Visual analysis method for the formation process of oxide layer on the surface of titanium or titanium alloy powder

Abstract

The present invention provides a visualization analysis method for the formation process of the surface oxide layer of titanium or titanium alloy powder, and the visualization analysis method comprises the following steps: selecting a physical field interface and a research state; wherein the physical field interface is a reaction engineering module and a rare substance transfer module; constructing a 1 / 4 circle geometric model; setting material properties; setting boundary conditions; constructing a grid; setting transient or steady state; solving; and post-processing to obtain the thickness of the surface oxide layer of titanium or titanium alloy powder and the mass percentage of the oxygen atoms in the oxide layer relative to the mass percentage of the titanium atoms. The visualization analysis method is based on computational fluid dynamics software, realizes the visualization of the formation process and distribution of the surface oxide layer of titanium or titanium alloy powder, reduces the amount of experiments, reduces the research cost, and optimizes the comprehensive performance of powder titanium alloy in actual production.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, and in particular to a visual analysis method for a process of oxide layer formation on the surface of titanium or titanium alloy powder. Background Art

[0002] Titanium is an important structural metal developed in the 1950s. It has the characteristics of low density, high specific strength, excellent corrosion resistance and high temperature resistance, and is widely used in aerospace, biomedical and civil fields. However, titanium itself has high activity, high melting point and low thermal conductivity, which makes it difficult to cut and process the material and has low production efficiency. Powder metallurgy can overcome the inherent defects of traditional casting machine processing technology, realize the near-net shape manufacturing of complex shaped parts, and the prepared samples have uniform structure and excellent performance.

[0003] In the actual production process, the powder raw materials will inevitably come into direct contact with the air, resulting in the pollution of powder titanium materials by oxygen and nitrogen elements in the air. Oxygen is the most important impurity element in titanium alloys, which has a significant impact on the densification and mechanical properties of the parts. Ti-6Al-4V alloy is the most widely used in titanium and titanium alloy engineering. For Ti-6Al-4V alloy, when the oxygen content exceeds the critical value of 0.32wt.%, the elongation at break of the alloy drops below 5%, and when the oxygen content exceeds 0.45wt.%, the material has basically no plastic characteristics.

[0004] Therefore, how to reduce interstitial oxygen contamination is a key problem in promoting the application of powdered titanium materials. It is of great significance to explore the formation process and oxygen content of the oxide layer in titanium and titanium alloy powders. However, the current research on the formation process of the oxide layer on the surface of titanium or titanium alloy powders in actual production is a complex issue that requires in-depth research, and there is a lack of effective visualization analysis methods. Summary of the invention

[0005] In view of the deficiencies in the prior art, the main purpose of the present invention is to provide a visualization analysis method for the surface oxide layer formation process of titanium or titanium alloy powder. The visualization analysis method performs simulation calculations based on computational fluid dynamics software to achieve visualization of the surface oxide layer formation process and distribution of titanium or titanium alloy powder, reduce the amount of experiments, reduce research costs, and optimize the comprehensive performance of powdered titanium alloys in actual production.

[0006] In order to achieve the above object, the present invention provides a visual analysis method for the formation process of an oxide layer on the surface of titanium or titanium alloy powder.

[0007] Based on computational fluid dynamics software, the visualization analysis method of the titanium or titanium alloy powder surface oxide layer formation process includes the following steps:

[0008] S1, module selection: select the physical field interface and the research state; wherein the physical field interface is the reaction engineering module and the dilute species transport module;

[0009] S2, model building: building a 1 / 4 circle geometric model;

[0010] S3, material property setting: setting material properties in the physical field interface;

[0011] S4, boundary condition setting;

[0012] S5, Mesh Build: Set specific mesh requirements in the Mesh tab, and then click Build All;

[0013] S6, Transient or Steady State Settings: Set the time unit, time step and tolerance in the Study tab;

[0014] S7, solving: after the setting of step S6 is completed, solving is performed;

[0015] S8, post-processing: After step S7 is completed, the results are analyzed in the result tab to obtain the thickness of the oxide layer on the surface of the titanium or titanium alloy powder and the mass percentage of the oxygen atoms in the oxide layer relative to the titanium atoms.

[0016] Furthermore, in step S1, the research state is set to transient research.

