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CN116275003B - Static suspension step trigger solidification method for regulating and controlling alloy phase selection - Google Patents

Static suspension step trigger solidification method for regulating and controlling alloy phase selection Download PDF

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CN116275003B
CN116275003B CN202310092865.4A CN202310092865A CN116275003B CN 116275003 B CN116275003 B CN 116275003B CN 202310092865 A CN202310092865 A CN 202310092865A CN 116275003 B CN116275003 B CN 116275003B
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王海鹏
王庆
胡亮
郑晨辉
魏炳波
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Northwestern Polytechnical University
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Abstract

The invention relates to an electrostatic suspension step triggering solidification method for regulating and controlling alloy phase selection, which realizes active phase selection of alloy residual liquid phase solidification. The method comprises the steps of firstly obtaining necessary density and specific heat data of alloy, then deducing a liquid alloy heat balance equation under an electrostatic suspension state to solve required heating power, solidifying an alloy primary phase at the required temperature through an electrostatic suspension trigger device under a step trigger solidification first-order target temperature, deducing a solid-liquid coexisting state alloy heat balance equation under the electrostatic suspension state to solve the required heating power, regulating and controlling the step trigger solidification second-order target temperature, and solidifying residual liquid phase in the alloy into the required phase composition through the trigger device. The static suspension step triggering solidification method provided by the invention can independently regulate and control the solidification supercooling degree of the primary phase and the residual liquid phase, thereby controlling the phase composition of the alloy.

Description

Static suspension step trigger solidification method for regulating and controlling alloy phase selection
Technical Field
The invention belongs to the technical field of electrostatic suspension, and relates to an electrostatic suspension step triggering solidification method for regulating and controlling alloy phase selection.
Background
The properties of the material are greatly affected by the phase composition of the material, and the traditional solidification method cannot actively regulate the phase selection behavior of the alloy. The electrostatic suspension technology is a novel material research means, and can realize deep supercooling solidification of the alloy, thereby influencing the phase selection behavior of the alloy in the solidification process. Therefore, achieving phase selection control of alloys by electrostatic suspension techniques is an important point in the development of high performance alloys.
The team discloses a method for preparing single crystal alloy by utilizing electrostatic suspension technology in a growing method of high-temperature refractory alloy spherical single crystal under the electrostatic suspension condition of the northwest industrial university, which is CN201911388068.0[ P ].2021-09-17 ], and realizes deep supercooled solidification of the alloy. However, the method cannot solidify the alloy at a specific supercooling degree, the phase selection behavior depends on randomness in deep supercooling solidification, and the phase composition of the obtained solidification structure cannot be actively regulated.
Aiming at the problem that an electrostatic suspension device cannot solidify alloy at a specific supercooling degree, the team develops an electrostatic suspension triggering solidification method as described in a document "M.X.Li,H.P.Wang,M.J.Lin,C.H.Zheng,B.Wei,Rapid Eutectic Growth Kinetics of Undercooled Nb-Si Alloys at Electrostatic Levitation State,Acta Mater.,237(2022)118157.". The static suspension triggering solidification method can solidify the liquid alloy at a specific supercooling degree. However, the static suspension triggering solidification method disclosed in the document can only control the generation temperature of the primary phase, and cannot independently control the generation temperature of the residual liquid phase. The phase composition of the primary interphase solidification structure in the alloy cannot be actively controlled.
The traditional solidification technology can not regulate and control the phase composition of the alloy in the solidification process, and the existing static suspension triggering solidification method can only regulate and control the phase composition of the primary phase. Up to the present, there is no method for regulating and controlling the solidification temperature of the residual liquid phase, and active control of the phase composition of the primary interphase solidification structure cannot be achieved.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides an electrostatic suspension step-triggered solidification method for regulating and controlling the selection of alloy phases, which solves the problem that the existing electrostatic suspension-triggered solidification method can only regulate and control primary phases, thereby actively controlling the phase composition of primary inter-phase solidification structures.
The invention provides an electrostatic suspension step triggering solidification method. The method comprises the steps of firstly obtaining necessary density and specific heat data of an alloy, then deriving a liquid alloy heat balance equation under an electrostatic suspension state, solving required heating power, applying the obtained heating power to enable the liquid alloy to be stabilized at a step-triggered solidification first-order target temperature, solidifying an alloy primary phase at the required temperature through an electrostatic suspension trigger device, then deriving a solid-liquid coexisting state alloy heat balance equation under the electrostatic suspension state, solving the required heating power, applying the obtained heating power to enable the solid-liquid coexisting state alloy to be stabilized at a step-triggered solidification second-order target temperature, regulating the step-triggered solidification second-order target temperature, and solidifying residual liquid in the alloy into the required phase by utilizing the trigger device.
