An electrostatic suspension step-triggered solidification method for regulating alloy phase selection

Abstract

The present invention relates to an electrostatic suspension step-triggered solidification method for regulating alloy phase selection, so as to realize active phase selection of solidification of residual liquid phase of alloy. The method first obtains the necessary density and specific heat data of the alloy; then derives the heat balance equation of liquid alloy under electrostatic suspension state, and solves the required heating power; at the first-order target temperature of step-triggered solidification, the primary phase of the alloy is solidified at the required temperature through an electrostatic suspension trigger device; then, the heat balance equation of solid-liquid coexistence alloy under electrostatic suspension state is derived, and the required heating power is solved; the second-order target temperature of step-triggered solidification is regulated, and the residual liquid phase in the alloy is solidified into the required phase composition through the trigger device. The electrostatic suspension step-triggered solidification method provided by the present invention can independently regulate the solidification supercooling of the primary phase and the residual liquid phase, thereby controlling the phase composition of the alloy.

Description

Technical Field

[0001] The invention belongs to the technical field of electrostatic suspension, and relates to an electrostatic suspension step-triggered solidification method for regulating alloy phase selection. Background Art

[0002] The performance of materials is largely affected by their phase composition, and traditional solidification methods cannot actively regulate the phase selection behavior of alloys. Electrostatic levitation technology is a new material research method that can achieve deep supercooling solidification of alloys, thereby affecting the phase selection behavior of alloys during solidification. Therefore, achieving phase selection control of alloys through electrostatic levitation technology has become the focus of high-performance alloy development.

[0003] The team disclosed a method for preparing single crystal alloys using electrostatic suspension technology in the patent "Northwestern Polytechnical University. Growth method of high-temperature and refractory alloy spherical single crystals under electrostatic suspension conditions: CN201911388068.0[P].2021-09-17.", which achieved deep supercooling solidification of the alloy. However, this method cannot solidify the alloy at a specific supercooling degree, and the phase selection behavior depends on the randomness in the deep supercooling solidification, and it is impossible to actively control the phase composition of the resulting solidification structure.

[0004] In response to the problem that the electrostatic suspension device cannot solidify the alloy at a specific supercooling degree, our team has developed an electrostatic suspension triggered solidification method, as described in the document "MXLi, HPWang, MJLin, CHZheng, B.Wei, Rapid Eutectic Growth Kinetics of Undercooled Nb-Si Alloys at Electrostatic LevitationState, Acta Mater., 237 (2022) 118157.". The electrostatic suspension triggered solidification method can solidify the liquid alloy at a specific supercooling degree. However, the electrostatic suspension triggered solidification method described in the document can only control the temperature of primary phase generation, and cannot independently regulate the temperature of the remaining liquid phase generation. It is impossible to actively control the phase composition of the primary interphase solidification structure in the alloy.

[0005] Traditional solidification technology cannot control the phase composition of the alloy during solidification, and the existing electrostatic suspension triggered solidification method can only control the phase composition of the primary phase. Up to now, there is no method to control the solidification temperature of the residual liquid phase, and it is impossible to actively control the phase composition of the solidification structure between the primary phases. Summary of the invention

[0006] Technical issues to be solved

[0007] In order to avoid the shortcomings of the prior art, the present invention proposes an electrostatic suspension step-triggered solidification method for regulating alloy phase selection, which overcomes the problem that the existing electrostatic suspension triggered solidification method can only regulate the primary phase, thereby actively controlling the phase composition of the solidification structure between the primary phases.

[0008] The present invention provides an electrostatic suspension step-triggered solidification method. The method first obtains the necessary density and specific heat data of the alloy; then derives the heat balance equation of the liquid alloy in the electrostatic suspension state to solve the required heating power; applies the obtained heating power to stabilize the liquid alloy at the first-order target temperature of the step-triggered solidification; through the electrostatic suspension trigger device, the primary phase of the alloy solidifies at the required temperature; then derives the heat balance equation of the solid-liquid coexistence state alloy in the electrostatic suspension state to solve the required heating power; applies the obtained heating power to stabilize the solid-liquid coexistence state alloy at the second-order target temperature of the step-triggered solidification; regulates the second-order target temperature of the step-triggered solidification, and uses the trigger device to solidify the remaining liquid in the alloy into the required phase composition.

[0009] Technical Solution

[0010] An electrostatic suspension step-triggered solidification method for regulating alloy phase selection, characterized by the following steps:

[0011] Step 1: Determine the density and specific heat related data of the prepared alloy, including the liquid density ρ of the alloy L , solid density ρ S , in kilograms per cubic meter; the solid density of the alloy corresponding to the primary phase is determined as ρ S,Primary , the liquid density of the alloy corresponding to the remaining liquid phase is ρ L,Residual , the unit is kilograms per cubic meter;

[0012] Determine the liquid specific heat c of the alloy P,L The unit is joule per Kelvin per mole, hereinafter referred to as joule per Kelvin per mole; the solid-state specific heat of the alloy corresponding to the primary phase is determined as c P,S,Primary The liquid specific heat of the alloy corresponding to the remaining liquid phase is c P,L,Residual , the unit is joule per joule per molar;

[0013] Step 2: Suspension melting of alloy:

[0014] A spherical alloy with a mass of m kg is placed in an electrostatic suspension device, the alloy is suspended and heated to melt above the liquidus to a completely liquid state, and the temperature T start Controlled above the liquidus, the unit is Kelvin, referred to as K;

[0015] Step 3: Adjust the heating power to cool the liquid alloy to the first-order target temperature T at a constant rate. 1n :

[0016] Adjust the electrostatic suspension heating power q1 to:

[0017]

[0018] Where m, M, c P,L, , ε, ρ L T and a are the mass, relative atomic mass, specific heat at constant pressure, emissivity, density, and temperature absorption efficiency of the liquid alloy. e, ,π,σ are respectively the ambient temperature, pi, and Stefan-Boltzmann constant; T1, t1, dT1 / dt1 are respectively the temperature, time, and temperature rate;

[0019] The sample is heated from temperature T start Cool down to temperature T at a rate of dT1 / dt1 1n ;

[0020] Step 4: Adjust the heating power to stabilize the liquid alloy at the first-order target temperature and implement first-order triggered solidification:

[0021] Adjust the electrostatic suspension heating power q2 to:

