Al-Zn-Mg-Cu alloy and identification method of its aging precipitation phase

Abstract

The present application provides an Al‑Zn‑Mg‑Cu alloy and a method for identifying an aging precipitation phase thereof. The Al‑Zn‑Mg‑Cu alloy aging precipitation phase identification method of the present application includes: preparing a transmission sample; obtaining a TEM bright field photograph; obtaining a SAED photograph; obtaining an HRTEM photograph; obtaining element distribution data of the precipitation phase; and determining the precipitation sequence of the precipitation phase. The method of the present application is simple and accurate, and can not only identify the precipitation phase of the microstructure of the Al‑Zn‑Mg‑Cu alloy, but also determine the precipitation order of the precipitation phase, and can characterize the precipitation sequence process of the precipitation phase, so that the nucleation and growth process of each precipitation phase of the Al‑Zn‑Mg‑Cu alloy can be understood, and the number and size of each precipitation phase of the Al‑Zn‑Mg‑Cu alloy can be regulated to provide assistance, which is beneficial to improving the alloy properties and manufacturing an Al‑Zn‑Mg‑Cu alloy with better mechanical properties.

Description

Technical Field

[0001] The present application relates to the technical field of metal material processing, and in particular to an Al-Zn-Mg-Cu alloy and an identification method of an aging precipitation phase thereof. Background Art

[0002] Al-Zn-Mg-Cu alloy is an ultra-high strength deformable aluminum alloy with the advantages of high specific strength and hardness, high toughness, good processing performance, and good corrosion resistance. It is an important structural material in the fields of automobiles, aerospace, and rail transportation.

[0003] As a type of age-hardened alloy, the number, size, distribution and precipitation process of the precipitated phase of Al-Zn-Mg-Cu alloy have significant effects on its mechanical properties. Therefore, understanding and identifying the precipitated phase and precipitation sequence of Al-Zn-Mg-Cu alloy is the key to manufacturing Al-Zn-Mg-Cu alloy with better mechanical properties. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a method for identifying an Al-Zn-Mg-Cu alloy and its aging precipitation phase, which can identify the precipitation phase and precipitation sequence process in the Al-Zn-Mg-Cu alloy.

[0005] In a first aspect, the present application provides a method for identifying an aging precipitation phase of an Al-Zn-Mg-Cu alloy, comprising:

[0006] The transmission sample is prepared by using the alloy sample to be tested after aging treatment;

[0007] Performing transmission analysis on the transmission sample to obtain a TEM bright field photograph of the transmission sample crystal;

[0008] Performing selected area electron diffraction patterns on a plurality of precipitated phases of different forms in the polycrystal in the transmission sample to obtain SAED photographs;

[0009] The characteristic region within the crystal of the transmission sample is magnified and photographed using a high-resolution electron microscope to obtain a HRTEM photograph;

[0010] Performing line scanning analysis on the intracrystalline precipitated phase of the transmission sample using a scanning transmission electron microscope-energy spectrum mode to obtain element distribution data of the precipitated phase;

[0011] The region of the precipitated phase in the crystal in the HRTEM image is subjected to Fourier transformation to obtain the diffraction spots of the precipitated phase;

[0012] The regions in the TEM bright field photo and the HRTEM photo that are spherical cluster-shaped are defined as predefined GP regions, the regions that are needle-shaped or disc-shaped are defined as predefined η' phases, and the regions that are rod-shaped or hexagonal are defined as predefined η phases;

[0013] Compare the diffraction spots of the precipitated phase in the SAED photo and the HRTEM photo, and define the consistent areas between the two as the diffraction spots of the target GP area, the diffraction spots of the target η' phase, and the diffraction spots of the target η phase;

[0014] The diffraction spots defined as the target η' phase in the HRTEM photo are defined as the diffraction spots of the η'1 phase, the diffraction spots of the η'2 phase and the diffraction spots of the η'3 phase respectively by comparing the sizes;

[0015] The diffraction spots defined as the target η phase in the HRTEM photo are defined as the diffraction spots of the η1 phase, the diffraction spots of the η2 phase and the diffraction spots of the η3 phase respectively by comparing the sizes;

[0016] The line scan results corresponding to the same morphology of the precipitated phase in the element distribution data of the precipitated phase are compared and analyzed, and the precipitation sequence of the precipitated phase is determined according to the changes of the Al element, the Zn element, the Cu element and the Mg element.