[0017] Furthermore, in step S2, the radius of the circle is 10-75 μm.

[0018] Furthermore, in step S3, in the transfer property setting of the dilute species transfer module, the diffusion coefficient D TiO2 Click User Defined and set the value to if(cTi <cTiO2,1e -20 ~1e -18 , 1e -22 ~1e -20 ); all other settings are 0.

[0019] Further, in step S3, the reaction formula is input into the reaction engineering module The temperature is set to 293.15~1073.15K, and the concentration of O2 in the initial value setting is 0.01mol / m 3 , the concentration of Ti is 94200 mol / m 3 , the concentration of TiO2 is 0.01 mol / m 3 .

[0020] Furthermore, in step S4, the titanium or titanium alloy powder surface in the boundary condition is set to reaction control, and the titanium or titanium alloy powder oxide layer is set to diffusion control; the O2 concentration at the boundary is set to 90000 mol / m3 ; The boundary conditions are set as: flux boundary conditions, concentration control, thin diffusion barrier layer, the diffusion coefficient in the layer is kept at the same order of magnitude as the diffusion of oxygen in TiO2; the distribution of the thin diffusion barrier layer is defined using a logical formula, and when the amount of Ti is reduced to half of the initial value, the diffusion in the matrix is ​​transformed into diffusion in the thin diffusion barrier layer.

[0021] Furthermore, in step S5, the 50nm thickness area on the surface of titanium or titanium alloy is precisely divided, the accuracy of each grid is 0.8-1nm, the maximum cell size is set to 1-1.1um, the minimum cell size is set to 0.0045-0.001um, the maximum cell growth rate is 1.2-1.3, and the curvature factor is 0.25-0.3.

[0022] Furthermore, in step S6, the time unit is set to min, the time step is set to range (0, 0.1, 0-1440), and the tolerance is set to physical field control.

[0023] Furthermore, the particle size of the titanium or titanium alloy powder is 10 to 150 um.

[0024] Furthermore, the computational fluid dynamics software is COMSOL Multiphysics 5.6 software.

[0025] The present invention introduces computer numerical simulation technology to study the oxygen absorption process on the surface of titanium or titanium alloy powder and the distribution of the oxide layer. According to the specific characteristics of the material, the reaction engineering module and the rare earth material transfer module are used to perform numerical simulation analysis, and the oxygen absorption process of the titanium or titanium alloy powder in the air is visualized. The results can be combined with experiments to achieve the purpose of controlling the oxygen content of the titanium or titanium alloy powder.

[0026] The present invention applies a visualization method to the oxygen absorption process of titanium or titanium alloy powder in the air, which can not only intuitively analyze the formation process of the oxide layer, but also calculate the oxygen content of the powder according to the reaction consumption.

[0027] The present invention can realize visualization of the oxygen absorption process of titanium or titanium alloy powder and can also be combined with a powder oxygen absorption experiment, and the two can complement each other.

[0028] The visualization analysis method proposed in the present invention has a certain universality and can meet the needs of visualization of the reactions of other materials in different environments.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention uses numerical simulation to visualize the oxygen absorption process of titanium or titanium alloy powder in the air, simplifies the oxygen content analysis process, and has practical reference significance for the oxygen content of raw material powder of powder metallurgy titanium or titanium alloy.

[0031] (2) While realizing the visualization of the oxygen absorption process, the present invention can adjust and set parameters, thereby controlling the oxygen content on the surface of titanium or titanium alloy powder to a certain extent, and can be combined with experiments to achieve the ultimate purpose of controlling the oxygen content of titanium or titanium alloy powder.