[0022]

[0023] Where: T 1n 、T e, ,π,σ are the first-order target temperature and ambient temperature respectively;

[0024] The sample is stabilized at the first-order target temperature T 1n , operate the trigger device, and the primary phase of the alloy solidifies;

[0025] Step 5: Adjust the heating power to cool the solid-liquid coexisting alloy to the second-order target temperature at a constant rate:

[0026] Adjust the electrostatic suspension heating power q3 to:

[0027]

[0028] Where: T3, t3, dT3 / dt3 are the temperature, time, and temperature rate of this stage respectively; f Primary 、M Primary 、c P,S,Primary , S,Primary are the volume fraction, relative atomic mass, specific heat, and density of the primary phase; ρ L,Residual 、M L,Residual 、c P,L,Redidual are the density, relative atomic mass and specific heat of the remaining liquid phase; V Total , ε Total 、m Total , Totalare the total volume, overall emissivity, mass, and overall average density of the alloy respectively;

[0029] The sample is heated from temperature T 1n Cool down to the second-order target temperature T at a rate of dT3 / dt3 2n ;

[0030] Step 6: Adjust the heating power to stabilize the solid-liquid coexisting alloy at the second-order target temperature and implement second-order triggered solidification:

[0031] Adjust the electrostatic suspension heating power q4 to:

[0032]

[0033] Where: T 2n is the second-order target temperature; ε Total 、m Total , Total are the overall emissivity, mass, and overall average density of the alloy, respectively;

[0034] The sample is stabilized at the second-order target temperature T 2n , operate the trigger device, and the remaining liquid phase of the alloy solidifies. After solidification occurs, the heating laser is immediately turned off to allow the alloy to cool naturally.

[0035] In the step 1, if the density and specific heat data of the alloy are not given in the literature, refer to the method disclosed in “CH Zheng, PF Zou, L. Hu, HP Wang, B. Wei, Composition dependence of thermophysical properties for liquid Zr-V alloys determined at electrostatic levitation state, J. Appl. Phys., 131 (2022) 165104.” for determination.

[0036] The electrostatic suspension device refers to the document “PF Zou, HP Wang, SJ Yang, L. Hu, B. Wei, Density Measurement and Atomic Structure Simulation of Metastable Liquid Ti-Ni Alloys, Metall. Mater. Trans. A, 49A (2018) 5488-5496.”.

[0037] The q1, q2, q3 and q4 in step 3, step 4, step 5 and step 6 are all electrostatic suspension heating powers q at different stages. The calculation with q1 is based on the relationship between heating power q1 and time q1=q1(t): The electrostatically suspended liquid alloy satisfies the thermal balance equation:

[0038]

[0039] Where m is the mass in kilograms; M is the relative atomic mass of the liquid alloy in kilograms per mole; c P,L is the specific heat of the liquid alloy at constant pressure, in joules per kelvin per mole; T is the temperature, in kelvins; t is the time, in seconds; ε is the emissivity of the liquid alloy; σ is the Stefan-Boltzmann constant, which is 5.67×10 -8 Watt per square meter per fourth power of Kelvin; T e is the ambient temperature, in Kelvin; A is the surface area of ​​the liquid alloy, in square meters; Q is the absorbed power, in watts; the absorbed power and heating power q1 satisfy:

[0040] aq1=Q

[0041] Where a is the absorption efficiency. After rearranging the heat balance equation, we can get the absorption power Q in watts:

[0042]

[0043] Among them: π is pi, ρ is L is the liquid density of the alloy, in kilograms per cubic meter;

[0044] The initial temperature is T start , the unit is K; the first-order target temperature is T 1n , the unit is Kelvin; take the temperature coefficient dT / dt as the constant R, the unit is Kelvin per second; record the cooling time as t cool , the unit is second; liquid density ρ L , liquid specific heat c P,L ; Mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, ambient temperature T e Substituting into the above formula, we get the relationship between the absorbed power Q and time, in watts

[0045] Q=Q(t)

[0046] Substituting the above equation into aq1=Q, we can obtain the relationship between heating power q1 and time, in watts.

[0047] Beneficial Effects

[0048] The present invention proposes an electrostatic suspension step-triggered solidification method for regulating alloy phase selection, which realizes active phase selection of the solidification of the residual liquid phase of the alloy. This method first obtains the necessary density and specific heat data of the alloy; then derives the heat balance equation of the liquid alloy under the electrostatic suspension state, and solves the required heating power; at the first-order target temperature of the step-triggered solidification, the primary phase of the alloy is solidified at the required temperature through the electrostatic suspension trigger device; then the heat balance equation of the solid-liquid coexistence alloy under the electrostatic suspension state is derived to solve the required heating power; regulates the second-order target temperature of the step-triggered solidification, and solidifies the residual liquid phase in the alloy into the required phase composition through the trigger device. The electrostatic suspension step-triggered solidification method provided by the present invention can independently regulate the solidification supercooling of the primary phase and the residual liquid phase, thereby controlling the phase composition of the alloy.

[0049] The present invention obtains a heating strategy for effectively controlling the temperature of the sample in the electrostatic suspension state by establishing a heat balance equation for the electrostatic suspension sample; innovatively proposes an electrostatic suspension step-triggered solidification method; due to the use of the step-triggered solidification method proposed by the present invention and the temperature control strategy described in the present invention, the supercooled solidification of the primary phase and the residual liquid phase is achieved, the solidification structure and phase composition of the alloy are changed, the formation of the metastable phase can be avoided, and the stable phase can be obtained without heat treatment. For niobium-silicon hypoeutectic alloys, the traditional method can only solidify to generate a brittle and unstable solidification structure, and even through an electrostatic suspension device, a stable silicide phase cannot be directly solidified. However, by adopting the step-triggered solidification method proposed by the present invention, a stable eutectic structure can be directly solidified from the liquid niobium-silicon alloy. It has the advantages of simple raw material ratio, no need to add alloying elements, no expensive refractory or rare earth alloying elements, no need for subsequent heat treatment process, short process flow, low energy consumption, and short preparation time, which provides a possibility for improving the development and production efficiency of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The figure is a typical temperature curve during the electrostatic suspension step solidification process of the niobium silicon alloy obtained according to the method of the present invention. The method of the present invention effectively controls the primary phase to solidify at the first-order target temperature and the remaining liquid phase to solidify at the second-order target temperature.

