Simulation method for improving plasticity of amorphous alloy under compression

Abstract

The application discloses a simulation method for improving plasticity of amorphous alloy under compression, which comprises the following steps: constructing an initial model of amorphous CoMn alloy; cooling to 300K at cooling rates of 10 10 , 10 11 , 10 12 and 10 13 K / s respectively under zero pressure to obtain four amorphous models; periodically replicating and extending the four amorphous models along the X axis by four times to obtain four compression models; setting the compression models as periodic boundary conditions in the X and Y directions and as free boundary in the Z direction; uniaxially compressing the four compression models along the X direction at a strain rate of 1x10 8 s ‑1 to obtain thermodynamic information; and analyzing the influence of nanocluster structure evolution formed by atomic condensation on the mechanical properties of the amorphous alloy. The application solves technical problems that atomic scale microstructure deformation process in a deformation process of MGs is difficult to obtain in experiments, simulates a formation process of a shear band of amorphous material and a microstructure mechanism and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, and in particular relates to a simulation method for improving the plasticity of amorphous alloys under compression conditions. Background Technology

[0002] As a novel alloy material, metallic glasses (MGs) have attracted considerable interest from scholars due to their excellent physical and chemical properties and enormous potential applications. However, most MGs, under compressive loading, tend to form shear transition zones (STZs) during deformation, which rapidly propagate throughout the system, generating shear bands. This results in poor plasticity, limiting their applicability as engineering materials. Because of their complex amorphous structure and lack of long-range order, it is difficult to understand the causes of their plastic deformation at the atomic scale. Therefore, it is necessary to conduct in-depth research on the relationship between the structural characteristics and mechanical properties of MGs.

[0003] Generally, atomic packing density is closely related to the plasticity of amorphous metals (MGs). Various short-range ordered (SRO) atomic clusters within the system generate free volumes during shear deformation. However, these free volumes are difficult to annihilate during compression, resulting in an increasing amount of free volume remaining in the amorphous system. Higher free volume content leads to stronger atomic diffusion. Regions where irreversible rearrangement of atomic configurations occurs are called shear transition zones (STZs). These regions consist of various clusters that are prone to deformation under external loads. Once STZs increase and merge, shear bands are formed, which are preferred locations for plastic flow. Typically, a single shear band can cause brittle fracture in MGs, leading to their failure.

[0004] Because it is difficult to obtain the atomic-scale microstructural deformation process of MGs deformation process in experiments, it is impossible to simulate the formation process and microstructural mechanism of shear bands in amorphous materials. Summary of the Invention:

[0005] The technical problem to be solved by this invention is to provide a simulation method for improving the plasticity of amorphous alloys under compression conditions, so as to solve the technical problem that existing experiments are difficult to obtain the atomic-scale microstructure deformation process of MGs deformation process, and therefore cannot simulate the formation process and microstructure mechanism of shear bands in amorphous materials.

[0006] Technical solution of the present invention:

[0007] A simulation method for improving the plasticity of amorphous alloys under compression conditions, the method comprising:

[0008] Step 1: Construct an initial model of the amorphous CoMn alloy, and then, under zero pressure, apply 10... 10 10 1110 12 and 10 13 Four amorphous models were obtained by cooling to 300K at a cooling rate of K / s.

[0009] Step 2: Periodically replicate and expand the four amorphous models along the X-axis by a factor of 4 to obtain four models with initial dimensions of [missing information]. The compression model;

[0010] Step 3: Set the compression model to periodic boundary conditions in the X and Y directions, and set it to a free boundary in the Z direction;

[0011] Step 4: Compress the four models along the X direction by 1×10 8 s -1 Thermodynamic information is obtained by uniaxial compression at the strain rate;

[0012] Step 5: Analyze the influence of the evolution of nanocluster structures formed by the condensation of atoms on the mechanical properties of amorphous alloys.

[0013] When constructing the initial model of the amorphous CoMn alloy, the interatomic interactions were performed using the optimized embedded atom potential (MEAM), and the initial model size was [size missing]. Contains 10,000 atoms; system runtime step count set to 10. -15 The initial temperature was set to 1800K, and the system was isothermally relaxed for 0.5 ns to reach equilibrium under the NPT ensemble.

[0014] In the MEAM potential, the total energy of the atoms in the system is calculated as follows:

[0015]

[0016] In the formula: F is the embedding energy, which is a function of the atomic electron density ρ; This represents a potential interaction; the content ratio of each type of atom in the CoMn alloy is 1:1, and the atoms of each type are randomly distributed in space.

[0017] Each compression model contains 40,000 atoms.

