CN111074124B - Thermomechanical treatment composite process for 7xxx aluminum alloy uniform structure and obtaining method thereof - Google Patents

Abstract

The invention provides a method for obtaining a thermomechanical treatment composite process of a 7xxx aluminum alloy uniform structure, which comprises the following steps of: analyzing the grain structure of the aluminum alloy billet prepared by spray deposition, and judging whether the billet can be directly subjected to thermal deformation or not according to the characteristics of the grain structure; carrying out high-temperature deformation research on the billet with the grain structure meeting the requirements, reserving the high-temperature deformation structure, observing the high-temperature deformation structure, and further judging whether the billet can be directly subjected to thermal deformation; setting extrusion deformation technological parameters for the alloy capable of being directly subjected to thermal deformation; and (3) carrying out research on homogenization process parameters of the extruded alloy to obtain the thermomechanical treatment composite process of the 7xxx aluminum alloy uniform structure. The thermomechanical treatment composite process for the 7xxx aluminum alloy uniform structure is economic, rapid, reasonable and effective, and provides a guide for the actual preparation of the 7xxx aluminum alloy. The invention also provides a thermomechanical treatment composite process of the 7xxx aluminum alloy uniform structure.

Description

Thermomechanical treatment composite process for 7xxx aluminum alloy uniform structure and obtaining method thereof

Technical Field

The invention relates to the technical field of aluminum alloys, in particular to a thermomechanical treatment composite process for a 7xxx aluminum alloy uniform structure and an obtaining method thereof.

Background

High-strength aluminum alloys (such as 2xxx, 7xxx and other heat-treatment-strengthened aluminum alloys) prepared by a fusion casting method are frequently used for structural components in the aerospace field due to high strength of the high-strength aluminum alloys, and because the components of the high-strength aluminum alloys are complex and have high alloying degree, the high-strength aluminum alloys are easy to form segregation of tissues and components, so that serious casting defects of uneven element distribution, macro segregation and the like exist in the high-strength aluminum alloys.

The 7xxx aluminum alloy has higher alloying degree and segregation degree than the 2xxx aluminum alloy, while the 7055 aluminum alloy is the alloy with the highest alloying degree, the most serious segregation and the largest casting stress in the 7xxx aluminum alloy, and generally needs to be subjected to long-time homogenization heat treatment to better reduce the internal macrosegregation and eliminate the casting stress, and the homogenization process consumes time and energy.

At present, the process of hot working deformation after 7xxx aluminum alloy preparation has long flow, high energy consumption, high processing cost and low production efficiency.

Disclosure of Invention

In view of the above, the invention aims to provide a thermomechanical treatment composite process of a 7xxx aluminum alloy uniform structure and an obtaining method thereof.

The invention provides a method for obtaining a thermomechanical treatment composite process of a 7xxx aluminum alloy uniform structure, which comprises the following steps of:

analyzing the grain structure of the prepared 7xxx aluminum alloy billet, and judging whether the billet can be directly subjected to thermal deformation according to the characteristics of the grain structure;

carrying out high-temperature deformation research on the billet with the grain structure meeting the requirements, reserving the high-temperature deformation structure, observing the high-temperature deformation structure, and further judging whether the billet can be directly subjected to thermal deformation;

setting extrusion deformation technological parameters for a billet which can be directly subjected to thermal deformation;

and (3) carrying out homogenization process parameter research on the extruded billet to obtain a homogenization heat treatment process (7xxx aluminum alloy homogeneous structure thermomechanical treatment composite process) of the billet.

In the present invention, the method of producing the 7xxx aluminum alloy ingots is preferably a spray deposition method; the casting temperature in the jet deposition process is preferably 780-950 ℃, more preferably 800-900 ℃, and most preferably 830-850 ℃; the optimized atomizing gas speed is 20-35 m³A/min, more preferably 25 to 30m³Min; the metal flow rate is preferably 8 to 55kg/min, more preferably 10 to 50kg/min, more preferably 20 to 40kg/min, and most preferably 25 to 35 kg/min; the gas metal ratio is preferably 0.5-2, and more preferably 1-1.5; the air pressure is preferably 0.5 to 1MPa, and more preferably 0.6 to 0.8 MPa; the spraying angle is preferably 25-35 degrees, and more preferably 30 degrees; the distance between the deposition disc and the spray head is preferably 150-290 mm, and more preferably 200-250 mm; the rotating speed of the deposition disc is preferably 100 to 200r/min, more preferably 120 to 180r/min, and most preferably 140 to 160 r/min.

