Estimation method for thermal isostatic compression loose defect hole periphery deformation structure space size of titanium alloy casting

Abstract

The invention provides a method for estimating the space size of a hole periphery deformation structure of a thermal isostatic compression loose defect of a titanium alloy casting. The method sequentially comprises the following steps: constructing original data, constructing a model, inputting the original data and parameters for simulation, simulating and calculating a hot isostatic pressing quasi-in-situ characterization test, establishing a quantitative relation between shrinkage porosity hole circumference stress and strain and deformation structure space size, correcting the model, and calculating by a calculation formula. An estimation model of the shrinkage defect hole periphery deformation structure is obtained; the method for estimating the three-dimensional space size of the hole periphery deformation structure of the shrinkage defect in the hot isostatic pressing process of the titanium alloy casting is accurately established by collecting the actual three-dimensional size of the shrinkage defect and the hole periphery deformation structure size in the hot isostatic pressing process and combining the prediction model.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal casting in aerospace, and particularly to a method for estimating the three-dimensional space of the deformed structure around shrinkage porosity defects during the hot isostatic pressing process of titanium alloy castings. Background Art

[0002] Titanium alloys have advantages such as high specific strength, excellent corrosion resistance, and high-temperature resistance. The forming methods include casting, deformation processing, and powder metallurgy, etc. Compared with other processing methods, titanium alloy castings prepared by the casting method have the advantages of low cost, high material utilization rate, and good stiffness, and are widely used in many fields such as aerospace, national defense, and shipbuilding. With the rapid development of technology in the aerospace field, the metallurgical quality and mechanical properties of precision titanium alloy castings are required to be higher and higher. The structures of titanium alloy components are becoming more and more complex, with many bosses, special-shaped holes, gussets and other structures, and the wall thickness is getting smaller and smaller, with the minimum wall thickness being about 2 mm - 4 mm. Therefore, even by using precision centrifugal casting, it is difficult to avoid internal defects such as porosity and shrinkage cavities, which directly affect the safety and reliability of the use of castings; the internationally common method is to introduce the hot isostatic pressing process to eliminate internal porosity, shrinkage cavities and other defects and obtain high-quality complex titanium alloy castings.

[0003] Hot isostatic pressing of titanium alloy castings refers to a process in which the titanium alloy casting together with the anti-deformation device is placed in a sealed container of a hot isostatic pressing furnace, and an inert gas is used as the medium to apply an equal pressure in all directions to the casting while raising the temperature, so as to reduce or eliminate the internal hole defects of the casting under the action of high temperature and high pressure.

[0004] During the hot isostatic pressing process, due to the combined action of the static load pressure and stress concentration of the hot isostatic pressing, the metal around the shrinkage porosity defect in the titanium alloy casting undergoes rheology towards the shrinkage center due to high-temperature elastic-plastic deformation and creep deformation. Finally, the shrinkage porosity defect is completely closed to form a fully dense titanium alloy casting, avoiding discontinuities in the geometric shape, material properties, and load-bearing capacity of the titanium alloy casting.

[0005] The uniformity of the microstructure and properties of titanium alloy structural components for advanced aero-engines has an important impact on their service performance. However, while the internal porosity defects such as porosity and shrinkage cavities in titanium alloy castings are pressed together, the microstructure around the pores undergoes plastic deformation under high stress and contracts in volume towards the shrinkage porosity, presenting an irregular radial microstructure feature outward along the periphery of the shrinkage porosity defect. Among them, equiaxed recrystallized grains are formed inside individual clusters or at the interfaces of clusters. Only a small amount of kinking deformation or microstructure coarsening occurs in individual clusters, and the microstructure features of different clusters are inconsistent, which is related to the crystal orientation of the α / β clusters around the pores and the magnitude and vector direction of the stress-strain around the pores. The matrix microstructure far from the periphery of the shrinkage porosity does not undergo plastic deformation, but only grain growth and lath coarsening occur. Therefore, the difference between the deformed microstructure around the shrinkage porosity and the matrix microstructure is very large. This microstructure difference will cause great difficulty in coordinated deformation, easily form local stress concentration, and lead to a decrease in the mechanical properties of the material, especially a significant decrease in fatigue and toughness. Moreover, the larger the area of the deformed microstructure around the pores, the more obvious the decrease in mechanical properties, and the smaller the distance between the position of the deformed microstructure around the pores and the surface, the more significant the impact. Therefore, mastering the time when the internal shrinkage porosity defects in titanium alloy castings are completely pressed together and the area of the deformed microstructure around the shrinkage porosity defects can provide effective data support for estimating the bearing capacity and service life calculation of titanium alloy castings.

[0006] Limited by the integrity requirements of titanium alloy castings in practical applications, the pressing time of internal shrinkage porosity defects in castings and the spatial dimensions of the deformed microstructure around the pores (including the microstructure in the annihilation zone) cannot be measured by the method of dissecting and characterizing the metallographic microstructure, nor can they be detected by commonly used industrial techniques such as X-ray non-destructive testing, real-time imaging, or X-CT. Moreover, the states of internal shrinkage porosity defects and the deformed microstructure around the pores in each casting are not consistent. Therefore, the method of dissecting the first piece of titanium alloy castings delivered in batches cannot obtain the three-dimensional spatial dimension data of the deformed microstructure inside each casting. Therefore, conventional non-destructive and destructive mechanical physical characterization methods cannot obtain the deformed area of the microstructure around the HIP shrinkage porosity, making it difficult to provide sufficient data support for the service life assessment and load design of titanium alloy castings in practical applications.