[0051] Figure 2 It is the microstructure of traditional solidified niobium silicon alloy, in which the primary phase is a rod-shaped eutectic composed of gray Nb3Si phase and white (Nb) phase.

[0052] Figure 3 This is the microstructure of the niobium silicon alloy prepared in Example 1, in which the primary interphase structure is completely different from that of the traditional solidification, and is a lamellar eutectic composed of a black αNb5Si3 phase and a white (Nb) phase.

[0053] Figure 4This is the microstructure of the niobium silicon alloy prepared in Example 2, in which the primary interphase structure is completely different from that of the traditional solidification, and is a lamellar eutectic composed of a black βNb5Si3 phase and a white (Nb) phase.

[0054] Figure 5 The X-ray diffraction patterns of the niobium silicon alloys prepared by conventional solidification and the method of the present invention are as follows: the alloy prepared by conventional solidification is (Nb)+Nb3Si phase, Example 1 is (Nb)+αNb5Si3, and Example 2 is (Nb)+βNb5Si3. DETAILED DESCRIPTION

[0055] The present invention will now be further described with reference to the embodiments and the accompanying drawings:

[0056] The technical solution adopted by the present invention to solve the technical problem is an electrostatic suspension step-triggered coagulation method, which is characterized by comprising the following steps:

[0057] Step 1: Obtain relevant alloy density and specific heat data to provide necessary data for subsequent steps:

[0058] Determine the density of the liquid and solid states of the prepared alloy as ρ L and ρ S , in kilograms per cubic meter. Determine the solid density of the alloy corresponding to the primary phase as ρ S,Primary , the liquid density of the alloy corresponding to the remaining liquid phase is ρ L,Residual , the unit is kilograms per cubic meter.

[0059] Determine the liquid specific heat c of the prepared alloy P,L The unit is joule per Kelvin per mole (hereinafter referred to as joule per Kelvin per mole). The solid-state specific heat of the alloy corresponding to the primary phase is determined as c P,S,Primary The liquid specific heat of the alloy corresponding to the remaining liquid phase is c P,L,Residual , the unit is joule per joule per molar.

[0060] If the density and specific heat data of the alloy are not given in the literature, refer to the method disclosed in “CH Zheng, PF Zou, L. Hu, HP Wang, B. Wei, Composition dependence of thermophysical properties for liquid Zr-Valloys determined at electrostatic levitation state, J. Appl. Phys., 131 (2022) 165104.” for determination.

[0061] Step 2: Suspension melting of alloy:

[0062] A spherical alloy with a mass of m kg is placed in an electrostatic suspension device, the alloy is suspended and heated to melt until it is completely liquid, and the temperature is set at T start Controlled above the liquidus line, the unit is Kelvin (hereinafter referred to as K).

[0063] The electrostatic suspension device refers to the document “PF Zou, HP Wang, SJ Yang, L. Hu, B. Wei, Density Measurement and Atomic Structure Simulation of Metastable Liquid Ti-Ni Alloys, Metall. Mater. Trans. A, 49A (2018) 5488-5496.”.

[0064] Step 3: Adjust the heating power to cool the liquid alloy to the first-order target temperature at a constant rate:

[0065] Considering the radiation heat dissipation, the electrostatically suspended liquid alloy obtained in step 2 satisfies the thermal balance equation:

[0066]

[0067] Where m is the mass in kilograms. M is the relative atomic mass of the liquid alloy in kilograms per mole. P,L is the specific heat of the liquid alloy at constant pressure, in joules per kelvin per mole. T is the temperature, in kelvins. t is the time, in seconds. ε is the emissivity of the liquid alloy. σ is the Stefan-Boltzmann constant, which is 5.67×10 -8 Watt per square meter per Kelvin (hereinafter referred to as W per square meter per Kelvin). e is the ambient temperature, in Kelvin. A is the surface area of ​​the liquid alloy, in square meters. Q is the absorbed power, in watts (hereinafter referred to as watts). The absorbed power and heating power q1 satisfy:

[0068] aq1=Q (1-2)

[0069] Where a is the absorption efficiency. Rearranging (1-1), we can get the absorption power Q, in watts.

[0070]

[0071] Where m is the mass in kilograms. M is the relative atomic mass of the liquid alloy in kilograms per mole. P,L is the specific heat of the liquid alloy at constant pressure, in joules per kelvin per mole. T is the temperature, in kelvins. t is the time, in seconds. π is the circumference of the circle. ε is the emissivity of the liquid alloy. σ is the Stefan-Boltzmann constant. T e is the ambient temperature, in Kelvin.L It is the liquid density of the alloy, in kilograms per cubic meter.

[0072] The initial temperature is T start , the unit is Kelvin. Let the first-order target temperature be T 1n , the unit is Kelvin. Take the temperature coefficient dT / dt as the constant R, the unit is Kelvin per second (hereinafter referred to as K per second). The cooling time is t cool , the unit is seconds. Liquid density ρ L , liquid specific heat c P,L Take the result obtained in step 1 and replace the mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, and ambient temperature T e Substituting into formula (1-3), we can get the relationship between the absorbed power Q and time, in watts.

[0073] Q=Q(t) (1-4)

[0074] Substituting equation (1-4) into equation (1-2), we can obtain the relationship between heating power q1 and time, in watts.

[0075]

[0076] Adjust the electrostatic suspension heating power q1 so that it satisfies the equation (1-5) with respect to time. The liquid alloy undergoes t cool The time is R per second to cool down to the first-order target temperature T 1n .

[0077] Step 4: Adjust the heating power to stabilize the liquid alloy at the first-order target temperature and implement first-order triggered solidification:

[0078] Let the first-order target temperature be the initial temperature T 1n The unit is K. The constant temperature time is t equ , the unit is seconds. Take the temperature coefficient dT / dt as 0 K per second. Liquid density ρ L , liquid specific heat c P,L Take the result obtained in step 1. Substitute mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, ambient temperature T e Substituting into formula (1-3), we can get the absorption power Q, in watts. Substituting into formula (1-5), we can get the heating power q2, in watts.

[0079]

[0080] Adjust the heating power to equal the obtained q2, and the liquid alloy undergoes t equ Time stable at temperature T 1n The trigger device is operated to solidify the primary phase of the alloy. The first stage of electrostatic suspension step solidification is completed, and the sample becomes a solid-liquid coexistence state.

