CN110751991B - Method for predicting dissolution fraction of delta phase of nickel-based alloy containing Nb under time-varying working condition - Google Patents

Abstract

The invention discloses a method for predicting a dissolution fraction of a nickel-based alloy delta phase containing Nb under a time-varying working condition. The method comprises the following steps: (1) obtaining a deformed Nb-containing nickel-based alloy sample by means of an isothermal hot compression experiment; (2) counting the residual content of the delta phase in the Nb-containing nickel-based alloy deformation sample under different deformation process parameters; (3) establishing a mathematical model for predicting the delta phase dynamic dissolution fraction of the Nb-containing nickel-based alloy in the deformation process of the strain rate; (4) and the prediction of the Nb-containing nickel-based alloy delta phase dynamic dissolution fraction under the working condition of the allergic rate is realized by a numerical difference and iterative accumulation method. The method can accurately predict the delta phase dynamic dissolution fraction of the Nb-containing nickel-based alloy in thermal deformation under the working condition of the strain rate, and provides a technical support for reasonably formulating the thermal processing process of the Nb-containing nickel-based alloy.

Description

A method for predicting the dissolution fraction of delta phase in Nb-containing nickel-based alloys under time-varying conditions

technical field

The invention belongs to the technical field of forging, and relates to a method for predicting the dissolution fraction of Nb-containing nickel-base alloy delta phase under time-varying working conditions.

Background technique

Nb-containing nickel-based alloys have excellent high-temperature mechanical properties, fatigue resistance and corrosion resistance, and are widely used in aerospace, transportation, and nuclear industries. During hot deformation, the evolution of the microstructure of Nb-containing nickel-based alloys is significantly affected by the deformation history and process parameters, which in turn have a great impact on the properties of Nb-containing nickel-based alloys structural parts. The δ phase is a typical precipitation phase in Nb-containing nickel-based alloys, and the lattice relationship with the matrix is semi-coherent or incoherent; in the hot deformation of Nb-containing nickel-based alloys, the δ phase can significantly stimulate dynamic recrystallization nucleation and nucleation. The growth of grains is inhibited and the effect of grain refinement is achieved. Properly retaining a part of the δ phase in the Nb-containing nickel-based alloy structural parts is beneficial to increase the path of crack propagation and consume deformation energy, inhibit the propagation of cracks, and promote the improvement of creep performance. However, excessive δ phase will cause local stress concentration in the Nb-containing nickel-based alloy during hot deformation, resulting in the reduction of the performance of the Nb-containing nickel-based alloy components. Therefore, it is of great significance to quantitatively predict the dynamic dissolution behavior of δ phase during hot deformation of Nb-containing nickel-based alloys.

At present, the related research on the dissolution behavior of δ phase in Nb-containing nickel-based alloys mainly focuses on two aspects: static dissolution behavior without external force and dynamic dissolution behavior under constant strain rate thermal deformation. The static dissolution process of the delta phase mainly includes the decomposition and diffusion process of the delta phase, which is affected by the holding temperature and time. During thermal deformation, dislocations are packed around the δ phase to form a high-density dislocation network/cell, resulting in uneven local stress distribution on the surface of the δ phase, and then bending and torsion fractures. At the same time, dislocations can become niobium Fast diffusion channels, intensifying the rapid dissolution of the delta phase. The existing dynamic dissolution kinetics of δ phase in hot deformation Nb-containing nickel-based alloys can only predict the dynamic dissolution law of hot deformation δ phase under constant strain rate conditions, and it is difficult to predict Nb-containing nickel-base alloys under non-constant strain rate conditions. Dynamic dissolution kinetics of the medium delta phase. Therefore, the present invention fully considers the influence of deformation history and deformation process parameters on the dynamic dissolved volume fraction of δ phase in the thermal deformation of variable strain rate, and proposes a method to predict the dynamic dissolved volume of δ phase in Nb-containing nickel-based alloys with variable strain rate thermal deformation. method of scoring. The invention, popularization and application of the method can effectively predict and control the residual content of delta phase in the Nb-containing nickel-based alloy, and provide technical support for the formulation of the Nb-containing nickel-based alloy die forging process.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for predicting the dissolution fraction of Nb-containing nickel-based alloy δ phase under time-varying working conditions, which solves the problem that the existing prediction method has a narrow application range and is difficult to meet the needs of engineering applications, and provides a reasonable solution for formulating Nb-containing nickel-based alloys. The base alloy hot working process provides technical support.

