Method for monitoring microstructure evolution of two-phase titanium alloy during rolling in quasi-situ

Abstract

The present application relates to a kind of methods for monitoring microstructure evolution of two-phase titanium alloy rolling in situ, comprising the following steps: S1, preparing titanium alloy slab sample to be observed;S2, carrying out microstructure calibration to titanium alloy slab sample to be observed;S3, installing measurement system in rolling process;S4, monitoring microstructure evolution of microstructure calibration alloy slab sample, comprising: S41, carrying out stacking treatment to microstructure calibration alloy slab sample to obtain laminated slab;S42, the N pass cold rolling;S43, microstructure determination;S44, obtain the required plate;S5, rolling parameter analysis and determination.The present application realizes comparatively directly dynamic monitoring macro / microstructure evolution characteristics or field domain changes of rolling surface and side of two-phase titanium alloy cold rolling by means of quasi in situ technique and micro area aggregation effect combined with laser confocal microscope and digital speckle measurement system, and the operation steps are simple and clear, which provides support and basis for reducing titanium alloy processing difficulty.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy processing, and in particular relates to a method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy. Background Art

[0002] As the global energy crisis intensifies, the development and application of marine resources has become a major development theme in the 21st century. Titanium alloys, with their excellent corrosion resistance, have stood out among many alloys and are known as "ocean metals." Compared to steel, aluminum, and other alloys, titanium and its alloys have attracted significant attention due to their high specific strength, resistance to corrosion from the marine atmosphere and seawater, and their non-toxicity and non-magnetic properties.

[0003] However, the high cost of titanium alloy products processed by traditional technology has limited the scope of application of titanium alloy. Thanks to the efforts of titanium workers, the use of electron beam (EB) melting technology can achieve the removal of high-temperature resistant high / low density impurities and the recovery and utilization of titanium alloy return materials. The titanium alloy flat ingots produced by EB melting technology can realize the high-efficiency short-process processing technology of "steel-titanium colinear" forging-free direct rolling. The implementation of this process greatly shortens the processing flow and significantly reduces the processing cost. However, although the performance of titanium alloy plates produced by the "rolling instead of forging" process meets the relevant standards, the control of organization and other aspects is still unstable.

[0004] In-situ characterization is an analytical technique that can dynamically and intuitively analyze material reaction processes in real time. This technique typically requires specialized equipment, such as in-situ X-ray diffraction and in-situ SEM / EBSD tensile testing platforms. The complex forces acting during the rolling process of titanium alloys make in-situ characterization extremely difficult.

[0005] Therefore, a simple, intuitive, and easy-to-implement method is needed to monitor the microstructure evolution of two-phase titanium alloys during actual rolling and to clarify the laws of microstructure evolution during titanium alloy rolling. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention provides a method for quasi-in-situ monitoring of the microstructural evolution of two-phase titanium alloys during rolling. This method can intuitively determine the macro / microstructural evolution laws during titanium alloy rolling, obtain the required microstructure of titanium alloy plates, and formulate a reasonable and effective "rolling instead of forging" process for EB-state titanium alloys, thereby significantly increasing production efficiency, thereby further expanding the processing and application potential of titanium alloys and enriching the application occasions of titanium alloys.

[0007] The present invention provides a method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy, comprising the following steps:

[0008] S1. preparing a titanium alloy slab sample to be observed;

[0009] A titanium alloy EB ingot sample is used for hot rolling and annealing to obtain a titanium alloy slab sample to be observed;

[0010] S2, structure calibration is performed on the titanium alloy slab sample to be observed, specifically including the following steps:

[0011] S21, polishing;

[0012] Two titanium alloy slab samples to be observed are selected, and the surfaces to be observed are polished by mechanical and chemical methods, so that each surface to be observed reaches a mirror degree after polishing;

[0013] S22, micro-area selection;

[0014] In order to use the micro-area aggregation effect, the selected two titanium alloy slab samples to be observed are selected by Vickers hardness dotting, and the selected areas are located on the RDxTD surface and the RDxND surface of the slab, RD is the rolling direction, TD is the width direction, and ND is the height direction through the upper and lower surfaces of the sample;

[0015] S23, structure calibration;

[0016] The selected micro-area of the titanium alloy slab sample to be observed in step S22 is etched by wiping to obtain a structure calibration titanium alloy slab sample, then the macro and micro structures of the selected micro-area are observed by using the super-depth module of the laser confocal microscope, and the macro and micro structure splicing large image of the selected micro-area is obtained by using the automatic splicing module of the laser confocal microscope;