[0081] Step 5: Adjust the heating power to cool the solid-liquid coexisting alloy to the second-order target temperature at a constant rate:

[0082] Considering radiation heat dissipation, the heat balance equation for electrostatically suspended solid-liquid coexisting alloy can be expressed as:

[0083]

[0084] Among them, m S and m L is the mass of the solid phase and the liquid phase in kilograms. P,S,Primary and c P,L,Residual is the specific heat of the solid and liquid phases at constant pressure, in joules per kelvin per mole. T is the temperature, in kelvins. t is the time, in seconds. ε Total is the total emissivity of the alloy. σ is the Stefan-Boltzmann constant. T e is the ambient temperature, in K. Q is the absorbed power, in Watts. Total is the total surface area of ​​the alloy in square meters. Total It can be estimated from the average gold density of the prepared alloy in liquid and solid state.

[0085]

[0086] Among them, ρ L and ρ S is the density of the prepared alloy in liquid and solid state, in kilograms per cubic meter, determined by the result obtained in step 1. Alloy solid phase mass m S and liquid mass m L It can be calculated from the overall volume of the alloy and the solid phase volume fraction.

[0087]

[0088] Among them, ρ S,Primary is the solid density of the primary phase, ρ L,Residual is the liquid density of the alloy corresponding to the residual liquid phase, in kilograms per cubic meter, determined by the result obtained in step 1. Primary is the solid volume fraction. V Total It is the total volume of the alloy, obtained from the overall average density and mass of the alloy, in cubic meters.

[0089]

[0090] Where m Total is the total mass of the alloy in kilograms. Total is the average density of the alloy, in kilograms per cubic meter. total , solid mass m S, liquid mass m L Substituting this into the heat balance equation, we get the absorbed power Q, in watts.

[0091]

[0092] where f Primary is the solid volume fraction. V Total is the total volume of the alloy in cubic meters. S,Primary and M Primary is the solid state density and relative atomic mass of the primary phase, in kilograms per cubic meter and kilograms per mole. P,S,Primary is the specific heat of the primary phase, in joules per mole. L,Residual and M L,Residual is the liquid phase density and relative atomic mass, in kilograms per cubic meter and kilograms per mole. P,L,Redidual ρ is the liquid specific heat of the alloy corresponding to the residual liquid phase, in units of joules per mole. S,Primary 、c P,S,Primary , L,Residual 、c P,L,Redidual Obtained from the result of step 1. T is temperature in K. t is time in seconds. ε Total is the total emissivity of the alloy. σ is the Stefan-Boltzmann constant. T e is the ambient temperature, in Kelvin. m Total is the total mass of the alloy in kilograms. Total It is the overall average density of the alloy in kilograms per cubic meter.

[0093] The initial temperature is T 1n , the unit is Kelvin. Let the second-order target temperature be T 2n , the unit is K. Let the temperature coefficient dT / dt be R K per second. Let the cooling time be t cool , the unit is seconds. The total mass of the alloy m Total , the overall emissivity ε Total , primary phase solid specific heat c P,S,Primary , primary phase solid density ρ S,Primary 、The remaining liquid phase corresponds to the alloy liquid density ρ L,Residual , relative atomic mass M L,Residual , liquid specific heat c P,L,Redidual Substituting into formula (1-10), we can obtain the relationship between the absorbed power Q and time t, in watts.

[0094] Q=Q(t) (1-11) Where t is time in seconds. Substituting equation (1-11) into equation (1-2), we can get the relationship between heating power q3 and time t in watts.

[0095]

[0096] Where t is the time in seconds.

[0097] Adjust the electrostatic suspension heating power q3 so that it satisfies the equation (1-12) with respect to time. cool The time is R per second to cool down to the second-order target temperature T 2n .

[0098] Step 6: Adjust the heating power to stabilize the solid-liquid coexisting alloy at the second-order target temperature and implement second-order triggered solidification:

[0099] The initial temperature is T 2n The unit is K. The constant temperature time is t equ , in seconds. Take the temperature coefficient dT / dt as 0 degrees per second. Total , the overall emissivity ε Total , primary phase solid specific heat c P,S,Primary , primary phase solid density ρ S,Primary 、The remaining liquid phase corresponds to the alloy liquid density ρ L,Residual , relative atomic mass M L,Residual , liquid specific heat c P,L,Redidual Substituting into formula (1-10), we can get the absorbed power Q in watts. Substituting into formula (1-2), we can get the input power q4 in watts.

[0100]

[0101] Adjust the heating power to equal the obtained q4, and the liquid alloy undergoes t equ Time stable at temperature T 2n The trigger device is operated to solidify the remaining liquid phase of the alloy. The heating laser is immediately turned off after solidification occurs, allowing the alloy to cool naturally. At this point, the electrostatic suspension step trigger solidification ends and the alloy sample is completely solidified.

[0102] The following examples are used to illustrate the present invention, using a chemical composition of Nb 90 Si 10 The niobium silicon alloy prepared by the conventional solidification method has a phase composition of (Nb) + Nb3Si, the alloy prepared in Example 1 has a phase composition of (Nb) + αNb5Si3, and the alloy prepared in Example 2 has a phase composition of (Nb) + βNb5Si3.

[0103] Example 1

[0104] This embodiment provides a niobium silicon alloy, the chemical composition of which is Nb 90 Si 10 ,The preparation process includes alloy parameter determination, alloy temperature control modeling and step triggered solidification. The following are the detailed steps.

[0105] Step 1: Obtain relevant alloy density and specific heat data to provide necessary data for subsequent steps:

[0106] The next step is to obtain Nb 90 Si 10 Density of alloy liquid state, niobium solid state density, eutectic alloy liquid state density, Nb 90 Si 10 Alloy liquid specific heat, eutectic alloy liquid specific heat, niobium solid specific heat:

[0107] Determination of Nb 90 Si 10 The density of the alloy in liquid and solid state is ρ L,Nb90Si10 and ρ S,Nb90Si10 , the unit is kilograms per cubic meter.

[0108]

[0109] Where T is the temperature in Kelvin. L is the alloy liquidus temperature, and its value is 2505 Kelvin.

