CN113265602A - Heat treatment method for rapidly improving strength of aluminum alloy - Google Patents
Heat treatment method for rapidly improving strength of aluminum alloy Download PDFInfo
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Abstract
The invention discloses an electric pulse circulation heat treatment method for rapidly improving the strength of an aluminum alloy, which comprises the following steps: firstly, carrying out solid solution and quenching treatment on an aluminum alloy sample; then, applying a certain constant load to the sample by using a creep machine; and then carrying out short-time electric pulse circulation heat treatment on the sample. The method utilizes the characteristics of rapid temperature rise and rapid temperature drop of the electric pulse to ensure that the alloy obtains a structure with fine grains and uniformly distributed precipitated phases, and rapidly prepares the high-strength aluminum alloy through synergistic strengthening and toughening effects of fine grain strengthening, precipitated phase strengthening and the like. Compared with the prior art that the strength of the aluminum alloy is improved by a T7751 three-level heat treatment system, the invention reduces the heat treatment process and energy consumption, and is simple and easy to implement, environment-friendly, high in efficiency and low in manufacturing cost.
Description
Technical Field
The invention relates to the technical field of heat treatment of metal materials, in particular to a heat treatment method for rapidly improving the strength of an aluminum alloy.
Background
The Al-Zn-Mg-Cu alloy is an ultrahigh-strength and high-toughness aluminum alloy, has high specific strength and hardness, good corrosion resistance and excellent processability and weldability, and is a key structural function material in high and new technical fields such as aerospace and the like. At present, the main preparation method of the high-strength Al-Zn-Mg-Cu alloy is the traditional heat treatment process of 'solid solution treatment → pre-deformation → pre-aging → regression treatment → re-aging'. However, the process has the problems of long flow path, low efficiency, large energy consumption and the like.
Compared with the traditional heat treatment equipment, the electric pulse auxiliary heat treatment equipment has compact arrangement, less investment, low energy consumption and no pollution, and is very suitable for the current green production strategy of low energy consumption and low pollution in China. In addition, due to the action of the thermal effect and the non-thermal effect of the pulse current, the microstructure of the metal material can be optimized rapidly, and the forming quality of the material is improved. Therefore, the pulse current auxiliary heat treatment technology is more and more emphasized by relevant units and scholars in China, and the deep exploration of the current auxiliary heat treatment technology is of great significance under the large background of the development of the manufacturing technology.
Disclosure of Invention
The invention aims to provide a heat treatment method for rapidly improving the strength of an aluminum alloy, so as to solve the problems of low efficiency and high energy consumption of the traditional heat treatment.
In order to achieve the aim, the invention provides a heat treatment method for rapidly improving the strength of an aluminum alloy, which comprises the following steps:
step 1: firstly, carrying out solution treatment on a high-strength Al-Zn-Mg-Cu aluminum alloy sample, and then quenching the aluminum alloy sample subjected to solution treatment;
step 2: clamping the quenched aluminum alloy sample on a creep machine, and applying a certain load to the aluminum alloy sample through the creep machine;
and step 3: carrying out electric pulse circulation heat treatment on the aluminum alloy sample subjected to the load application; the method specifically comprises the following steps: opening a pulse power supply device, introducing pulse current to the aluminum alloy sample subjected to load application, rapidly heating the aluminum alloy sample to 170-190 ℃, closing the pulse power supply device when the time of introducing the pulse current reaches preset time, starting cooling the aluminum alloy sample, opening the pulse power supply device again when the time of closing the pulse power supply reaches the preset time, and repeating the steps; the number of times of cyclic heating is 5-15, and the preset time of cyclic heating and cooling each time is 3-6 min.
In the invention, the maximum temperature of the electric pulse cyclic heat treatment is set to be 170-190 ℃, the cycle frequency is set to be 5-15 times, and when the cyclic temperature rise and temperature drop time is set to be 3-6 min each time, precipitated phases can be fully precipitated and the growth of the precipitated phases is inhibited, so that the effect of rapidly strengthening the aluminum alloy is achieved.