[0017] In one embodiment, the η' phase includes four variants, which are respectively a first variant, a second variant, a third variant and a fourth variant. The common crystal band axis of the first variant and the second variant is [10-10] / /

[110] Al, the crystal band axis of the third variant is [2-423] / /

[110] Al, and the crystal band axis of the fourth variant is [-24-23] / /

[110] Al; wherein, the diffraction spots of the η'1 phase correspond to the first variant, the diffraction spots of the η'2 phase correspond to the second variant, and the diffraction spots of the η'3 phase correspond to the third variant and the fourth variant.

[0018] In one embodiment, the size of the diffraction spot of the η'1 phase is smaller than the size of the diffraction spot of the η'2 phase, and the size of the diffraction spot of the η'2 phase is smaller than the size of the diffraction spot of the η'3 phase.

[0019] In one embodiment, the size of the diffraction spot of the η1 phase is smaller than the size of the diffraction spot of the η2 phase, and the size of the diffraction spot of the η2 phase is smaller than the size of the diffraction spot of the η3 phase.

[0020] In one embodiment, the precipitation sequence of the precipitated phase in the alloy sample to be tested is determined to be GP region→η'1 phase→η'2 phase→η'3 phase→η1 phase→η2 phase→η3 phase.

[0021] In one embodiment, when the precipitation sequence of the precipitated phase in the alloy sample to be tested is GP zone → η'1 phase → η'2 phase → η'3 phase → η1 phase → η2 phase → η3 phase, the change process of the Al element, Zn element, Cu element and Mg element is that the content of the Al element gradually decreases, and the contents of the Zn element, Cu element and Mg element gradually increase, wherein the change rates of the Zn element and Cu element contents are the same, and the change rates of the Zn element content and the Cu element content are both higher than the change rate of the Mg element content.

[0022] In a second aspect, the present application provides an Al-Zn-Mg-Cu alloy, which is identified using the method for identifying the aging precipitation phase of the Al-Zn-Mg-Cu alloy as described in any of the aforementioned embodiments.

[0023] In one embodiment, the Al—Zn—Mg—Cu alloy is subjected to an aging process.

[0024] In one embodiment, the content of the GP zone in the microstructure of the Al—Zn—Mg—Cu alloy is greater than the content of the η phase, and the content of the η′ phase is greater than the content of the η phase.

[0025] In one embodiment, the weight ratio of the chemical components in the Al-Zn-Mg-Cu alloy is Zn 7.8-8.2%; Mg 2.0-2.2%; Cu 2.1-2.4%; Zr 0.08-0.12%; Ti 0.06%; Fe<0.10; Si<0.10%, and the balance is Al.

[0026] The beneficial effects of this application compared with the prior art are:

[0027] The method for identifying the aging precipitation phase of the Al-Zn-Mg-Cu alloy provided in the present application is simple and accurate, and can not only identify the precipitation phase of the microstructure of the Al-Zn-Mg-Cu alloy, but also determine the precipitation order of the precipitation phase, and can characterize the precipitation sequence process of the precipitation phase in the Al-Zn-Mg-Cu alloy, so as to understand the nucleation and growth process of each precipitation phase of the Al-Zn-Mg-Cu alloy, provide assistance for regulating the number and size of each precipitation phase of the Al-Zn-Mg-Cu alloy, and be beneficial to improving the alloy properties and manufacturing an Al-Zn-Mg-Cu alloy with better mechanical properties, i.e., an Al-Zn-Mg-Cu alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A flow chart of a method for identifying aging precipitation phases in an Al-Zn-Mg-Cu alloy provided in one embodiment of the present application.

[0030] Figure 2 This is a TEM bright field photograph provided in one embodiment of the present application.

[0031] Figure 3 This is a SAED photo provided by an embodiment of the present application.

[0032] Figure 4 This is a HRTEM photo provided for one embodiment of the present application.

[0033] Figure 5 Diffraction spots of the precipitated phase in the HRTEM photograph provided in one embodiment of the present application.

[0034] Figure 6 Schematic diagram of four variants of the η' phase provided in one embodiment of the present application.

[0035] Figure 7 The element distribution data of the precipitated phase provided for one embodiment of the present application. DETAILED DESCRIPTION

[0036] The terms “first”, “second”, “third”, etc. are only used for distinguishing descriptions and do not indicate the order of arrangement, nor can they be understood as indicating or implying relative importance.