[0110] The remaining liquid phase of the alloy is a niobium-silicon eutectic with a silicon atomic ratio of 17.3%. Its liquid density is measured to be ρ L,Eutectic , the unit is kilograms per cubic meter.

[0111] ρ L,Eutectic =7.32×10 3 -3.73×10 -1 (TT E ) (2-2)

[0112] Where T is the temperature in Kelvin. E is the alloy eutectic temperature, and its value is 2189 K.

[0113] The primary phase of the alloy is (Nb), and its density can be approximated by the data of pure niobium. The solid niobium density ρ is obtained according to the literature "SJ Yang, L. Hu, L. Wang, B. Wei, Heterogeneous nucleation and dendritic growth within undercooled liquid niobium under electrostatic levitation condition, Chem. Phys. Lett., 684 (2017) 316-320." S,Nb for

[0114] ρ S,Nb =7.92×10 -3 -3.98×10-1 (TT m ), (2-3)

[0115] The unit is kilograms per cubic meter. Where T is the temperature, the unit is Kelvin. m is the melting point of niobium, which is 2750 K.

[0116] Determination of liquid Nb 90 Si 10 The specific heat of the alloy is c P,L,Nb90Si10 , the unit is joule per joule per molar.

[0117] c P,Nb90Si10 =ξ Nb90Si10 ε Nb90Si10 =(137.43-4.91×10 -2 (TT L )+2.65×10 -5 (TT L ) 2 )×0.2375 (2-4)

[0118] Where T is the temperature in Kelvin. L,Nb90Si10 Yes Nb 90 Si 10 The heat radiation ratio of the alloy, the unit is joule per kJ per mole. ε Nb90Si10 Nb 90 Si 10 The emissivity of the alloy. T L is the alloy liquidus temperature, which is 2505 K.

[0119] The liquid specific heat of the niobium-silicon eutectic alloy with a silicon atomic ratio of 17.3% is determined to be c P,L,Eutectic , the unit is joule per joule per molar.

[0120] c P,L,Eutectic =ξ L,Eutectic ε Eutectic =(150.48-6.43×10 -2 (TT E )+3.21×10 -5 (TT E ) 2 )×0.2065 (2-5)

[0121] Where T is the temperature in Kelvin. L,Eutectic It is the thermal radiation ratio of liquid niobium-silicon eutectic alloy, and its unit is joule per kJ per mole. ε Eutectic is the emissivity of the niobium-silicon eutectic alloy. E is the alloy eutectic temperature, and its value is 2189 K.

[0122] According to the literature "Gale, WF, in: Totemeier TC (Ed.), Smithells Metals Reference Book (Eighth Edition), Butterworth-Heinemann, Oxford, 2004.", the specific heat of solid niobium c is obtained. PS,Nb for

[0123] c PS,Nb =24.03+3.18×10 -3 T, (2-6)

[0124] The unit is joule per kelvin per molar. Where T is the temperature, the unit is kelvin.

[0125] The method for determining the alloy density and specific heat refers to the document “CH Zheng, PF Zou, L. Hu, HP Wang, B. Wei, Composition dependence of thermophysical properties for liquid Zr-Valloys determined at electrostatic levitation state, J. Appl. Phys., 131 (2022) 165104.”.

[0126] Step 2: Suspension melting of alloy:

[0127] A spherical Nb with a mass of m kg 100-x Si x The alloy was placed in an electrostatic suspension device, where m is 6.6×10 -5 Kilograms. The alloy is suspended and heated to melt until it is completely liquid, and the temperature T start Controlled above the liquidus line, the unit is open.

[0128] The electrostatic suspension device refers to the document “PF Zou, HP Wang, SJ Yang, L. Hu, B. Wei, Density Measurement and Atomic Structure Simulation of Metastable Liquid Ti-Ni Alloys, Metall. Mater. Trans. A, 49A (2018) 5488-5496.”.

[0129] Step 3: Adjust the heating power to cool the liquid alloy to the first-order target temperature at a constant rate:

[0130] Considering the radiation heat dissipation, the electrostatically suspended liquid alloy obtained in step 2 satisfies the thermal balance equation:

[0131]

[0132] Where m is the mass in kilograms. M is the relative atomic mass of the liquid alloy in kilograms per mole. P,L is the specific heat of the liquid alloy at constant pressure, in joules per kelvin per mole. T is the temperature, in kelvins. t is the time, in seconds. ε is the emissivity of the liquid alloy. σ is the Stefan-Boltzmann constant, which is 5.67×10 -8 Watt per square meter per fourth power. e is the ambient temperature, in Kelvin. A is the surface area of ​​the liquid alloy, in square meters. Q is the absorbed power, in watts. The absorbed power and heating power q1 satisfy:

[0133] aq1=Q (2-8)

[0134] Where a is the absorption efficiency. Approximating the liquid alloy to a sphere, the surface area A can be expressed as,

[0135]

[0136] Where π is the circumference of a circle. m is the mass of the liquid alloy in kilograms. ρ L is the density of liquid alloy, in kilograms per cubic meter. Considering the heating laser and sample size in the electrostatic suspension device, the sample energy absorption efficiency a is calibrated to 12% (±0.5%). Substituting equation (2-9) into equation (2-7), the absorbed power Q can be obtained, in watts.

[0137]

[0138] Where m is the mass in kilograms. M is the relative atomic mass of the liquid alloy in kilograms per mole. P,L is the specific heat of the liquid alloy at constant pressure, in joules per kelvin per mole. T is the temperature, in kelvins. t is the time, in seconds. π is the circumference of the circle. ε is the emissivity of the liquid alloy. σ is the Stefan-Boltzmann constant. T e is the ambient temperature, in Kelvin. L It is the liquid density of the alloy, in kilograms per cubic meter.

[0139] Take the initial temperature as T start The first-order target temperature is 2515 degrees Celsius. 1n The temperature coefficient dT / dt is -20 K / s. Liquid density ρ L , liquid specific heat c P,L Take the result obtained in step 1 and replace the mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, and ambient temperature T eSubstituting into formula (2-10), we can obtain the relationship between the absorbed power Q and time, in watts.

[0140] Q = 10.59-0.36t+4.15×10 -3 t 2 (2-11)

[0141] Substituting equation (2-11) into equation (2-8), we can obtain the relationship between heating power q1 and time, in watts.

