TM), D(Cm)), where t is the aging time (s) and D(Cm) is the diffusion coefficient (m) related to the solute atom concentration. 2 / s), Cr is the equilibrium concentration of solute atoms at the precipitated phase interface (at.%), Δt is the small time interval, and R(t-Δt) is the radius of the strengthening phase calculated at the previous Δt time.

[0054] When Cm ≤ Cr, the strengthening phase begins to coarsen, then R = f(t, t0, t) pa Ce(TM), TM, D(Cm), R(t) pa )), where t pa The peak efficiency time (s) is the moment when Cm≤Cr first appears.

[0055] The functional relationships mentioned above can be implemented using existing computational models or through custom optimization.

[0056] The establishment of the yield strength prediction model considering solid solution strengthening and second-phase precipitation strengthening specifically includes:

[0057] σ y =σ0+σ ss (Cm)+σ ppt (t, t0, J, f) v (t,t0,t pa , J, R)), where σ0 is the inherent strength of the alloy (MPa), σ ss Contribution to solid solution strengthening of solute atoms (MPa), σ ppt For the second-phase enhancement contribution (MPa), f v This represents the volume fraction of the precipitated phase.

[0058] (5) Based on the results of the calculation of hot cracking sensitivity and yield strength, the mechanical properties of high-strength aluminum alloy are tested by electric arc additive single wall specimen. The composition ratio obtained in step (4) is screened, and the composition ratio that meets the mechanical properties is selected as the composition of Al-Cu-Mn high-strength aluminum alloy for electric arc additive manufacturing that takes into account both hot cracking sensitivity and strength.

[0059] The mechanical performance indicators to be tested and their corresponding requirements include:

[0060] At room temperature, parallel and perpendicular to the deposition direction: tensile strength greater than or equal to 430 MPa, yield strength greater than or equal to 350 MPa, and elongation after fracture greater than or equal to 6%.

[0061] Under high temperature conditions of 220℃, parallel to and perpendicular to the deposition direction: tensile strength greater than or equal to 350MPa, yield strength greater than or equal to 330MPa, and elongation after fracture greater than or equal to 6%.

[0062] Example 1

[0063] The composition design of the Al-Cu-Mn-Cd-Sc alloy for arc additive manufacturing and the test results of its mechanical properties are as follows:

[0064] (1) Calculation of the hot cracking susceptibility index of the standard composition of Al-Cu-Mn high-strength aluminum alloy. Using Thermal-Calc thermodynamic software, the solidification path of the 2219 aluminum alloy standard composition listed in Table 1 was calculated. The cooling rate was set to 100 K / s, and the secondary dendrite spacing was set to 10 μm. Figure 2 The thermal cracking sensitivity index at the end of solidification is shown, and the calculated value is E0 = 1805℃.

[0065] Table 1. Composition and Hot Cracking Sensitivity of Standard 2219 Aluminum Alloy

[0066]

[0067] (2) Based on |dT / d(fs) 0.5 Composition optimization design was conducted based on the hot cracking sensitivity index |dT / d(fs). Using the standard composition of 2219 aluminum alloy listed in Table 1, and taking the contents of added elements Cd, Sc, and the main alloying element Cu as variables, a 3-factor, 3-level design was employed to create Al-Cu-Mn-Cd-Sc alloys with different composition ratios, and the hot cracking sensitivity index |dT / d(fs) was calculated. 0.5 According to the optimization results, the Cu content is 5.6–6.8 wt%, the Cd content is 0.05–0.20 wt%, the Sc content is 0.06–0.20 wt%, and the hot cracking sensitivity index is below 1985℃.

[0068] (3) Screening of high-aluminum alloy composition for low-thermal-cracking-sensitive arc additive manufacturing. From the composition range of step (2), two Cu contents (6.5 wt% and 6.0 wt%) and two Sc contents (0.16 wt% and 0.08 wt%) were selected, with Cd (0.12 wt%) fixed. Other elemental compositions were controlled according to Table 1. Wires with a diameter of 1.2 mm were prepared, and single-wall test panels were formed by arc additive manufacturing and processed into… Figure 3 The plate circumferential weld test specimens shown were then subjected to circumferential weld welding tests under restraint conditions. The proportion of solidification crack length to total weld length for the four alloy compositions was statistically analyzed, and two compositions with low hot cracking sensitivity were selected. Alloy #1: Cu 6.5wt%, Sc 0.08wt%, Cd 0.12wt%. Alloy #2: Cu 6.0wt%, Sc 0.16wt%, Cd 0.12wt%.