The composition of the 7xxx aluminum alloy ingot is not particularly limited by the invention, and the composition of the 7xxx aluminum alloy ingot known to those skilled in the art can be adopted; in the present invention, the composition of the 7xxx aluminum alloy ingot may be as shown in table 1:

TABLE 1 ingredient list of 7XXX series high-strength and high-toughness aluminium alloy

In the invention, the grain structure of the billet is preferably in an equiaxial shape, the grain size is preferably 30-72 micrometers, more preferably 40-60 micrometers, and most preferably 45-55 micrometers; the grain structure is not uniformly distributed.

In the present invention, the ingot grain structure preferably has no primary grain boundaries, no dendrites, and a coarser secondary phase at the grain boundaries.

In the present invention, the method for judging whether the grain structure meets the requirement preferably includes:

the crystal grain structure of the billet has no obvious dendritic crystal and no macrosegregation, and the crystal grains are fine and in an equiaxial shape, so that the thermal deformation can be directly carried out.

In the present invention, during the high temperature deformation study, it is preferable that: setting the deformation temperature to be 340-460 ℃, and preferably 340 ℃, 380 ℃, 420 ℃ and 460 ℃; the compression amount of deformation is 55-65%, preferably 58-62%, and more preferably 60%; the deformation rate is 0.001 to 1s^-1More preferably 0.001s^-1、0.01s^-1、0.1s^-1And 1s^-1(ii) a The temperature rise speed is 4-6 ℃/s, and more preferably 5 ℃/s; and (3) heating to the deformation temperature, and then preserving the heat for 2-4 min, preferably 3 min.

In the present invention, the method of retaining the hyperthermal deformed tissue preferably includes:

in the high-temperature deformation research process, the billet is thermally compressed to 45-55%, preferably 48-52% and more preferably 50% of the original height, and then water quenching is carried out, so that a high-temperature deformation structure is reserved.

In the present invention, the method of further judging whether the ingot can be directly heat-deformed includes:

in the high-temperature deformation research process, the billet has no cracks, and the thermal deformation can be directly carried out if the structure deformation is uniform.

In the present invention, the extrusion deformation process parameters preferably include: the extrusion temperature is 410-430 ℃, more preferably 415-425 ℃, and most preferably 420 ℃; the extrusion ratio is preferably 6 to 7, more preferably 6.2 to 6.4, and most preferably 6.25.

In the present invention, the study method of the homogenization process parameters preferably includes:

and selecting upper and lower limits as homogenization temperatures according to the upper limit and the overburning temperature of the quenching sensitive temperature interval of the billet, wherein the upper limit of the quenching sensitive temperature interval of the billet is the lower limit of the homogenization temperature, the overburning temperature of the billet is the upper limit of the homogenization temperature, the homogenization time is gradually prolonged from the lower limit, the components of the second phase are judged through an energy spectrum after homogenization, if a large amount of Fe-free phases exist in the second phase, the homogenization effect is not enough, the homogenization temperature needs to be increased, and the process is repeated until the Fe-free phases in the second phase basically disappear.

In the invention, a second phase can be precipitated when the temperature is kept below the upper limit of the quenching sensitive temperature range, so that the homogenization effect is influenced; when the heating temperature is higher than the melting point of the eutectic with low melting point, the phenomenon of remelting the eutectic with low melting point and the crystal boundary is called as overburning.

In the present invention, the method of obtaining the homogenization process parameters according to the research result of the homogenization process parameters preferably includes:

firstly, carrying out primary homogenization treatment at low temperature by prolonging the heat preservation time, representing the redissolution effect by the average size change of a second phase not containing Fe, and obtaining the temperature and the heat preservation time of the primary homogenization treatment when the average size change of the second phase is very small after the heat preservation time reaches a certain degree; then raising the temperature to carry out secondary homogenization treatment;

and in the process of secondary homogenization treatment, the heat preservation time is prolonged, and the redissolution effect is represented by the average size change of the second phase not containing Fe continuously until all the second phase not containing Fe disappears, so that the temperature and the heat preservation time of the secondary homogenization treatment are obtained.