[0017] S3, installation of a measurement system in a rolling process;

[0018] The measurement system is a non-contact digital speckle full-field strain measurement system, a non-contact digital speckle full-field strain measurement system is installed on one side of the cold rolling mill, the light source irradiation center and the high-speed camera lens center are aligned with the center of the calibrated area on the RDxND surface of the slab, so that the non-contact digital speckle full-field strain measurement system can obtain the coordinate, displacement field and strain field in the thickness direction of the slab in real time during rolling, and can also obtain the field changes on the upper, middle and lower parts of the calibrated area on the RDxND surface of the slab;

[0019] S4, monitoring of the structure evolution of the structure calibration titanium alloy slab sample;

[0020] S41, the structure calibration titanium alloy slab sample is stacked to obtain a stacked slab;

[0021] First, two titanium alloy slab samples with microstructure calibration are stacked along the RD direction, and the bonding surface is the RD×TD surface with microstructure calibration. The microstructure calibration cannot exceed the median line of the RD×TD surface, and the microstructure calibration is staggered with the median line as the boundary when stacking. The four corners of the stacked two slabs are fixed by spot welding. After spot welding, the four edges of the slab with doubled thickness are re-grinded to obtain the laminated rolled slab.

[0022] S42, Nth cold rolling;

[0023] Then, the laminated slab is cold rolled on a two-roll cold rolling mill for the Nth pass, with the cold rolling deformation of each pass exceeding 3% and less than 10%, where N is a positive integer starting from 1 and increasing by 1 for each cold rolling pass;

[0024] S43, organizational determination;

[0025] The laminated slab sample after the Nth cold rolling in step S42 is separated to form two titanium alloy slab samples for tissue calibration. The macro and micro structures of the micro-region calibrated in step S23 are then observed using the ultra-depth-of-field module of a laser confocal microscope, and an automatic mosaic function is used to obtain a large mosaic image of the micro-region.

[0026] S44, obtaining the required plate;

[0027] Repeat steps S41-S43 to perform the next rolling process until a plate with the desired macro and micro structures is obtained;

[0028] S5. Rolling parameter analysis and determination;

[0029] According to step S4, real-time monitoring of the macro and microstructures of the micro-areas of the rolled surface and side surfaces of the titanium alloy slab sample to be observed during the cold rolling process is achieved; combined with the data obtained by the non-contact digital speckle full-field strain measurement system, the titanium alloy structure during the rolling process is monitored and analyzed, and the number of cold rolling passes or deformation amount required to obtain the required plate is determined based on the monitoring and analysis results.

[0030] Preferably, said S1 comprises the following steps:

[0031] S11, titanium alloy EB ingot sample preparation;

[0032] First, the phase transition point of commercial-grade titanium alloy EB ingot is determined based on metallographic method. T β Then, several titanium alloy EB ingot samples for hot rolling were cut from the titanium alloy EB flat ingot by wire cutting; finally, each surface of the titanium alloy EB ingot sample was polished to a bright finish and chamfered at the same time;

[0033] S12, hot rolling the titanium alloy EB ingot sample;

[0034] The titanium alloy EB ingot samples were hot rolled to obtain hot rolled plates;

[0035] S13, annealing treatment;

[0036] Full annealing treatment is adopted, the annealing process is 700~850℃, and the heat preservation is 15~120min. After the heat preservation is completed, the hot-rolled plate is taken out of the furnace and air-cooled;

[0037] S14, dividing the annealed hot-rolled plate to obtain a titanium alloy slab sample to be observed;

[0038] The annealed hot-rolled plate is divided into several pieces of the same size on the online cutting line, and the length × width ≤ 30mm × 10mm, and then each surface is milled flat on a milling machine to obtain the titanium alloy slab sample to be observed; the thickness of the titanium alloy slab sample to be observed is not higher than 2mm, but must exceed 1.5mm.