[0007] Although it is difficult to measure the spatial dimensions of the deformed microstructure around the shrinkage porosity in titanium alloy castings by conventional methods, there is a quantitative relationship among the spatial dimensions of the deformed microstructure around the shrinkage porosity, the spatial dimensions of the shrinkage porosity defects, and the stress / strain quantity and spatial dimensions around the shrinkage porosity in titanium alloy castings at different HIP times; therefore, establishing the quantitative relationship among the spatial dimensions of the deformed microstructure around the shrinkage porosity, the spatial dimensions of the shrinkage porosity defects, and the stress / strain quantity and spatial dimensions around the shrinkage porosity is the key to calculating the spatial dimensions of the deformed microstructure around the shrinkage porosity during the HIP process. Summary of the Invention

[0008] The technical problem solved by the present invention is to provide a method for estimating the spatial dimensions of the deformed structure around the shrinkage porosity defects in titanium alloy castings during hot isostatic pressing. This method can realize the estimation of the three-dimensional spatial dimensions of the deformed structure around the internal shrinkage porosity in titanium alloy castings during hot isostatic pressing, and can provide important information support for the service performance evaluation of high-reliability titanium alloy castings.

[0009] In view of this, the present application provides a method for estimating the spatial dimensions of the deformed structure around the shrinkage porosity defects in titanium alloy castings, including the following steps:

[0010] S1) Perform three-dimensional dimensional scanning and spatial dimensional reconstruction on the appearance and internal shrinkage porosity defects of the titanium alloy casting, and respectively measure the average values of the original β grain and α / β / colony characteristic dimensions of the titanium alloy casting to obtain the characteristic dimension data for calculation.

[0011] S2) Input the property parameters affecting the titanium alloy casting, the average values of the characteristic dimensions, and the process parameters of hot isostatic pressing into the numerical simulation software, select the thermo-elastoplastic-creep constitutive model, and establish a prediction model for the equivalent stress-strain around the shrinkage porosity, a prediction model for the three-dimensional spatial dimensions of the shrinkage porosity defect, a prediction model for the geometric dimensions of the deformed structure around the shrinkage porosity, and a prediction model for the closing time of the shrinkage porosity defect during the hot isostatic pressing process of the titanium alloy casting.

[0012] S3) Perform mesh division on the characteristic dimension data for calculation in step S1) to obtain the initial mesh data for hot isostatic pressing simulation.

[0013] S4) Use the prediction models in step S2) and the initial mesh data in step S3) to perform simulation calculations on the magnitude distribution of the equivalent stress-strain around the internal shrinkage porosity in the titanium alloy casting, the three-dimensional spatial dimensions of the shrinkage porosity defect, the dimensions of the deformed structure around the shrinkage porosity, and the closing time of the shrinkage porosity defect.

[0014] S5) Perform hot isostatic pressing quasi-in-situ tests on the titanium alloy casting in step S1) for different times, perform three-dimensional dimensional scanning on the obtained titanium alloy casting to obtain the appearance dimensions of the casting and the three-dimensional spatial dimensions of the internal shrinkage porosity defect at different times; dissect the obtained titanium alloy castings at different times, and then measure the distribution area of the deformed structure around the shrinkage porosity on the plane passing through the geometric center of the shrinkage hole defect, and determine the closing situation of the shrinkage porosity defect.

[0015] S6) Establish a quantitative relationship between the magnitude and spatial distribution dimensions of the stress / strain around the internal shrinkage porosity in the titanium alloy casting at different times during hot isostatic pressing - the original characteristic dimensions of the titanium alloy casting structure - the dimensions of the deformed structure around the pore circumference.

[0016] S7) Compare the simulation calculation results in step S4) with the characterization results in step S5) and step S6), and then iteratively correct the prediction model in step S2) to obtain the corrected prediction model.

[0017] S8) Based on the quantitative relationship established in step S6) and the corrected prediction model in S7), obtain the calculation formula for the spatial dimensions of the shrinkage porosity peripheral deformation structure of the titanium alloy casting after hot isostatic pressing;

[0018] In step S5), if the plane is single, the spatial dimension of the shrinkage porosity peripheral deformation structure in step S8) is the area of the shrinkage hole peripheral deformation, and the calculation formula is shown in formulas (Ⅰ) and (Ⅱ):

[0019] In step S5), if the plane is multiple, the spatial dimension of the shrinkage porosity peripheral deformation structure in step S8) is the volume of the shrinkage hole peripheral deformation, and the calculation formula is shown in formulas (Ⅲ) and (Ⅳ):

[0020]

[0021] Among them, Amp is the area of the shrinkage porosity peripheral deformation structure, mm -2 , Ap is the area of the shrinkage porosity peripheral plastic zone, mm -2 , Vmp is the volume of the shrinkage porosity peripheral deformation structure, mm -3 , Vp is the volume of the shrinkage porosity peripheral plastic zone, mm -3 , σ f is the equivalent stress, MPa, E is the elastic modulus, Pa, r is the distance from the center of the shrinkage defect, mm, ν is the Poisson's ratio, negative value, μ is the shear modulus, Pa, ρ is the density, g / cm 3 , Dβ is the original β grain size, mm, Rc is the α / β cluster size, mm, Bm is the material constant, Rc is the α / β cluster size, mm.

[0022] Preferably, in step S1), the appearance dimensions of the titanium alloy casting are measured by the blue light method, the coordinate measuring method or the caliper measuring method;

[0023] The position and size of the internal shrinkage defects of the titanium alloy casting are determined by X-ray flaw detection, real-time imaging method or 3D-X-ray computed tomography method;

[0024] The characteristic dimensions of the microstructure around the internal shrinkage defect holes are determined by a metallographic microscope or a scanning electron microscope.