In the invention, the homogenization parameters are composed of temperature and time, the importance of the temperature is stronger than that of the time, the lower the temperature is, the better the temperature is, the time can be properly prolonged under the condition of ensuring the effect, because the temperature is lower, the control is easier, the energy consumption is low, the overburning is not easy, and the crystal grains can not excessively grow, therefore, the homogenization process is preferably to perform primary homogenization treatment at low temperature and then to perform secondary homogenization treatment at high temperature.

In the present invention, in the primary homogenization treatment and the secondary homogenization treatment, the temperature is preferably raised at intervals of 20 ℃ and the extended holding time is preferably at intervals of an integer of hours. In the invention, the temperature of the primary homogenization treatment is preferably 445-455 ℃, and the heat preservation time is preferably 5-7 hours; the temperature of the secondary homogenization treatment is preferably 465-474 ℃, and the heat preservation time is preferably 0.5-1.5 hours.

The invention provides a thermomechanical treatment composite process for a 7xxx aluminum alloy uniform structure, wherein the obtaining method of the thermomechanical treatment composite process for the 7xxx aluminum alloy uniform structure is consistent with the technical scheme, and is not repeated herein; the thermomechanical treatment composite process of the 7xxx aluminum alloy uniform structure comprises the following steps:

preparing a billet by adopting a spray deposition method, wherein the billet is a 7xxx aluminum alloy;

carrying out hot extrusion on the billet to obtain an extrusion piece;

preserving the heat of the extrusion piece for 5-7 hours at 445-455 ℃, and then preserving the heat for 0.5-1.5 hours at 465-474 ℃ to obtain a heat treatment piece;

and aging the heat-treated piece.

In the invention, the process parameters in the spray deposition process are consistent with those in the spray deposition process of the technical scheme, and are not described again; the composition of the 7xxx aluminum alloy is consistent with the technical scheme, and is not described in detail herein.

In the present invention, the process parameters in the hot extrusion process are consistent with the extrusion deformation process parameters in the above technical scheme, and are not described herein again.

In the present invention, the extrusion is preferably heat-treated at 450 ℃ for 6 hours and then at 470 ℃ for 1 hour.

The aging method is not particularly limited, and the skilled in the art can select different aging processes to perform aging treatment on the heat-treated piece according to the needs of actual conditions.

The invention is suitable for 7055 cast ingot with uniform cast ingot structure and small macrosegregation by spray deposition. The grain structure of an alloy billet prepared by general spray deposition is mainly characterized by being equiaxial, original grain boundaries similar to those of a powder metallurgy process do not exist, dendrites in the aluminum alloy prepared by a traditional casting method are not found, and coarse second phases exist on the grain boundaries; after the characteristics of the structure are determined by research, the alloy can be subjected to hot working deformation.

To accurately understand the effect of thermal deformation on spray-deposited 7055 aluminum alloy, thermal simulation studies of spray-deposited 7055 aluminum alloy were conducted, with deformation temperatures typically set at 340 ℃ and 380 ℃ for lower temperatures, and at 420 ℃ and 460 ℃ for higher temperatures, with a 60% compressive deformation, and with deformation rate parameters of 0.001s each^-1、0.01s^-1、0.1s^-1And 1s^-1And in the thermal simulation process, the heating speed is 5 ℃/s, and when the thermal simulation equipment is heated to the deformation temperature, the thermal insulation is carried out for 3 min. Hot-pressing to 50% of original height of ingot, immediately water-quenching, and retaining high-temperature deformation structure. And performing SEM observation on the alloy with different deformation parameters, and observing whether cracks exist or not so as to further determine whether the alloy can be directly subjected to thermal deformation or not.

After thermal deformation research, after determining that the alloy can be directly thermally deformed, setting extrusion deformation parameters according to actual extrusion conditions in production, wherein the extrusion temperature is 420 ℃, and the extrusion ratio is 6.25. And carrying out homogenization system research on the extruded alloy, wherein the homogenization system research follows the research aim that the lower the temperature is, the better the temperature is, the shorter the time is, the factors of the temperature and the time are fully considered, and the primary homogenization temperature is determined to be 450 ℃.