[0039] Preferably, the S12 is specifically implemented as follows:

[0040] Hot rolling is carried out on a two-roll reversible hot rolling mill, and the roller speed is adjustable in the range of 0~80r / min; the holding temperature of the titanium alloy EB ingot sample does not exceed the phase transition point during the rolling process. T β , and in T β When the temperature is above -50℃ and the holding time is more than 30min and less than 90min, the surface of the sample should be evenly wrapped with insulation cotton with a thickness of 3~5mm when the sample is transported out of the oven;

[0041] During the rolling process, the total deformation of the hot-rolled plate is no less than 80% after multiple passes of single-pass rolling, and the deformation of each pass is less than or equal to 30%. The final thickness of the hot-rolled plate is greater than 2mm. After rolling, the hot-rolled plate is air-cooled.

[0042] Preferably, the step S22 further includes:

[0043] The width of the selected area in the TD direction is not less than 5 mm, the length in the RD direction is not more than 2 mm, the load used for Vickers hardness marking is not less than 100 N, and the marking interval is not less than 50 μm, so as to achieve macroscopic observation of the calibration area of ​​the slab.

[0044] Preferably, the wiping method in step S23 is specifically as follows:

[0045] In the wiping method, a corrosion reagent is used for tissue calibration. The specific operation steps of the wiping method are as follows: use tweezers to clamp a ball of absorbent cotton, and then immerse it in the corrosion reagent. After the absorbent cotton is completely soaked, wipe it on the surface of the selected micro-area of ​​the slab for more than 10 seconds or wipe more than 20 times to produce a corrosion effect on the selected micro-area surface.

[0046] Preferably, in the step S42, if the deformation amount of each pass is 5%, the value range of N for different types of titanium alloy is as follows:

[0047] For A series: TA10 titanium alloy N≤13, TA15 titanium alloy N≤8, TA18 titanium alloy N≤12, TA22 titanium alloy N≤10;

[0048] For B series: TB2 titanium alloy N≤12, TB5 titanium alloy N≤15, TB8 titanium alloy N≤14, Ti-1300 titanium alloy N≤7;

[0049] For C series: TC1 titanium alloy N≤9, TC2 titanium alloy N≤10, TC4 titanium alloy N≤6, TC6 titanium alloy N≤6, TC16 titanium alloy N≤16.

[0050] Preferably, the step S44 further comprises:

[0051] If the microstructure of the selected micro area cannot be calibrated after the intermediate pass cold rolling, the steps S22 and S23 need to be repeated at the original micro area position before the steps S41-S43 are continued.

[0052] Compared with the prior art, the present application has the following beneficial effects:

[0053] 1. The present application combines the quasi in-situ technology and the micro pit aggregation effect and applies them to titanium alloy, and the laser confocal microscope can be used to realize the dynamic monitoring of the macro / microstructure evolution characteristics of the two-phase titanium alloy during cold rolling, and the microstructure difference between the middle and the edge of the plate can be determined. The operation steps of the present application are simple and clear, and easy to realize, without the aid of some precise specific devices, such as in-situ X-ray diffraction, in-situ SEM / EBSD tensile platform, etc.

[0054] 2. The digital speckle full-field strain measurement system used in the present application can also clearly determine the field variation characteristics of the side, middle and lower parts of the titanium alloy during rolling, and determine the microstructure evolution law of different parts of the side by combining the micro pit aggregation effect, so as to realize the effect of in-situ monitoring of the rolling side.

[0055] 3. The present application provides support and basis for obtaining the required microstructure of titanium alloy plate, optimizing the processing parameters suitable for EB two-phase titanium alloy, and reducing the processing difficulty of such titanium alloy, so as to further expand the processing and application potential of titanium alloy, and enrich the application occasions of titanium alloy. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 The flow chart of the method for quasi in-situ monitoring of microstructure evolution of two-phase titanium alloy during rolling;

[0057] Figure 2 Schematic diagram for micro-zone selection of the present application;

[0058] Figure 3 Schematic diagram for laminated slab of the present application;

[0059] Figure 4 Schematic diagram for installation position of the non-contact digital speckle full-field strain measurement system of the present application;

[0060] Figure 5a Schematic diagram for microstructure of the two-phase titanium alloy before cold rolling of the present application;

[0061] Figure 5b Schematic diagram for microstructure of the two-phase titanium alloy after a certain pass of cold rolling of the present application;

[0062] Figure 6 Schematic diagram for the rolling process of the titanium alloy slab after microstructure calibration of the present application. DETAILED DESCRIPTION

[0063] The exemplary embodiments, features and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numbers in the drawings represent functionally identical or similar elements. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0064] The present application provides a method for monitoring the microstructure evolution of a two-phase titanium alloy during rolling in situ, as shown in Figure 1 The steps are as follows:

[0065] S1, preparing a titanium alloy slab sample to be observed.

