Method for predicting inhibition effect of doped elements on cracks of diamond / titanium connection interface based on first principle

Abstract

The invention discloses a method for predicting the inhibition effect of doped elements on cracks of a diamond / titanium connection interface based on a first principle. The method comprises the following steps: constructing a crystal model of diamond and nickel-based brazing filler metal; segmenting the crystal model, and carrying out a Z-axis atomic layer number convergence test; interface models of different positions are constructed, and a clean interface with the best bonding performance is calculated; and doping the clean interface by adopting different elements, respectively calculating charge density, differential charge density and state density data of the clean interface and the doped interface, and carrying out comparative analysis. According to the method, the interface model charge density, the differential charge density and the state density can be analyzed from the atomic scale in combination with inter-atomic bonding information, the effect prediction of the doped elements is completed within a short time, the long experimental period of guiding design from design to implementation to brazing interface characterization of traditional brazing filler metal is avoided, and the method has the advantages of being simple in structure, convenient to operate and high in practicability. The cost is saved while the research period is greatly shortened, and resource waste is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of brazing, and in particular to a method for predicting the crack suppression effect of doping elements on a diamond / titanium connection interface based on first principles. Background Art

[0002] Diamond combines numerous excellent physical and chemical properties, including high hardness, high wear resistance, low friction coefficient, high thermal conductivity, and good corrosion resistance, making it an ideal material for machining tools. Brazed diamond tools achieve a strong metallurgical bond between the diamond, brazing alloy, and substrate. This not only increases the diamond's holding strength and edge height, but also improves its self-sharpening and cutting properties. Currently, they have become the mainstream material for high-speed, high-load cutting and grinding operations.

[0003] Diamond has poor brazing properties. Its hard and brittle nature makes it difficult to use as a cutting tool on its own. It must be joined to other tougher materials, such as titanium, to produce high-performance diamond tools. Nickel-based amorphous brazing filler metal, currently the most widely used and researched material for diamond brazing, presents the following major challenges: First, nickel-based brazing filler metals contain a high concentration of the catalytic element Ni and the brazing temperature is high, which can easily cause diamond to graphitize and suffer significant thermal damage during the brazing process. Second, the high strength of nickel-based brazing filler metals and the significant difference in thermal expansion coefficient between nickel-based brazing filler metals and diamonds subject diamonds to significant thermal stress, leading to stress concentration and even microcracks after brazing, seriously affecting the performance and life of diamond tools.

[0004] During the brazing process, defects such as post-weld cracks will adversely affect the service performance of brazed diamond tools. How to quickly and efficiently predict and inhibit the generation of cracks at the diamond / titanium connection interface is one of the difficulties in the field of brazed diamond tools. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the existing technology cannot quickly and efficiently predict and suppress the generation of cracks in the diamond / titanium connection interface, and to provide a method for predicting the effect of doping elements on the crack suppression effect of the diamond / titanium connection interface based on first principles.

[0006] In order to solve the above-mentioned technical problems, the present invention adopts a technical solution: a method for predicting the crack suppression effect of doping elements on the diamond / titanium connection interface based on first principles, comprising the following steps:

[0007] Step S1, using Materials Studio software to construct crystal models of diamond and nickel-based brazing filler metals, respectively, and perform geometric optimization on the crystal models;

[0008] Step S2, using different crystal plane indices to segment the diamond model and the nickel-based solder model, and performing a Z-axis atomic layer number convergence test to obtain a stable crystal model;

[0009] Step S3, constructing interface models at different positions using two stable crystal models and performing geometric optimization on the interface models, and calculating the clean interface with the best bonding performance using the adhesion work calculation formula;

[0010] In step S4, different elements are used to dope the clean interface with the best bonding performance in step S3, and the charge density, differential charge density, and state density data of the clean interface and the doped interface are calculated respectively. The data of the clean interface and the doped interface are compared and analyzed to predict the inhibitory effect of the doping elements on the cracks in the diamond / titanium connection interface.