Compared with the thermomechanical treatment composite process of other 7xxx aluminum alloys: and (3) casting 7055 ingots → 465-470 ℃/24 h-40 h (or spray deposition 7055 ingots 450 ℃/24h +470 ℃/2h) → hot extrusion → 470 ℃/1h → aging.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is an EBSD picture (500X) of a spray deposited 7055 aluminum alloy ingot prepared in example 1 of the present invention;

FIG. 2 is an EBSD picture (1000X) of a spray deposited 7055 aluminum alloy ingot prepared according to example 1 of the present invention;

FIG. 3 is a statistical plot of the grain size distribution of a spray deposited 7055 aluminum alloy ingot prepared in accordance with example 1 of the present invention;

FIG. 4 is an SEM picture (1000X) of a spray deposited 7055 aluminum alloy ingot prepared according to example 1 of the present invention;

FIG. 5 is an SEM picture (2000X) of a spray deposited 7055 aluminum alloy ingot prepared according to example 1 of the present invention;

FIG. 6 shows that the heat compression temperature in example 1 of the present invention was 340 ℃ and the strain rate was 1s^-1Time-varying backscattered electron images of the deformed tissue;

FIG. 7 shows that the heat compression temperature in example 1 of the present invention was 340 ℃ and the strain rate was 0.001s^-1Time-varying backscattered electron images of the deformed tissue;

FIG. 8 shows that the heat compression temperature in example 1 of the present invention was 380 ℃ and the strain rate was 1s^-1Time-varying backscattered electron images of the deformed tissue;

FIG. 9 shows that the heat compression temperature in example 1 of the present invention was 380 ℃ and the strain rate was 0.001s^-1Time-varying backscattered electron images of the deformed tissue;

FIG. 10 shows that the heat compression temperature in example 1 of the present invention was 420 ℃ and the strain rate was 1s^-1Timely deformed tissue dorsum powderA radio image;

FIG. 11 is a graph showing a thermal compression temperature of 420 ℃ and a strain rate of 0.001s in example 1 of the present invention^-1Time-varying backscattered electron images of the deformed tissue;

FIG. 12 shows that the heat compression temperature in example 1 of the present invention is 460 ℃ and the strain rate is 1s^-1Time-varying backscattered electron images of the deformed tissue;

FIG. 13 shows that the heat compression temperature in example 1 of the present invention is 460 ℃ and the strain rate is 0.001s^-1Time-varying backscattered electron images of the deformed tissue;

FIG. 14 shows 460 deg.C/0.001 s in example 1 of the present invention^-1A deformed SEM picture;

FIG. 15 shows 460 deg.C/0.001 s in example 1 of the present invention^-1The deformed second phase surface scanning energy spectrum (Al);

FIG. 16 shows 460 deg.C/0.001 s in example 1 of the present invention^-1The deformed second phase surface scanning energy spectrum (Zn);

FIG. 17 shows 460 deg.C/0.001 s in example 1 of the present invention^-1A deformed second phase surface scanning energy spectrum (Mg);

FIG. 18 shows 460 deg.C/0.001 s in example 1 of the present invention^-1A deformed second phase surface scanning spectrum (Cu);

FIG. 19 shows 460 deg.C/0.001 s in example 1 of the present invention^-1The deformed second phase surface scanning energy spectrum (Zr);

FIG. 20 is a back-scattered electron image of the alloy after extrusion at 420 ℃ in example 1 of the present invention;

FIG. 21 is a back-scattered electron image of the alloy after extrusion at 420 ℃ for 4 hours at 450 ℃ in example 1 of the present invention;

FIG. 22 is a back-scattered electron image of the alloy after extrusion at 420 ℃ for 6 hours at 450 ℃ in example 1 of the present invention;

FIG. 23 is a back-scattered electron image of the alloy extruded at 420 ℃ for 8 hours at 450 ℃ in example 1 of the present invention;