Technical proposal
An electrostatic suspension step triggering solidification method for regulating and controlling alloy phase selection is characterized by comprising the following steps:
Step 1, determining the density and specific heat related data of the prepared alloy, wherein the data comprise the liquid density rho L and the solid density rho S of the alloy, the unit is kilogram per cubic meter, the solid density rho S,Primary of the alloy corresponding to a primary phase and the liquid density rho L,Residual of the alloy corresponding to a residual liquid phase;
Determining the liquid specific heat of the alloy c P,L in joules per kelvin per mole, hereinafter abbreviated as coke per mole, determining the solid specific heat of the alloy corresponding to the primary phase as c P,S,Primary, and the liquid specific heat of the alloy corresponding to the remaining liquid phase as c P,L,Residual in joules per mole;
step 2, suspension melting of alloy:
Placing spherical alloy with mass of m kg into an electrostatic suspension device, heating the alloy in suspension until the alloy is melted to be in a complete liquid state above a liquidus line, and controlling the temperature T start to be above the liquidus line, wherein the unit is Kelvin, which is called open for short;
step 3, adjusting heating power to enable the liquid alloy to be cooled to a first-order target temperature T 1n at a constant speed:
The electrostatic levitation heating power q 1 is adjusted to be:
Wherein M, M, c P,L,、ε、ρL and a are respectively the mass, relative atomic mass, specific heat under constant pressure, emissivity, density and temperature absorption efficiency of the liquid alloy. T e,, pi and sigma are respectively the ambient temperature, the circumference ratio and the Stefan-Boltzmann constant, and T 1、t1、dT1/dt1 is respectively the temperature, the time and the temperature rate;
the sample is cooled from the temperature T start to the temperature T 1n at the speed of dT 1/dt1;
Step 4, adjusting heating power to enable the liquid alloy to be stabilized at a first-order target temperature and implementing first-order trigger solidification:
The electrostatic levitation heating power q 2 is adjusted to be:
wherein T 1n、Te,, pi and sigma are first-order target temperature and environment temperature respectively;
the sample is stabilized at a first-order target temperature T 1n, a trigger device is operated, and an alloy primary phase is solidified;
step 5, adjusting heating power to enable the solid-liquid coexisting alloy to be cooled to a second-order target temperature at a constant rate:
the electrostatic levitation heating power q 3 is adjusted to be:
Wherein T 3、t3、dT3/dt3 is the temperature, time and temperature rate of the stage respectively, f Primary、MPrimary、cP,S,Primary、ρS,Primary is the volume fraction, relative atomic mass, specific heat and density of the primary phase respectively, ρ L,Residual、ML,Residual、cP,L,Redidual is the density, relative atomic mass and specific heat of the residual liquid phase respectively, and V Total、εTotal、mTotal、ρTotal is the total volume, total emissivity, mass and total average density of the alloy respectively;
The sample is cooled from the temperature T 1n to a second-order target temperature T 2n at the speed of dT 3/dt3;
and 6, adjusting heating power to enable the solid-liquid coexisting alloy to be stabilized at a second-order target temperature and implementing second-order trigger solidification:
The electrostatic levitation heating power q 4 is adjusted to be:
Wherein T 2n is the second-order target temperature, epsilon Total、mTotal、ρTotal is the total emissivity, mass and total average density of the alloy respectively;
The sample is stabilized at a second-order target temperature T 2n, a trigger device is operated, the alloy residual liquid phase is solidified, and heating laser is immediately turned off after solidification occurs, so that the alloy is naturally cooled.
The density and specific heat data of the alloy are determined in step 1 by referring to the method disclosed in "C.H.Zheng,P.F.Zou,L.Hu,H.P.Wang,B.Wei,Composition dependence of thermophysical properties for liquid Zr-V alloys determined at electrostatic levitation state,J.Appl.Phys.,131(2022)165104." if the density and specific heat data are not given in the literature.
The electrostatic levitation device is described in the literature "P.F.Zou,H.P.Wang,S.J.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.".