[0011] As a further optimization of the method for predicting the crack suppression effect of doping elements on the diamond / titanium bonding interface based on first principles of the present invention: the nickel-based solder model in step S1 is established based on the eutectic phase TiNi3 selected from the "cluster + connected atom model" theory; the geometric optimization of the crystal model in step S1 is specifically as follows: the Brillouin zone is summed using a 1×1×1 k grid point, the plane wave cutoff energy is selected as 400 eV, and the convergence standard of the system energy is 1×10 -6 eV / atom, internal stress less than 0.05GPa, displacement less than

[0012] As a further optimization of the method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles of the present invention, the convergence test in step S2 is specifically as follows: the Brillouin zone is summed using a 5×5×1 k-grid point, the plane wave cutoff energy is selected as 381 eV, and the convergence standard of the system energy is 2×10 -6 eV / atom, internal stress less than 0.1GPa, displacement less than

[0013] As a further optimization of the method of the present invention for predicting the crack suppression effect of doping elements on the diamond / titanium connection interface based on first principles: the positions of the interface model in step S3 include three positions: top position, bridge position and vacancy position.

[0014] As a further optimization of the method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles of the present invention, the geometric optimization of the interface model in step S3 is specifically as follows: the Brillouin zone is summed using a 6×6×1 k-grid point, the plane wave cutoff energy is selected as 400 eV, and the convergence standard of the system energy is 1×10 -5 eV / atom, internal stress less than 0.05GPa, displacement less than The thickness of the vacuum layer in the Z direction perpendicular to the plane is set to This avoids interlayer interactions introduced by periodicity.

[0015] As a further optimization of the method of the present invention for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles: the calculation formula of the adhesion work in step S3 is as follows:

[0016] W ad =(E A +E B -E A / B ) / A

[0017] Among them, E A and E B are the total energy of the crystal structure model of diamond surface and nickel-based brazing filler metal surface, E A / B is the clean interface model energy, and A is the cross-sectional area of ​​the interface clean interface model.

[0018] As a further optimization of the method of the present invention for predicting the crack suppression effect of doping elements on the diamond / titanium connection interface based on first principles: it also includes step S5, performing pre-brazing treatment on the diamond base material, assembling the nickel-based amorphous brazing material, setting up the brazing process and brazing, characterizing the post-weld sample, observing whether cracks appear, and assisting the comparative analysis results of step S4 with the results of the joint micromorphology analysis to predict the crack suppression effect of the doping elements on the diamond / titanium connection interface.

[0019] As a further optimization of the method of the present invention for predicting the crack inhibition effect of doping elements on the diamond / titanium connection interface based on first principles: the brazing pretreatment in step S5 is specifically: polishing with 800-1200# silicon carbide sandpaper, and cleaning and degreasing in acetone solution with an ultrasonic cleaner.

[0020] As a further optimization of the method of predicting the crack suppression effect of doping elements on the diamond / titanium connection interface based on the first principles of the present invention: the brazing in step S5 is specifically as follows: the brazing temperature is between 900℃ and 1100℃, and the vacuum degree is set to 10 -2 Pa, keep warm for 15 minutes and cool with the furnace.

[0021] As a further optimization of the method of the present invention for predicting the crack suppression effect of doping elements on the diamond / titanium connection interface based on first principles: the characterization means in step S5 include SEM, EDS and TEM.