[0066] The titanium alloy EB ingot sample is used for hot rolling and annealing to obtain the titanium alloy slab sample to be observed, including the following steps:

[0067] S11, preparation of the titanium alloy EB ingot sample.

[0068] First, the phase transition point of the commercial titanium alloy EB ingot is determined based on the metallographic method T β The metallographic method is used to determine the phase transition point of the commercial titanium alloy EB ingot, and the material used in the subsequent test belongs to the same region of the EB ingot. Then, the titanium alloy EB ingot sample for hot rolling is cut from the titanium alloy EB flat ingot using a wire cutting machine. In order to match the rolling conditions in actual production, the length, width and height directions of the sample used in subsequent hot rolling are parallel to the EB ingot drawing ingot, thickness and width directions, and the sample length x width x height ≥ 120 mm x 50 mm x 35 mm. Finally, the surfaces of the titanium alloy EB ingot sample are polished to a bright finish to prevent the effects of cutting marks and other factors on the rolling test. At the same time, the titanium alloy EB ingot sample needs to be chamfered to avoid stress or strain concentration on the edge of the sample during rolling, which may cause the rolling plate to crack.

[0069] The titanium alloy EB ingot in this embodiment is preferably a two-phase titanium alloy, and the titanium alloy in the subsequent steps in this embodiment refers to a two-phase titanium alloy.

[0070] S12, hot rolling the titanium alloy EB ingot sample.

[0071] The hot rolling of the titanium alloy EB ingot sample obtains a hot-rolled plate. The hot rolling is performed on a two-high reversible hot rolling mill with a roll diameter of 550 mm, and the rolling speed is adjustable, ranging from 0 to 80 r / min. The holding temperature of the titanium alloy EB ingot sample during rolling is not more than the phase transition point T β , and is not less than T β -50℃, and the holding time is more than 30 min and less than 90 min. In order to prevent the temperature from dropping too fast during the sample transportation out of the furnace, the surface of the sample is uniformly wrapped with heat insulation cotton with a thickness of 3-5 mm.

[0072] Specific operation process: before rolling, the surface of the titanium alloy EB ingot sample is uniformly coated with a special high-temperature glass protective agent for titanium alloy rolling and air-dried to a paste, and then the sample is wrapped with heat insulation cotton, and then sent into a box furnace for heating and holding. After the holding is completed, the titanium alloy EB ingot sample is transported out of the furnace and quickly rolled to obtain a hot-rolled plate. The total deformation amount after single-fire multi-pass rolling in the rolling process is not less than 80%, and the deformation amount of each pass is less than or equal to 30%, and the final thickness of the hot-rolled plate is higher than 2 mm. After rolling, the hot-rolled plate is air-cooled.

[0073] Since titanium alloy is extremely sensitive to temperature, attention should be paid to temperature recovery and temperature drop during hot rolling, so transportation or rolling should be completed in a short time; titanium alloy is an oxygenophilic metal, which is easily oxidized at high temperature, so the main purpose of the high-temperature glass protective agent is to prevent oxidation, in addition, the protective agent also has the functions of heat preservation and friction reduction.

[0074] S13, annealing treatment.

[0075] Titanium alloy is a difficult-to-deform metal, even when hot working, there is a high deformation resistance, and the internal work hardening is extremely severe, so after hot working, annealing treatment is needed, and then subsequent deformation can be carried out.

[0076] For the two-phase titanium alloy in this study, after hot rolling, on the one hand, in order to eliminate the internal residual stress, on the other hand, in order to facilitate the realization of the subsequent in-situ monitoring means, a full annealing treatment is adopted. The annealing process is 700-850℃, and the holding time is 15-120 min. After the holding is completed, the hot-rolled plate sample is cooled in the air.

[0077] As with the heat preservation process before hot rolling, the surface of the hot-rolled plate also needs to be evenly coated with a titanium alloy heat treatment special high-temperature glass protective agent before annealing, which mainly functions to prevent oxidation.

[0078] S14, the annealed hot-rolled plate is cut to obtain a titanium alloy slab sample to be observed.