FIG. 24 is a back-scattered electron image of example 1 of the present invention, which was incubated at 450 ℃ for 6 hours and then at 470 ℃ for 1 hour.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Fig. 1 to fig. 3 are EBSD (electron back scattering diffraction) photographs and statistical graphs of grain size distribution of a spray-deposited 7055 aluminum alloy ingot at different magnifications, and the main characteristics of the grain structure of the alloy ingot are as follows: the crystal grains are equiaxed, the size of each crystal grain is 30-72 mu m, the size distribution is not uniform, and the crystal grains with the diameter of about 45 mu m are used for the most proportion; the specific process and technological parameters of the jet deposition are as follows:

melting-atomizing-spraying-depositing-solidifying, 5 stages; the process has high solidification speed, and the temperature drop speed can reach 10^3-5K/s, the formed ingot blank has a fine equiaxed crystal structure and small component segregation. The main technological parameters are as follows: the pouring temperature is 850 ℃, and the atomizing gas speed is 30m³The flow rate of metal is 35kg/min, the ratio of gas to metal is 1, the air pressure is 0.8MPa, the spraying angle is 30 degrees, the distance between a deposition disc and a spray head is 220mm, and the rotating speed of the deposition disc is 150 r/min.

The composition of the obtained 7055 aluminum alloy billet is (wt%): zn 8.31, Mg 2.07, Cu 2.46, Zr 0.12, Fe 0.078, Si 0.056, and the balance of Al.

Fig. 4-5 are SEM photographs of spray-deposited 7055 aluminum alloy ingots, where the structure of the spray-deposited 7055 aluminum alloy ingots did not show primary grain boundaries similar to those of powder metallurgy, nor dendrites in aluminum alloys prepared by conventional fusion casting methods, but coarse secondary phases were present at the grain boundaries.

In the above research, it was found that the 7055 aluminum alloy ingot deposited by spraying has no obvious dendritic structure, no macrosegregation, fine crystal grains, equiaxial shape, and direct thermal deformation conditions.

Research on high-temperature deformation behavior of 7055 aluminum alloy billet sprayed and deposited by using Gleeble3500 thermal simulation machineThe thermal compression deformation conditions are intended to be: the deformation temperature is 340 ℃ and 380 ℃ at lower temperature, and 420 ℃ and 460 ℃ at higher temperature, the compression deformation is 60 percent, and the deformation rate parameters are respectively 0.001s^-1、0.01s^-1、0.1s^-1And 1s^-1And in the thermal simulation process, the heating speed is 5 ℃/s, and when the thermal simulation equipment is heated to the deformation temperature, the thermal insulation is carried out for 3 min. And immediately performing water quenching after hot compression to 50% of the original height, and keeping the high-temperature deformation structure. The maximum strain rate and the minimum strain rate at each temperature were selected, and a total of 8 samples were further subjected to tissue observation and analysis, as shown in fig. 6 to 13, the thermal compression parameters of the 8 samples were (temperature, strain rate): (a)340 ℃ for 1s^-1；(b)340℃,0.001s^-1；(c)380℃,1s^-1；(d)380℃,0.001s^-1；(e)420℃,1s^-1；(f)420℃,0.001s^-1；(g)460℃,1s^-1；(h)460℃,0.001s^-1。

FIG. 14 shows the temperature at the highest deformation temperature and the deformation rate at the lowest deformation rate of 460 ℃/0.001s^-1SEM pictures after deformation, low strain rate (0.001 s) when the deformation temperature is relatively high (460 ℃ C.)^-1) (FIG. 13), the effect of the second phase is significantly better than the high strain rate, the intragranular second phase is essentially eliminated, and the second phase on the crystal is approximately half redissolved. At the same deformation temperature (460 ℃), and at a high strain rate (1 s)^-1) In the deformed alloy, although the intragranular second phase was much dissolved, a significant residual second phase was still observed, and the number of second phases at the grain boundaries was also significantly larger than that in fig. 13. This is because the higher the deformation rate, the shorter the deformation time, and the insufficient time for the second phase to dissolve back, at a fixed deformation temperature; meanwhile, the higher the deformation temperature is, the more obvious the redissolution effect is.