As a still further scheme of the invention: in step 3, the specific parameters of the electric pulse are as follows: the pulse current is 300-600A, the pulse frequency is 100-500 HZ, and the duty ratio is 10-50%.
As a still further scheme of the invention: in the step 1, the specific process is as follows: firstly, placing an aluminum alloy sample in an aging furnace at 470 ℃ for heat preservation for 1h to complete solution treatment, and then placing the sample after the solution treatment in water at 20 ℃ for quenching in 3s after discharging.
As a still further scheme of the invention: in the step 2, the concrete process of clamping the sample on the creep machine is as follows:
an upper insulating chuck is arranged at an upper cross beam of the creep machine through a connecting pin, and a lower insulating chuck is arranged at a lower cross beam of the creep machine through a connecting pin; fixing the quenched aluminum alloy sample between an upper insulating chuck and a lower insulating chuck of the creep machine, and fully contacting positive and negative electrode clamping blocks of a pulse power supply device with the upper end and the lower end of the quenched aluminum alloy sample respectively to reduce contact resistance; so that the pulse power supply device can transmit pulse current to the aluminum alloy sample through the lead and the positive and negative electrode clamping blocks.
As a still further scheme of the invention: in the step 2, the creep machine applies a load of 0-200 MPa to the sample.
As a still further scheme of the invention: and in the step 3, monitoring the surface temperature of the aluminum alloy sample in the electric pulse cyclic heating process by using a data recorder.
The invention adopts electric pulse circulation heat treatment to rapidly improve the strength of the aluminum alloy: on one hand, the temperature of the sample can be quickly raised through short-time electric pulse circulating heat treatment, the diffusion of atoms is promoted, precipitated phases are quickly precipitated and uniformly distributed, and the growth of the precipitated phases is inhibited through quick cooling, so that fine and uniformly distributed coherent precipitated phases are obtained; on the other hand, due to the thermal effect and the non-thermal effect of the pulse current, the recrystallization nucleation barrier is reduced, recrystallization is promoted, and meanwhile, the growth of crystal grains is inhibited due to rapid cooling, so that relatively fine crystal grain sizes are obtained. Thus, the fine crystal grains and the fine uniformly distributed coherent precipitated phases improve the strength of the aluminum alloy.
Compared with the prior art, the invention has the following beneficial effects:
(1) the heat treatment method comprises the steps of firstly carrying out solid solution and quenching treatment on the aluminum alloy, then applying a constant load to the aluminum alloy, and then carrying out short-time electric pulse circulating heat treatment, wherein the characteristics of rapid temperature rise and rapid temperature drop of electric pulse current are utilized to ensure that the alloy obtains a structure with fine grains and uniformly distributed precipitated phases, and the microstructure of the aluminum alloy is improved through the synergistic strengthening and toughening effects of fine grain strengthening, precipitated phase strengthening and the like, so that the aim of rapidly strengthening the aluminum alloy is fulfilled. The invention does not need to use a T7751 three-level heat treatment system to improve the strength of the aluminum alloy, reduces the heat treatment process and energy consumption, and has the advantages of simplicity, easy operation, environmental protection, high efficiency and low manufacturing cost.
(2) The heat treatment method has the advantages of simple process, high efficiency, low energy consumption, environmental protection, easy realization of large-scale production and wide application prospect.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a temperature profile of electric pulse cycle treatment in example 1 of the present invention;
FIG. 2 is a TEM image of 10 cycles of heat treatment by electric pulses in example 1 of the present invention;
fig. 3 is a TEM picture of a sample in the comparative example T7751 state.
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.
Example 1:
firstly, a 7150 aluminum alloy sample in a T7751 state is placed in an aging furnace at 470 ℃ for heat preservation for 1h for solution treatment, the sample is taken out of the furnace and placed in water at 20 ℃ for quenching in 3s, and the tensile strength, yield strength and elongation of the quenched aluminum alloy sample are 503.9MPa, 330MPa and 26.84%, respectively.