[0079] The annealed hot-rolled plate is cut into several pieces of the same size online, and the length x width is ≤30 mm x 10 mm, and then each surface is milled to be flat on a milling machine to obtain a titanium alloy slab sample to be observed. The thickness of the titanium alloy slab sample to be observed is not higher than 2 mm, but needs to exceed 1.5 mm. The main purpose is to prevent the slab from being too thin in the subsequent cold rolling process, and its deformation is too severe when cold rolling, thereby destroying the subsequent normal observation.

[0080] For two-phase titanium alloys, the microstructure to be concerned in subsequent cold rolling mainly considers equiaxed or duplex structure.

[0081] S2, the titanium alloy slab sample to be observed is subjected to organization calibration.

[0082] S21, polishing.

[0083] Two titanium alloy slab samples to be observed are selected, and the surfaces to be observed are polished by mechanical and chemical methods. The polishing reagent is a solution of alkaline silica sol, hydrogen peroxide and water. After polishing, each surface to be observed reaches a mirror degree.

[0084] Polishing meets the requirements of the titanium alloy slab sample to be observed during cold rolling: each surface of the titanium alloy slab sample to be observed needs to be flat, and the opposite surfaces (up and down, front and back, and left and right) need to be parallel. The purpose of this requirement is to prevent the slab from being unstable due to uneven stress during cold rolling.

[0085] S22, micro-area selection.

[0086] The two selected titanium alloy slab samples to be observed are subjected to Vickers hardness dot selection, which is to take advantage of the "micro-area aggregation effect". The selected area is located on the RD x TD surface and the RD x ND surface of the slab, and the TD direction is not less than 5 mm wide, the RD direction is not more than 2 mm long, and the ND direction is the height direction through the upper and lower surfaces of the sample. The TD is the width direction, and the RD is the rolling direction. The load used when dotting Vickers hardness is not less than 100 N, and the dotting interval is not less than 50 μm. As shown in Figure 2 The micro-area range is marked out by dotting Vickers hardness, thereby achieving the macro effect after micro-area aggregation.

[0087] Before dotting Vickers hardness, the titanium alloy slab sample to be observed needs to be placed in an ultrasonic cleaner for vibration for more than 3 min to remove stains, metal debris and the like remaining on the surface of the slab.

[0088] The reason for selecting micro-areas for Vickers hardness is that Vickers hardness spotting causes less damage to the sample surface and has less impact on surrounding tissue. On the other hand, the distance between two individual points or pits is 50μm or greater. Although this value is smaller than the limit size of human visual recognition (reportedly 100-150μm), if a load of 100N or more is used on the Vickers hardness tester, deep quadrangular pyramid pits can be produced. When the pit spacing is no less than 50μm, the enriched pits can achieve a macroscopic effect visible to the naked eye, i.e., a "micro-area aggregation effect." This allows macroscopic observation of the slab's calibration area, maximizing the effectiveness of the micro-area aggregation effect.

[0089] S23. Tissue calibration.

[0090] The microregion selected on the titanium alloy slab sample to be observed in step S22 is etched using the wiping method to obtain a titanium alloy slab sample for structural calibration. The macro and microstructures of the selected microregion are then observed using the ultra-depth-of-field module of a laser confocal microscope, and the automatic mosaic module of the laser confocal microscope is used to obtain a large mosaic image of the macro and microstructures of the selected microregion.

[0091] In the wiping method, an existing corrosion reagent is used for tissue calibration. The corrosion reagent is usually prepared from a mixed aqueous solution of hydrofluoric acid and nitric acid.

[0092] The specific operation steps of the wiping method are as follows: use tweezers to clamp a ball of absorbent cotton, and then immerse it in the prepared corrosion reagent. After the absorbent cotton is completely soaked, wipe it on the surface of the selected micro-area of ​​the slab for more than 10 seconds or more than 20 times to make the surface change significantly, that is, to achieve the macro- and micro-structural corrosion effect. It should be noted that before wiping corrosion, the slab of the calibrated micro-area needs to be vibrated in an ultrasonic cleaner for more than 3 minutes to remove secondary debris, stains and other debris adhering to the surface. New absorbent cotton needs to be replaced after each wiping to prevent the absorbent cotton from condensing and hardening into blocks or flakes, thereby scratching the surface of the slab micro-area.

[0093] The laser confocal microscope features an automatic mosaic module, which can generate a large mosaic of the macro and microstructures of a selected microregion. Finally, this mosaic of macro and microstructures is used to analyze the structural changes from the core to the edge of the sample during rolling.

[0094] S3. Install the measurement system during rolling process.