[0032] (3) The method for visualizing the oxygen absorption process of the present invention is used in titanium or titanium alloy powder, and the simulated oxygen content and oxide layer thickness can be consistent with the experimental data, which can support each other and indicate the applicability of the visualization method to the oxygen absorption process of conventional metal powders. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0034] Figure 1 A geometric model diagram of titanium or titanium alloy powder in an embodiment of the present invention;

[0035] Figure 2 A mesh division diagram of a geometric model in an embodiment of the present invention;

[0036] Figure 3 This is a cloud diagram of oxygen element distribution in the oxide layer of the titanium powder model in Example 1 of the present invention when the oxidation reaction occurs at a temperature of 293.15K for 10 minutes;

[0037] Figure 4 This is a cloud diagram of oxygen element distribution in the oxide layer of the titanium powder model in Example 1 of the present invention when the oxidation reaction occurs at a temperature of 293.15K for 30 minutes;

[0038] Figure 5 This is a cloud diagram of oxygen element distribution in the oxide layer of the titanium powder model in Example 1 of the present invention when the oxidation reaction occurs at a temperature of 293.15K for 120 minutes;

[0039] Figure 6 This is a cloud diagram of oxygen element distribution in the oxide layer of the titanium powder model in Example 1 of the present invention when the oxidation reaction occurs at a temperature of 293.15K for 24 hours;

[0040] Figure 7 This is the Ti-O phase diagram used as the basis for calculating the oxygen content in the embodiments of the present invention. DETAILED DESCRIPTION

[0041] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0042] The visualization analysis method in the present invention is based on computational fluid dynamics software COMSOL Multiphysics 5.6, and uses a reaction engineering module and a rare species transfer module to perform finite element numerical simulation analysis on the oxidation process of titanium or titanium alloy powder in an air environment.

[0043] The visual analysis method specifically includes the following steps:

[0044] S1, module selection: select the physical field interface to be used and select the research status.

[0045] The physical field interfaces selected for addition are the Reaction Engineering Module and the Transport of Diluted Species Module.

[0046] The study status is set to Time Dependent Study.

[0047] S2, model construction: Use the geometry model module of COMSOL 5.6 software to construct a geometry model suitable for simulation.

[0048] In the experiment of the present invention, the average particle size of titanium or titanium alloy powder is 10 to 150 μm. In order to facilitate simulation calculation, the geometric model is simplified to 1 / 4 of a circle with a radius of 10 to 75 μm. Figure 1 shown.

[0049] If the powder particle size is too small, the powder activity will be higher and it will be easier to agglomerate; if the powder particle size is too large, the loose density will be lower, sintering will be difficult, and the activity will be too low, resulting in a low oxygen content.

[0050] S3, Material property setting: Set material properties such as the initial value of material concentration in the selected physical field interface.

[0051] Based on the diffusion coefficient of O in Ti being on the order of 10 -20 ~10 -18 mol / (m 2 s), the diffusion coefficient of O in TiO2 is 10 -22 ~10 -20 mol / (m 2s), in the Transport Properties setting of the Diluted Species Module, the diffusion coefficient D TiO2 Click User Defined and set the value to if(cTi <cTiO2,1e -20 ~1e -18 , 1e -22 ~1e -20 ), and all other items are set to 0.

[0052] Enter the reaction formula in the reaction engineering module The temperature is set to 293.15~1073.15K, and the concentration of O2 in the initial value setting is 0.01mol / m 3 , the concentration of Ti is 94200 mol / m 3 , the concentration of TiO2 is 0.01 mol / m 3 .

[0053] Arrhenius equation was created by Arrhenius of Sweden. It is an empirical formula for the change of chemical reaction rate constant with temperature: K = A exp (-Ea / RT) (exponential). Among them, K is the rate constant, R is the molar gas constant, T is the thermodynamic temperature, Ea is the apparent activation energy, and A is the pre-exponential factor (also called frequency factor). The temperature must be set below 1073.15K, because above this temperature the oxide layer will decompose.

[0054] As a diffusion controlled system, the oxidation process of titanium or titanium alloy powder complies with Fick's first law: Where: C i is the oxygen concentration in the atmosphere, J i is the diffusion flux, R i is the chemical reaction rate, u is the flow field velocity, and since all reactions do not involve the liquid phase, u is taken as 0.

[0055] S4, boundary condition setting: set the titanium or titanium alloy powder surface in the boundary condition to reaction control, and the titanium or titanium alloy powder oxide layer to diffusion control; set the O2 concentration at the boundary to 90000 mol / m 3 ; The boundary conditions are set as: flux boundary conditions, concentration control, thin diffusion barrier layer, the diffusion coefficient in the layer is kept at the same order of magnitude as the diffusion of oxygen in TiO2; the distribution of the thin diffusion barrier layer is defined using a logical formula, and when the amount of Ti is reduced to half of the initial value, the diffusion in the matrix is ​​transformed into diffusion in the thin diffusion barrier layer.