[0037] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of the present application, it should be noted that the terms "inside", "outside", "left", "right", "up", "down", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the products of the present application are usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0039] In the description of this application, unless otherwise clearly specified and limited, the terms "set", "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements.

[0040] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings.

[0041] Please refer to Figure 1 , which is a flow chart of the method for identifying the aging precipitation phase of the Al-Zn-Mg-Cu alloy provided in the embodiment of the present application. Please refer to Figure 2-Figure 7 , which are Figure 1 The schematic diagram of the steps of the embodiment shown, wherein: Figure 2 This is a TEM bright field photograph provided in one embodiment of the present application. Figure 3 The SAED photo provided in one embodiment of the present application is: Figure 4 This is a HRTEM photo provided in one embodiment of the present application. Figure 5 The diffraction spots of the precipitated phase in the HRTEM photo provided in one embodiment of the present application are as follows: Figure 6 Schematic diagram of four variants of the η' phase provided in one embodiment of the present application, Figure 7 The element distribution data of the precipitated phase provided for one embodiment of the present application.

[0042] The identification method of the aging precipitation phase of the Al-Zn-Mg-Cu alloy is simple and accurate, and can not only identify the precipitation phase of the microstructure of the Al-Zn-Mg-Cu alloy, but also determine the precipitation order of the precipitation phase, and can characterize the precipitation sequence process of the precipitation phase in the Al-Zn-Mg-Cu alloy, so as to understand the nucleation and growth process of each precipitation phase of the Al-Zn-Mg-Cu alloy, provide help for regulating the number and size of each precipitation phase of the Al-Zn-Mg-Cu alloy, which is beneficial to improving the alloy properties and manufacturing the Al-Zn-Mg-Cu alloy with better mechanical properties.

[0043] The present Al-Zn-Mg-Cu alloy aging precipitation phase identification method comprises the following steps: step S101 to step S111.

[0044] Step S101: using the alloy sample to be tested after aging treatment to prepare a transmission sample.

[0045] The alloy sample to be tested in this step is an Al-Zn-Mg-Cu alloy, which can be a finished product directly obtained, or prepared, or obtained by treating a finished alloy plate of about 2 mm through a preset process. The weight ratio of the chemical composition in the alloy sample to be tested is Zn 7.8-8.2%; Mg 2.0-2.2%; Cu 2.1-2.4%; Zr 0.08-0.12%; Ti 0.06%; Fe<0.10; Si<0.10%, and the balance is Al.

[0046] This step is to prepare a transmission sample for the subsequent steps S102 to S111. Since the subsequent steps S102 to S111 include analysis using a transmission electron microscope, in order to obtain a better imaging effect, there are certain requirements for the thickness of the transmission sample.

[0047] In one embodiment, the step of preparing the transmission sample in this step includes: first cutting the alloy sample to be tested after aging treatment into sample slices with a thickness of 0.1-0.5 mm and a diameter of 3 mm, then pre-thinning by manual grinding or chemical thinning to reduce the thickness of the sample slice to 20-50 μm, and finally performing final thinning by electrolytic polishing to reduce the thickness of the sample slice to 50-200 nm to obtain the final transmission sample.

[0048] In one embodiment, the aging treatment step of this step includes: firstly performing a pre-aging treatment at a temperature of 100° C. for 2 hours, and then performing an aging treatment at a temperature of 185° C. for 0.5 hours.

[0049] Step S102: Perform transmission analysis on the transmission sample to obtain a TEM bright field photograph of the transmission sample crystal.

[0050] This step uses a transmission electron microscope (TEM) for photography, and the TEM bright field photograph is obtained in this step. In the bright field mode, the entire field of view is relatively bright, which is more conducive to observing the size, dimensions, morphology, intracrystalline area and other information of the transmission sample.

[0051] In one embodiment, the transmission sample is cleaned and mounted on a sample holder on a sample rod of a transmission electron microscope. The sample rod with the transmission sample is then inserted into a sample stage of the transmission electron microscope and evacuated. The transmission electron microscope is then debugged and photographed. The TEM bright field photograph of the transmission sample crystal is shown in FIG. Figure 2 shown.

[0052] Step S103: performing selected area electron diffraction patterns on a plurality of precipitated phases of different forms in the polycrystal in the transmission sample to obtain SAED photographs.