[0095] The measurement system in this embodiment uses a non-contact digital speckle full-field strain measurement system. The non-contact digital speckle full-field strain measurement system is installed on one side of the cold rolling mill. The center of the light source and the center of the high-speed camera lens are both aligned with the center of the calibrated area of ​​the slab RD×ND surface. Figure 4As shown in the figure, the non-contact digital speckle full-field strain measurement system can obtain the coordinates, displacement field and strain field of the slab thickness direction in real time during rolling, and at the same time obtain the field changes of the upper, middle and lower parts of the area marked on the RD×ND surface of the slab.

[0096] S4. Monitor the microstructure evolution of the titanium alloy slab sample for microstructure calibration.

[0097] S41. Stacking the tissue-calibrated titanium alloy slab samples to obtain laminated slabs.

[0098] First, two titanium alloy slab samples with microstructure calibration are stacked along the RD direction, and the bonding surface is the RD×TD surface with micro-area selection and microstructure calibration. Then, the four corners of the stacked two slabs are fixed by spot welding, which is approximately a slab with doubled thickness in the RD direction. After spot welding, the four edges of the doubled thickness slab are re-polished to obtain a laminated slab. See the schematic diagram. Figure 3 When stacking, be sure to hold the boards vertically in the ND direction, forming them in one stack. The four edges of the RD×TD surfaces of the two boards must be aligned to avoid scratches on the inside.

[0099] from Figure 2 、 Figure 3 It can be seen that the microstructure calibration cannot exceed the midline, and when stacked, the microstructure calibration on two microstructure-calibrated alloy slab samples is misaligned, with the midline being the boundary between them. This is because titanium alloy corrosion corrodes away a certain component phase, and the remaining component phase is prone to sharp areas. If the superimposed surfaces are stacked relative to the microstructure calibration area, they are very likely to be severely damaged, thus delaying subsequent observations. This is also the reason why they are polished to a mirror finish, cleaned in an ultrasonic cleaner, and stored vertically.

[0100] S42, Nth cold rolling.

[0101] Then, the stacked slab is cold-rolled for the Nth time on a two-roll cold rolling mill with a roll diameter of 200 mm.

[0102] The deformation of each cold rolling pass is more than 3% and less than 10%, where N is a positive integer starting from 1. N increases by 1 for each cold rolling pass.

[0103] If the cold rolling deformation of each pass is 5%, N has a certain range of values ​​for different types of titanium alloys (all considering the annealed state, and other cold rolling deformations can be converted by analogy). The range of N is determined by the cold rolling deformation limit of the titanium alloy, that is, the starting limit of the inward expansion of the crack. The following examples list the range of N values ​​for some common titanium alloys when using the method of the present invention:

[0104] For A series: TA10 titanium alloy N≤13, TA15 titanium alloy N≤8, TA18 titanium alloy N≤12, TA22 titanium alloy N≤10, etc.

[0105] For B series: TB2 titanium alloy N≤12, TB5 titanium alloy N≤15, TB8 titanium alloy N≤14, Ti-1300 titanium alloy N≤7, etc.

[0106] For C series: TC1 titanium alloy N≤9, TC2 titanium alloy N≤10, TC4 titanium alloy N≤6, TC6 titanium alloy N≤6, TC16 titanium alloy N≤16, etc.

[0107] S43. Organizational determination.

[0108] The laminated slab sample after the Nth cold rolling in step S42 is separated into two tissue-calibrated titanium alloy slab samples. The macro- and micro-structures of the micro-area calibrated in step S23 are then observed using the ultra-depth-of-field module of the laser confocal microscope, and the automatic mosaic function is used to obtain a large mosaic image of the micro-area.

[0109] Then, it is compared with the micro-area splicing map before cold rolling to determine whether the structure after the rolling pass is the desired macro and micro structure. Figure 5a Schematic diagram of the microstructure of the two-phase titanium alloy before cold rolling in step S2; Figure 5b Schematic diagram of the microstructure of a two-phase titanium alloy after a single cold rolling pass. Comparing the two images reveals the microstructural evolution before and after cold rolling. Furthermore, the combined images can be used to compare and analyze the differences in microstructure between the edge and core of the plate, as well as between the RD×TD and RD×ND planes.

[0110] S44. Obtain the required plate.

[0111] Repeat steps S41-S43 to perform the next rolling process until a plate with the desired macro- and microstructure is obtained.