The concrete steps of the present invention are:

Step 1: Obtain the true stress-true strain curves of Nb-containing nickel-based alloys under different deformation process parameters by means of high-temperature compression deformation experiments, and retain the microstructure after thermal deformation by water quenching;

Step 2: observe and analyze the microstructure of the Nb-containing nickel-based alloy after high temperature deformation, and count the remaining content of δ phase in the Nb-containing nickel-based alloy under different deformation conditions;

Step 3: Establish a model that can predict the dynamic dissolution kinetics of δ phase in Nb-containing nickel-based alloys during high-temperature deformation at variable strain rates as follows:

In the formula: X _{δ, N} is the dissolved volume fraction of δ phase in Nb-containing nickel-based alloy after deformation, X _δ is the dissolved volume fraction of δ phase in Nb-containing nickel-based alloy during deformation, ε is true strain, ε _i and ε _i-1 are the corresponding true strains at the end of the i-th and i-1 deformation stages, respectively, k _δ , _{m δ} , n _k , nm , Q _δ and Q' _δ are material parameters, R is the universal gas constant ( 8.314J·mol ^-1 ·K ^-1 );

Step 4: Predict the dynamic dissolved volume fraction of delta phase during high temperature deformation of Nb-containing nickel-based alloys at variable strain rates.

Description of drawings

Fig.1 Metallographic diagram of initial microstructure of GH4169 alloy sample;

Figure 2. High temperature rheological curve of GH4169 alloy under typical variable strain rate conditions;

ε_I＝0.36；(b)T＝980℃,

ε_I＝0.36；Fig. 3 Metallographic diagram of the remaining δ phase of GH4169 alloy after high temperature deformation under typical variable strain rate conditions: (a) T=980℃,

ε _I = 0.36; (b) T = 980°C,

_εI = 0.36;

Fig. 4 Dynamically dissolved volume fraction of δ phase of GH4169 alloy during high temperature deformation with variable strain rate;

Fig. 5 The comparison between the predicted and experimental results of the dynamic dissolved volume fraction of δ phase of GH4169 alloy after high temperature deformation under the condition of variable strain rate;

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific implementation cases.

The present invention is a method for predicting the dissolution fraction of delta phase of Nb-containing nickel-based alloys under time-varying conditions. The following is an example of predicting the dynamic dissolution fraction of δ phase in the thermal deformation of a typical Nb-containing nickel-based alloy (GH4169 alloy) at variable strain rates, and the specific implementation details involved in the present invention are described in detail, and the method includes:

Step 1: Perform high temperature compression experiments with variable strain rates on the GH4169 alloy to obtain the true stress-true strain curves of the specimens under different deformation process parameters, and retain the microstructure after thermal deformation by water quenching. The specific parameters of the high temperature compression experiment are: the deformation temperature is 900-1050°C, the strain rate is 0.0001s ^-1 -50s ^-1 , and the deformation degree is 30%-70%.

Step 2: Observe and analyze the metallographic pictures of the remaining δ phase in the GH4169 alloy under different deformation conditions through a metallographic microscope. The GH4169 alloy sample after high temperature compression in step 1 was cut from the center along the compression direction, and the section was polished, polished and etched, rinsed and dried, and then obtained under different deformation process parameters by metallographic microscope. Distribution law of remaining delta phase in GH4169 alloy.

Step 3: Calculate the volume fraction (V _D ) of the remaining δ phase in the GH4169 alloy under different deformation process parameters by using the Image-Pro Plus software, and then obtain the dynamic dissolved volume fraction of the δ phase in the GH4169 alloy under the corresponding deformation conditions:

where V ₀ and V _D are the volume fraction of δ phase before and after hot deformation of GH4169 alloy, respectively.