[0069] (4) Prediction of yield strength of high-aluminum alloys produced by arc additive manufacturing. Based on the molar fraction ratio of main and microalloying elements, an aging precipitation kinetic model of Al-Cu-Cd alloy considering the effect of microalloying elements was established to calculate the changes in Cu mass fraction and the radius, quantity, and volume fraction of θ' nano-reinforcing phase during aging. Then, a yield strength prediction model considering solid solution strengthening and second-phase precipitation strengthening was established to calculate the change in yield strength with aging temperature and time. For the two alloys mentioned above, after aging at 175℃ for 6 hours, the yield strength of alloy #1 reached 385 MPa, and the yield strength of alloy #2 reached 360 MPa.

[0070] (5) Using the two alloy wires mentioned above, single-wall specimens of 200mm×100mm×22mm were produced by arc additive manufacturing. The specimens were solution-treated at 535-540℃ for 3 hours, water-quenched, and aged at 175℃ for 6 hours. Samples were then cut and tested for room temperature tensile mechanical properties. Mechanical properties of alloy #1: Transverse: Tensile strength 469MPa, Yield strength 401MPa, Elongation after fracture 6.0%. Longitudinal: Tensile strength 432MPa, Yield strength 395MPa, Elongation after fracture 3.0%. Mechanical properties of alloy #2: Transverse: Tensile strength 455MPa, Yield strength 367MPa, Elongation after fracture 10.0%. Longitudinal: Tensile strength 448MPa, Yield strength 361MPa, Elongation after fracture 8.0%. Due to its low Cu content, alloy #2 has fewer residual brittle Al2Cu phases in the interlaminar layers, resulting in better elongation after fracture and a yield strength that is more than 20% higher than that of 2219 aluminum alloy.

[0071] Example 2

[0072] The composition design of the Al-Cu-Mn-Ag-Mg-Sc alloy for arc additive manufacturing and the test results of its mechanical properties are as follows:

[0073] (1) Calculation of the hot cracking susceptibility index of the standard composition of Al-Cu-Mn high-strength aluminum alloy. Using Thermal-Calc thermodynamic software, the solidification path of the 2219 aluminum alloy standard composition listed in Table 1 was calculated. The cooling rate was set to 100 K / s, and the secondary dendrite spacing was set to 10 μm. Figure 2 The thermal cracking sensitivity index at the end of solidification is shown, and the calculated value is E0 = 1805℃.

[0074] (2) Based on |dT / d(fs) 0.5 Composition optimization design was conducted based on the hot cracking sensitivity index |dT / d(fs). Using the standard composition of 2219 aluminum alloy listed in Table 1, and taking the contents of added elements Ag, Mg, Sc, and the main alloying element Cu as variables, Al-Cu-Ag-Mg alloys with different composition ratios were designed using a 4-factor, 3-level approach, and the hot cracking sensitivity index |dT / d(fs) was calculated. 0.5According to the optimization results, the Cu content is 5.0-5.5 wt%, the Ag content is 0.4-0.7 wt%, the Mg content is 0.5-0.8 wt%, the Sc content is 0.10-0.20 wt%, and the hot cracking sensitivity index is lower than 1985℃.

[0075] (3) Screening of high-aluminum alloy composition for low-thermal-cracking-sensitive arc additive manufacturing. From the composition range of step (2), two Cu contents (5.5 wt% and 5.0 wt%) and two Mg contents (0.5 wt% and 0.8 wt%) were selected. The contents of Ag (0.6 wt%) and Sc (0.16 wt%) were fixed, and the composition of other elements was controlled according to Table 1 (excluding Zr). Wires with a diameter of 1.2 mm were prepared, and single-wall test panels were formed by arc additive manufacturing and processed into… Figure 3 The plate circumferential weld test specimens shown were then subjected to circumferential weld welding tests under restraint conditions. The proportion of solidification crack length to total weld length for the four alloy compositions was statistically analyzed, and two compositions with low hot cracking sensitivity were selected. Alloy #3: Cu 5.5wt%, Mg 0.8wt%, Ag 0.6wt%, Sc 0.16wt%. Alloy #4: Cu 5.0wt%, Mg 0.5wt%, Ag 0.6wt%, Sc 0.16wt%.