[0025] Preferably, in step S2), the property parameters include thermal conductivity, specific heat capacity, Young's modulus, Poisson's ratio, density and yield strength;

[0026] And / or, the process parameters include the temperature, pressure and time of hot isostatic pressing;

[0027] And / or, the numerical simulation software includes ABAQUS finite element software, DEFORM finite element software or MARC finite element software;

[0028] Preferably, in step S2), for the thermo-elastic part in the thermo-elasto-plastic creep constitutive model, the elastic modulus of the titanium alloy at different temperatures is tested. For the plastic part, the Arrhenius equation is used to calculate the deformation behavior and activation energy of the titanium alloy, and a strain-compensated elasto-plastic constitutive model is constructed. The Norton creep constitutive model is used to fit the creep curve, and combined with the elasto-plastic constitutive model, a thermo-elasto-plastic creep constitutive model is constructed.

[0029] Preferably, in step S3), the application software for mesh generation includes ABAQUS finite element software or DEFORM finite element software;

[0030] Preferably, in step S5), the parameters of the hot isostatic pressing quasi-in-situ test include heating rate, pressure, temperature, holding and pressurizing time, and furnace cooling rate.

[0031] Preferably, in step S5), the position of the geometric center of the shrinkage cavity defect is determined by the three-dimensional spatial size of the internal porosity defect.

[0032] Preferably, in step S5), the measurement method for the distribution area of the deformed microstructure around the porosity is the metallographic method; the methods for determining the closure of the porosity defect include X-ray flaw detection, real-time imaging method, 3D-XCT method, or anatomical metallographic method.

[0033] Preferably, in step S6), the deformed microstructure around the hole includes lath kink structure, equiaxed structure, and recrystallized structure; the size of the deformed microstructure around the hole is calculated according to the area of the outermost end of the kink or equiaxed crystal structure or recrystallized structure from the boundary of the porosity defect hole.

[0034] Preferably, in step S7), the correction is the correction of the geometric correction coefficient and the loading correction coefficient.

[0035] The present application provides a method for estimating the spatial dimensions of the deformed microstructure around the shrinkage porosity in titanium alloy castings during hot isostatic pressing. Based on the thermo-elastoplastic-creep constitutive model of titanium alloy, a prediction model for the equivalent stress-strain around the shrinkage cavity, a prediction model for the three-dimensional spatial dimensions of the microporosity defect, and a prediction model for the closing time of the microporosity defect are established during the hot isostatic pressing process of titanium alloy castings. And according to the quasi-in-situ dimensional scanning, non-destructive testing, and microstructure dissection and characterization methods during the actual hot isostatic pressing process, the three-dimensional dimensions of the actual microporosity defect at different times during hot isostatic pressing and the spatial geometric dimensions of the deformed microstructure around the pore with the geometric center of the microporosity as the center are collected. Based on the quasi-in-situ data collected during the hot isostatic pressing process, the above prediction models are iteratively corrected. At the same time, based on the original β grain size and α / β bundle characteristic size of titanium alloy, a quantitative relationship among the three-dimensional dimensions of the microporosity defect, the equivalent stress-strain around the microporosity, and the three-dimensional dimensions of the deformed microstructure (annihilation zone microstructure) around the pore is established. Finally, based on the above prediction models and the quantitative relationship among the three, a calculation method for the three-dimensional spatial dimensions of the deformed microstructure (annihilation zone) around the shrinkage porosity inside the titanium alloy is realized.

[0036] By combining and iteratively correcting the prediction model with the quasi-in-situ data of the hot isostatic pressing treatment of actual titanium alloy castings, this method realizes the accurate estimation of the three-dimensional space of shrinkage cavity defects and the deformed microstructure around the pore during the hot isostatic pressing process of titanium alloy castings. Brief Description of the Drawings

[0037] Figure 1 It is a three-dimensional morphology photo of the internal shrinkage cavity of the ZTC4 titanium alloy casting provided by the embodiment of the present invention;

[0038] Figure 2 It is a metallographic structure photo of the ZTC4 titanium alloy casting provided by the embodiment of the present invention;

[0039] Figure 3 It is a hot isostatic pressing process regime curve graph of the ZTC4 titanium alloy casting provided by the embodiment of the present invention;

[0040] Figure 4 It is the geometric model meshing of the prediction model of the ZTC4 titanium alloy casting provided by the embodiment of the present invention;

[0041] Figure 5 It is the simulation calculation result of the prediction model of the ZTC4 titanium alloy casting provided by the embodiment of the present invention;

[0042] Figure 6 It is a photo of the morphology of the deformed microstructure around the pore during the hot isostatic pressing of the ZTC4 titanium alloy casting provided by the embodiment of the present invention. Detailed Embodiments

[0043] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0044] In view of the influence of hot isostatic pressing on porosity defects such as internal porosity and shrinkage cavities in titanium alloy castings and the problem that it is difficult to directly detect the spatial dimensions of the deformed microstructure around shrinkage porosity in titanium alloy castings in the prior art, the present application provides a method for estimating the three-dimensional space of shrinkage porosity defects and the deformed microstructure around pores during the hot isostatic pressing process of titanium alloy castings. By combining numerical simulation and dissection tests, a method for estimating the three-dimensional space dimensions of shrinkage porosity defects and the deformed microstructure around pores in titanium alloy castings during hot isostatic pressing is established. Through the estimation method provided by the present application, the three-dimensional space dimensions of the deformed microstructure around shrinkage pores inside titanium alloy castings can be estimated, providing more accurate data for the service performance design of titanium alloy castings used in military fields such as aviation, aerospace, and weapons. The embodiment of the present invention discloses a method for estimating the spatial dimensions of the deformed microstructure around shrinkage porosity defects during the hot isostatic pressing of titanium alloy castings, including the following steps:

[0045] S1) Perform three-dimensional size scanning and spatial size reconstruction on the appearance and internal shrinkage porosity defects of the titanium alloy casting, and measure the average values of the original β grain size and α / β / colony characteristic sizes of the titanium alloy casting respectively to obtain the characteristic size data for calculation;

[0046] S2) Input the property parameters affecting the titanium alloy casting, the average value of the characteristic size, and the process parameters of hot isostatic pressing into the numerical simulation software, select the thermo-elastoplastic-creep constitutive model, and establish a prediction model for the equivalent stress-strain around shrinkage porosity, a prediction model for the three-dimensional space size of shrinkage porosity defects, a prediction model for the geometric size of the deformed microstructure around shrinkage pores, and a prediction model for the closing time of shrinkage porosity defects during the hot isostatic pressing process of the titanium alloy casting;

[0047] S3) Perform mesh division on the characteristic size data for calculation in step S1) to obtain the initial mesh data for hot isostatic pressing simulation;

[0048] S4) Use the prediction models in step S2) and the initial mesh data in step S3) to perform simulation calculations on the distribution of the equivalent stress-strain around the internal shrinkage pores of the titanium alloy casting, the three-dimensional space size of shrinkage porosity defects, the size of the deformed microstructure around shrinkage porosity, and the closing time of shrinkage porosity defects;

[0049] S5) Perform hot isostatic pressing quasi-in-situ tests on the titanium alloy casting in step S1) for different times, perform three-dimensional size scanning on the obtained titanium alloy casting to obtain the appearance size of the casting and the three-dimensional space size of internal shrinkage porosity defects at different times; dissect the obtained titanium alloy castings at different times, and then measure the distribution area of the deformed microstructure around shrinkage pores on the plane passing through the geometric center of the shrinkage cavity defect, and determine the closing situation of the shrinkage porosity defect;

[0050] S6) Establish the quantitative relationship among the size and spatial distribution of the stress / strain around the internal shrinkage porosity in the titanium alloy casting under different HIP times - the original characteristic size of the titanium alloy casting microstructure - the size of the deformed microstructure around the porosity;

[0051] S7) Compare the simulation results in step S4) with the characterization results in steps S5) and S6), and then iteratively correct the prediction model in step S2) to obtain a corrected prediction model;

[0052] S8) Based on the quantitative relationship established in step S6) and the corrected prediction model in S7), obtain the calculation formula for the spatial size of the deformed microstructure around the shrinkage porosity of the HIP-treated titanium alloy casting;

[0053] In step S5), if the plane is single, then the spatial size of the deformed microstructure around the shrinkage porosity in step S8) is the area of the deformed circumference of the shrinkage hole, and the calculation formulas are shown in formulas (Ⅰ) and (Ⅱ):

[0054] In step S5), if the plane is multiple, then the spatial size of the deformed microstructure around the shrinkage porosity in step S8) is the volume of the deformed circumference of the shrinkage hole, and the calculation formulas are shown in formulas (Ⅲ) and (Ⅳ):

[0055]

[0056]

[0057] where Amp is the area of the deformed microstructure around the shrinkage porosity, in mm -2 , Ap is the area of the plastic zone around the shrinkage porosity, in mm -2 , Vmp is the volume of the deformed microstructure around the shrinkage porosity, in mm -3 , Vp is the volume of the plastic zone around the shrinkage porosity, in mm -3 , σ f is the equivalent stress, in MPa, E is the elastic modulus, in Pa, r is the distance from the center of the shrinkage defect, in mm, ν is the Poisson's ratio, negative value, μ is the shear modulus, in Pa, ρ is the density, in g / cm 3 , Dβ is the original β grain size, in mm, Rc is the α / β cluster size, in mm, Bm is the material constant, and Rc is the α / β cluster size, in mm.

[0058] In the method for estimating the three-dimensional space of shrinkage porosity defects and pore-peripheral deformed structures during the hot isostatic pressing process of titanium alloy castings provided in this application, the original data of the titanium alloy castings is first constructed, that is, the appearance and internal shrinkage porosity defects of the titanium alloy castings are scanned in three-dimensional dimensions and the spatial dimensions are reconstructed. At the same time, the average values of the original β grain size and α / β / colony characteristic sizes of the titanium alloy castings are measured respectively to obtain the data for calculation; in this process, specifically, the 3D-X-ray computed tomography technique (3D X-CT) or other non-destructive testing methods with the same function are used to scan the dimensions and perform non-destructive testing on the appearance and internal porosity, shrinkage cavities (shrinkage porosity), and other casting defects of the as-cast or pre-treated (surface strengthened, pre-machined, etc.) titanium alloy castings (including single castings, attached cast specimens, components, etc.) and reconstruct the spatial dimensions, and then output the 3D X-CT point cloud data for mesh generation or other data for simulation calculation; the metallographic method is used to measure and calculate the average values of the original β grain size and α / β colony characteristic sizes of the cast titanium alloy.

[0059] In some specific embodiments, for the above-mentioned original data construction step, the scanning method is specifically as follows: for the external dimensions of the titanium alloy castings, the blue light method, the coordinate measuring method or the Kash measurement method can be directly used for measurement; the X-ray flaw detection, real-time imaging method or 3D-X-ray computed tomography method is used to determine the position and size of the internal shrinkage cavity defects of the titanium alloy castings. Further, the metallurgical microscope or the scanning electron microscope is used to determine the characteristic sizes of the microstructure around the internal shrinkage porosity defects, and combined with the above-mentioned measurement of the average values of the original β grain size and α / β / colony characteristic sizes, the three-dimensional space dimension data of the titanium alloy castings and the internal shrinkage porosity defects are constructed.

