Method for measuring and analyzing precipitation process of aluminum alloy under condition of ultrafast cooling rate

Abstract

The invention relates to a method for measuring and analyzing an aluminum alloy precipitation process under an ultrafast cooling rate condition. The method comprises the following steps: (1) preparing materials; (2) solution treatment; (3) ultrafast quenching (5-4 * 10 < 5 > K / s); (4) artificial aging; (5) a two-step reheating method and thermal analysis: S1: primary reheating: heating each test sample subjected to artificial aging in the step (4) to a solution treatment temperature at a rate of 103K / s-104K / s, and recording a heat flow curve; s2, solution treatment and ultrafast cooling are carried out again; s3, reheating for the second time: reheating the test sample to the solution treatment temperature at the heating rate same as that in the S1, and recording a baseline heat flow curve; and S4, differential analysis: obtaining the total enthalpy change of the precipitation reaction in the cooling and aging processes through the difference of the two heat flow curves, and realizing the quantitative measurement and analysis of the precipitation behavior by the quenching vacancy.

Description

Technical Field

[0001] The present invention relates to the field of metal material analysis and testing, and in particular to a method for measuring and analyzing the precipitation process of an aluminum alloy under ultrafast cooling rate conditions. Background Art

[0002] Aluminum alloys, particularly the 7xxx (Al-Zn-Mg(-Cu)) series, are widely used in the aerospace and automotive industries due to their excellent mechanical properties and corrosion resistance. The strengthening mechanism of these alloys is primarily precipitation strengthening, with the formation of precipitates, such as the η' phase, dependent on the diffusion behavior of solute atoms and quench vacancies. Traditional analytical testing methods, due to limited cooling rates, have made it difficult to systematically study the effects of quench vacancies on subsequent precipitation reactions during quenching. Quench vacancies, as key diffusion defects, have a direct impact on subsequent aging precipitation processes and material properties.

[0003] Existing techniques, such as differential scanning calorimetry (DSC) and positron annihilation lifetime spectroscopy (PALS), are limited by the maximum cooling rate of the equipment and cannot accurately measure the effect of quenching vacancies on precipitation reactions under ultrafast cooling conditions. Therefore, developing a method suitable for measuring and analyzing the precipitation process in aluminum alloys under ultrafast cooling conditions is of great significance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions in response to the above-mentioned existing technology. The method is suitable for measuring and analyzing the influence of quenching vacancies on the precipitation reaction under ultrafast cooling rate conditions.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for measuring and analyzing the precipitation process of aluminum alloy under ultra-fast cooling rate conditions, characterized in that it includes the following steps: (1) Material preparation: prepare aluminum alloy, perform surface treatment on the aluminum alloy, and then cut it into multiple test samples; (2) Solution treatment: Each test sample in step (1) is heated to the solution treatment temperature and kept at this temperature for a set time to allow the alloy elements to be fully dissolved; (3) Ultrafast quenching: The multiple test samples in step (2) are divided into multiple groups, each group includes at least one test sample, the cooling rate of the test samples in each group is different, and the cooling rate of the test samples in the same group is the same. 5K / s cooling rate equipment, which rapidly cools each test sample in step (2) from the solution treatment temperature to a specified temperature (room temperature to -196°C) to obtain different concentrations of quenched vacancies; (4) Artificial aging: placing each test sample after quenching in step (3) at the aging temperature and performing artificial aging treatment according to the set time to promote the formation of precipitation phase; (5) Two-step reheating method and thermal analysis: S1: One-time reheating: Each test sample that has been artificially aged in step (4) was heated at 10³K / s~10 4 K / s to the solution treatment temperature, record the heat flow curve, and obtain the total endothermic peak including the dissolution of the precipitate phase during cooling and aging; S2: Re-solution treatment and ultra-fast cooling: After each test sample heated in S1 is subjected to solution treatment at the solution treatment temperature and holding time set in step (2), 4 K / s~10 5 Cooling to the specified temperature in step (3) (room temperature ~ -196 °C) at an ultrafast cooling rate of 1000 K / s, which is sufficient to completely suppress the precipitation reaction during the cooling process; S3: Second reheating: The test sample cooled in S2 was reheated to the solution treatment temperature at the same heating rate as in S1, and the baseline heat flow curve was recorded; S4: Differential analysis: By taking the difference between two heat flow curves, the total enthalpy change of the precipitation reaction during the cooling and aging process is obtained, enabling quantitative measurement and analysis of the effect of quenching vacancies on precipitation behavior.