Q 1、q2、q3 and q 4 in the step 3, the step 4, the step 5 and the step 6 are electrostatic suspension heating power q in different stages, and q 1 is calculated according to the relation q 1＝q1 (t) between the heating power q 1 and time, wherein the electrostatic suspension liquid alloy satisfies a heat balance equation:
Wherein M is the mass, M is the relative atomic mass of the liquid alloy in kilograms per mole, c P,L is the constant pressure specific heat of the liquid alloy in grams per mole, T is the temperature in grams per mole, T is the time in seconds, ε is the emissivity of the liquid alloy, σ is the Stefan-Boltzmann constant, 5.67 x 10 -8 watts per square meter, T e is the ambient temperature, A is the surface area of the liquid alloy in square meter, Q is the absorbed power in watts, and the absorbed power and the heating power Q 1 satisfy:
aq1=Q
wherein a is absorption efficiency, a heat balance equation is arranged to obtain absorption power Q, and the unit is watt:
Wherein pi is the circumferential rate, ρ L is the alloy liquid density, and the unit is kilogram per cubic meter;
The initial temperature is recorded as T start, the first-order target temperature is recorded as T 1n, the first-order target temperature is recorded as on, the temperature coefficient dT/dT is recorded as a constant R, the unit is Kelvin per second, the cooling time is recorded as T cool, the unit is seconds, the liquid density rho L and the liquid specific heat c P,L, the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e are substituted into the above to obtain the relation between the absorption power Q and the time, and the unit is W
Q=Q(t)
Substituting the above formula into the formula aq 1 =q, the relationship between the heating power Q 1 and time is obtained in watts.
Advantageous effects
The static suspension step triggering solidification method for regulating and controlling the alloy phase selection provided by the invention realizes the active phase selection of the solidification of the alloy residual liquid phase. The method comprises the steps of firstly obtaining necessary density and specific heat data of alloy, then deducing a liquid alloy heat balance equation under an electrostatic suspension state to solve required heating power, solidifying an alloy primary phase at the required temperature through an electrostatic suspension trigger device under a step trigger solidification first-order target temperature, deducing a solid-liquid coexisting state alloy heat balance equation under the electrostatic suspension state to solve the required heating power, regulating and controlling the step trigger solidification second-order target temperature, and solidifying residual liquid phase in the alloy into the required phase composition through the trigger device. The static suspension step triggering solidification method provided by the invention can independently regulate and control the solidification supercooling degree of the primary phase and the residual liquid phase, thereby controlling the phase composition of the alloy.
The invention establishes a thermal equilibrium equation of an electrostatic suspension sample to obtain a heating strategy for effectively controlling the temperature of the sample in an electrostatic suspension state, creatively proposes a static suspension step-triggered solidification method, and adopts the step-triggered solidification method to realize supercooled solidification of a primary phase and a residual liquid phase by using the temperature control strategy, so that solidification structures and phase compositions of the alloy are changed, generation of metastable phases can be avoided, and stable phases can be obtained without heat treatment. For niobium-silicon hypoeutectic alloy, the traditional method can only be solidified to generate a solidification structure with large brittleness and instability, and even though an electrostatic suspension device is used, stable silicide phase cannot be directly solidified. The step triggering solidification method provided by the invention can be adopted to directly solidify the liquid niobium-silicon alloy to generate a stable eutectic structure. The method has the advantages of simple raw material proportion, no need of adding alloying elements, no need of high-cost refractory or rare earth alloying elements, no need of subsequent heat treatment process, short process flow, low energy consumption and short preparation time, and provides possibility for improving the development and production efficiency of the alloy.
Drawings
FIG. 1 is a typical temperature profile during the electrostatic suspension step solidification of a niobium-silicon alloy obtained according to the method of the present invention, which effectively controls solidification of the primary phase at a first order target temperature and solidification of the remaining liquid phase at a second order target temperature.
FIG. 2 is a microstructure of a conventional solidified niobium silicon alloy in which the primary phase is a rod-like eutectic of gray Nb 3 Si phase and white (Nb) phase.
Fig. 3 is a microstructure of the niobium silicon alloy prepared in example 1, in which the primary interphase structure is totally different from the conventional solidification, and is a lamellar eutectic composed of black αnb 5Si3 phase and white (Nb) phase.
Fig. 4 is a microstructure of the niobium silicon alloy prepared in example 2, in which the primary interphase structure is totally different from the conventional solidification, and is a lamellar eutectic composed of a black βnb 5Si3 phase and a white (Nb) phase.