The typical dynamic dissolution volume fraction of δ phase of GH4169 alloy during high temperature deformation with variable strain rate is shown in Fig. 4.

Step 4: Establish a mathematical model for predicting the dynamic dissolution volume fraction of δ phase in the high temperature deformation process of GH4169 alloy with variable strain rate; The values of the material parameters (k _δ , _{m δ} , n _k , nm , Q _δ and Q' _δ ) in the prediction model were fitted by regression methods. Finally, the kinetic equation of dynamic dissolution of δ phase during high temperature deformation of Nb-containing nickel-based alloys at variable strain rates is:

Step 5: Predict the dynamic dissolved volume fraction of delta phase during high temperature deformation at variable strain rate of GH4169 alloy.

In order to verify the established prediction model of the dynamic dissolved volume fraction of δ phase during high temperature deformation with variable strain rate of GH4169 alloy, the comparison between the experimental and predicted values of the dynamic dissolved volume fraction of δ phase was carried out, as shown in Figure 5. The results show that the experimental value and the predicted value of the mathematical model of the dynamic dissolved volume fraction of δ phase in the process of high temperature deformation with variable strain rate established according to the method provided by the present invention are in good agreement. It is shown that the method of the present invention can accurately predict the dynamic dissolution volume fraction of δ phase in the high temperature deformation process of Nb-containing nickel-based alloys at variable strain rates, so as to effectively control the residual content of δ-phase in niobium-containing Nb-containing nickel-based alloys and the mold of Nb-containing nickel-based alloys. Technical support was provided for the formulation of the forging process.

The examples of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific embodiments, the above-mentioned specific embodiments are only exemplary, not limiting, any inventions that do not exceed the claims of the present invention, All are within the protection of the present invention.

Claims (1)

1. a method for predicting the dissolution fraction of Nb-containing nickel-base alloy δ phase under time-varying working conditions, characterized in that: the method fully considers the influence of process parameters on the dynamic dissolution behavior of δ-phase in the Nb-containing nickel-base alloy during deformation , a mathematical model for predicting the dissolved volume fraction of δ phase of Nb-containing nickel-based alloys in hot deformation under variable strain rate conditions is established, which includes the following steps: Step 1: Under the conditions that the deformation temperature is 900°C to 1050°C and the strain rate of each deformation stage is 0.0001s ^-1 to 50s ^-1 , the isothermal hot compression experiment of the Nb-containing nickel-based alloy is carried out, and the high temperature of the Nb-containing nickel-based alloy is obtained. Rheological curves and deformed samples; Step 2: Experiment to observe the microstructure of the deformed sample under different process parameters, count the remaining content of δ phase in the Nb-containing nickel-based alloy under different process parameters, and then obtain the dissolved volume fraction of δ phase; Step 3: Establish a mathematical model for predicting the dissolved volume fraction of δ phase of Nb-containing nickel-based alloys under the condition of variable strain rate. The model is:

In formula (1): X _{δ, N} is the dissolved volume fraction of δ phase in the Nb-containing nickel-based alloy after deformation, X _δ is the dissolved volume fraction of δ phase in the Nb-containing nickel-based alloy during deformation, and ε is the true strain , ε _i and ε _i-1 are the corresponding true strains at the end of the i-th and i-1 deformation stages, respectively, k _δ , _{m δ} , n _k , nm , Q _δ and Q _δ ' are material parameters, R is the general gas constant; Step 4: Substitute the experimental data measured in step 2 into the model formula (1) established in step 3, and use regression processing to determine the k _δ , _{m δ} , n _k , nm , Q _δ and Q _δ ' materials in the model parameters; based on the numerical difference method, the iterative accumulation algorithm program is written and embedded in the simulation software to realize the update of the deformation process parameters and material parameters at any iterative step, and then predict the δ phase in the Nb-containing nickel-based alloys in the thermal deformation under the condition of variable strain rate. The dissolved volume fraction.

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