[0006] In order to further study the effect of quenching vacancies on the precipitation reaction, the method further includes step (6), comparing the enthalpy changes at different cooling rates obtained in steps (2) to (5), determining the critical cooling rate for reaching quenching vacancy saturation, and determining the influence of quenching vacancies on the precipitation reaction.

[0007] In order to further study the effect of quenching vacancies on precipitation reaction, in step (4), each group includes at least two test samples, and the test samples in the same group are artificially aged at different temperatures. In step (6), the enthalpy changes at different cooling rates and different aging temperatures are compared to determine the critical cooling rate (e.g., 10 4 K / s), to determine the influence of quenching vacancies on precipitation reaction.

[0008] In the above scheme, in steps (2) to (5), the equipment for heating and cooling the test sample is a Differential Fast Scanning Calorimeter (DFSC).

[0009] Preferably, in step (1), the surface treatment method of the aluminum alloy is: grinding the aluminum alloy with SiC sandpaper of different mesh sizes to a thickness of 5 to 70 microns, and polishing the surface with SiC sandpaper.

[0010] Preferably, in step (3), the specified temperature is room temperature to -196°C.

[0011] Compared with the existing technology, the advantages of the present invention are: the method of the present invention can systematically control the concentration of quenching vacancies in aluminum alloys under quenching conditions of ultrafast cooling rates, and through a two-step reheating method, achieve high-precision measurement of the precipitation reaction enthalpy change and precipitate phase content after ultrafast quenching, and determine the influence of quenching vacancies on the precipitation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a picture of an AA7150 aluminum alloy sample placed in the center of the heating zone of a differential rapid scanning calorimeter (DFSC). Its position is just above the center of the heating zone, which is conducive to the detection of temperature change signals. Figure 2 Schematic diagram of the temperature and time program during the differential rapid scanning calorimetry measurement process in Example 1 of the present invention; Figure 3 1 is a differential diagram of heat flow curves of AA7150 aluminum alloy after being treated by a two-step reheating method at different cooling rates in Example 1 of the present invention; Figure 4 The relationship curves of enthalpy change at different artificial aging temperatures versus cooling rates for the AA7150 aluminum alloy after solution treatment, ultra-rapid quenching, artificial aging, and two-step heating treatment in Example 1 of the present invention are shown; Figure 5 This is a curve showing the relationship between the enthalpy change at an artificial aging temperature of 130° C. and different cooling rates of the AA7068 aluminum alloy after solution treatment, ultra-rapid quenching, artificial aging, and two-step heating treatment in Example 2 of the present invention. DETAILED DESCRIPTION