[0053] This step is the selected area electron diffraction (SAED) step. Selected area electron diffraction realizes the in-situ analysis of the morphological characteristics and crystallographic properties of the crystal sample by the micro-area correspondence between the selected area morphology observation and the electron diffraction structure analysis. It can also calculate a lot of information about the lattice of the material based on the pattern in the obtained SAED photo, and obtain qualitative analysis of the interplanar spacing and angle. The SAED photo obtained in this step is as follows: Figure 3 shown.

[0054] In one embodiment, selected area electron diffraction can select the sample area that produces diffraction and limit the size of the selected area with the help of a selected area light bar set on the objective lens plane, thereby achieving microscopic correspondence between morphological observation and electron diffraction.

[0055] Step S104: Enlarging the characteristic region within the crystal of the transmission sample and photographing it with a high-resolution electron microscope to obtain a HRTEM photograph.

[0056] This step is a high-resolution transmission electron microscope (HRTEM) step. The HRTEM photos obtained have high resolution and can provide crystal surface information to observe the internal structure of the crystal, atomic arrangement, and many fine structures (such as dislocations, twins, etc.). Figure 4 shown.

[0057] In this step, the intracrystalline characteristic region of the transmission sample is the region of the precipitated phase in the crystal of the transmission sample, which is manually selected. The manually selected intracrystalline characteristic region needs to be obtained after overall observation through TEM bright field photos, for example Figure 2 The area selected by the dotted box.

[0058] Step S105: using a scanning transmission electron microscope-energy spectrum mode to perform line scanning analysis on the intracrystalline precipitation phase of the transmission sample to obtain element distribution data of the precipitation phase.

[0059] This step is a scanning transmission electron microscope-energy dispersive spectrometer (STEM-EDS). In this step, a transmission electron microscope or a scanning electron microscope can be used in conjunction with an energy dispersive spectrometer. In the STEM mode, an electron beam is used to scan the surface of the sample, and the electron penetrates the sample to form an image. The operation is fast, and the imaging is particularly accurate. At the same time, EDS line scans and elemental mapping are used to analyze the types and contents of the components of the transmission sample micro-area to obtain the elemental distribution data of the precipitated phase. The elemental distribution data of the precipitated phase is obtained as follows: Figure 7 shown.

[0060] In one embodiment, the scanning transmission electron microscope in this step is a scanning transmission electron microscope with a high-angle annular dark field probe (HAADF-STEM).

[0061] It should be noted that the transmission electron microscope equipment used in step S105, step S104, step S103 and step S102 can be the same, or the equipment used in step S105, step S104, step S103 and step S102 can be different, using dedicated equipment respectively.

[0062] When the transmission electron microscope equipment used in step S105, step S104, step S103 and step S102 is the same, step S105, step S104, step S103 and step S102 are different modes of the transmission electron microscope equipment respectively.

[0063] For example, step S102 is a TEM bright field photograph obtained in low magnification (normal resolution) mode, which is mainly used to observe the microscopic morphology and structure of the material and to observe the whole. Although the shape of the precipitated phase can be roughly observed, it is not clear enough. Therefore, this embodiment also obtains a locally enlarged HRTEM photograph obtained in high magnification (high resolution) mode through step S104 to further clearly observe the internal structure of the crystal and obtain the precipitated phase and crystal surface information. Furthermore, this embodiment further analyzes and determines the distribution through STEM-EDS in step S105.

[0064] In addition, this embodiment also performs in-situ analysis of the morphological characteristics and crystallographic properties of the crystal sample through the SAED photograph obtained in step S103, and can calculate a lot of information about the lattice of the material based on the pattern in the SAED photograph, and obtain a qualitative analysis of the crystal plane spacing and angle. This embodiment combines the SAED photograph obtained in step S103 with the HRTEM photograph obtained in step S104 to verify each other, so that the final result can be more accurate.

[0065] Step S106: Perform Fourier transformation on the region of the precipitated phase in the crystal in the HRTEM image to obtain diffraction spots of the precipitated phase.

[0066] This step is an image processing step for HRTEM photos. This step can be performed using preset software (e.g. Digital Micrograph software). The region of the intracrystalline precipitated phase in the HRTEM photos in this step is a typical region selected manually.

[0067] In this step, the fast Fourier transform (FFT) algorithm is used to transform the manually selected area in the HRTEM photo to obtain an FFT transformation image, which is equivalent to an electron diffraction image, so as to better analyze the precipitated phase. Figure 5 shown.