[0022] The present invention has the following beneficial effects: the first-principles method proposed in the present invention for predicting cracks at the connection interface can be used from the atomic scale, combined with information on interatomic bonding, and analyze the charge density, differential charge density, and state density of the interface model, to complete the prediction of the effect of doping elements in a short period of time, bypassing the long experimental cycle of traditional solder from design to implementation to brazing interface characterization and then guiding design, greatly shortening the research cycle while saving costs and avoiding waste of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the crystal structure model of diamond and nickel-based brazing filler metal;

[0024] Figure 2 This is a test model for the convergence of diamond and nickel-based brazing alloys after slicing;

[0025] Figure 3 Clean interface and doped interface model for diamond / nickel-based brazing alloy;

[0026] Figure 4 The charge density diagram of the clean interface and doped interface of diamond / nickel-based brazing alloy;

[0027] Figure 5 The differential charge density diagram of the clean interface and doped interface of diamond / nickel-based brazing alloy;

[0028] Figure 6 The density of states diagram of the clean interface and doped interface of diamond / nickel-based brazing alloy;

[0029] Figure 7 This is the microstructure diagram of the diamond / titanium interface brazed without Al-containing brazing filler metal;

[0030] Figure 8 This is the microstructure diagram of the diamond / titanium interface brazed with Al-containing brazing filler metal. DETAILED DESCRIPTION

[0031] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with examples, but the content of the present invention is not limited to the following examples.

[0032] <First-principles prediction of the effect of doping elements on crack suppression at the diamond / titanium interface>

[0033] The method mainly includes the following steps:

[0034] Step S1, using Materials Studio software to construct crystal models of diamond and nickel-based brazing filler metals, respectively, and perform geometric optimization on the crystal models;

[0035] The nickel-based solder model is established based on the eutectic phase TiNi3 selected from the "cluster + connected atom model" theory.

[0036] The geometric optimization of the crystal model is as follows: the Brillouin zone is summed using a 1×1×1 k-grid point, the plane wave cutoff energy is selected as 400 eV, and the system energy convergence criterion is 1×10 -6 eV / atom, internal stress less than 0.05GPa, displacement less than

[0037] Step S2, segmenting the diamond model and the nickel-based solder model using different crystal plane indices, and performing a Z-axis atomic layer number convergence test to obtain a stable crystal model;

[0038] The convergence test is as follows: the Brillouin zone is summed using a 5×5×1 k-grid, the plane wave cutoff energy is selected as 381 eV, and the convergence standard of the system energy is 2×10 -6 eV / atom, internal stress less than 0.1GPa, displacement less than

[0039] Step S3, constructing interface models at different positions using two stable crystal models and performing geometric optimization on the interface models, and calculating the clean interface with the best bonding performance using the adhesion work calculation formula;

[0040] The positions of the interface model include top position, bridge position and empty position;

[0041] The geometric optimization of the interface model is as follows: the Brillouin zone is summed using a 6×6×1 k-grid, the plane wave cutoff energy is selected as 400 eV, and the convergence criterion of the system energy is 1×10 -5 eV / atom, internal stress less than 0.05GPa, displacement less than The thickness of the vacuum layer in the Z direction perpendicular to the plane is set to This avoids interlayer interactions introduced by periodicity.

[0042] The calculation formula of adhesion work is as follows: W ad =(E A +E B -E A / B ) / A

[0043] Among them, E A and E B are the total energy of the crystal structure model of diamond surface and nickel-based brazing filler metal surface, E A / B is the clean interface model energy, and A is the cross-sectional area of ​​the interface clean interface model.

[0044] In step S4, different elements are used to dope the clean interface with the best bonding performance in step S3, and the charge density, differential charge density, and state density data of the clean interface and the doped interface are calculated respectively. The data of the clean interface and the doped interface are compared and analyzed to predict the inhibitory effect of the doping elements on the cracks in the diamond / titanium connection interface.

[0045] In step S5, the diamond base material is pre-treated before brazing, the nickel-based amorphous brazing material is assembled, the brazing process is set up and brazing is performed, and the sample after welding is characterized (characterization methods include SEM, EDS and TEM) to observe whether cracks appear. The comparative analysis results of step S4 are assisted by the results of the joint micromorphology analysis to predict the inhibitory effect of the doping elements on the cracks at the diamond / titanium connection interface.