[0013] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments. Example 1

[0014] The method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions of this embodiment includes the following steps: (1) Material preparation: Prepare aluminum alloy and perform surface treatment on the aluminum alloy: Specifically, grind the aluminum alloy to a thickness of 30 μm with SiC sandpaper of different mesh sizes, and polish the surface with 1200 mesh or 2500 mesh SiC sandpaper, and then cut it into multiple 800 nanogram cubes or slices under an optical microscope as subsequent test samples; the aluminum alloy in this embodiment is AA7150 aluminum alloy, and the AA7150 aluminum alloy is placed on the heating zone of a differential rapid scanning calorimeter under an optical microscope, see the attached Figure 1 ; (2) Solution treatment: Each test sample in step (1) is heated to the solution treatment temperature and kept at this temperature for a set time to allow the test sample to fully dissolve; specifically, using a differential scanning calorimeter (DFSC) device, each test sample is heated to 480°C and kept at this temperature for 5 minutes; (3) Ultrafast quenching: It can achieve 5~4×10 5 K / s cooling rate equipment, the test samples of step (2) are quickly cooled and quenched from the solution treatment temperature to -196 ° C; the specific operation method is: the multiple test samples of step (2) are divided into multiple groups, each group includes three test samples, the cooling rate of each group of test samples is different, and the cooling rate of the test samples in the same group is the same, so as to obtain different concentrations of quenching vacancies; in this embodiment, the multiple groups of test samples are cooled at 5, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, Rapid cooling and quenching from the solution treatment temperature to -196°C at a cooling rate of 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 400000 K / s. The test samples were cooled using a differential scanning calorimeter (DFSC). (4) Artificial aging: The test samples after quenching in step (3) are placed at different aging temperatures and artificially aged for a set time to promote the formation of precipitated phases; specifically, the three test samples in the same group are artificially aged at aging temperatures of 70°C, 90°C, and 110°C, respectively, for a set time of 10 minutes, and the artificial aging equipment used is a differential rapid scanning calorimeter (DFSC); (5) Two-step reheating method and thermal analysis to obtain the endothermic peak of the precipitated phase dissolution and calculate the enthalpy change: S1: One-time reheating: Each test sample artificially aged in step (4) was heated to the solution treatment temperature at a rate of 10³K / s, and the heat flow curve was recorded to obtain the total endothermic peak including the dissolution of the precipitated phase during cooling and aging, and the integrated enthalpy change was calculated; S2: Re-solution treatment and ultra-fast cooling: After being heated in S1, each test sample was subjected to solution treatment according to the solution treatment temperature and holding time in step (2), that is, each test sample after being heated in S1 was kept at the solution treatment temperature of 480°C for 5 minutes, and then kept at 10 5 K / s to a lower temperature of -196 °C, which is sufficient to completely suppress the precipitation reaction during the cooling process (i.e., the precipitation reaction enthalpy becomes zero); S3: Second reheating: Reheat each test sample after cooling in S2 to the solution treatment temperature at the same heating rate as in S1, record the baseline heat flow curve (without precipitation reaction endothermic peak), and obtain the baseline; S4: Differential analysis: By taking the difference between two heat flow curves, the total enthalpy change of the precipitation reaction during cooling and aging is obtained, enabling quantitative measurement and analysis of the effect of quenching vacancies on precipitation behavior. The equipment for heating and cooling the test sample in step (5) is a differential rapid scanning calorimeter (DFSC).

[0015] (6) Results analysis: Compare the enthalpy changes of the test samples at different cooling rates and aging temperatures in steps (2) to (5) to determine the critical cooling rate (e.g., 10 4 K / s), to determine the influence of quenching vacancies on precipitation reaction.

[0016] The temperature and time diagram of the test procedure used in the above embodiment 1 is shown in the attached Figure 2 ,exist Figure 2 In the graph, the horizontal axis is time and the vertical axis is temperature. The curve first shows that the sample is kept at the solution treatment temperature (480℃) and then cooled at a set ultrafast cooling rate (such as 5~4×10 5 K / s) to a lower temperature. Subsequently, the sample is kept at different artificial aging temperatures (such as 70℃, 90℃ or 110℃) for a period of time (such as 10 minutes) to promote the formation of precipitation phase. After artificial aging, the sample is heated at a high heating rate (10 3 K / s) for the first reheating and record the heat flow curve of the precipitate dissolution. Then, the sample was kept at the solution treatment temperature and cooled at an ultrafast cooling rate (10 5K / s) to a lower temperature, during which the precipitation reaction is completely suppressed. A second reheating is then performed at the same rate, and a baseline heat flow curve is recorded.

[0017] The heat flow curve of step S4 in the above embodiment 1 is shown in the attached Figure 3 , Figure 3 The curve plots heat flow (mW) on the ordinate and temperature (°C) on the abscissa. The change in the peak value of the curve indicates that the amount and type of precipitated phases in the alloy change with increasing cooling rate. This figure provides important experimental evidence for the quantitative analysis of the relationship between quenching vacancies and precipitation behavior and the underlying mechanism of this influencing factor.

[0018] Attachment Figure 4 Not only the enthalpy changes of Example 1 at different cooling rates in step (3) are compared, but also the enthalpy changes of Example 1 at different aging temperatures in step (4) are compared.