[0068] Step S107: define the spherical cluster-shaped areas in the TEM bright field photo and the HRTEM photo as predefined GP areas, define the needle-shaped or disk-shaped areas as predefined η' phases, and define the rod-shaped or hexagonal areas as predefined η phases.

[0069] In this step, through manual observation, the type of precipitation phase represented by the pattern in the typical area of ​​the TEM bright field photograph and the HRTEM photograph is preliminarily defined according to the pattern morphology structure of the typical area in the TEM bright field photograph and the HRTEM photograph. Subsequently, by combining with the detection result of step S108, they are mutually verified, so that the final definition result can be made more accurate.

[0070] It should be noted that the types of precipitated phases that can be confirmed in this step are GP zone, η' phase and η phase.

[0071] In one embodiment, if Figure 2 and Figure 4 As shown, the pattern that may be the precipitation phase is selected by using a dotted frame and predefined according to the shape.

[0072] exist Figure 4 In the HRTEM photos shown, the dotted-line framed area in part a is in the shape of a spherical cluster, which is defined as the predefined GP area; the dotted-line framed area in parts b, c and d is in the shape of a slender needle, which is defined as the predefined η' phase; the dotted-line framed area in parts e, f and g is in the shape of a short and thick rod or hexagonal shape, which is defined as the predefined η phase.

[0073] exist Figure 2In the a part of the TEM bright field photo shown, the dotted line boxed area a1 is defined as Al; the dotted line boxed area a2 is spherical cluster-shaped, which is defined as the predefined GP zone, represented by GPⅠZone; the dotted line boxed area a3 is slender needle-shaped, which is defined as the predefined η' phase, represented by η1' v2 a4 dashed line box area is disc-shaped, which is defined as the predefined η' phase, and η1' v3 a5 dotted line box area is shaped like a thin needle, which is defined as the predefined η' phase, and η2' v2 express.

[0074] exist Figure 2 In part b, the area selected by the dashed line b1 is shaped like a long and thin needle, which is defined as the predefined η' phase. v2 b2 The dotted line boxed area is in the shape of a rod, which is defined as the predefined η phase, represented by η1; b3 The dotted line boxed area is in the shape of a slender needle, which is defined as the predefined η' phase, represented by η2' v2 b4 The dotted line boxed area is spherical cluster-shaped, which is defined as the predefined GP zone, represented by GPⅡZone; b5 The dotted line boxed area is slender needle-shaped, which is defined as the predefined η' phase, represented by η3' v3 express.

[0075] exist Figure 2 In part c, the shape of the area selected by the dashed line c1 is short and thick rod-shaped, which is defined as the predefined η phase, denoted by η3; the shape of the area selected by the dashed line c2 is short and thick rod-shaped, which is defined as the predefined η phase, denoted by η1; the shape of the area selected by the dashed line c3 is long and thin needle-shaped, which is defined as the predefined η' phase, denoted by η1' v2 Indicates; the shape of the area selected by the dotted line c4 is a short and thick rod, which is defined as the predefined η phase, represented by η2.

[0076] Step S108: Compare the diffraction spots of the precipitated phase in the SAED photo and the HRTEM photo, and define the consistent areas between the two as the diffraction spots of the target GP area, the diffraction spots of the target η' phase and the diffraction spots of the target η phase.

[0077] This step is to combine the SAED photo obtained in step S103, the HRTEM photo obtained in step S104, and the FFT transformation diagram obtained in step S106, and verify each other, so that the final defined precipitation phase type result can be more accurate. This step can be manually checked or checked by a predetermined program in an electronic device.

[0078] In one embodiment, the diffraction spots at the predefined GP area determined in step S107 are first found, and then the same position in the SEAD photo is searched. When a pattern with the same morphology can be found at the same position in the SEAD photo, it means that the predefined GP area determined in step S107 is correct, and its name is changed to the target GP area, and the pattern at the position in the SAED photo and the HRTEM photo is defined as the diffraction spots of the target GP area. When a pattern with the same morphology cannot be found at the same position in the SEAD photo, it means that the predefined GP area determined in step S107 is wrong, and it is necessary to return to step S107 to search for the predefined GP area again, or return to step S104 to re-acquire the HRTEM photo, or perform an alarm process and determine whether the transmission sample is wrong, or make a judgment on the next area.