[0056] S5, Mesh construction: After setting up step S4, set the specific mesh requirements in the Mesh tab, and then click Build All.

[0057] The thickness of the oxide layer is generally 5 to 20 nm, which is much smaller than the radius of the titanium or titanium alloy powder particles, and the surface grid needs to be separately divided.

[0058] In order to improve the calculation accuracy, the 50nm thickness area on the surface of titanium or titanium alloy powder is precisely divided, the accuracy of each grid is 0.8~1nm, the maximum unit size is set to 1~1.1um, the minimum unit size is set to 0.0045~0.001um, the maximum unit growth rate is 1.2~1.3, and the curvature factor is 0.25~0.3, see Figure 2 If the grid precision value is higher than 1nm, the accuracy of the calculation cannot be guaranteed and there will be relatively large errors; while if the grid precision value is lower than 0.8nm, the calculation takes a long time and has little effect on the accuracy of the calculation results.

[0059] S6, transient or steady-state settings: After the S5 step is set, set the time unit, time step, etc. in the study tab.

[0060] The time unit is set to min, the time step is set to range (0, 0.1, 0~1440), and the tolerance is set to physical field control.

[0061] S7, solving: after the setting of step S6 is completed, solving is performed;

[0062] S8, post-processing: After step S7 is completed, the oxygen concentration from the outside to the inside of the oxide layer on the surface of the titanium or titanium alloy powder can be seen in the 2D plot group option in the result tab of the COMSOL Multiphysics 5.6 software, and the thickness and distribution of the oxide layer can be analyzed.

[0063] The visual analysis method for the formation process of the oxide layer on the surface of titanium or titanium alloy powder in the present invention will be described in detail below through specific examples.

[0064] Embodiment 1:

[0065] S1, module selection: select to add reaction engineering module and dilute species transfer module in adding physical fields, and select transient study as the research state.

[0066] S2, build geometric model: simplify the titanium or titanium alloy powder model to 1 / 4 of a circle with a radius of 15μm, add five layers with a thickness of 0.002um, use Boolean operations to divide it into four parts, and take one of them for calculation. To facilitate mesh refinement, hide the first four boundaries, or hide all five (the fifth is 10nm and can be used as an auxiliary line).

[0067] S3, Material Properties Setting: Enter the reaction formula in the Reaction Engineering Module tab The temperature is set to 293.15K and the initial value is set to 0.01 mol / m 3 , the concentration of Ti is 94200 mol / m 3 , the concentration of TiO2 is 0.01 mol / m 3 .

[0068] In the Diluted Species Transport module, set the oxygen concentration to 90,000 mol / m 3 , which represents the oxygen concentration in the air. In the transport property settings, the diffusion coefficient D TiO2 Click User Defined and set the value to if(cTi <cTiO2,1e -20 , 1e -22 ), and set the others to 0.

[0069] S4, boundary condition setting: the titanium or titanium alloy powder surface in the boundary condition is set to reaction control, and the titanium or titanium alloy powder oxide layer is set to diffusion control; the O2 concentration at the boundary is set to 90000 mol / m 3 ; Use flux boundary conditions, concentration control, and a thin diffusion barrier layer. The diffusion coefficient in the layer is kept at the same order of magnitude as the diffusion of oxygen in TiO2. Use a logical formula to define the distribution of the thin diffusion barrier layer. When the amount of Ti is reduced to half of the initial value, the diffusion in the matrix is ​​transformed into the diffusion of the thin diffusion barrier layer.

[0070] S5, grid setting: the 50nm thick area on the powder surface is accurately divided, the accuracy of each grid is 1nm, the maximum cell size is set to 1.01um, the minimum cell size is set to 0.001um, the maximum cell growth rate is set to 1.3, and the curvature factor is set to 0.3.

[0071] "Mesh" contains 22617 elements, minimum quality: 0.526; average quality: 0.8358.

[0072] S6, Transient or Steady State Setup: On the Study tab, select Generate Default Plots and Generate Convergence Plots. Set the Time Unit to min, the Time Step to range(0, 0.1, 1440), and the Tolerance to Physics Controlled.