[0060] The present application further conducts model construction, that is, input the property parameters affecting titanium alloy castings, the average value of the characteristic dimensions, and the process parameters of hot isostatic pressing into the numerical simulation software, select the thermo-elastoplastic-creep constitutive model, and establish the prediction model of the equivalent stress-strain around porosity during the hot isostatic pressing process of titanium alloy castings, the prediction model of the three-dimensional spatial size of porosity defects, the geometric size of the deformed microstructure around the porosity holes, and the prediction model of the closing time of porosity defects; in this step, the numerical simulation software includes ABAQUS finite element software, DEFORM finite element software, or MARC finite element software; the property parameters of the titanium alloy castings include thermal conductivity, specific heat capacity, Young's modulus, Poisson's ratio, density, yield strength, etc., which can be measured by experimental methods or calculated by simulating the chemical composition of the titanium alloy castings; the process parameters of the hot isostatic pressing include the heating rate, temperature, pressure, time, etc. of the hot isostatic pressing, which can be formulated according to the composition of the titanium alloy castings. On the basis of these parameters, combined with the thermo-elastoplastic-creep constitutive model, a variety of prediction models are established; among them, for the thermo-elastic part in the thermo-elastoplastic-creep constitutive model, the elastic modulus is calculated using Hooke's law, for the plastic part, the Arrhenius equation is used to calculate the deformation behavior and activation energy of the titanium alloy, and by modifying the parameters of the titanium alloy material, a strain-compensated elastoplastic constitutive model is constructed; the Norton creep constitutive model is used to fit the creep curve, and combined with the elastoplastic constitutive model, a thermo-elastoplastic-creep constitutive model is constructed.

[0061] According to the present invention, then input the original data and parameters for simulation; that is, perform mesh division on the above-mentioned characteristic dimension data for calculation to obtain the initial mesh data for hot isostatic pressing simulation; that is, input the three-dimensional spatial size cloud data of the titanium alloy and its internal porosity into ABAQUS or DEFORM finite element software or simulation software with the same function and perform preliminary mesh division as the initial data for hot isostatic pressing simulation. Then perform simulation calculations to simulate and calculate the equivalent stress-strain magnitude distribution around the internal porosity holes of the titanium alloy casting, the three-dimensional spatial size of the porosity defect, the size of the deformed microstructure around the porosity, and the closing time of the porosity defect by using the above initial mesh data and the hot isostatic pressing prediction model.

[0062] This application then conducts hot isostatic pressing (HIP) quasi-in-situ tests on titanium alloy castings for different durations. That is, the titanium alloy castings are first placed in a HIP furnace, and appropriate heating rates, pressures, holding and pressurizing times, and furnace cooling rates are selected according to the alloy composition for HIP treatment. Subsequently, HIP quasi-in-situ characterization tests are carried out. That is, three-dimensional dimensional scanning is first performed on the appearance dimensions and the three-dimensional space dimensions of internal shrinkage porosity of the titanium alloy castings after HIP for different durations to obtain the appearance dimensions and the three-dimensional space dimensions of internal shrinkage porosity at different moments of HIP. Moreover, the HIP-treated castings are dissected, preferably using the metallographic method, to measure the distribution of the deformed tissue (annihilation zone) around the shrinkage porosity holes on a single or multiple planes passing through the geometric center of the shrinkage hole defect. And preferably, through X-ray flaw detection, real-time imaging method, 3D-XCT, and dissected metallographic method, the closure condition of the shrinkage porosity defect is determined. The position of the geometric center of the above-mentioned shrinkage hole defect can be determined according to the results of the three-dimensional space dimensions of the shrinkage porosity defect.

[0063] In this application, a quantitative relationship between the stress-strain around the shrinkage porosity holes and the spatial dimensions of the deformed tissue is established based on the above HIP quasi-in-situ tests. To ensure accuracy, it is preferred to conduct a large number of HIP quasi-in-situ tests, and then establish a quantitative relationship between the magnitude and spatial distribution dimensions of the stress-strain around the shrinkage porosity holes - the original characteristic dimensions of the titanium alloy casting structure (average values of the original β grain and α / β bundle characteristic dimensions) - the dimensions of the deformed tissue around the holes. Preferably, through multiple rounds of iteration, the accuracy rate of the quantitative relationship is improved. Among them, the characteristic dimensions of the titanium alloy casting structure include the original β grain and the average value of the α / β bundle characteristic dimensions, and metallographic specimens can be cut from the titanium alloy casting or the attached cast specimens of the same furnace batch, and methods such as the area method and the intercept point method can be used for measurement. The deformed tissue around the holes includes lath kink tissue, equiaxed tissue, recrystallized tissue, etc. The dimensions of the deformed tissue around the holes are calculated according to the area where the outermost ends of the kink or equiaxed crystal tissue or recrystallized tissue are away from the boundary of the shrinkage porosity hole.

[0064] This application then compares the simulation calculation results with the characterization results of the HIP-treated titanium alloy castings, and then iteratively corrects the prediction model to further improve the calculation accuracy of the equivalent stress-strain magnitude distribution around the shrinkage porosity holes and the closure time of the shrinkage porosity defects during the HIP process. The closure time of the shrinkage porosity defects is confirmed by non-destructive testing of the shrinkage porosity defects and / or the dissected metallographic method. The correction of the prediction model mainly targets the geometric correction coefficient and the loading correction coefficient, and the intrinsic parameters of the titanium alloy castings are not corrected.