FIGS. 15 to 19 show 460 ℃ per 0.001s under the conditions of the highest deformation temperature and the slowest deformation rate^-1The deformed EDS (Electron microscopy) image shows that the EDS image passes through 460 ℃ for 0.001s^-1The hot-compressed samples, in which the major components of the secondary phase remaining at the grain boundaries were Zn element and Mg element, were analyzed from the EBSD phase of the above-described spray-deposited base alloyTwo phases are eta-MgZn₂Phase, which shows that the deformation rate is slow if the temperature is high during the hot deformation process of the alloy, most of the second phase in the original alloy can be dissolved back into the matrix, and only a few coarse eta-MgZn on the grain boundary₂The phases did not completely redissolve.

No cracks were found in the above results, and at the same time, the white second phase was largely dissolved, so that the spray-deposited 7055 aluminum alloy ingot could be directly hot worked.

Directly carrying out hot extrusion on a spray-deposited 7055 aluminum alloy billet, wherein the extrusion temperature is 420 ℃, the extrusion ratio is 6.25, and carrying out homogenization (solid solution strengthening) system research on the alloy in the extruded state: the lower limit of the homogenization temperature is 445 ℃, the upper limit of the homogenization temperature is 474 ℃, in the research process, the temperature is increased by 20 ℃ as an interval, the heat preservation time is prolonged by 1 hour as an interval, and fig. 20 is a back scattered electron image of the alloy after being extruded at 420 ℃, so that a large number of white second phases are still present in the alloy after being extruded at 420 ℃, and the white second phases are mainly MgZn₂Phase (1); FIG. 21 is a back scattering electron image of the alloy after being extruded at 420 ℃ and being kept at 450 ℃ for 4h, at this time, most of the white second phase in the crystal in the alloy is dissolved back, and the discontinuous white second phase MgZn exists on the crystal boundary₂Phase (1); FIG. 22 is a back-scattered electron image taken at 450 ℃ for 6 h; FIG. 23 is a back-scattered electron image of 450 ℃ incubation for 8 h.

FIGS. 22 and 23 show that the samples of the alloy after the heat preservation at 450 ℃ for 6h and 8h are not much different, the second phase in the crystal is almost completely dissolved, and the second phase on the grain boundary is also mostly dissolved. Thus, the 450 ℃ incubation time of 6 hours has substantially reached the solubility limit at that temperature and no longer is necessary. In order to further enhance the homogenization (solid solution) effect, heat preservation at a higher temperature is required. FIG. 24 is a back-scattered electron image of the alloy after heat preservation at 450 ℃ for 6h and then at 470 ℃ for 1h, wherein only sporadic second phases remain in the alloy after heat preservation at 470 ℃ for 1h, and the energy spectrum shows that the alloy comprises the following elements (wt%): 54.5% of Al, 32.1% of Cu and 13.4% of Fe as insoluble impurities₇Cu₂An Fe phase. Therefore, the strengthening solution process of the extruded alloy is determined to be 450 ℃/6h +470 ℃/1 h.

Therefore, the low-energy-consumption thermal processing homogenization composite process for the 7055 aluminum alloy billet sprayed and deposited in the embodiment 1 of the invention comprises the following steps: spray deposition ingot → hot extrusion → 450 ℃/6h +470 ℃/1h → aging.

Example 2

Preparing a 7055 aluminum alloy billet with the same composition according to the spray deposition process in the example 1; carrying out hot extrusion on the obtained aluminum alloy billet, wherein the extrusion temperature is 420 ℃, and the extrusion ratio is 6.25, so as to obtain an extruded alloy; preserving the obtained extruded alloy at 450 ℃ for 6 hours, then preserving the heat at 470 ℃ for 1 hour for heat treatment to obtain a heat-treated alloy; and carrying out aging treatment on the obtained heat treatment alloy at the temperature of 120 ℃/12h to obtain the 7055 aluminum alloy subjected to hot working.

The mechanical property of the thermally processed 7055 aluminum alloy prepared in the embodiment 2 of the present invention is detected (according to the standard method of GB/T228-: the average mechanical properties are that the yield strength, the tensile strength and the elongation are respectively as follows: 712MPa, 730MPa, 7.2 percent. The 7055 aluminum alloy with good performance can be obtained by the hot working process adopted in the embodiment 2 of the invention.