[0079] First, find the diffraction spots determined as the predefined η' phase in step S107, and then search for the same position in the SEAD photo. When a pattern with the same morphology can be found at the same position in the SEAD photo, it means that the predefined η' phase determined in step S107 is correct, and its name is changed to the target η' phase, and the pattern at the position in the SAED photo and HRTEM photo is defined as the diffraction spots of the target η' phase. When a pattern with the same morphology cannot be found at the same position in the SEAD photo, it means that the predefined η' phase determined in step S107 is wrong, and it is necessary to return to step S107 to search for the predefined η' phase again, or return to step S104 to reacquire the HRTEM photo, or perform warning processing and determine whether the transmission sample is wrong, or make a judgment on the next area.

[0080] First, find the diffraction spots determined as the predefined η phase in step S107, and then search for the same position in the SEAD photo. When a pattern with the same morphology can be found at the same position in the SEAD photo, it means that the predefined η phase determined in step S107 is correct, and its name is changed to the target η phase, and the pattern at the position in the SAED photo and HRTEM photo is defined as the diffraction spot of the target η phase. When a pattern with the same morphology cannot be found at the same position in the SEAD photo, it means that the predefined η phase determined in step S107 is wrong, and it is necessary to return to step S107 to search for the predefined η phase again, or return to step S104 to re-acquire the HRTEM photo, or perform warning processing and determine whether the transmission sample is wrong, or make a judgment on the next area.

[0081] In one embodiment, Figure 3 , Figure 4 and Figure 5 Combined and mutually verified, the final defined precipitation phase type can be determined.

[0082] exist Figure 3In the SEAD photo, the arrows in parts a and b point to the diffraction spots of the target η' phase, and the arrows in part c point to the diffraction spots of the target η phase. Figure 3 The diffraction spots of the target GP area are not shown.

[0083] exist Figure 5 In the FFT transformation diagram, the arrow in part a1 points to Al; the arrow in part a2 points to the diffraction spot of the target GP area; the arrows in parts a3, a4 and a5 point to the diffraction spots of the target η' phase; the arrow in part a6 points to the diffraction spot of the target η phase.

[0084] exist Figure 4 In the HRTEM photo, the dotted-line boxed area in part a is the target GP area; the dotted-line boxed areas in parts b, c and d are the target η' phase; and the dotted-line boxed areas in parts e, f and g are the target η phase.

[0085] Step S109: The diffraction spots defined as the target η' phase in the HRTEM image are defined as the diffraction spots of the η'1 phase, the diffraction spots of the η'2 phase and the diffraction spots of the η'3 phase respectively by comparing the sizes.

[0086] This step is to further distinguish the diffraction spots of the target η' phase determined in step S108 into η'1 phase, η'2 phase and η'3 phase according to the size data. Specifically, the size of the diffraction spot of the η'1 phase is smaller than the size of the diffraction spot of the η'2 phase, and the size of the diffraction spot of the η'2 phase is smaller than the size of the diffraction spot of the η'3 phase. Furthermore, the growth rate of the size of the η'1 phase, η'2 phase and η'3 phase in the thickness direction is greater than the growth rate in the diameter direction.

[0087] In one embodiment, a preset software (e.g., Digital Micrograph software) is used to analyze all diffraction spots defined as the target η' phase in the HRTEM photo, obtain the size information of each diffraction spot of the target η' phase, and then sort them according to size, and further distinguish the diffraction spots of the target η' phase into η'1 phase, η'2 phase, and η'3 phase.

[0088] It should be noted that if Figure 6 As shown, the η' phase actually includes four variants, which are the first variant η' v1 , the second variant η' v2 , the third variant η' v3 and the fourth variant η' v4 , the first variant η' v1 and the second variant n' v2 The common crystal axis is [10-10] / /

[110] Al, and the third variant η' v3The crystal zone axis is [2-423] / /

[110] Al, and the fourth variant η' v4 The crystal zone axis is [-24-23] / /

[110] Al; the diffraction spots of the η'1 phase are similar to those of the first variant η' v1 Correspondingly, the diffraction spots of the η'2 phase are similar to those of the second variant η' v2 Correspondingly, the diffraction spots of the η'3 phase are similar to those of the third variant η' v3 and the fourth variant η' v4 correspond.

[0089] In one embodiment, if Figure 4 As shown, the areas selected by dashed lines in parts b, c and d are further divided into η'1 phase, η'2 phase and η'3 phase according to their size.

[0090] like Figure 5 As shown, the areas pointed by arrows in parts a3, a4 and a5 are further divided into the first variant n' according to their size. v1 , the second variant η' v2 and the third variant η' v3 , so that the η'1 phase, η'2 phase and η'3 phase can be determined.