[0065] Finally, based on the above quantitative relationship and prediction model, a calculation formula for the spatial dimensions of the deformed tissue around the shrinkage porosity holes of the HIP-treated titanium alloy castings is obtained. In the actual detection step, if the plane passing through the geometric center of the shrinkage hole defect is a single plane, the spatial dimensions of the deformed tissue around the shrinkage porosity holes are the area of the deformed perimeter of the shrinkage hole, and the calculation formulas are shown in Formulas (Ⅰ) and (Ⅱ):

[0066] If there are multiple such planes, preferably with the criterion of forming a solid, by measuring multiple different planes, the spatial dimension of the deformed structure around the microporosity is the volume of the deformed structure around the shrinkage cavity, and the calculation formulas are as shown in Formulas (Ⅲ) and (Ⅳ):

[0067]

[0068] where Amp is the area of the deformed structure around the microporosity, in mm -2 , Ap is the area of the plastic zone around the microporosity, in mm -2 , Vmp is the volume of the deformed structure around the microporosity, in mm -3 , Vp is the volume of the plastic zone around the microporosity, in mm -3 , σ f is the equivalent stress, in MPa, E is the elastic modulus, in Pa, r is the distance from the center of the microporosity defect, in mm, ν is the Poisson's ratio, a negative value, μ is the shear modulus, in Pa, ρ is the density, in g / cm 3 , Dβ is the original β grain size, in mm, Rc is the α / β cluster size, in mm, Bm is the material constant, and Rc is the α / β cluster size, in mm.

[0069] Furthermore, to verify the accuracy of the model, at least 3 titanium alloy castings are selected, and hot isostatic pressing simulation calculations and quasi-in-situ dissection characterization tests are carried out according to the above steps to verify the accuracy of the initial prediction model and determine the final prediction model.

[0070] In this application, the titanium alloy casting is a titanium alloy well-known to those skilled in the art, which is a titanium alloy obtained by the casting method. By way of example, the titanium alloy casting includes ZTC4, ZTA7, ZTA15, ZT60 titanium alloys, etc.

[0071] The three-dimensional space estimation method for the circumferential deformation structure of shrinkage porosity defects during the hot isostatic pressing process of titanium alloy castings provided by this application includes the following steps: First, scan the external dimensions and locate the internal shrinkage porosity defects to construct the original data. Second, construct a thermo-elastoplastic-creep constitutive model applicable to the hot isostatic pressing process of titanium alloy castings. Third, input the original data into the simulation software and perform mesh division. Fourth, simulate and calculate the equivalent stress-strain magnitude distribution, three-dimensional space size of shrinkage porosity defects, closing time of shrinkage porosity defects, etc. Fifth, conduct a hot isostatic pressing test on titanium alloy castings. Sixth, quasi-in-situ characterize the external dimensions of the castings and the three-dimensional space size of internal shrinkage porosity defects at different times during the hot isostatic pressing test, as well as the area of the circumferential deformation structure (annihilation zone) of shrinkage porosity through several planes passing through the geometric center of the shrinkage porosity defects. Seventh, based on the quasi-in-situ characterization results in the sixth step, establish a quantitative relationship between "equivalent stress-strain around shrinkage porosity" and "spatial size of the circumferential deformation structure". Eighth, according to the test results in the sixth step, iteratively correct the prediction model in the third step multiple times to improve the calculation accuracy. Ninth, select no less than three castings to correct the corrected model. Tenth, calculate the three-dimensional space size of the circumferential deformation structure around internal shrinkage porosity in titanium alloy castings. Through the three-dimensional space size calculation method for the circumferential deformation structure (annihilation zone) of shrinkage porosity defects during the hot isostatic pressing process of a titanium alloy casting provided by this application, taking an actual titanium alloy casting with shrinkage porosity defects as the test object, first, based on the thermo-elastoplastic-creep constitutive model of titanium alloy, establish prediction models for equivalent stress-strain around shrinkage porosity, three-dimensional space size of shrinkage porosity defects, closing time of shrinkage porosity defects, etc. during the hot isostatic pressing process of titanium alloy castings, and through the quasi-in-situ size scanning and tissue dissection characterization methods during the hot isostatic pressing process, collect the three-dimensional size data of shrinkage porosity defects and circumferential deformation structures at different times during the hot isostatic pressing process, and iteratively correct the above prediction models. Second, based on the original β grain size and α / β bundle characteristic size of titanium alloy, establish a quantitative relationship between the equivalent stress-strain around shrinkage porosity and the three-dimensional space size of the circumferential deformation structure (annihilation zone tissue). Finally, based on the above prediction models and the quantitative relationship between "equivalent stress-strain around shrinkage porosity" and "three-dimensional space size of the circumferential deformation structure", estimate the three-dimensional space size of the circumferential deformation structure (annihilation zone) of internal shrinkage porosity defects in titanium alloy.

[0072] The estimation method provided by this application uses the actual internal shrinkage porosity defects in cast titanium alloy rather than simplified spherical or ellipsoidal defects as the test object for hot isostatic pressing simulation. By collecting the three-dimensional sizes of actual shrinkage porosity defects and the sizes of circumferential deformation structures during the hot isostatic pressing process, an estimation method and a calculation method for the three-dimensional space size of the circumferential deformation structure of shrinkage porosity defects during the hot isostatic pressing process of titanium alloy castings are accurately established.

[0073] To further understand the present invention, the following is a detailed description of the method for estimating the shrinkage porosity defect and the three-dimensional space of the deformed structure around the hole during the hot isostatic pressing process of titanium alloy castings provided by the present invention in combination with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0074] In the following embodiments, the composition of the titanium alloy casting is ZTC4 (Ti-6Al-4V wt%).