[0018] Before compression in step 4, isothermal relaxation for 500 ps is used to eliminate instabilities caused by boundary effects and internal atomic stresses, so that the compression model reaches a stable state.

[0019] During uniaxial compression, the compression process is controlled by the NVT ensemble; thermodynamic information is recorded at 1ps intervals, including the velocity, coordinates and potential energy of each atom, which is used to measure the microstructure under different uniaxial loads.

[0020] The beneficial effects of this invention are:

[0021] This invention proposes a simulation method to improve the plasticity of amorphous alloys. This simulation method can understand the deformation mechanism of amorphous alloys under compression conditions from the atomic-scale microstructure. Furthermore, this simulation method reveals the effect of different cooling rates on the plasticity of amorphous alloys, simulates the formation process of shear bands and changes in the microstructure of amorphous materials, and provides theoretical guidance for experiments.

[0022] This invention can accurately utilize molecular dynamics simulation methods to obtain the relationship between different cooling rates and plasticity. It can effectively simulate the plasticity enhancement of amorphous materials under uniaxial compression, thereby simulating the formation process and microstructure mechanism of shear bands in amorphous materials. This helps to establish a structure-property relationship based on nanoclusters, which has great theoretical guiding significance for improving the mechanical properties of amorphous alloys and shortening the research and development cycle.

[0023] This invention solves the technical problem of obtaining the atomic-scale microstructure deformation process of MGs deformation process in existing experimental techniques, and simulates the formation process and microstructure mechanism of shear bands in amorphous materials. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the present invention;

[0025] Figure 2 These are amorphous compression models with different cooling rates in the embodiments of the present invention;

[0026] Figure 3 These are stress-strain curves of amorphous compression models with different cooling rates in embodiments of the present invention;

[0027] Figure 4 These are atomic shear strain diagrams of amorphous compression models with different cooling rates in embodiments of the present invention;

[0028] Figure 5 These are the molar volume and average atomic packing density of the compression model in this embodiment of the invention;

[0029] The markings in the attached diagram indicate the stress change Δσ = σ. y -σ f The larger the stress change Δσ, the worse the plasticity of the material.

[0030] Figure 4 (a) is a schematic diagram of the cooling rate of R1; (b) is a schematic diagram of the cooling rate of R2; (c) is a schematic diagram of the cooling rate of R3; and (d) is a schematic diagram of the cooling rate of R4. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0032] Example. A simulation method for improving the plasticity of amorphous alloys under compression conditions, such as... Figure 1 As shown, it includes the following steps:

[0033] ① An initial model of the amorphous CoMn alloy was constructed, using optimized interatomic embedding potentials (MEAM) for interatomic interactions. The initial model size was [size missing]. It contains 10,000 atoms. The system runtime step count is set to 10. -15 The initial temperature was set to 1800 K, and the system was isothermally relaxed for 0.5 ns to reach equilibrium under the NPT (total atomic number N, total pressure P, and temperature T remain constant) ensemble. Then, at zero pressure, which was chosen to eliminate the influence of pressure on the simulation results during rapid solidification; R1, R2, R3, and R4 (10 10 10 11 10 12 and 10 13 Four amorphous models were obtained by cooling the samples at a rate of K / s to 300K.

[0034] ② The four amorphous models obtained in step ① are periodically replicated and expanded by 4 times along the X-axis. Since the initial model has the longest length on the X-axis, compression is performed along the X-axis to better simulate the state of the material under compression.

[0035] Obtain 4 initial sizes The compression model contains 40,000 atoms in each compression model. Since amorphous materials are disordered structures, large systems can be obtained through periodic replication. This method can quickly explore the influence of shape, volume, and porosity on the mechanical properties of amorphous materials, providing theoretical guidance for the preparation of bulk amorphous materials.

[0036] ③ Based on the compression model obtained in step ②, the X and Y directions are set as periodic boundary conditions, and the Z direction is set as a free boundary. In order to eliminate the boundary effects caused by periodic replication, isothermal relaxation for 500 ps is performed before compression to eliminate the instabilities and internal atomic stresses caused by these boundary effects, and the compression model reaches a stable state.

[0037] ④. Compress the four models along the X direction at a speed of 1×10⁻⁶. 8 s -1 Uniaxial compression was performed at a constant strain rate, with the compression process controlled by an NVT (total number of atoms N, total volume V, and temperature T kept constant), which facilitates the observation of shear band formation. Thermodynamic information was acquired at 1 ps intervals, including the velocity, coordinates, and potential energy of each atom, to measure the microstructure under different uniaxial loads. The resulting compression effect is shown in the figure. Figure 3 As shown, the stress change Δσ = σ y -σf The larger the stress change Δσ, the worse the plasticity of the material. The peak stress σ y It can reflect the yield strength of a material.