[0091] Step S110: The diffraction spots defined as the target η phase in the HRTEM photo are defined as the diffraction spots of the η1 phase, the diffraction spots of the η2 phase and the diffraction spots of the η3 phase respectively by comparing the sizes.

[0092] This step is to further distinguish the diffraction spots of the target η phase determined in step S108 into η1 phase, η2 phase and η3 phase according to the size data. Specifically, the size of the diffraction spot of the η1 phase is smaller than the size of the diffraction spot of the η2 phase, and the size of the diffraction spot of the η2 phase is smaller than the size of the diffraction spot of the η3 phase. Furthermore, the growth rate of the size of the η1 phase, η2 phase and η3 phase in the thickness direction is greater than the growth rate in the diameter direction.

[0093] In one embodiment, a preset software (e.g., Digital Micrograph software) is used to analyze all diffraction spots defined as the target η phase in the HRTEM photo, obtain the size information of each diffraction spot of the target η phase, and then sort them according to size, and further distinguish the diffraction spots of the target η phase into η1 phase, η2 phase, and η3 phase.

[0094] In one embodiment, if Figure 4 As shown, the areas selected by dashed lines in parts e, f and g are further divided into η1 phase, η2 phase and η3 phase. Figure 5 The distinction between η1 phase, η2 phase and η3 phase is not shown.

[0095] Step S111: comparing and analyzing the line scan results corresponding to the same morphology of the precipitated phase in the element distribution data of the precipitated phase, and determining the precipitation sequence of the precipitated phase according to the changes of the Al element, the Zn element, the Cu element and the Mg element.

[0096] This step is to further analyze and determine the distribution by using the STEM-EDS of step S105, thereby determining the precipitation process of the precipitated phase. For example, according to the line scanning result analysis in step S105, the Al element content information, Zn element content information, Cu element content information and Mg element content information in each precipitated phase are obtained, and then the content information is sorted according to the size, the precipitation process of the precipitated phase is determined, and the precipitation sequence information is obtained.

[0097] In one embodiment, the elements in the GP region, η'1 phase, η'2 phase, η'3 phase, η1 phase, η2 phase and η3 phase are distributed as follows: Figure 7 As shown, the horizontal axis represents the interval (Position), the unit is nanometer, the vertical axis represents the concentration (Intensity / counts), and the middle curve of the figure represents the content curves of the Al element, the Zn element, the Cu element and the Mg element respectively. The operator takes the content values ​​of each element of each precipitation phase in the same interval for comparative analysis, and determines that the precipitation sequence of the precipitation phase in the alloy sample to be tested is GP zone→η'1 phase→η'2 phase→η'3 phase→η1 phase→η2 phase→η3 phase. Wherein, when the precipitation sequence of the precipitation phase in the alloy sample to be tested is GP zone→η'1 phase→η'2 phase→η'3 phase→η1 phase→η2 phase→η3 phase, the change process of the Al element, the Zn element, the Cu element and the Mg element is that the content of the Al element gradually decreases, and the content of the Zn element, the Cu element and the Mg element gradually increase, wherein the content of the Zn element and the Cu element change at the same speed, and the change speed of the Zn element content and the change speed of the Cu element content are both higher than the change speed of the Mg element content.

[0098] An Al-Zn-Mg-Cu alloy is identified by using the identification method of the Al-Zn-Mg-Cu alloy aging precipitation phase as described in any of the above embodiments. The Al-Zn-Mg-Cu alloy is treated by an aging process. The content of the GP zone in the microstructure of the Al-Zn-Mg-Cu alloy is greater than the content of the η phase, and the content of the η' phase is greater than the content of the η phase. The weight ratio of the chemical components in the Al-Zn-Mg-Cu alloy is Zn7.8-8.2%; Mg 2.0-2.2%; Cu 2.1-2.4%; Zr 0.08-0.12%; Ti0.06%; Fe<0.10; Si<0.10%, and the balance is Al.

[0099] Since the above-mentioned method for identifying the aging precipitation phase of the Al-Zn-Mg-Cu alloy has the above-mentioned technical effects, the Al-Zn-Mg-Cu alloy identified by the method for identifying the aging precipitation phase of the Al-Zn-Mg-Cu alloy according to any of the above-mentioned embodiments also has the same technical effects.