[0076] (4) Prediction of yield strength of high-aluminum alloys produced by arc additive manufacturing. Based on the molar fraction ratio of main and microalloying elements, an aging precipitation kinetic model for Al-Cu-Ag-Mg alloys considering the effect of microalloying elements was established to calculate the changes in the radius, quantity, and volume fraction of the Ω-strengthening phase during aging. Then, a yield strength prediction model considering solid solution strengthening and second-phase precipitation strengthening was established to calculate the change in yield strength with aging temperature and time. For the two alloys mentioned above, after aging at 160℃ for 12 hours, the yield strength of alloy #3 reached 415 MPa, and the yield strength of alloy #4 reached 403 MPa.

[0077] (5) Using the two alloy wires mentioned above, single-wall specimens of 200mm×100mm×22mm were produced by arc additive manufacturing. The specimens were solution-treated at 518-523℃ for 3 hours, water-quenched, and aged at 160℃ for 12 hours. Samples were then cut and tested for tensile mechanical properties at 220℃. Mechanical properties of alloy #3: Transverse: Tensile strength 372MPa; Yield strength 365MPa; Elongation after fracture 6.5%. Longitudinal: Tensile strength 370MPa; Yield strength 363MPa; Elongation after fracture 5.5%. Mechanical properties of alloy #4: Transverse: Tensile strength 363MPa; Yield strength 358MPa; Elongation after fracture 7.5%. Longitudinal: Tensile strength 359MPa; Yield strength 355MPa; Elongation after fracture 8.0%. Due to its low Cu content, alloy #4 has fewer residual brittle crystalline phases in the interlaminar layers, resulting in a better elongation after fracture. The mechanical properties at 220℃ are improved by 30% compared to 2219 aluminum alloy.

[0078] This invention is applied to the design of high-performance aluminum alloy composition for large lightweight components such as new aerospace equipment and launch vehicles using arc additive manufacturing, solving the problems of low yield strength or high crack sensitivity of conventional arc additive aluminum alloys.

[0079] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0080] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength, characterized in that, Includes the following steps: (1) Calculate the baseline value E0 of the hot cracking sensitivity index of the standard composition of Al-Cu-Mn high-strength aluminum alloy. (2) Using the elemental contents of Cu+Cd+Sc and Cu+Ag+Mg+Sc as variables, the orthogonal experimental design method was adopted to design different component ratios, calculate the hot cracking sensitivity index E1 under each component ratio, and take the component ratio with E1 less than 1.1E0 as the preferred component ratio of high strength aluminum alloy. (3) For each high-strength aluminum alloy composition selected in step (2): prepare wire, arc additive forming single wall test plate, and process into flat circumferential weld test piece, and conduct circumferential weld welding test under restraint conditions; count the proportion of solidification crack length of circumferential weld to the total weld length, verify the hot cracking sensitivity of high-strength aluminum alloys with different compositions, and then screen out the composition with low hot cracking sensitivity. (4) Based on the molar fraction ratio of main and microalloying elements in the composition ratio selected in step (3), establish an aging precipitation kinetic model of Al-Cu-Mn-X alloy considering the effect of microalloying elements, calculate the changes in Cu mass fraction and the radius, quantity and volume fraction of nano-strengthening phase during aging; establish a yield strength prediction model considering solid solution strengthening and second phase precipitation strengthening, use the calculation results of the aging precipitation kinetic model as input, calculate the change in yield strength with aging temperature and time, and then select the composition ratio that meets the yield strength condition, where X represents one of Cd+Sc or Ag+Mg+Sc; (5) Based on the results of the calculation of hot cracking sensitivity and yield strength, the mechanical properties of high-strength aluminum alloy are tested by electric arc additive single wall specimens. The component ratio that meets the mechanical properties requirements in step (4) is selected as the Al-Cu-Mn high-strength aluminum alloy composition for electric arc additive manufacturing that takes into account both hot cracking sensitivity and strength.

2. The method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength according to claim 1, characterized in that, The baseline value E0 for calculating the hot cracking susceptibility index of the standard composition of Al-Cu-Mn high-strength aluminum alloys specifically includes: The solidification path of Al-Cu-Mn alloy under standard composition was calculated using Thermal-Calc thermodynamic software, i.e., the temperature-solid mass fraction (T-fs) curve. The square root curve (T-fs) of temperature-solid mass fraction was extracted when the solid mass fraction at the end of solidification was 0.9-0.