[0142] q0=88.23-3.02t+3.46×10 -2 t 2 (2-12)

[0143] Adjust the electrostatic suspension heating power q1 so that it satisfies the equation (2-12) with time. The liquid alloy cools down to the first-order target temperature of 2375 K at a rate of 20 K per second over 7.0 seconds.

[0144] Step 4: Adjust the heating power to stabilize the liquid alloy at the first-order target temperature and implement first-order triggered solidification:

[0145] The initial temperature is set to the first-order target temperature of 2375 K. The temperature coefficient dT / dt is set to 0 K per second. The constant temperature time is t equ is 17.6 seconds. Liquid density ρ L , liquid specific heat c P,L Take the result obtained in step 1. Substitute mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, ambient temperature T e Substituting into formula (2-10), we get the absorption power Q, which is 8.77 W. Substituting into formula (2-8), we get the heating power q2, which is 73±3 W.

[0146] The heating power was adjusted to be equal to the obtained q2, and the liquid alloy stabilized at 2375 K after 17.6 seconds. The trigger device was operated, and the primary phase of the alloy solidified. The first stage of electrostatic suspension step solidification was completed, and the sample became a solid-liquid coexistence state.

[0147] Step 5: Adjust the heating power to cool the solid-liquid coexisting alloy to the second-order target temperature at a constant rate:

[0148] Considering radiation heat dissipation, the heat balance equation for electrostatically suspended solid-liquid coexisting alloy can be expressed as:

[0149]

[0150] Among them, m S and m L is the mass of the solid phase and the liquid phase in kilograms. P,S,Primary and c P,L,Residualis the specific heat of the solid and liquid phases at constant pressure, in joules per kelvin per mole. T is the temperature, in kelvins. t is the time, in seconds. ε Total is the total emissivity of the alloy. σ is the Stefan-Boltzmann constant. T e is the ambient temperature, in K. Q is the absorbed power, in Watts. Total is the total surface area of ​​the alloy, in square meters. The total surface area A of the alloy can be obtained from its mass and average density.

[0151]

[0152] Where π is the ratio of the circumference of a circle. Total is the total mass of the alloy in kilograms. Total is the overall average density of the alloy, in kilograms per cubic meter. Total It can be estimated from the average gold density of the prepared alloy in liquid and solid state.

[0153]

[0154] Among them, ρ L and ρ S is the density of the prepared alloy in liquid and solid state, in kilograms per cubic meter, determined by the result obtained in step 1. Alloy solid phase mass m S and liquid mass m L It can be calculated from the overall volume of the alloy and the solid phase volume fraction.

[0155]

[0156] Among them, ρ S,Primary is the solid density of the primary phase, ρ L,Residual is the liquid density of the alloy corresponding to the residual liquid phase, in kilograms per cubic meter, determined by the result obtained in step 1. Primary is the solid volume fraction, which is 0.56. Total It is the total volume of the alloy, obtained from the overall average density and mass of the alloy, in cubic meters.

[0157]

[0158] Where m Total is the total mass of the alloy in kilograms. Total is the average density of the alloy, in kilograms per cubic meter. total , solid mass m S , liquid mass m L Substituting this into the heat balance equation, we get the absorbed power Q, in watts.

[0159]

[0160] where f Primary is the solid volume fraction. V Total is the total volume of the alloy in cubic meters. S,Primary and M Primary is the solid state density and relative atomic mass of the primary phase, in kilograms per cubic meter and kilograms per mole. P,S,Primary is the specific heat of the primary phase, in joules per mole. L,Residual and M L,Residual is the liquid phase density and relative atomic mass, in kilograms per cubic meter and kilograms per mole. P,L,Redidual ρ is the liquid specific heat of the alloy corresponding to the residual liquid phase, in units of joules per mole. S,Primary 、c P,S,Primary , L,Residual 、c P,L,Redidual Obtained from the result of step 1. T is temperature in K. t is time in seconds. ε Total is the total emissivity of the alloy. σ is the Stefan-Boltzmann constant. T e is the ambient temperature, in Kelvin. m Total is the total mass of the alloy in kilograms. Total It is the overall average density of the alloy in kilograms per cubic meter.

[0161] The initial temperature is 2375 K. The second-order target temperature is T 2n is 2102K. Let the temperature coefficient dT / dt be -10K per second. Then the cooling time t cool is 27.3 seconds. The total mass of the alloy m Total , the overall emissivity ε Total , primary phase solid specific heat c P,S,Primary , primary phase solid density ρ S,Primary 、The remaining liquid phase corresponds to the alloy liquid density ρ L,Residual , relative atomic mass M L,Residual , liquid specific heat c P,L,Redidual Substituting into formula (2-18), we can obtain the relationship between absorbed power Q and time t, in watts.

[0162] Q = 8.47-0.15 × 10 -2 t+8.59×10 -4 t 2 (2-19)

[0163] Where t is time in seconds. Substituting equation (2-19) into equation (2-8), we can get the relationship between heating power q3 and time t in watts.

[0164] q3=70.61-1.24t+7.16×10 -3t 2 (2-20)

[0165] Where t is the time in seconds.

[0166] The electrostatic suspension heating power q3 is adjusted so that it satisfies the equation (2-20) with respect to time. The solid-liquid coexistence alloy is cooled down at a rate of -10 K per second to the second-order target temperature of 2102 K in 27.3 seconds.

[0167] Step 6: Adjust the heating power to stabilize the solid-liquid coexisting alloy at the second-order target temperature and implement second-order triggered solidification:

[0168] The initial temperature is set to the second-order target temperature of 2102 degrees Kelvin. The temperature coefficient dT / dt is set to 0 degrees Kelvin per second. The constant temperature time is t equ is 59.5 seconds. Primary phase solid density ρ S,Primary , primary phase solid specific heat c P,S,Primary , residual liquid phase density ρ L,Residual , the remaining liquid phase heat c P,L,Redidual Estimated from the result of step 1. The total mass of the alloy m Total , the overall emissivity ε Total , overall density ρ L,Total Substituting into formula (2-18), we can get the absorption power Q as 5.29 watts. Substituting into formula (2-8), we can get the heating power q4 as 44±2 watts.