[0112] If the structure of the selected micro-area cannot be calibrated after a certain cold rolling pass, it is necessary to repeat steps S22 and S23 at the original micro-area position before continuing to execute S41-S43. Figure 6 Shown is a schematic diagram of the titanium alloy slab rolling process that has been organized and calibrated.

[0113] S5. Analysis and determination of rolling parameters.

[0114] S51. Effect of rolling process on titanium alloy structure.

[0115] According to step S2, the initial microstructure and macrostructure of the titanium alloy slab sample are obtained to achieve microstructure calibration. According to step S4, the macrostructure and microstructure of the microstructure of the rolled surface and side surfaces of the titanium alloy slab sample are monitored in real time during cold rolling. After the microstructure is determined, the information collected by the non-contact digital speckle full-field strain measurement system in step S3 is used to determine the field changes at different locations on the slab side in the ND direction. Combined with the data obtained by the non-contact digital speckle full-field strain measurement system, the titanium alloy microstructure during rolling can be monitored and analyzed.

[0116] S52. Determine the number of cold rolling passes or the amount of deformation.

[0117] By comparing and analyzing the macro and microstructures of the selected micro-areas before and after each cold rolling pass in step S43, the number of cold rolling passes or the amount of deformation required to obtain the desired plate is determined, providing support and reference for the design and optimization of the cold rolling process in subsequent titanium alloy processing and production.

[0118] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy, characterized by: It includes the following steps: S1. preparing a titanium alloy slab sample to be observed; The titanium alloy EB ingot sample is hot rolled and annealed to obtain the titanium alloy slab sample to be observed; S2. Performing tissue calibration on the titanium alloy slab sample to be observed, specifically comprising the following steps: S21, polishing; Two titanium alloy slab samples to be observed were selected, and the surfaces to be observed were polished by mechanochemical method until each surface to be observed reached the mirror finish after polishing. S22, micro-area selection; In order to take advantage of the micro-region aggregation effect, the Vickers hardness of the two titanium alloy slab samples to be observed was selected. The selected areas were located on the RD×TD plane and RD×ND plane of the slab. RD is the rolling direction, TD is the width direction, and ND is the height direction that runs through the upper and lower surfaces of the sample. S23, tissue calibration; The micro-region selected on the titanium alloy slab sample to be observed in step S22 is corroded by a wiping method to obtain a tissue-calibrated titanium alloy slab sample, and then the ultra-depth-of-field module of a laser confocal microscope is used to observe the macro- and micro-structures of the selected micro-region, and the automatic mosaic module of the laser confocal microscope is used to obtain a large mosaic image of the macro- and micro-structures of the selected micro-region; S3. Install the measurement system during rolling; The measurement system uses a non-contact digital speckle full-field strain measurement system. This system is installed on one side of the cold rolling mill. The center of the light source and the center of the high-speed camera lens are both aligned with the center of the area marked on the RD×ND surface of the slab. This allows the non-contact digital speckle full-field strain measurement system to obtain the coordinates, displacement field, and strain field in the thickness direction of the slab during rolling in real time. It can also obtain the field changes in the upper, middle, and lower parts of the area marked on the RD×ND surface of the slab. S4, monitoring the microstructural evolution of the titanium alloy slab sample for microstructural calibration; S41, stacking the microstructure-calibrated titanium alloy slab samples to obtain laminated slabs; First, two titanium alloy slab samples with microstructure calibration are stacked along the RD direction, and the bonding surface is the RD×TD surface with microstructure calibration. The microstructure calibration cannot exceed the median line of the RD×TD surface, and the microstructure calibration is staggered with the median line as the boundary when stacking. The four corners of the stacked two slabs are fixed by spot welding. After spot welding, the four edges of the slab with doubled thickness are re-grinded to obtain the laminated rolled slab. S42, Nth cold rolling; Then, the laminated slab is cold rolled on a two-roll cold rolling mill for the Nth pass, with the cold rolling deformation of each pass exceeding 3% and less than 10%, where N is a positive integer starting from 1 and increasing by 1 for each cold rolling pass; S43, organizational determination; The laminated slab sample after the Nth cold rolling in step S42 is separated to form two titanium alloy slab samples for tissue calibration. The macro and micro structures of the micro-region calibrated in step S23 are then observed using the ultra-depth-of-field module of a laser confocal microscope, and an automatic mosaic function is used to obtain a large mosaic image of the micro-region. S44, obtaining the required plate; Repeat steps S41-S43 to perform the next rolling process until a plate with the desired macro and micro structures is obtained; S5. Rolling parameter analysis and determination; According to step S4, real-time monitoring of the macro and microstructures of the micro-areas of the rolled surface and side surfaces of the titanium alloy slab sample to be observed during the cold rolling process is achieved; combined with the data obtained by the non-contact digital speckle full-field strain measurement system, the titanium alloy structure during the rolling process is monitored and analyzed, and the number of cold rolling passes or deformation amount required to obtain the required plate is determined based on the monitoring and analysis results.