[0019] Figure 4 The horizontal axis is the cooling rate (K / s), and the vertical axis is the enthalpy change (J / g), which represents the heat released by the precipitation reaction. The curve reflects the effect of cooling rate on the total amount of precipitated phase under different artificial aging temperatures (70℃, 90℃, 110℃). The curve shows that with the increase of cooling rate, the precipitation enthalpy gradually increases, indicating that at a higher cooling rate, the number of quenching vacancies in the material increases, thereby forming more precipitated phases in the subsequent artificial aging stage. When the cooling rate is higher than a certain threshold (such as 10 4 K / s), the curve stabilizes, indicating that quenching vacancies have reached saturation and the amount of precipitated phases no longer increases significantly. This figure clearly demonstrates that the method of the present invention achieves precise control and measurement of the amount of precipitated phases in aluminum alloys by regulating the cooling rate, verifying the effectiveness of the ultrafast quenching combined with the two-step reheating method. Example 2

[0020] The method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions of this embodiment includes the following steps: (1) Material preparation: Prepare aluminum alloy, grind the metal sample to a thickness of 45 μm using SiC sandpaper of different mesh sizes, and polish the surface using 1200-mesh or 2500-mesh SiC sandpaper. Then, cut the sample into multiple 500-nanogram cubes or slices under an optical microscope as test samples. The aluminum alloy in this embodiment is AA7068 aluminum alloy, and the AA7068 alloy is placed on the heating zone of a differential rapid scanning calorimeter under an optical microscope. (2) Solution treatment: Each test sample of step (1) is heated to the solution treatment temperature and kept at this temperature for a set time to allow the alloy elements to be fully dissolved; specifically, the AA7068 alloy is heated to 480°C using a differential scanning calorimeter (DFSC) device and kept at this temperature for 10 minutes; (3) Ultra-fast quenching: The use of 5~4×10 5 K / s cooling rate equipment, each test sample in step (2) is rapidly cooled and quenched from the solution treatment temperature to room temperature at different cooling rates; the specific operation method is as follows: a plurality of test samples are divided into a plurality of groups, each group includes a test sample; specifically in this embodiment, the plurality of groups of test samples are cooled at 5, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 20 00, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, and 100000 K / s for rapid cooling and quenching from the solution treatment temperature to room temperature. The equipment for cooling the test samples adopts differential rapid scanning calorimetry (DFSC); (4) Artificial aging: placing each test sample after quenching in step (3) at an aging temperature and performing artificial aging treatment according to a set time to promote the formation of precipitated phases; specifically, artificial aging is performed on each test sample after quenching at 130°C for 10 minutes, and the equipment for artificial aging adopts a differential rapid scanning calorimeter (DFSC); (5) Two-step reheating method and thermal analysis to obtain the endothermic peak of the precipitated phase dissolution and calculate the enthalpy change: S1: One-time reheating: Each test sample that has been artificially aged in step (4) is 3 K / s to 480℃, record the heat flow curve, obtain the total endothermic peak including the dissolution of the precipitated phase during cooling and aging, and calculate the integrated enthalpy change; S2: Re-solution treatment and ultra-fast cooling: After being heated in S1, each test sample was subjected to solution treatment according to the solution treatment temperature and holding time in step (2), that is, each test sample after being heated in S1 was kept at the solution treatment temperature of 480°C for 10 minutes, and then kept at 10 5 K / s to room temperature, which is sufficient to completely suppress the precipitation reaction during cooling (i.e., the precipitation reaction enthalpy becomes zero); S3: Second reheating: The sample cooled in S2 was reheated to the solution treatment temperature at the same heating rate as in S1, and the baseline heat flow curve (without precipitation reaction endothermic peak) was recorded to obtain the baseline; S4: Differential analysis: By taking the difference between two heat flow curves, the total enthalpy change of the precipitation reaction during cooling and aging is obtained, enabling quantitative measurement and analysis of the effect of quenching vacancies on precipitation behavior. The equipment for heating and cooling the test sample in step (5) is a differential rapid scanning calorimeter (DFSC).