[0100] It should be noted that, in the absence of conflict, the features in the embodiments of this application may be combined with each other.

[0101] The above are only embodiments of the present application and are not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for identifying aging precipitation phase of Al-Zn-Mg-Cu alloy, characterized in that: include: The transmission sample is prepared by using the alloy sample to be tested after aging treatment; Performing transmission analysis on the transmission sample to obtain a TEM bright field photograph of the transmission sample crystal; Performing selected area electron diffraction patterns on a plurality of precipitated phases of different forms in the polycrystal in the transmission sample to obtain SAED photographs; The characteristic region within the crystal of the transmission sample is magnified and photographed using a high-resolution electron microscope to obtain a HRTEM photograph; Performing line scanning analysis on the intracrystalline precipitated phase of the transmission sample using a scanning transmission electron microscope-energy spectrum mode to obtain element distribution data of the precipitated phase; The region of the precipitated phase in the crystal in the HRTEM image is subjected to Fourier transformation to obtain the diffraction spots of the precipitated phase; The regions in the TEM bright field photo and the HRTEM photo that are spherical cluster-shaped are defined as predefined GP regions, the regions that are needle-shaped or disc-shaped are defined as predefined η' phases, and the regions that are rod-shaped or hexagonal are defined as predefined η phases; Compare the diffraction spots of the precipitated phase in the SAED photo and the HRTEM photo, and define the consistent areas between the two as the diffraction spots of the target GP area, the diffraction spots of the target η' phase, and the diffraction spots of the target η phase; The diffraction spots defined as the target η' phase in the HRTEM photo are defined as the diffraction spots of the η'1 phase, the diffraction spots of the η'2 phase and the diffraction spots of the η'3 phase respectively by comparing the sizes; The diffraction spots defined as the target η phase in the HRTEM photo are defined as the diffraction spots of the η1 phase, the diffraction spots of the η2 phase and the diffraction spots of the η3 phase respectively by comparing the sizes; The line scan results corresponding to the same morphology of the precipitated phase in the element distribution data of the precipitated phase are compared and analyzed, and the precipitation sequence of the precipitated phase is determined according to the changes of the Al element, the Zn element, the Cu element and the Mg element.

2. The method for identifying aging precipitation phase of Al-Zn-Mg-Cu alloy according to claim 1, characterized in that: The η' phase includes four variants, which are respectively a first variant, a second variant, a third variant and a fourth variant. The common crystal zone axis of the first variant and the second variant is [10-10] / / [110]Al, the crystal zone axis of the third variant is [2-423] / / [110]Al, and the crystal zone axis of the fourth variant is [-24-23] / / [110]Al. Among them, the diffraction spots of the η'1 phase correspond to the first variant, the diffraction spots of the η'2 phase correspond to the second variant, and the diffraction spots of the η'3 phase correspond to the third variant and the fourth variant.

3. The method for identifying aging precipitation phase of Al-Zn-Mg-Cu alloy according to claim 1, characterized in that: The size of the diffraction spot of the η'1 phase is smaller than the size of the diffraction spot of the η'2 phase, and the size of the diffraction spot of the η'2 phase is smaller than the size of the diffraction spot of the η'3 phase.

4. The method for identifying aging precipitation phase of Al-Zn-Mg-Cu alloy according to claim 1, characterized in that: The size of the diffraction spot of the η1 phase is smaller than the size of the diffraction spot of the η2 phase, and the size of the diffraction spot of the η2 phase is smaller than the size of the diffraction spot of the η3 phase.

5. A method for identifying aging precipitation phases of Al-Zn-Mg-Cu alloy according to any one of claims 1 to 4, characterized in that: The precipitation sequence of the precipitated phase in the alloy sample to be tested is determined to be GP region→η'1 phase→η'2 phase→η'3 phase→η1 phase→η2 phase→η3 phase.

6. The method for identifying aging precipitation phase of Al-Zn-Mg-Cu alloy according to claim 5, characterized in that: When the precipitation sequence of the precipitated phase in the alloy sample to be tested is GP zone→η'1 phase→η'2 phase→η'3 phase→η1 phase→η2 phase→η3 phase, the change process of the Al element, Zn element, Cu element and Mg element is that the content of the Al element gradually decreases, and the contents of the Zn element, Cu element and Mg element gradually increase, wherein the change rates of the Zn element and Cu element contents are the same, and the change rates of the Zn element content and the change rates of the Cu element content are both higher than the change rate of the Mg element content.

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