[0046] The brazing pre-treatment is as follows: polishing with 800-1200# silicon carbide sandpaper, and cleaning and degreasing in acetone solution with an ultrasonic cleaning machine.

[0047] The specific brazing process is as follows: the brazing temperature is between 900-1100℃, and the vacuum degree is set to 10 -2 Pa, keep warm for 15 minutes and cool with the furnace.

[0048] <Example>

[0049] Materials studio was used to perform crystal modeling, and diamond and TiNi3 crystal structure models were established (such as Figure 1 ), and the geometry was optimized. The specific optimization parameters were: summing the Brillouin zone with a 1×1×1 k-grid point, a plane wave cutoff energy of 400 eV, and a convergence criterion of 1×10 -6 eV / atom, internal stress less than 0.05GPa, displacement less than

[0050] The crystal plane index (010) was selected to split the nickel-based solder model, and the crystal plane index (111) was selected to split the diamond model. To ensure that the energy of the crystal model is in a steady state, the Z-axis atomic layer number convergence test was performed on the crystal model after the splitting process, and the results showed that 9 layers of TiNi3 atoms and 5 layers of C double-layer atoms converged (as shown in Figure 2). Figure 2 shown).

[0051] Based on the Redefine lattice, a diamond / TiNi3 clean interface model was constructed (e.g. Figure 3 a) and perform geometric optimization calculations on the clean interface model of diamond / TiNi3. The specific optimization parameters are: summing the Brillouin zone with a 6×6×1 k-grid point, a plane wave cutoff energy of 400 eV, and a convergence criterion of 1×10 -5eV / atom, internal stress less than 0.05GPa, displacement less than In addition, the thickness of the vacuum layer in the Z direction perpendicular to the plane is set to Thus, the interlayer interaction introduced by periodicity is avoided. Obtain the charge density diagram of the interface model (such as Figure 4 a) Differential charge density diagram of the interface model (e.g. Figure 5 a) Density of states diagrams of different atoms under the same functional conditions (e.g. Figure 6 a).

[0052] Since Al is not a strong carbide element, this embodiment uses Al atoms to in-situ replace the Ti atoms in the second layer of the clean interface with the highest adhesion work in the nickel-based solder (e.g. Figure 3 b), obtain the replaced doping interface, perform geometric optimization calculation on the doping interface model, and obtain the charge density diagram of the interface model (such as Figure 4 b) differential charge density diagram of the interface model (e.g. Figure 5 b) Density of states diagrams of different atoms under the same functional conditions (e.g. Figure 6 b).

[0053] Comparative analysis of the clean interface model and the doped interface model:

[0054] By comparing and analyzing the charge density diagram, Figure 4 In the analysis of the clean interface (a) and the doped interface (b), it is clearly observed that there is electron cloud overlap between the Ni atoms and the second layer of Ti atoms at the diamond (111) / TiNi3(001) interface. However, by comparing the second layer of Al atoms and the surrounding Ni atoms in the doped interface (b), it is found that the electron cloud overlap between Al and the surrounding Ni atoms is not obvious. It is concluded that the charge density is stronger and the electron cloud overlap area is larger in the clean interface. Therefore, the strength of the bond between Ni and the surrounding atoms in the doped interface is weaker than that in the clean interface.

[0055] Figure 5 In the figure, red indicates the charge accumulation area, and blue indicates the electron loss area. Comparing the second-layer Ti and Al atoms of the clean interface (a) and the doped interface (b), it is found that both are surrounded by blue, which means that both Ti and Al atoms have lost electrons. In the clean interface (a), there is a more continuous red area around the second-layer Ti atoms, indicating that Ti forms a stronger covalent bond with the surrounding atoms. In the doped interface (b), the stability and continuity of the red area around the second-layer Al atoms are significantly lower than those of Ti atoms, indicating that the covalent bond strength formed by Al atoms with the surrounding atoms is lower than that of Ti atoms.