Comparative example 1

Preparing a 7055 aluminum alloy billet with the same composition according to the spray deposition process in the example 1; keeping the obtained aluminum alloy billet at 450 ℃ for 24 hours, and keeping the temperature at 470 ℃ for 2 hours to obtain heat treatment alloy; carrying out hot extrusion on the obtained heat treatment alloy, wherein the extrusion temperature is 420 ℃, and the extrusion ratio is 6.25, so as to obtain an extruded alloy; and (3) carrying out aging treatment on the obtained extrusion alloy after preserving heat at 470 ℃ for 1 hour, wherein the aging treatment process is 120 ℃/12h, and obtaining the hot-processed 7055 aluminum alloy.

The mechanical properties of the hot-worked 7055 aluminum alloy obtained in comparative example 1 of the present invention were measured by the method of example 1, and the results of the measurements were that the average mechanical properties were yield strength, tensile strength, and elongation: 593MPa, 658MPa and 9.2%.

From the above examples, the present invention provides a method for obtaining a 7xxx aluminum alloy homogeneous structure by a thermomechanical treatment composite process, comprising: analyzing the grain structure of the aluminum alloy billet prepared by spray deposition, and judging whether the billet can be directly subjected to thermal deformation or not according to the characteristics of the grain structure; carrying out high-temperature deformation research on the billet with the grain structure meeting the requirements, reserving the high-temperature deformation structure, observing the high-temperature deformation structure, and further judging whether the billet can be directly subjected to thermal deformation; setting extrusion deformation technological parameters for the alloy capable of being directly subjected to thermal deformation; and (3) carrying out research on homogenization process parameters of the extruded alloy to obtain the thermomechanical treatment composite process of the 7xxx aluminum alloy uniform structure. The thermomechanical treatment composite process for the 7xxx aluminum alloy uniform structure, which is obtained by the method, is economical, rapid, reasonable and effective, and provides a guide basis for determining the preparation of the actual spray deposition 7xxx aluminum alloy.

Claims (3)

1. The method for obtaining the thermomechanical treatment composite process of the 7xxx aluminum alloy uniform structure comprises the following steps:

analyzing the grain structure of the prepared 7xxx aluminum alloy billet, and judging whether the billet can be directly subjected to thermal deformation according to the characteristics of the grain structure;

carrying out high-temperature deformation research on the billet with the grain structure meeting the requirements, reserving the high-temperature deformation structure, observing the high-temperature deformation structure, and further judging whether the billet can be directly subjected to thermal deformation;

setting extrusion deformation technological parameters for a billet which can be directly subjected to thermal deformation;

carrying out research on homogenization process parameters of the extruded billet to obtain a thermomechanical treatment composite process of a 7xxx aluminum alloy uniform structure;

the method for judging whether the grain structure meets the requirements comprises the following steps:

the crystal grain structure of the billet has no obvious dendritic crystal structure and no macrosegregation, and the crystal grains are fine and in an equiaxial shape, so that the thermal deformation can be directly carried out;

in the high temperature deformation research process: setting the deformation temperature of thermal compression to be 340-460 ℃, the deformation compression amount of the thermal compression to be 55-65%, and the deformation rate of the thermal compression to be 0.001-1 s^-1The temperature rising speed is 4-6 ℃/s, and the heat preservation time for rising the temperature to the deformation temperature is 2-c4min；

The method for retaining the high-temperature deformation tissue comprises the following steps:

in the high-temperature deformation research, performing water quenching after the billet is thermally compressed to 45-55% of the original height, and reserving a high-temperature deformation structure;

the method for further judging whether the billet can be directly subjected to thermal deformation comprises the following steps:

in the high-temperature deformation research process, the billet is not cracked, the tissue deformation is uniform, and the thermal deformation can be directly carried out;

the research method of the homogenization process parameters comprises the following steps:

according to the upper limit and the lower limit of the quenching sensitive temperature interval of the billet, the homogenization time is gradually prolonged from the lower limit as the upper limit and the lower limit of the homogenization temperature selection, the second phase component is judged through the energy spectrum, if a large amount of non-Fe-containing phases exist, the homogenization effect is not enough, the temperature needs to be increased, and the process is repeated until the non-Fe-containing phases basically disappear.

2. The method of claim 1, wherein the grain size is 30 to 72 microns.

3. The method of claim 1, wherein the extrusion deformation process parameters comprise: the extrusion temperature is 410-430 ℃, and the extrusion ratio is 6-7.

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