[0169] Adjust the heating power to equal the obtained q4, and the liquid alloy stabilizes at 2102 K after 59.5 seconds. Operate the trigger device, and the remaining liquid phase of the alloy solidifies. Immediately after solidification occurs, turn off the heating laser and let the alloy cool naturally. At this point, the electrostatic suspension step triggers the solidification and the alloy is completely solidified.

[0170] Through the above steps, the step trigger temperature curve in the alloy preparation process can be obtained. Figure 1 .from Figure 1 It can be seen that the calculation results obtained by using the present invention can well control the primary phase of the alloy to solidify at the first-order target temperature of 2375°C, and the remaining liquid phase of the alloy to solidify at the second-order target temperature of 2102°C. Figure 2 The Nb prepared by the traditional solidification method is given. 90 Si 10 The solidification structure of the alloy has a rod-shaped eutectic composed of a white phase and a gray phase as the primary phase. Figure 3 The solidification structure obtained by the steps of Example 1 has a primary interphase structure that is completely different from that of traditional solidification and is a black and white two-phase lamellar eutectic. Figure 5Their X-ray diffraction patterns are given, and the conventional solidified niobium silicon alloy is composed of the brittle and unstable (Nb)+Nb3Si phase, while Example 1 is composed of the stable (Nb)+αNb5Si3 phase. This shows that the electrostatic suspension step-triggered solidification method proposed in the present invention can effectively regulate the alloy phase composition and microstructure.

[0171] Example 2

[0172] This embodiment provides a niobium silicon alloy, the chemical composition of which is Nb 90 Si 10 The preparation process is the same as that of Example 1, except that the first-order target temperature T in step 3, step 4, step 5, and step 6 is 1n , second-order target temperature T 2n And the value of the temperature coefficient dT / dt.

[0173] Step 3: Adjust the heating power to cool the liquid alloy to the first-order target temperature at a constant rate:

[0174] Take the initial temperature as T start The first-order target temperature is 2515 degrees Celsius. 1n The temperature coefficient dT / dt is -13 K / s. Liquid density ρ L , liquid specific heat c P,L Take the result obtained in step 1 and replace the mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, and ambient temperature T e Substituting into formula (2-10), we can obtain the relationship between the absorbed power Q and time, in watts.

[0175] Q = 10.76-0.23t+1.72×10 -2 t 2 (3-1)

[0176] Substituting equation (3-1) into equation (2-8), we can obtain the relationship between heating power q1 and time, in watts.

[0177] q1=89.67-1.96t+4.14×10 -2 t 2 (3-2)

[0178] The electrostatic suspension heating power q1 is adjusted so that it satisfies the equation (3-2) with respect to time. The liquid alloy cools down to the first-order target temperature of 2325 K at a rate of 13 K per second over 14.6 seconds.

[0179] Step 4: Adjust the heating power to stabilize the liquid alloy at the first-order target temperature and implement first-order triggered solidification:

[0180] The initial temperature is set to the first-order target temperature of 2325 K. The temperature coefficient dT / dt is set to 0 K per second. The constant temperature time is t equ is 7.7 seconds. Liquid density ρ L , liquid specific heat c P,L Take the result obtained in step 1. Substitute mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, ambient temperature T e Substituting into formula (2-10), we get the absorption power Q, which is 8.04 W. Substituting into formula (2-8), we get the heating power q2, which is 67±3 W.

[0181] The heating power was adjusted to be equal to the obtained q2, and the liquid alloy stabilized at 2325 K in 7.7 seconds. The trigger device was operated, and the primary phase of the alloy solidified. The first stage of electrostatic suspension step solidification was completed, and the sample became a solid-liquid coexistence state.

[0182] Step 5: Adjust the heating power to cool the solid-liquid coexisting alloy to the second-order target temperature at a constant rate:

[0183] The initial temperature is 2325 K. The second-order target temperature is T 2n is 2117 K. The temperature coefficient dT / dt is -13 K per second. Then the cooling time t cool is 16.0 seconds. The total mass of the alloy m Total , the overall emissivity ε Total , primary phase solid specific heat c P,S,Primary , primary phase solid density ρ S,Primary 、The remaining liquid phase corresponds to the alloy liquid density ρ L,Residual , relative atomic mass M L,Residual , liquid specific heat c P,L,Redidual Substituting into formula (2-18), we can obtain the relationship between absorbed power Q and time t, in watts.

[0184] Q = 7.68-0.18t+1.43×10 -3 t 2 (3-3)

[0185] Where t is time in seconds. Substituting equation (3-3) into equation (2-8), we can get the relationship between heating power q3 and time t in watts.

[0186] q3=64.01-1.51t+1.19×10 -2 t 2 (3-4)

[0187] Where t is the time in seconds.

[0188] The electrostatic suspension heating power q3 is adjusted so that it satisfies the equation (3-4) with respect to time. The solid-liquid coexistence alloy is cooled down to the second-order target temperature of 2117 K at a rate of 13 K per second in 16.0 seconds.

[0189] Step 6: Adjust the heating power to stabilize the solid-liquid coexisting alloy at the second-order target temperature and implement second-order triggered solidification:

[0190] The initial temperature is set to the second-order target temperature of 2117 degrees Kelvin. The temperature coefficient dT / dt is set to 0 degrees Kelvin per second. The constant temperature time is t equ is 12.9 seconds. Primary phase solid density ρ S,Primary , primary phase solid specific heat c P,S,Primary , residual liquid phase density ρ L,Residual , the remaining liquid phase heat c P,L,Redidual Estimated from the result of step 1. The total mass of the alloy m Total , the overall emissivity ε Total , overall density ρ L,Total Substituting into formula (2-18), we can get the absorption power Q as 5.45 watts. Substituting into formula (2-8), we can get the heating power q4 as 45±2 watts.

[0191] Adjust the heating power to equal the obtained q4, and the liquid alloy stabilizes at 2117 K after 12.9 seconds. Operate the trigger device, and the remaining liquid phase of the alloy solidifies. Immediately after solidification occurs, turn off the heating laser and allow the alloy to cool naturally. At this point, the electrostatic suspension step triggers the solidification and the alloy is completely solidified.

[0192] Figure 4 The solidification structure obtained by the steps of Example 1 has a primary interphase structure that is completely different from that of traditional solidification and is a black and white two-phase lamellar eutectic. Figure 5 The X-ray diffraction patterns of the alloys prepared by different preparation methods are given. The conventional solidified niobium silicon alloy is composed of (Nb) + Nb3Si phase, while Example 2 is composed of (Nb) + βNb5Si3 phase. This shows that the electrostatic suspension step-triggered solidification method proposed in the present invention can effectively regulate the alloy phase composition and microstructure.