[0056] Figure 6From the perspective of PDOS, the Ti-Ni bond between the second-layer Ti atoms and Ni atoms in the clean interface (a) comes from the hybridization of Ti-2d orbitals with Ni-2d orbitals in the range of -7eV to 7eV. The Al-Ni bond between the second-layer Al atoms and Ni atoms in the doped interface (b) comes from the hybridization of Al-2s orbitals with Ni-2s orbitals. In addition, the obvious delocalization near the Fermi level of the clean interface indicates that the surface Ti and Ni atoms have both ionic and covalent bond characteristics.

[0057] In summary, the charge accumulation characteristics near Ti atoms and Al atoms are significantly different. Ti atoms lose more charge and transfer it to Ni atoms, forming strong covalent bonds between them. Although this will improve the strength of nickel-based solder, it will destroy its good plasticity, toughness and ductility. Therefore, the concentration of Ti element in the solder should not be too high. Therefore, based on the theory of "cluster + connected atom model", replacing one Ti atom in the solder with an Al atom by a similar element is predicted to improve the plasticity, toughness and ductility of the solder. In addition, when Al atoms are doped inside the NiTi3 matrix, there is no significant effect on the charge accumulation pattern between Ti atoms and C atoms at the interface, which is the same as the bonding behavior at the clean interface. Therefore, based on the theory of "cluster + connected atom model", replacing one Ti atom in the solder with an Al atom by a similar element is predicted to improve the plasticity, toughness and ductility of the solder.

[0058] The diamond was pre-treated for brazing (polished with 800-1200# silicon carbide sandpaper and cleaned and degreased in acetone solution using an ultrasonic cleaner), the brazing material was assembled, and the brazing process was set (the brazing temperature was 1050℃ and the vacuum degree was set to 10 -2 Pa, heat preservation for 15 min and cooling with furnace), carry out brazing experiments, characterize the welded samples and observe whether there are cracks.

[0059] Among them, the composition of the solder before doping is: Ni 51.38 Ti 17.94 Zr 11.34 Cr 13.02 V 6.33 (wt.%).

[0060] Among them, the composition of the doped solder is: Ni 52.75 Ti 12.31 Zr 11.64 Cr 13.36 V 6.50 Al 3.44 (wt.%).

[0061] Figure 7 The microstructure of the diamond / titanium interface during brazing at 1050℃ before doping. Figure 8The microstructure diagram of the diamond / titanium interface brazed at 1050°C after adding one Al atom to replace one Ti atom in the brazing filler metal found that the brazing filler metal with Al atoms replacing Ti atoms climbed significantly on the diamond surface and formed a good wrapping layer without defects such as cracks and voids. The diamond surface was intact and the outline was clear. This characterization can assist the first-principles prediction of the crack inhibition effect of doping elements on the diamond / titanium connection interface.

[0062] The first-principles method proposed in this invention for predicting cracks at the connection interface can analyze the charge density, differential charge density, and state density of the interface model from the atomic scale, revealing the behavior mechanism of the diamond / titanium interface brazed with nickel-based brazing alloys. Based on the "cluster + connecting atom" theory, Ti atoms are replaced with Al atoms, which hinders the formation of Ti carbides, ultimately improving the toughness of the brazing alloy and inhibiting the occurrence of brazing cracks.

[0063] The prediction method provided by this invention has a wide range of applications, including crack prediction for brazing diamond / titanium filler metals, but is not limited to predictions for the same filler metal and parent metal. By changing the filler metal and parent metal models, adjusting the calculation parameters, or changing the doping atoms, the method can be extended to predict crack growth inhibition in various fillers within the brazing field.

[0064] The first-principles method proposed in the present invention for predicting cracks at the connection interface is used to carry out brazing experiments on nickel-based brazing filler metal designed based on the "cluster + connecting atom" theory, replacing Ti atoms in the main cluster formula TiNi3 with Al atoms. By comparing the microstructure morphology of the brazing filler metal before and after the replacement, the growth of cracks in the brazing filler metal is successfully suppressed, which is experimentally verified and improves production efficiency. The method is simple and feasible.