[0038] ⑤ The influence of the evolution of nanocluster structures formed by the condensation of atoms on the mechanical properties of amorphous alloys is analyzed using the maximum standard cluster analysis method (LaSCA). This method is objective, effective, unique and complete.

[0039] Analysis of the two main clusters, icosahedrons and defective icosahedrons, revealed that increased content of these two types of clusters hinders the plastic flow of amorphous materials. This indicates that the resistance to the initiation of plastic flow is high in systems with low cooling rates, making it easier for shear transition zones to concentrate and form shear bands, resulting in poor plasticity. Large nanoclusters composed of these two types of clusters are disrupted during compression, causing stress localization and concentration. This reduces the resistance to the initiation of plastic flow in the system, making it less prone to shear transition zone concentration and shear band formation, thus improving the plasticity of the amorphous material. Furthermore, with increasing cooling rate, the molar volume and atomic average packing density of the amorphous system increase, while the yield strength decreases. The plasticity of the alloy improves, and the deformation mode gradually changes from localized deformation to non-localized deformation.

[0040] The atomic interactions in the aforementioned steps employ an optimized embedded atom potential (MEAM). Molecular dynamics simulations are based on this potential function, which accurately describes the interactions occurring between atoms—a crucial condition. The total energy serves to further clarify the potential function. This atomic potential accurately reflects the interactions between atoms. In the MEAM potential, the total energy of the atoms within the system is calculated as follows:

[0041]

[0042] Where F is the embedding energy, which is a function of the atomic electron density ρ; This represents a potential interaction. A potential interaction is the sum of the interactions between atom i and all its nearest neighbor atom j within the cutoff distance. Furthermore, in the above steps, the content ratio of each type of atom in the CoMn alloy is 1:1, and the atoms of each type are randomly distributed in space.

[0043] All the above calculation results are based on the LAMMPS software, and the data analysis was performed using software compiled from Origin and Python.

Claims

1. A simulation method for improving the plasticity of amorphous alloys under compression conditions, characterized in that: The method includes: Step 1: Construct an initial model of the amorphous CoMn alloy, and then, under zero pressure, apply 10... 10 10 11 10 12 and 10 13 Four amorphous models were obtained by cooling to 300 K at a cooling rate of K / s. Step 2: Periodically replicate and expand the four amorphous models along the X-axis by 4 times to obtain four compressed models with an initial size of 230.4 Å (X) × 57.56 Å (Y) × 57.56 Å (Z); Step 3: Set the compression model to periodic boundary conditions in the X and Y directions, and set it to a free boundary in the Z direction; Step 4: Compress the four models along the X direction by 1×10 8 s -1 Thermodynamic information is obtained by uniaxial compression at the strain rate; During uniaxial compression, the compression process is controlled by the NVT ensemble; thermodynamic information is recorded at 1ps intervals, including the velocity, coordinates and potential energy of each atom, which is used to measure the microstructure under different uniaxial loads. Step 5: Use the LaSCA (Latest Standard Cluster Analysis) method to analyze the effect of the evolution of nanocluster structures formed by the condensation of atoms on the mechanical properties of amorphous alloys.

2. The simulation method for improving the plasticity of amorphous alloys under compression conditions according to claim 1, characterized in that: When constructing the initial model of the amorphous CoMn alloy, the interatomic interactions were performed using the optimized embedded atom potential (MEAM). The initial model size was 57.56 Å(X) × 57.56 Å(Y) × 57.56 Å(Z), containing 10,000 atoms; the system runtime step was set to 10. −15 The initial temperature was set to 1800K, and the system was isothermally relaxed for 0.5 ns to reach equilibrium under the NPT ensemble.

3. The simulation method for improving the plasticity of amorphous alloys under compression conditions according to claim 2, characterized in that: In the MEAM potential, the total energy of the atoms in the system is calculated as follows: ； In the formula: F is the embedding energy, which is a function of the atomic electron density ρ; ø represents a pair potential interaction; the content ratio of each type of atom in the CoMn alloy is 1:1, and the atoms of each type are randomly distributed in space.

4. The simulation method for improving the plasticity of amorphous alloys under compression conditions according to claim 1, characterized in that: Each compression model contains 40,000 atoms.

5. The simulation method for improving the plasticity of amorphous alloys under compression conditions according to claim 1, characterized in that: Before compression in step 4, isothermal relaxation for 500 ps is used to eliminate instabilities caused by boundary effects and internal atomic stresses, so that the compression model reaches a stable state.

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