99. 0.5 The maximum absolute value of the slope |dT / d(fs) 0.5 )|max, which is the solidification hot crack index, serves as the benchmark value E0 for the hot crack sensitivity index of this standard composition.

3. The method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength according to claim 2, characterized in that, The cooling rate was 100 K / s and the secondary dendrite spacing was 10 μm when the solidification path was calculated.

4. The method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength according to claim 2, characterized in that, Calculate the hot cracking susceptibility index E1 for each component ratio, under the following conditions: When the solid mass fraction at the end of solidification is 0.9-0.99, E1=|dT / d(fs) 0.5 )|max.

5. The method for designing the composition of arc-additive aluminum alloys that takes into account both hot cracking sensitivity and strength according to claim 1, characterized in that, The selected low-thermal-cracking-susceptibility component ratio is specifically as follows: Let f1 be the measured value of the ratio of the solidification crack length of the circumferential weld to the total weld length corresponding to the high-strength aluminum alloy composition selected in step (2), and f0 be the ratio of the solidification crack length of the circumferential weld to the total weld length corresponding to the standard composition of the high-strength aluminum alloy. Select composition ratios with f1 less than 1.1f0.

6. The method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength according to claim 1, characterized in that, The nano-reinforcing phase includes: Cd segregation at the interface, {100} α-Al Al2Cu transition phase θ' precipitated at the habit surface; Ag-Mg binary segregation at the interface, {111} α-Al The Al2Cu-like transition phase Ω is precipitated on the habitual surface.

7. The method for designing the composition of arc-additive aluminum alloys that takes into account both hot cracking sensitivity and strength according to claim 1, characterized in that, Establish a kinetic model for the aging precipitation of Al-Cu-Mn-X alloys that considers the effects of microalloying elements, specifically including: Cluster incubation time: t0 = f(C0), where C0 is the initial molar concentration of solute atoms; Enhanced phase nucleation rate: J = f(Cm, Ce(TM), TM), where TM is the aging temperature, Cm is the average molar concentration of solute atoms, Ce is the average molar concentration of solute atoms in equilibrium, and Ce(TM) is the average molar concentration of solute atoms in equilibrium at the aging temperature TM. Strengthening phase radius: R = f(t, t0, Cm, Cr(R(t-Δt), Ce(TM)), Ce(TM), D(Cm)), where t is the aging time, D(Cm) is the diffusion coefficient related to the solute atom concentration, Cr is the equilibrium concentration of solute atoms at the precipitated phase interface, Δt is the small time interval, and R(t-Δt) is the strengthening phase radius calculated before time Δt. When Cm ≤ Cr, the strengthening phase begins to coarsen, then R = f(t, t0, t) pa Ce(TM), TM, D(Cm), R(t) pa )), where t pa The peak efficiency time is the moment when Cm≤Cr first appears.

8. The method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength according to claim 7, characterized in that, A yield strength prediction model considering solid solution strengthening and second-phase precipitation strengthening is established, specifically including: σ y =σ0+σ ss (Cm)+σ ppt (t,t0,J,f v (t,t0,t pa ,J,R)) Where σ0 is the inherent strength of the alloy (MPa), σ ss Contribution to solid solution strengthening of solute atoms (MPa), σ ppt For the second-phase enhancement contribution (MPa), f v This represents the volume fraction of the precipitated phase.

9. The method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength according to claim 1, characterized in that, The component ratios that meet the yield strength requirements are selected as follows: The component ratios with a room temperature yield strength greater than or equal to 350 MPa were selected.

10. The method for designing the composition of arc-additive aluminum alloys that balances hot cracking sensitivity and strength according to claim 1, characterized in that, The mechanical performance indicators to be tested in step (5) and the corresponding indicator requirements include: At room temperature, parallel and perpendicular to the deposition direction: tensile strength greater than or equal to 430 MPa, yield strength greater than or equal to 350 MPa, and elongation after fracture greater than or equal to 6%. Under high temperature conditions of 220℃, parallel to and perpendicular to the deposition direction: tensile strength greater than or equal to 350MPa, yield strength greater than or equal to 330MPa, and elongation after fracture greater than or equal to 6%.

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