2. The method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy according to claim 1, characterized in that: The S1 specifically includes the following steps: S11, titanium alloy EB ingot sample preparation; First, the phase transition point of commercial-grade titanium alloy EB ingot is determined based on metallographic method. T β Then, several titanium alloy EB ingot samples for hot rolling were cut from the titanium alloy EB flat ingot by wire cutting; finally, each surface of the titanium alloy EB ingot sample was polished to a bright finish and chamfered at the same time; S12, hot rolling the titanium alloy EB ingot sample; The titanium alloy EB ingot samples were hot rolled to obtain hot rolled plates; S13, annealing treatment; The annealing process is 700~850℃ and the temperature is kept at 15℃. After 120 minutes of heat preservation, the hot-rolled plate is taken out of the furnace and air-cooled; S14, dividing the annealed hot-rolled plate to obtain a titanium alloy slab sample to be observed; The annealed hot-rolled plate is divided into several pieces of the same size on the online cutting line, and the length × width ≤ 30mm × 10mm, and then each surface is milled flat on a milling machine to obtain the titanium alloy slab sample to be observed; the thickness of the titanium alloy slab sample to be observed is not higher than 2mm, but must exceed 1.5mm.

3. The method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy according to claim 2, characterized in that: The S12 is specifically implemented as follows: Hot rolling is carried out on a two-roll reversible hot rolling mill, and the roll speed is adjustable within the range of 0 80r / min; the holding temperature of the titanium alloy EB ingot sample during rolling does not exceed the phase transition point T β , and in T β Above -50℃, the holding time is more than 30min and less than 90min, and the sample is evenly wrapped with a thickness of 3 when it is transported out of the oven. 5mm thermal insulation cotton; During the rolling process, the total deformation is not less than 80% after single-fire multi-pass rolling, and the deformation of each rolling pass is less than or equal to 30%. The final thickness of the hot-rolled plate is higher than 2mm; After rolling, the hot rolled plate is air cooled.

4. The method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy according to claim 1, characterized in that: The step S22 further includes: The width of the selected area in the TD direction is not less than 5 mm, the length in the RD direction is not more than 2 mm, the load used for Vickers hardness marking is not less than 100 N, and the marking interval is not less than 50 μm, so as to achieve macroscopic observation of the calibration area of ​​the slab.

5. The method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy according to claim 1, characterized in that: The wiping method in step S23 is specifically as follows: In the wiping method, a corrosion reagent is used for tissue calibration. The specific operation steps of the wiping method are as follows: use tweezers to clamp a ball of absorbent cotton, and then immerse it in the corrosion reagent. After the absorbent cotton is completely soaked, wipe it on the surface of the selected micro-area of ​​the slab for more than 10 seconds or wipe more than 20 times to produce a corrosion effect on the selected micro-area surface.

6. The method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy according to claim 1, characterized in that: In step S42, if the cold rolling deformation in each pass is 5%, the value range of N for different types of titanium alloys is as follows: For A series: TA10 titanium alloy N≤13, TA15 titanium alloy N≤8, TA18 titanium alloy N≤12, TA22 titanium alloy N≤10; For B series: TB2 titanium alloy N≤12, TB5 titanium alloy N≤15, TB8 titanium alloy N≤14, Ti-1300 titanium alloy N≤7; For C series: TC1 titanium alloy N≤9, TC2 titanium alloy N≤10, TC4 titanium alloy N≤6, TC6 titanium alloy N≤6, TC16 titanium alloy N≤16.

7. The method for quasi-in-situ monitoring of microstructure evolution during rolling of a two-phase titanium alloy according to claim 1, characterized in that: Step S44 also includes: If the structure of the selected micro-region cannot be calibrated after a certain cold rolling pass, it is necessary to repeat steps S22 and S23 at the original micro-region position before continuing to execute S41-S43.

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