And then, placing the quenched aluminum alloy sample in a creep machine, starting the creep machine to apply a load to the aluminum alloy sample to 200MPa, enabling the creep machine to be tightly attached to the sample through positive and negative electrode clamping blocks, connecting the positive and negative electrode clamping blocks with a lead, and transmitting pulse current of a pulse power supply device to the positive and negative electrode clamping blocks through the lead and then to the aluminum alloy sample.
Then, the pulse power supply is turned on to perform electric pulse heating on the aluminum alloy sample, when the heating time reaches 3min, the pulse power supply is turned off, the aluminum alloy sample starts to cool, when the cooling time reaches 3min, one-time electric pulse circulation heat treatment is completed, the pulse power supply is turned on again, and the like, 10-time electric pulse circulation heat treatment is performed, and the temperature change curve is shown in fig. 1. In this step, the electrical pulse parameters are set as: frequency 500HZ, duty cycle 50%, current magnitude 560A.
In this example, after 10 times of electric pulse cycle heat treatment, the tensile strength of the aluminum alloy sample was 584.9MPa, the yield strength was 522MPa, and the elongation was 12.28%; the whole process time is less than 3 h. The TEM microstructure of the sample after 10 times of the electric pulse cycle heat treatment is shown in FIG. 2, and it can be seen that the fine coherent precipitated phases are uniformly distributed on the aluminum matrix after the electric pulse cycle heat treatment.
Example 2:
firstly, putting a 7150 aluminum alloy sample in a T7751 state in an aging furnace at 470 ℃ for heat preservation for 1h for solution treatment, and putting the sample in 20 ℃ water for quenching after being taken out of the furnace for 3 s;
then, placing the quenched aluminum alloy sample in a creep machine, starting the creep machine to apply a force to the sample to 200MPa, enabling the creep machine to be tightly attached to the aluminum alloy sample through positive and negative electrode clamping blocks, connecting the positive and negative electrode clamping blocks with a lead, and transmitting pulse current of a pulse power supply device to the positive and negative electrode clamping blocks through the lead and then to the aluminum alloy sample;
then, a pulse power supply is started to carry out electric pulse heating on the aluminum alloy sample, when the heating time reaches 3min, the pulse power supply is turned off, the sample starts to cool, when the cooling time reaches 3min, one-time electric pulse circulation heat treatment is finished, the pulse power supply is turned on again, and the like to carry out 5-time electric pulse circulation heat treatment; wherein the electrical pulse parameters are set as: frequency 500HZ, duty cycle 50%, current magnitude 560A.
In this example, after 5 times of electric pulse cycle heat treatment, the tensile strength of the sample was 542.2MPa, the yield strength was 457MPa, and the elongation was 12.5%; the whole process time is less than 2 h.
Example 3:
firstly, putting a 7150 aluminum alloy sample in a T7751 state in an aging furnace at 470 ℃ for heat preservation for 1h for solution treatment, and putting the sample in 20 ℃ water for quenching after being taken out of the furnace for 3 s;
then, placing the quenched aluminum alloy sample in a creep machine, starting the creep machine to apply a force to the sample to 200MPa, enabling the creep machine to be tightly attached to the aluminum alloy sample through positive and negative electrode clamping blocks, connecting the positive and negative electrode clamping blocks with a lead, and transmitting pulse current of a pulse power supply device to the positive and negative electrode clamping blocks through the lead and then to the aluminum alloy sample;
then, a pulse power supply is started to carry out electric pulse heating on the sample, when the heating time reaches 3min, the pulse power supply is turned off, the sample starts to be cooled, when the cooling time reaches 3min, one-time electric pulse circulation heat treatment is finished, the pulse power supply is turned on again, and the like, and 15-time electric pulse circulation heat treatment is carried out; the electrical pulse parameters are set as: frequency 500HZ, duty cycle 50%, current magnitude 560A.
In this example, after 15 times of electric pulse cycle heat treatment, the tensile strength of the sample was 581.7MPa, the yield strength was 512MPa, and the elongation was 12.18%; the whole process time is less than 4 h.