[0073] S7, Solution: The oxygen concentration can be obtained by calculation. The calculation can be performed on different studies and corresponding results can be obtained.

[0074] S8, post-processing: After step S7 is completed, the results are analyzed in the results tab of COMSOL 5.6 software. In the 2D plot group tab, the data set and time can be changed, and the distribution of the corresponding oxide layer will also change. The expression is set to max(eps 2,cO2), the unit is mol / m 3 .

[0075] Examples 2 to 7 use the same visualization analysis method as Example 1, with the only difference being the setting of parameters such as the radius of the circle in the geometric model, the temperature, diffusion coefficient, and time step in the material properties. The simulation parameters of the visualization analysis method for the formation process of the surface oxide layer of titanium or titanium alloy powder in Examples 1 to 7 are summarized as shown in Table 1.

[0076] Table 1 Summary of simulation parameters of the visualization analysis method in Examples 1 to 7

[0077]

[0078] At the same time, the present invention also summarizes the visual analysis results of the formation process of the surface oxide layer of the titanium or titanium alloy powder in Examples 1 to 7, as shown in Table 2 for details.

[0079] Table 2 Summary of visualization analysis results in Examples 1 to 5

[0080]

[0081] Note: The density of titanium is 4.54g / cm 3 ; The mass of a single titanium powder particle is 3.58×10 -8 g.

[0082] From the visual analysis results, it can be seen that the thickness of the oxide layer in Example 1 is 11.2nm, and the volume of the oxide layer is 17.8μm 3 , since the density of titanium is 4.54g / cm 3 , the mass of titanium that undergoes oxidation is 8.08×10 -11 g, and the oxygen consumed in the reaction is 5.50×10 -11 g, but since dissolved oxygen was ignored when the model was established, the total oxygen content was calculated to correct the result, see Figure 7 The Ti-O phase diagram is shown. According to the Ti-O phase diagram, at 293.15K, the molar fraction of oxygen in α-Ti is 32%. The result needs to be corrected when calculating the total oxygen content. The mass of dissolved oxygen is calculated to be 2.36×10 -11 g, and the corrected total oxygen content was 7.86×10 -11 g, based on the mass of a single titanium powder particle of 3.58 × 10 -8 g, and the mass percentage of oxygen atoms in the oxide layer relative to titanium atoms was obtained to be 0.21 wt.%.

[0083] By analyzing the visualization results of Example 1, Example 5 and Example 6, it can be seen that under the same simulation temperature and diffusion coefficient conditions (grid setting and particle size have no effect on oxygen content), the oxidation process is mainly concentrated in the early stage. The oxidation degree has reached 96% in the first 120 minutes, and the oxidation degree has reached 98% at 480 minutes. The subsequent oxidation process is very slow, which also indirectly confirms that the method of the present invention can realize the dynamic visualization of the oxygen absorption process of titanium or titanium alloy powder.

[0084] In addition, combined Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the visualization results analysis shows that the initial growth rate of the oxide layer is relatively fast. In Example 1, when the simulated oxidation time is 10 minutes, the thickness of the oxide layer increases rapidly, and the degree of oxidation on the surface of the Ti powder model is relatively high, and almost no oxidation reaction occurs in the center of the Ti powder model. At 30 minutes, the thickness of the oxide layer is close to 10.5nm. After that, as time goes by, the thickness of the oxide layer increases, but the increase is not obvious.

[0085] The simulation results of the present invention show that the oxide layer is formed quickly at the beginning, and as the thickness increases, the growth rate of the oxide layer gradually decreases; oxygen is concentrated on the powder surface, the oxygen content in the center of the powder is extremely low, and the surface oxygen does not diffuse into the interior of the matrix.

[0086] By analyzing the visualization results of Example 1 and Example 4, it can be seen that under the same simulation temperature and time conditions (grid setting and particle size have no effect on oxygen content), the simulation results of the two show that the order of magnitude of the diffusion coefficient has a very obvious effect on the thickness of the oxide layer and the oxygen content. When the diffusion coefficient differs by two orders of magnitude, the oxygen content increases by 1.57 times.

[0087] It can be concluded from Fick's diffusion equation that the diffusion coefficient is the mass or molar number of a substance diffused vertically through a unit area along the diffusion direction under the condition of unit concentration gradient per unit time. The diffusion coefficient directly determines the rate of chemical reaction.