FIG. 5 is an X-ray diffraction pattern of a niobium-silicon alloy prepared by conventional solidification and the method of the present invention, the alloy prepared by conventional solidification being (Nb) +Nb 3 Si phase, example 1 being (Nb) +αNb 5Si3, and example 2 being (Nb) +βNb 5Si3.
Detailed Description
The invention will now be further described with reference to examples, figures:
The technical scheme adopted by the invention for solving the technical problems is an electrostatic suspension step triggering solidification method, which is characterized by comprising the following steps:
Step one, acquiring related alloy density and specific heat data, and providing necessary data for the subsequent steps:
The densities of the liquid and solid states of the prepared alloy are determined to be ρ L and ρ S, and the unit is kilogram per cubic meter. The solid density of the alloy corresponding to the primary phase is determined to be ρ S,Primary, and the liquid density of the alloy corresponding to the residual liquid phase is determined to be ρ L,Residual, with the unit being kilogram per cubic meter.
The specific heat of the liquid state c P,L of the prepared alloy was determined in joules per kelvin per mole (hereinafter abbreviated as coke per mole). And determining the solid specific heat of the alloy corresponding to the primary phase as c P,S,Primary, and the liquid specific heat of the alloy corresponding to the residual liquid phase as c P,L,Residual, wherein the unit is coke per mole.
If the density, specific heat data of the alloy is not given in the literature, it is determined with reference to the method disclosed in "C.H.Zheng,P.F.Zou,L.Hu,H.P.Wang,B.Wei,Composition dependence of thermophysical properties for liquid Zr-Valloys determined at electrostatic levitation state,J.Appl.Phys.,131(2022)165104.".
Step two, suspension melting of alloy:
spherical alloy with mass of m kg is placed in an electrostatic suspension device, the alloy is heated and melted to be in a complete liquid state in suspension, and the temperature T start is controlled above liquidus line, and the unit is Kelvin (hereinafter referred to as open).
The electrostatic levitation device is described in the literature "P.F.Zou,H.P.Wang,S.J.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.".
Step three, adjusting heating power to enable the liquid alloy to be cooled to a first-order target temperature at a constant speed:
considering radiation heat dissipation, the electrostatic suspension liquid alloy obtained in the second step meets a heat balance equation:
Where m is mass and the unit is kg. M is the relative atomic mass of the liquid alloy in kilograms per mole. c P,L is the constant pressure specific heat of the liquid alloy, and the unit is coke per mole. T is the temperature in units of on. t is time and the unit is seconds. Epsilon is the emissivity of the liquid alloy. Sigma is a Stefan-Boltzmann constant of 5.67×10 -8 watts per square meter per Kelvin square (hereinafter abbreviated as watts per square meter). T e is ambient temperature in units of on. A is the surface area of the liquid alloy, and the unit is square meters. Q is the absorption power in watts (hereinafter simply referred to as watts). The absorption power and the heating power q 1 satisfy the following conditions:
aq1=Q (1-2)
where a is the absorption efficiency. The absorption power Q is obtained by arranging the formula (1-1) in units of watts.
Where m is mass and the unit is kg. M is the relative atomic mass of the liquid alloy in kilograms per mole. c P,L is the constant pressure specific heat of the liquid alloy, and the unit is coke per mole. T is the temperature in units of on. t is time and the unit is seconds. Pi is the circumference ratio. Epsilon is the emissivity of the liquid alloy. Sigma is the Stefan-Boltzmann constant. T e is ambient temperature in units of on. ρ L is the alloy liquid density in kilograms per cubic meter.
The initial temperature is noted as T start in units of on. The first order target temperature is noted as T 1n in units of ON. Let the temperature coefficient dT/dT be a constant R in Kelvin per second (hereinafter referred to as "Kelvin per second"). The cooling time is noted as t cool in seconds. And (3) substituting the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e into the formula (1-3) to obtain the relationship between the absorption power Q and time in watts, wherein the results are obtained in the step one of the liquid density rho L and the liquid specific heat c P,L.
Q=Q(t) (1-4)
By substituting the formula (1-4) into the formula (1-2), the relation between the heating power q 1 and time can be obtained in watts.
The electrostatic levitation-heating power q 1 is adjusted so as to satisfy the formula (1-5) with time. The liquid alloy is cooled to a first order target temperature T 1n at R kelvin per second over a time T cool.