Claims

1. An electrostatic suspension step-triggered solidification method for regulating alloy phase selection, characterized in that Here are the steps: Step 1: Determine the density and specific heat related data of the prepared alloy, including the liquid density ρ of the alloy L , solid density ρ S , in kilograms per cubic meter; the solid density of the alloy corresponding to the primary phase is determined as ρ S,Primary , the liquid density of the alloy corresponding to the remaining liquid phase is ρ L,Residual , the unit is kilograms per cubic meter; Determine the liquid specific heat c of the alloy P,L The unit is joule per Kelvin per mole, hereinafter referred to as joule per Kelvin per mole; the solid-state specific heat of the alloy corresponding to the primary phase is determined as c P,S,Primary The liquid specific heat of the alloy corresponding to the remaining liquid phase is c P,L,Residual , the unit is joule per joule per molar; Step 2: Suspension melting of alloy: A spherical alloy with a mass of m kg is placed in an electrostatic suspension device, the alloy is suspended and heated to melt above the liquidus to a completely liquid state, and the temperature T start Controlled above the liquidus, the unit is Kelvin, referred to as K; Step 3: Adjust the heating power to cool the liquid alloy to the first-order target temperature T at a constant rate. 1n : Adjust the electrostatic suspension heating power q1 to: Where m, M, c P,L , ε, ρ L , a are the mass, relative atomic mass, specific heat at constant pressure, emissivity, density, and temperature absorption efficiency of the liquid alloy respectively; T e ,,π,σare the ambient temperature, pi, and Stefan-Boltzmann constant respectively; T1, t1, dT1 / dt1 are the temperature, time, and temperature rate respectively; The sample is heated from temperature T start Cool down to temperature T at a rate of dT1 / dt1 1n ; Step 4: Adjust the heating power to stabilize the liquid alloy at the first-order target temperature and implement first-order triggered solidification: Adjust the electrostatic suspension heating power q2 to: Where: T 1n 、T e , π, σ are the first-order target temperature and ambient temperature respectively; The sample is stabilized at the first-order target temperature T 1n , operate the trigger device, and the primary phase of the alloy solidifies; Step 5: Adjust the heating power to cool the solid-liquid coexisting alloy to the second-order target temperature at a constant rate: Adjust the electrostatic suspension heating power q3 to: Where: T3, t3, dT3 / dt3 are the temperature, time, and temperature rate of this stage respectively; f Primary 、M Primary 、c P,S,Primary , S,Primary are the volume fraction, relative atomic mass, specific heat, and density of the primary phase; ρ L,Residual 、M L,Residual 、c P,L,Redidual are the density, relative atomic mass and specific heat of the remaining liquid phase; V Total , ε Total 、m Total , Total are the total volume, overall emissivity, mass, and overall average density of the alloy respectively; The sample is heated from temperature T 1n Cool down to the second-order target temperature T at a rate of dT3 / dt3 2n ; Step 6: Adjust the heating power to stabilize the solid-liquid coexistence alloy at the second-order target temperature and implement second-order triggered solidification: adjust the electrostatic suspension heating power q4 to: Where: T 2n is the second-order target temperature; ε Total 、m Total , Total are the overall emissivity, mass, and overall average density of the alloy, respectively; The sample is stabilized at the second-order target temperature T 2n , operate the trigger device, and the remaining liquid phase of the alloy solidifies. After solidification occurs, the heating laser is immediately turned off to allow the alloy to cool naturally.

2. The electrostatic suspension step-triggered solidification method for regulating alloy phase selection according to claim 1, characterized in that: In step 1, if the density and specific heat data of the alloy are not given in the literature, refer to "CH Zheng, PF Zou, L. Hu, HP Wang, B. Wei, Composition dependence of thermophysical properties for liquid Zr-V alloys determined at electrostatic levitation state, J. Appl. Phys., 131 (2022) 165104.” was determined by the method disclosed in.

3. The electrostatic suspension step-triggered solidification method for regulating alloy phase selection according to claim 1, characterized in that: The electrostatic suspension device refers to the document "PF Zou, HP Wang, SJ Yang, L. Hu, B. Wei, Density Measurement and Atomic Structure Simulation of Metastable Liquid Ti-Ni Alloys, Metall. Mater. Trans. A, 49A (2018) 5488-5496.".

4. The electrostatic suspension step-triggered solidification method for regulating alloy phase selection according to claim 1, characterized in that: The q1, q2, q3 and q4 in step 3, step 4, step 5 and step 6 are all electrostatic suspension heating powers q at different stages. The calculation with q1 is based on the relationship between heating power q1 and time q1=q1(t): The electrostatically suspended liquid alloy satisfies the thermal balance equation: Where m is the mass in kilograms; M is the relative atomic mass of the liquid alloy in kilograms per mole; c P,L is the specific heat of liquid alloy at constant pressure, in joules per kelvin per mole; T is the temperature, in kelvins; t is the time in seconds; ε is the emissivity of the liquid alloy; σ is the Stefan-Boltzmann constant, which is 5.67×10 -8 Watt per square meter per fourth power of Kelvin; T e is the ambient temperature, in Kelvin; A is the surface area of ​​the liquid alloy, in square meters; Q is the absorbed power, in watts; the absorbed power and heating power q1 satisfy: aq1=Q Where a is the absorption efficiency. After rearranging the heat balance equation, we can get the absorption power Q in watts: Among them: π is pi, ρ is L is the liquid density of the alloy, in kilograms per cubic meter; The initial temperature is T start , the unit is K; the first-order target temperature is T 1n , the unit is on; Take the temperature coefficient dT / dt as the constant R, the unit is Kelvin per second; record the cooling time as t cool , the unit is second; liquid density ρ L , liquid specific heat c P,L ; Mass m, relative atomic mass M, emissivity ε, Stefan-Boltzmann constant σ, ambient temperature T e Substituting into the above formula, we get the relationship between the absorbed power Q and time, in watts Q=Q(t) Substituting the above equation into aq1=Q, we can obtain the relationship between heating power q1 and time, in watts.

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