[0065] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for predicting the crack suppression effect of doping elements on diamond / titanium interface based on first principles, characterized by: The following steps are involved: Step S1, using Materials Studio software to construct crystal models of diamond and nickel-based brazing filler metals, respectively, and perform geometric optimization on the crystal models; Step S2, segmenting the diamond model and the nickel-based solder model using different crystal plane indices, and performing a Z-axis atomic layer number convergence test to obtain a stable crystal model; Step S3, constructing interface models at different positions using two stable crystal models and performing geometric optimization on the interface models, and calculating the clean interface with the best bonding performance using the adhesion work calculation formula; In step S4, different elements are used to dope the clean interface with the best bonding performance in step S3, and the charge density, differential charge density, and state density data of the clean interface and the doped interface are calculated respectively. The data of the clean interface and the doped interface are compared and analyzed to predict the inhibitory effect of the doping elements on the cracks in the diamond / titanium connection interface.

2. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 1, characterized in that: The nickel-based solder model in step S1 is established based on the eutectic phase TiNi3 selected from the "cluster + connected atom model" theory; the geometric optimization of the crystal model in step S1 is specifically as follows: the Brillouin zone is summed using a 1×1×1 k-grid point, the plane wave cutoff energy is selected as 400 eV, and the convergence standard of the system energy is 1×10 -6 eV / atom, internal stress less than 0.05GPa, displacement less than 3. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 1, characterized in that: The convergence test in step S2 is specifically as follows: summing the Brillouin zone using a 5×5×1 k-grid point, selecting a plane wave cutoff energy of 381 eV, and a convergence standard of 2×10 -6 eV / atom, internal stress less than 0.1GPa, displacement less than 4. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 1, characterized in that: The positions of the interface model in step S3 include three positions: top position, bridge position and empty position.

5. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 1, characterized in that: The geometric optimization of the interface model in step S3 is specifically as follows: the Brillouin zone is summed using a 6×6×1 k-grid point, the plane wave cutoff energy is selected as 400 eV, and the convergence standard of the system energy is 1×10 -5 eV / atom, internal stress less than 0.05GPa, displacement less than The thickness of the vacuum layer in the Z direction perpendicular to the plane is set to This avoids interlayer interactions introduced by periodicity.

6. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 1, characterized in that: The calculation formula of the adhesion work in step S3 is as follows: W ad =(E A +E B -HAVE BEEN A / B ) / A Among them, E A and E B are the total energy of the crystal structure model of diamond surface and nickel-based brazing filler metal surface, E A / B is the clean interface model energy, and A is the cross-sectional area of ​​the interface clean interface model.

7. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 1, characterized in that: The method also includes step S5, which includes pre-treating the diamond base material before brazing, assembling the nickel-based amorphous brazing material, setting up a brazing process and performing brazing, characterizing the sample after welding, and observing whether cracks appear. The comparative analysis results of step S4 are assisted by the results of the joint micromorphology analysis to predict the inhibitory effect of the doping elements on the cracks at the diamond / titanium connection interface.

8. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 7, characterized in that: The brazing pre-treatment in step S5 specifically includes: polishing with 800-1200# silicon carbide sandpaper, and cleaning and degreasing in acetone solution with an ultrasonic cleaning machine.

9. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 7, characterized in that: The brazing in step S5 is specifically as follows: the brazing temperature is between 900°C and 1100°C, and the vacuum degree is set to 10 -2 Pa, keep warm for 15 minutes and cool with the furnace.

10. The method for predicting the crack suppression effect of doping elements on the diamond / titanium interface based on first principles as claimed in claim 7, characterized in that: The characterization methods in step S5 include SEM, EDS and TEM.

Images