Regulating heating power to stabilize the liquid alloy at the first-order target temperature and implementing first-order trigger solidification:
The first order target temperature is noted as the initial temperature T 1n in units of on. The constant temperature time is noted as t equ in seconds. The temperature coefficient dT/dT was taken to be 0 kelvin per second. The liquid density ρ L and the liquid specific heat c P,L are obtained in the first step. The absorption power Q is obtained by substituting the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e into the formula (1-3), and the unit is W. By substituting the formula (1-5), the heating power q 2 in watts can be obtained.
The heating power was adjusted to be equal to the resulting q 2 and the liquid alloy was stable at temperature T 1n over time T equ. And operating the trigger device, and solidifying the primary phase of the alloy. And (3) finishing the first stage of static suspension step solidification, and changing the sample into a solid-liquid coexisting state.
Fifthly, adjusting heating power to enable the solid-liquid coexisting alloy to be cooled to a second-order target temperature at a constant rate:
Considering radiation heat dissipation, for an alloy in which static suspension and solid-liquid coexist, the heat balance equation can be expressed as:
Wherein m S and m L are mass of solid phase and liquid phase, and unit is kg. c P,S,Primary and c P,L,Residual are the specific heat of constant pressure of the solid and liquid phases in units of coke per mole. T is the temperature in units of on. t is time and the unit is seconds. Epsilon Total is the overall emissivity of the alloy. Sigma is the Stefan-Boltzmann constant. T e is ambient temperature in units of on. Q is the absorbed power in watts. A Total is the total surface area of the alloy in square meters. ρ Total can be estimated from the average value of the density of the liquid and solid gold of the prepared alloy,
Wherein ρ L and ρ S are densities of liquid and solid states of the prepared alloy, and the unit is kilogram per cubic meter, and the density is determined by the result obtained in the step one. The alloy solid phase mass m S and liquid phase mass m L can be calculated from the alloy total volume and solid phase volume fraction.
Wherein ρ S,Primary is the solid density of the primary phase, ρ L,Residual is the liquid density of the alloy corresponding to the remaining liquid phase, and the unit is kg per cubic meter, which is determined by the result obtained in the step one. f Primary is the solid phase volume fraction. V Total is the total volume of the alloy, obtained from the overall average density and mass of the alloy in cubic meters.
Wherein m Total is the total mass of the alloy, and the unit is kg. ρ Total is the overall average density of the alloy in kilograms per cubic meter. The total surface area A total, the solid phase mass m S and the liquid phase mass m L of the alloy are brought into a thermal equilibrium equation, and the absorption power Q is obtained in watts.
Where f Primary is the solid phase volume fraction. V Total is the total volume of the alloy in cubic meters. ρ S,Primary and M Primary are the solid density and relative atomic mass of the primary phase in kilograms per cubic meter and kilograms per mole. c P,S,Primary is the specific heat of the primary phase in units of coke per mole. ρ L,Residual and M L,Residual are the liquid phase density and relative atomic mass in kilograms per cubic meter and kilograms per mole. c P,L,Redidual is the liquid specific heat of the alloy corresponding to the residual liquid phase, and the unit is coke per mole. ρ S,Primary、cP,S,Primary、ρL,Residual、cP,L,Redidual is obtained from the result obtained in step one. T is the temperature in units of on. t is time and the unit is seconds. Epsilon Total is the overall emissivity of the alloy. Sigma is the Stefan-Boltzmann constant. T e is ambient temperature in units of on. m Total is the total mass of the alloy, in kilograms. ρ Total is the overall average density of the alloy in kilograms per cubic meter.
The initial temperature is noted as T 1n in units of on. The second order target temperature is noted as T 2n in units of on. The temperature coefficient dT/dT is R kelvin per second. The cooling time is noted as t cool in seconds. The relation between the absorption power Q and the time t can be obtained by substituting the total mass M Total, the total emissivity epsilon Total, the primary phase solid specific heat c P,S,Primary, the primary phase solid density rho S,Primary, the residual liquid phase corresponding alloy liquid density rho L,Residual, the relative atomic mass M L,Residual and the liquid specific heat c P,L,Redidual into the formula (1-10).
Q=Q(t) (1-11)
Where t is time and the units are seconds. By substituting the formula (1-11) into the formula (1-2), the relation between the heating power q 3 and the time t can be obtained in watts.