[0088] At the same time, the present invention also conducted verification experiments on the simulation results in Examples 1 to 7, wherein the verification experiments adopted a standard detection method commonly used in the art, including the following steps:

[0089] (1) Initial state of materials: oxygen-free pure titanium powder is stored in a constant temperature box or muffle furnace and placed open, and the powder is in a flat and loose state; wherein:

[0090] The powder particle size is 10-150um, the holding temperature is 293.15-1073.15K, the holding time is ≤1440min, and the oxygen concentration in the ventilated gas is kept at the oxygen concentration in the atmosphere (0.01mol / m 3 ), in order to obtain the influence of different temperatures and different holding times on the oxygen content and distribution of the powder.

[0091] (2) The oxygen content of the powder was measured using a LECO ONH oxygen, nitrogen and hydrogen analyzer, and the thickness of the oxide layer on the powder surface was measured using focused ion beam cutting technology and transmission electron microscopy characterization technology.

[0092] The principle of measuring the oxygen content of powder by LECO ONH oxygen-nitrogen-hydrogen analyzer is: using graphite (C) to reduce the oxygen in titanium powder into CO2, and measuring CO2 to infer the oxygen content in the powder.

[0093] The focused ion beam (FIB) system is a microdissection instrument that uses an electric lens to focus an ion beam into a very small size. The focused ion beam bombards the sample surface, exciting secondary electrons, neutral atoms, secondary ions and photons, etc. These signals are collected and processed to display the surface morphology of the sample.

[0094] The powder treated in the first step was divided into two parts. One part of the powder was used to measure the oxygen content using a LECO ONH oxygen, nitrogen and hydrogen analyzer, and the other part of the powder was used to quantitatively analyze the thickness of the oxide layer on the powder surface using focused ion beam technology and transmission electron microscopy characterization technology.

[0095] The process parameters and results of verification experiments 1 to 7 corresponding to embodiments 1 to 7 are summarized below, as shown in Table 3 for details.

[0096] Table 3 Summary of process parameters and results of verification experiments 1 to 7

[0097]

[0098] Combining Table 2 and Table 3, it can be seen that the simulation results in Examples 1 to 7 are slightly different from the actual results of their respective corresponding verification experiments 1 to 7. The error in the oxide layer thickness is within 1 nm, and the error in the oxygen content is within 0.1%, both of which are within the measurement error range. The simulation results match the verification results well and can corroborate each other.

[0099] The present invention introduces a visualization analysis method to efficiently obtain the thickness and distribution of the oxide layer caused by oxygen absorption of titanium or titanium alloy powder in the air, indicating that the visualization method for the formation process and distribution of the oxide layer on the surface of titanium or titanium alloy powder proposed in the present invention has a certain universality.

[0100] The selection of simulation parameters and the influence on the results in the visual analysis method of the formation process of the surface oxide layer of titanium or titanium alloy powder of the present invention will be described in detail below through comparative examples.

[0101] Among them, comparative examples 1 to 2 adopt the same visualization analysis method as in embodiments 1 to 7, and the only difference is the setting of parameters such as powder particle size, temperature, diffusion coefficient and time step in material properties in comparative examples 1 to 2. The simulation parameters of the visualization analysis method in comparative examples 1 to 2 are summarized as shown in Table 4.

[0102] At the same time, the visualization analysis results in Comparative Examples 1 to 2 are summarized, see Table 5 for details.

[0103] Table 4 Summary of simulation parameters of the visualization analysis method in Comparative Examples 1 to 2

[0104]

[0105] Table 5 Summary of visualization analysis results in comparative examples 1 to 2

[0106]

[0107] Note: The density of titanium is 4.54g / cm 3 ; The mass of a single titanium powder particle is 3.58×10 -8 g.

[0108] At the same time, the present invention also conducted verification experiments on the simulation results in Comparative Examples 1 to 2, and summarized the process parameters and results of verification experiments 8 to 9 of Comparative Examples 1 to 2, as shown in Table 6 for details.