[0075] Embodiment 1

[0076] 1) Using the investment precision casting method, prepare a ZTC4 titanium alloy specimen of 15 mm × 20 mm × 20 mm;

[0077] Characterize the three-dimensional morphology of shrinkage cavities inside the specimen by using real-time imaging and 3D X-CT methods respectively, Figure 1 as shown;

[0078] Observe the metallographic structure of the ZTC4 titanium alloy specimen, and measure the original β grain size (Dβ) and α / β colony size (Rc), as Figure 2 shown;

[0079] Formulate the hot isostatic pressing regime for the ZTC4 titanium alloy specimen, and the process curve is as Figure 3 shown;

[0080] 2) Through a series of tests, obtain the thermophysical property parameters of ZTC4 titanium alloy related to temperature, as shown in Table 1; and construct an elastoplastic model formula and a Norton creep model relationship, as shown in Equation 1 and Equation 2 respectively. The parameter values at different temperatures in Equation 2 are shown in Table 2; establish a prediction model for the equivalent stress-strain around the shrinkage porosity, a prediction model for the three-dimensional size of the shrinkage porosity defect, a prediction model for the geometric size of the deformed structure around the shrinkage porosity hole, and a prediction model for the closing time of the shrinkage porosity defect during the hot isostatic pressing process of titanium alloy castings;

[0081] Table 1 Thermophysical property parameter data sheet of ZTC4 titanium alloy related to temperature

[0082]

[0083]

[0084] Among them, is the strain rate, A, α, and n are different material constants independent of the deformation temperature, Q is the deformation activation energy, kJ / mol; σ is the stress, R is the gas constant, T is the hot isostatic pressing temperature, and h is the Planck constant;

[0085] In the above Equation 1, n = 5.9213, Q = 428.957 KJ / mol;

[0086] ε = Bσ m (Equation 2);

[0087] Among them, B is a material constant and m is the Norton stress exponent;

[0088] In the above formula (2), the parameters B and m are shown in Table 2;

[0089] Table 2 Parameter data table of formula (2) at different temperatures

[0090] Temperature / °C B m 500 <![CDATA[1.5×10 -29 > 9.5 700 <![CDATA[2.4×10 -11 > 4.2 900 <![CDATA[1.2×10 -5 > 1.7

[0091] 3) Input the three-dimensional size data of the ZTC4 titanium alloy specimen and internal shrinkage porosity defects into the ABAQUS finite element software and perform mesh division, as Figure 4 shown;

[0092] 4) According to the prediction model in step 2) and the mesh data in step 3), simulate and calculate the equivalent stress-strain magnitude distribution around the internal shrinkage porosity holes of the titanium alloy casting, the three-dimensional spatial size of the shrinkage porosity defect, the size of the deformed microstructure around the shrinkage porosity, and the closing time of the shrinkage porosity defect;

[0093] 5) Conduct hot isostatic pressing quasi-in-situ tests on the titanium alloy casting at different times. The parameters involved in the hot isostatic pressing test include: temperature, pressure, and time. Then, perform three-dimensional size scanning on the obtained titanium alloy casting; dissect the titanium alloy casting, and then measure the distribution area of the deformed microstructure around the shrinkage porosity holes on multiple planes passing through the geometric center of the shrinkage hole to obtain the volume (Vmp) of the deformed microstructure in the annihilation area of the internal shrinkage porosity defect of the ZTC4 titanium alloy specimen at different times of hot isostatic pressing, as Figure 6 shown; and determine the closing condition of the shrinkage porosity defect;

[0094] 6) Establish the quantitative relationship among the magnitude of the stress / strain around the internal shrinkage porosity holes of the titanium alloy casting at different times of hot isostatic pressing, the spatial distribution size in step 1, the characteristic size of the titanium alloy casting microstructure, and the size of the deformed microstructure around the hole in step 5;

[0095] 7) Compare the simulation calculation results in step 4) with the characterization results in step 5), and then iteratively correct the prediction model in step 2) to obtain the corrected prediction model;

[0096] 8) Based on the quantitative relationship established in step 6) and the corrected prediction model in step 7), obtain the quantitative relationship between the center coordinates (x, y, z) of the internal shrinkage porosity defect of the ZTC4 titanium alloy specimen at different times of hot isostatic pressing and the stress-strain distribution around the hole. According to the original β grain (Dβ) and α / β cluster size (Rc) in step 1) above, the plastic volume (Vp) around the hole calculated by simulation in step 4), the center coordinates (0, r) of the shrinkage porosity defect, and the actual deformed microstructure volume (Vmp) in step 5), construct a three-dimensional spatial size calculation model for the deformed microstructure around the hole during hot isostatic pressing, as shown in the following formula;

[0097]

[0098] Among them, Amp is the area of the deformed tissue around the shrinkage porosity, in mm -2 , Ap is the area of the plastic zone around the shrinkage porosity, in mm -2 , Vmp is the volume of the deformed tissue around the shrinkage porosity, in mm -3 , Vp is the volume of the plastic zone around the shrinkage porosity, in mm -3 , σ f is the equivalent stress, in MPa, E is the elastic modulus, in Pa, r is the distance from the center of the shrinkage defect, in mm, ν is the Poisson's ratio, negative value, μ is the shear modulus, in Pa, ρ is the density, in g / cm 3 , Dβ is the original β grain size, in mm, Rc is the α / β cluster size, in mm, Bm is the material constant, Rc is the α / β cluster size, in mm.