Where t is time and the units are seconds.
The electrostatic levitation-heating power q 3 is adjusted so as to satisfy the formula (1-12) with time. The solid-liquid coexisting alloy was cooled to a second order target temperature T 2n at R kelvin per second over a time T cool.
Step six, adjusting heating power to enable the solid-liquid coexisting alloy to be stabilized at a second-order target temperature and implementing second-order trigger solidification:
The initial temperature is noted as T 2n in units of on. The constant temperature time is noted as t equ in seconds. The temperature coefficient dT/dT was taken to be 0 kelvin per second. The total mass M Total, the total emissivity epsilon Total, the primary phase solid specific heat c P,S,Primary, the primary phase solid density rho S,Primary, the liquid density rho L,Residual of the alloy corresponding to the residual liquid phase, the relative atomic mass M L,Residual and the liquid specific heat c P,L,Redidual are substituted into (1-10), so that the absorption power Q can be obtained, and the unit is watt. Substituting the power into the formula (1-2) to obtain the input power q 4, wherein the unit is watt.
The heating power was adjusted to be equal to the resulting q 4 and the liquid alloy was stable at temperature T 2n over time T equ. And operating the trigger device to solidify the alloy residual liquid phase. And immediately turning off the heating laser after solidification occurs, so that the alloy is naturally cooled. To this end, the electrostatic suspension step triggered solidification was completed and the alloy sample was completely solidified.
The following examples illustrate the invention using a niobium silicon alloy of chemical composition Nb 90Si10 having the phase composition (Nb) +nb 3 Si prepared by conventional solidification methods, the alloy phase composition prepared in example 1 being (Nb) +αnb 5Si3, the alloy phase composition prepared in example 2 being (Nb) +βnb 5Si3.
Example 1
The embodiment provides a niobium-silicon alloy, which comprises the following chemical components of Nb 90Si10, wherein the preparation process comprises alloy parameter measurement, alloy temperature control modeling and step triggering solidification, and the following steps are detailed.
Step one, acquiring related alloy density and specific heat data, and providing necessary data for the subsequent steps:
The following steps need to obtain the solid density of Nb 90Si10 alloy liquid, the solid density of niobium, the liquid density of eutectic alloy, the liquid specific heat of Nb 90Si10 alloy, the liquid specific heat of eutectic alloy and the solid specific heat of niobium:
The densities of the liquid and solid state of the Nb 90Si10 alloy were measured as ρ L,Nb90Si10 and ρ S,Nb90Si10 in kilograms per cubic meter.
Where T is the temperature and the units are on. T L is the liquidus temperature of the alloy and the value is 2505.
The residual liquid phase of the alloy is niobium-silicon eutectic with the silicon atom proportion of 17.3 percent. The liquid density was measured as ρ L,Eutectic in kilograms per cubic meter.
ρL,Eutectic＝7.32×103-3.73×10-1(T-TE) (2-2)
Where T is the temperature and the units are on. T E is the eutectic temperature of the alloy, and the numerical value is 2189.
The alloy primary phase is (Nb) and its density can be approximated by pure niobium data. Obtaining solid niobium density ρ S,Nb as in document "S.J.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."
ρS,Nb＝7.92×10-3-3.98×10-1(T-Tm), (2-3)
The units are kilograms per cubic meter. Where T is the temperature and the units are on. T m is the melting point of niobium and has a value of 2750.
The specific heat of the liquid Nb 90Si10 alloy was measured to be c P,L,Nb90Si10 in units of coke per mole.
cP,Nb90Si10＝ξNb90Si10εNb90Si10＝(137.43-4.91×10-2(T-TL)+2.65×10-5(T-TL)2)×0.2375 (2-4)
Where T is the temperature and the units are on. ζ L,Nb90Si10 is the heat radiation ratio of the Nb 90Si10 alloy in units of coke per mole. Epsilon Nb90Si10 is the emissivity of the Nb 90Si10 alloy. T L is the liquidus temperature of the alloy and has a value of 2505.
The liquid specific heat of the niobium-silicon eutectic alloy with the silicon atom ratio of 17.3 percent is measured to be c P,L,Eutectic, and the unit is coke per mole.
cP,L,Eutectic＝ξL,EutecticεEutectic＝(150.48-6.43×10-2(T-TE)+3.21×10-5(T-TE)2)×0.2065 (2-5)
Where T is the temperature and the units are on. ζ L,Eutectic is the heat radiation ratio of the liquid niobium-silicon eutectic alloy in units of coke per mole. Epsilon Eutectic is the emissivity of the niobium-silicon eutectic alloy. T E is the eutectic temperature of the alloy, and the numerical value is 2189.