[0109] Table 6 Summary of process parameters and results of verification experiments 6 to 7

[0110]

[0111] It can be seen from Table 5 and Table 6 that there is a huge gap between the simulation results and the verification results in Comparative Examples 1 and 2. In particular, since the insulation temperature in Comparative Example 1 exceeds the upper temperature limit given by the present invention, the oxide layer will decompose, resulting in incorrect simulation calculation results; and in Comparative Example 2, since the diffusion coefficient is not within the range given by the present invention, it shows that the diffusion coefficient of oxygen in titanium and titanium dioxide is incorrect, which leads to incorrect simulation calculation results.

[0112] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A visual analysis method for the formation process of the oxide layer on the surface of titanium or titanium alloy powder, characterized in that: The visualization analysis method is based on computational fluid dynamics software and includes the following steps: S1, module selection: select the physical field interface and the research state; wherein the physical field interface is the reaction engineering module and the dilute species transport module; S2, model building: building a 1 / 4 circle geometric model; S3, material property setting: set material properties in the physical field interface; in the transfer property setting of the dilute species transfer module, the diffusion coefficient D TiO2 Click User Defined and set the value to if(cTi <cTiO2,1e -20 ~1e -18 , 1e -22 ~1e -20 ); other settings are all 0; enter the reaction formula in the reaction engineering module The temperature is set to 293.15~1073.15K, and the concentration of O2 in the initial value setting is 0.01mol / m 3 , the concentration of Ti is 94200 mol / m 3 , the concentration of TiO2 is 0.01 mol / m 3 ; S4, boundary condition setting; S5, Mesh Build: Set specific mesh requirements in the Mesh tab, and then click Build All; S6, Transient or Steady State Settings: Set the time unit, time step and tolerance in the Study tab; S7, solving: after the setting of step S6 is completed, solving is performed; S8, post-processing: After step S7 is completed, the results are analyzed in the result tab to obtain the thickness of the oxide layer on the surface of the titanium or titanium alloy powder and the mass percentage of the oxygen atoms in the oxide layer relative to the titanium atoms.

2. The method for visualizing and analyzing the formation process of the oxide layer on the surface of titanium or titanium alloy powder according to claim 1, characterized in that: In step S1, the study status is set to transient study.

3. The method for visualizing and analyzing the formation process of the oxide layer on the surface of titanium or titanium alloy powder according to claim 1, characterized in that: In step S2, the radius of the circle is 10 to 75 μm.

4. The method for visualizing and analyzing the formation process of the oxide layer on the surface of titanium or titanium alloy powder according to claim 1, characterized in that: In step S4, the titanium or titanium alloy powder surface in the boundary condition is set to reaction control, and the titanium or titanium alloy powder oxide layer is set to diffusion control; the O2 concentration at the boundary is set to 90000 mol / m 3 ; The boundary conditions are set as: flux boundary conditions, concentration control, thin diffusion barrier layer, the diffusion coefficient in the layer is kept at the same order of magnitude as the diffusion of oxygen in TiO2; the distribution of the thin diffusion barrier layer is defined using a logical formula, and when the amount of Ti is reduced to half of the initial value, the diffusion in the matrix is ​​transformed into diffusion in the thin diffusion barrier layer.

5. The method for visualizing and analyzing the formation process of the oxide layer on the surface of titanium or titanium alloy powder according to claim 1, characterized in that: In step S5, the 50nm thickness area on the surface of titanium or titanium alloy is precisely divided, the accuracy of each grid is 0.8-1nm, the maximum unit size is set to 1-1.1um, the minimum unit size is set to 0.0045-0.001um, the maximum unit growth rate is 1.2-1.3, and the curvature factor is 0.25-0.

3.

6. The method for visualizing and analyzing the formation process of the oxide layer on the surface of titanium or titanium alloy powder according to claim 1, characterized in that: In step S6, the time unit is set to min, the time step is set to range (0, 0.1, 0-1440), and the tolerance is set to physical field control.

7. The method for visualizing and analyzing the formation process of the oxide layer on the surface of titanium or titanium alloy powder according to claim 1, characterized in that: The particle size of the titanium or titanium alloy powder is 10 to 150 μm.

8. The method for visualizing and analyzing the formation process of the oxide layer on the surface of titanium or titanium alloy powder according to claim 1, characterized in that: The computational fluid dynamics software is COMSOL Multiphysics 5.6 software.

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