[0021] (6) Results analysis: Compare the enthalpy changes of the test samples at different cooling rates in steps (2) to (5), see Appendix Figure 5 , determine the influence of quenching vacancies on precipitation reaction.

[0022] Figure 5 The horizontal axis represents the cooling rate (K / s), and the vertical axis represents the enthalpy change (mJ), which represents the heat released by the precipitation reaction. The curve reflects the effect of cooling rate on the total amount of precipitates at an artificial aging temperature of 130°C. The curve shows that the precipitation enthalpy gradually increases with increasing cooling rate, indicating that higher cooling rates increase the number of quenching vacancies in the material, leading to the formation of more precipitates during the subsequent artificial aging stage.

[0023] The differential rapid scanning calorimeter (DFSC) used in the present invention is a Spark III differential rapid scanning calorimeter produced by FMR eV.

Claims

1. A method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions, characterized by: The steps include: (1) Material preparation: prepare aluminum alloy, perform surface treatment on the aluminum alloy, and then cut it into multiple test samples; (2) Solution treatment: Each test sample in step (1) is heated to the solution treatment temperature and kept at this temperature for a set time to allow the alloy elements to be fully dissolved; (3) Ultrafast quenching: The multiple test samples in step (2) are divided into multiple groups, each group includes at least one test sample, the cooling rate of the test samples in each group is different, and the cooling rate of the test samples in the same group is the same. 5 K / s cooling rate equipment, which rapidly cools each test sample in step (2) from the solution treatment temperature to a specified temperature to obtain different concentrations of quenching vacancies; (4) Artificial aging: placing each test sample after quenching in step (3) at the aging temperature and performing artificial aging treatment according to the set time to promote the formation of precipitation phase; (5) Two-step reheating method and thermal analysis: S1: One-time reheating: Each test sample that has been artificially aged in step (4) is 3 K / s~10 4 K / s to the solution treatment temperature, record the heat flow curve, and obtain the total endothermic peak including the dissolution of the precipitate phase during cooling and aging; S2: Re-solution treatment and ultra-fast cooling: After the test samples heated in S1 are subjected to solution treatment at the solution treatment temperature and holding time set in step (2), 4 K / s~10 5 Cooling to the specified temperature in step (3) at an ultrafast cooling rate of 1000 K / s, which is sufficient to completely suppress the precipitation reaction during the cooling process; S3: Second reheating: The test sample cooled in S2 was reheated to the solution treatment temperature at the same heating rate as in S1, and the baseline heat flow curve was recorded; S4: Differential analysis: By taking the difference between two heat flow curves, the total enthalpy change of the precipitation reaction during the cooling and aging process is obtained, enabling quantitative measurement and analysis of the effect of quenching vacancies on precipitation behavior.

2. The method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions according to claim 1, characterized in that: The method further includes step (6), comparing the enthalpy changes at different cooling rates obtained in the tests in steps (2) to (5), determining the critical cooling rate for reaching quenching vacancy saturation, and determining the influence of quenching vacancies on the precipitation reaction.

3. The method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions according to claim 2, characterized in that: In step (4), each group includes at least two test samples, and the test samples in the same group are artificially aged at different temperatures. In step (6), the enthalpy changes at different cooling rates and different aging temperatures are compared to determine the critical cooling rate for reaching quenching vacancy saturation and the influence of quenching vacancies on precipitation reaction.

4. The method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions according to claim 1, 2 or 3, characterized in that: In steps (2) to (5), the equipment for heating and cooling the test sample is a differential rapid scanning calorimeter.

5. The method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions according to claim 1, 2 or 3, characterized in that: In the step (1), the surface treatment method of the aluminum alloy is: grinding the aluminum alloy with SiC sandpaper of different mesh sizes to a thickness of 5 to 70 microns, and polishing the surface with SiC sandpaper.

6. The method for measuring and analyzing the precipitation process of aluminum alloy under ultrafast cooling rate conditions according to claim 1, 2 or 3, characterized in that: In the step (3), the specified temperature is room temperature to -196°C.

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