According to literature "Gale,W.F,in:Totemeier T C(Ed.),Smithells Metals Reference Book(Eighth Edition),Butterworth-Heinemann,Oxford,2004.", solid niobium is obtained with specific heat c PS,Nb as
cPS,Nb＝24.03+3.18×10-3T, (2-6)
The units are coke per mole. Where T is the temperature and the units are on.
The method for measuring the density and specific heat of the alloy is referred to in the literature "C.H.Zheng,P.F.Zou,L.Hu,H.P.Wang,B.Wei,Composition dependence of thermophysical properties for liquid Zr-V alloys determined at electrostatic levitation state,J.Appl.Phys.,131(2022)165104.".
Step two, suspension melting of alloy:
Spherical Nb 100-xSix alloy with mass m kg was placed in an electrostatic suspension apparatus, where m was 6.6x10 -5 kg. The alloy is melted in suspension by heating to a fully liquid state and the temperature T start is controlled above the liquidus in units of on.
The electrostatic levitation device is described in the literature "P.F.Zou,H.P.Wang,S.J.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.".
Step three, adjusting heating power to enable the liquid alloy to be cooled to a first-order target temperature at a constant speed:
considering radiation heat dissipation, the electrostatic suspension liquid alloy obtained in the second step meets a heat balance equation:
Where m is mass and the unit is kg. M is the relative atomic mass of the liquid alloy in kilograms per mole. c P,L is the constant pressure specific heat of the liquid alloy, and the unit is coke per mole. T is the temperature in units of on. t is time and the unit is seconds. Epsilon is the emissivity of the liquid alloy. Sigma is the Stefan-Boltzmann constant, 5.67 x 10 -8 watts per square meter per square per square. T e is ambient temperature in units of on. A is the surface area of the liquid alloy, and the unit is square meters. Q is the absorbed power in watts. The absorption power and the heating power q 1 satisfy the following conditions:
aq1=Q (2-8)
Where a is the absorption efficiency. The liquid alloy is approximated as a sphere, the surface area a may be expressed as,
Where pi is the circumference ratio. m is the mass of the liquid alloy, and the unit is kg. ρ L is the liquid alloy density in kilograms per cubic meter. The sample energy absorption efficiency a was calibrated to be 12% (±0.5%) considering the heating laser and sample size of the electrostatic suspension device. Substituting equation (2-9) into equation (2-7) yields the absorbed power Q in watts.
Where m is mass and the unit is kg. M is the relative atomic mass of the liquid alloy in kilograms per mole. c P,L is the constant pressure specific heat of the liquid alloy, and the unit is coke per mole. T is the temperature in units of on. t is time and the unit is seconds. Pi is the circumference ratio. Epsilon is the emissivity of the liquid alloy. Sigma is the Stefan-Boltzmann constant. T e is ambient temperature in units of on. ρ L is the alloy liquid density in kilograms per cubic meter.
The initial temperature was taken to be T start at 2515. The first order target temperature T 1n is 2375 on. The temperature coefficient dT/dT was taken to be-20 kelvin/sec. And (3) taking the results obtained in the step one from the liquid density ρ L and the liquid specific heat c P,L, substituting the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e into the formula (2-10), and obtaining the relation between the absorption power Q and the time, wherein the unit is W.
Q=10.59-0.36t+4.15×10-3t2 (2-11)
By substituting the formula (2-11) into the formula (2-8), the relation between the heating power q 1 and time can be obtained in watts.
q0＝88.23-3.02t+3.46×10-2t2 (2-12)
The electrostatic levitation heating power q 1 is adjusted so that the time and the equation (2-12) are satisfied. The liquid alloy was cooled to a first order target temperature of 2375 at 20 kelvin per second over a period of 7.0 seconds.
Regulating heating power to stabilize the liquid alloy at the first-order target temperature and implementing first-order trigger solidification:
The initial temperature is taken as the first order target temperature 2375. The temperature coefficient dT/dT was taken to be 0 kelvin per second. The constant temperature time was t equ and 17.6 seconds. The liquid density ρ L and the liquid specific heat c P,L are obtained in the first step. The absorption power Q is 8.77W by substituting the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e into the formula (2-10). By substituting the formula (2-8), the heating power q 2 was 73.+ -. 3 Watts.