[0099] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0100] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for estimating the spatial size of the deformation structure around the hole of a titanium alloy casting during hot isostatic compression, comprising the following steps: S1) performing three-dimensional scanning and spatial dimension reconstruction on the appearance and internal shrinkage defects of the titanium alloy casting, respectively measuring the original β grains and the average value of the α / β / cluster characteristic dimensions of the titanium alloy casting, and obtaining characteristic dimension data for calculation; S2) inputting the property parameters affecting the titanium alloy casting, the average value of the characteristic dimensions and the process parameters of hot isostatic pressing into the numerical simulation software, selecting the thermoelastic-plastic-creep constitutive model, and establishing the equivalent stress-strain prediction model around the shrinkage during the hot isostatic pressing of the titanium alloy casting, the three-dimensional spatial size prediction model of the shrinkage defect, the geometric size of the deformation structure around the shrinkage hole and the shrinkage defect closure time prediction model; S3) meshing the characteristic size data for calculation in step S1) to obtain initial mesh data for hot isostatic pressing simulation; S4) using the prediction model of step S2) and the initial grid data of step S3) to simulate and calculate the equivalent stress-strain size distribution around the internal shrinkage holes of the titanium alloy casting, the three-dimensional spatial size of the shrinkage defects, the size of the deformation structure around the shrinkage holes, and the shrinkage defect closure time; S5) subjecting the titanium alloy casting in step S1) to a quasi-in-situ hot isostatic pressing test at different times, and performing a three-dimensional scanning on the obtained titanium alloy casting to obtain the casting appearance dimensions and the three-dimensional spatial dimensions of the internal shrinkage defects at different times; dissecting the titanium alloy castings obtained at different times, and then measuring the distribution area of ​​the deformation structure around the shrinkage hole passing through the geometric center plane of the shrinkage hole defect, and determining the closure status of the shrinkage defect; S6) according to step S5), a quantitative relationship between the size and spatial distribution size of the internal shrinkage hole circumference stress / strain of the titanium alloy casting at different hot isostatic pressing times - the original characteristic size of the titanium alloy casting structure - the size of the deformation structure around the hole is established; S7) comparing the simulation calculation result of step S4) with the characterization results of step S5) and step S6), and iteratively correcting the prediction model of step S2) to obtain a corrected prediction model; S8) based on the quantitative relationship established in step S6) and the prediction model corrected in step S7), a calculation formula for the spatial size of the deformation structure around the shrinkage hole of the titanium alloy casting after hot isostatic pressing is obtained; In step S5), the plane is single, then the spatial size of the deformation organization around the shrinkage hole in step S8) is the area of ​​the deformation around the shrinkage hole, and the calculation formula is shown in formula (I) and formula (II): In step S5), there are multiple planes, and the spatial size of the deformation organization around the shrinkage hole in step S8) is the volume of the deformation around the shrinkage hole, and the calculation formula is shown in formula (III) and formula (IV): Where Amp is the deformation tissue area around the shrinkage hole, mm -2 , Ap is the plastic area around the shrinkage hole, mm -2 , Vmp is the volume of deformed tissue around shrinkage pores, mm -3 , Vp is the volume of the plastic zone around the shrinkage hole, mm -3 , σ f is the equivalent stress, MPa, E is the elastic modulus, Pa, r is the distance from the center of the shrinkage defect, mm, ν is the Poisson's ratio, a negative value, μ is the shear modulus, Pa, ρ is the density, g / cm 3 , Dβ is the original β grain size, mm, Rc is the α / β cluster size, mm, Bm is the material constant, Rc is the α / β cluster size, mm.

2. The estimation method according to claim 1, characterized in that: In step S1), the appearance dimensions of the titanium alloy casting are measured by a blue light method, a three-coordinate method or a caliper measurement method; Determine the location and size of internal shrinkage defects in titanium alloy castings using X-ray flaw detection, real-time imaging or 3D-X-ray computed tomography; The characteristic size of the microstructure around the internal shrinkage defect hole is determined by metallographic microscope or scanning electron microscope.

3. The estimation method according to claim 1, characterized in that: In step S2), the property parameters include thermal conductivity, specific heat capacity, Young's modulus, Poisson's ratio, density and yield strength; And / or, the process parameters include temperature, pressure and time of hot isostatic pressing; And / or, the numerical simulation software includes ABAQUS finite element software, DEFORM finite element software or MARC finite element software.

4. The estimation method according to claim 1, characterized in that: In step S2), in the thermoelastic-plastic-creep constitutive model, for the thermoelastic part, the elastic modulus of the titanium alloy at different temperatures is tested, and for the plastic part, the Arrhenius equation is used to calculate the deformation behavior and activation energy of the titanium alloy, and a strain-compensated elastoplastic constitutive model is constructed; the Norton creep constitutive model is used to fit the creep curve, and the thermoelastic-plastic-creep constitutive model is constructed in combination with the elastoplastic constitutive model.

5. The estimation method according to claim 1, characterized in that: In step S3), the meshing application software includes ABAQUS finite element software or DEFORM finite element software.

6. The estimation method according to claim 1, characterized in that: In step S5), the parameters of the hot isostatic pressing quasi-in-situ test include heating rate, pressure, temperature, heat and pressure holding time and furnace cooling rate.

7. The estimation method according to claim 1, characterized in that: In step S5), the position of the geometric center of the shrinkage defect is determined by the three-dimensional spatial size of the internal shrinkage defect.

8. The estimation method according to claim 1, characterized in that: In step S5), the method for measuring the distribution area of ​​the deformed tissue around the shrinkage hole is metallographic method; the method for determining the closure status of the shrinkage defect includes X-ray flaw detection, real-time imaging method, 3D-XCT method or anatomical metallographic method.

9. The estimation method according to claim 1, characterized in that: In step S6), the circumferential deformation structure includes lath kink structure, equiaxed structure, and recrystallized structure; the size of the circumferential deformation structure is calculated according to the area from the outermost end of the kink or equiaxed crystal structure or recrystallized structure to the boundary of the shrinkage defect hole.

10. The estimation method according to claim 1, characterized in that: In step S7), the correction is a correction of the geometric correction coefficient and the loading correction coefficient.

Images