Comparative example:
firstly, carrying out solution quenching treatment on a T7751 aluminum alloy sample, wherein the solution temperature is 470 ℃, keeping the temperature for 1h, and quenching the sample in 20 ℃ water for 3s after the sample is taken out of a furnace;
then, pre-aging is carried out, wherein the pre-aging temperature is 120 ℃, and the pre-aging time is 24 hours; then carrying out regression treatment, wherein the regression temperature is 180 ℃, and the regression time is 30 min;
finally, performing reaging, wherein the reaging temperature is 120 ℃, and the aging is 24 h; the tensile strength of the obtained sample is 594.9MPa, the yield strength is 549MPa, and the elongation is 9.6%; the time of the whole process is more than 49 h;
after the T7751 conditioning, the TEM microstructure of the sample is shown in FIG. 3, with coarse, non-coherent precipitate phases distributed on the aluminum matrix.
The first table shows the mechanical properties and treatment time of the aluminum alloy samples under four different heat treatment conditions of example 1, example 2, example 3 and comparative example.
TABLE mechanical Properties and treatment times of aluminum alloy specimens under different conditions
The above table shows that the heat treatment method of the invention improves the microstructure of the aluminum alloy by utilizing the characteristics of rapid temperature rise and rapid temperature drop of the strong pulse current, and realizes the purpose of rapid strengthening of the aluminum alloy; by cyclic pulse heating, the treatment time is greatly shortened.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A heat treatment method for rapidly improving the strength of an aluminum alloy is characterized by comprising the following steps:
step 1: firstly, carrying out solution treatment on an aluminum alloy sample, and then quenching the aluminum alloy sample after the solution treatment;
step 2: clamping the quenched aluminum alloy sample on a creep machine, and applying a certain load to the aluminum alloy sample through the creep machine;
and step 3: carrying out electric pulse circulation heat treatment on the aluminum alloy sample subjected to the load application; the method specifically comprises the following steps: opening a pulse power supply device, introducing pulse current into the loaded aluminum alloy sample to quickly heat the aluminum alloy sample to 170-190 ℃, closing the pulse power supply device when the time of introducing the pulse current reaches preset time, starting cooling the aluminum alloy sample, opening the pulse power supply device again when the time of closing the pulse power supply reaches the preset time, and repeating the steps; the number of times of cyclic heating is 5-15, and the preset time of cyclic heating and cooling each time is 3-6 min.
2. The thermal processing method according to claim 1, wherein in step 3, the specific parameters of the electric pulse are: the pulse current is 300-600A, the pulse frequency is 100-500 HZ, and the duty ratio is 10-50%.
3. The heat treatment method according to claim 1, wherein in the step 1, the specific process is as follows: firstly, placing an aluminum alloy sample in an aging furnace at 470 ℃ for heat preservation for 1h to complete solution treatment, and then placing the sample after the solution treatment in water at 20 ℃ for quenching in 3s after discharging.
4. The heat treatment method according to claim 1, wherein in the step 2, the sample is clamped on the creep machine by the following specific process:
an upper insulating chuck is arranged at an upper cross beam of the creep machine through a connecting pin, and a lower insulating chuck is arranged at a lower cross beam of the creep machine through a connecting pin;
and fixing the quenched aluminum alloy sample between an upper insulating chuck and a lower insulating chuck of the creep machine, and fully contacting positive and negative electrode clamping blocks of a pulse power supply device with the upper end and the lower end of the quenched aluminum alloy sample respectively to reduce contact resistance.
5. The heat treatment method according to claim 1, wherein in the step 2, the creep machine applies a load of 0 to 200MPa to the aluminum alloy test piece.
6. The heat treatment method according to claim 1, wherein in the step 3, the surface temperature of the aluminum alloy sample during the electric pulse cyclic heating process is monitored by using a data recorder.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113684430A (en) * | 2021-08-18 | 2021-11-23 | 上海交通大学 | Heating and cooling circulation heat treatment method near primary precipitation phase initial melting temperature of cast alloy |
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Cited By (2)
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