The heating power was adjusted to be equal to the resulting q 2 and the liquid alloy was allowed to settle at 2375 on a 17.6 second time. And operating the trigger device, and solidifying the primary phase of the alloy. And (3) finishing the first stage of static suspension step solidification, and changing the sample into a solid-liquid coexisting state.
Fifthly, adjusting heating power to enable the solid-liquid coexisting alloy to be cooled to a second-order target temperature at a constant rate:
Considering radiation heat dissipation, for an alloy in which static suspension and solid-liquid coexist, the heat balance equation can be expressed as:
Wherein m S and m L are mass of solid phase and liquid phase, and unit is kg. c P,S,Primary and c P,L,Residual are the specific heat of constant pressure of the solid and liquid phases in units of coke per mole. T is the temperature in units of on. t is time and the unit is seconds. Epsilon Total is the overall emissivity of the alloy. Sigma is the Stefan-Boltzmann constant. T e is ambient temperature in units of on. Q is the absorbed power in watts. A Total is the total surface area of the alloy in square meters. The overall surface area a of the alloy can be derived from its mass and average density,
Where pi is the circumference ratio. m Total is the total mass of the alloy, in kilograms. ρ Total is the overall average density of the alloy in kilograms per cubic meter. ρ Total can be estimated from the average value of the density of the liquid and solid gold of the prepared alloy,
Wherein ρ L and ρ S are densities of liquid and solid states of the prepared alloy, and the unit is kilogram per cubic meter, and the density is determined by the result obtained in the step one. The alloy solid phase mass m S and liquid phase mass m L can be calculated from the alloy total volume and solid phase volume fraction.
Wherein ρ S,Primary is the solid density of the primary phase, ρ L,Residual is the liquid density of the alloy corresponding to the remaining liquid phase, and the unit is kg per cubic meter, which is determined by the result obtained in the step one. f Primary is the solid phase volume fraction, determined to be 0.56.V Total is the total volume of the alloy, obtained from the overall average density and mass of the alloy in cubic meters.
Wherein m Total is the total mass of the alloy, and the unit is kg. ρ Total is the overall average density of the alloy in kilograms per cubic meter. The total surface area A total, the solid phase mass m S and the liquid phase mass m L of the alloy are brought into a thermal equilibrium equation, and the absorption power Q is obtained in watts.
Where f Primary is the solid phase volume fraction. V Total is the total volume of the alloy in cubic meters. ρ S,Primary and M Primary are the solid density and relative atomic mass of the primary phase in kilograms per cubic meter and kilograms per mole. c P,S,Primary is the specific heat of the primary phase in units of coke per mole. ρ L,Residual and M L,Residual are the liquid phase density and relative atomic mass in kilograms per cubic meter and kilograms per mole. c P,L,Redidual is the liquid specific heat of the alloy corresponding to the residual liquid phase, and the unit is coke per mole. ρ S,Primary、cP,S,Primary、ρL,Residual、cP,L,Redidual is obtained from the result obtained in step one. T is the temperature in units of on. t is time and the unit is seconds. Epsilon Total is the overall emissivity of the alloy. Sigma is the Stefan-Boltzmann constant. T e is ambient temperature in units of on. m Total is the total mass of the alloy, in kilograms. ρ Total is the overall average density of the alloy in kilograms per cubic meter.
The initial temperature was recorded as 2375 kelvin. The second order target temperature T 2n is noted as 2102 on. The temperature coefficient dT/dT is-10 kelvin per second. The cool down time t cool is 27.3 seconds. The relation between the absorption power Q and the time t can be obtained by substituting the total mass M Total, the total emissivity epsilon Total, the primary phase solid specific heat c P,S,Primary, the primary phase solid density rho S,Primary, the residual liquid phase corresponding alloy liquid density rho L,Residual, the relative atomic mass M L,Residual and the liquid specific heat c P,L,Redidual into the formula (2-18).
Q=8.47-0.15×10-2t+8.59×10-4t2 (2-19)
Where t is time and the units are seconds. By substituting the expression (2-19) into the expression (2-8), the relation between the heating power q 3 and the time t can be obtained in watts.
q3＝70.61-1.24t+7.16×10-3t2 (2-20)
Where t is time and the units are seconds.
The electrostatic levitation heating power q 3 is adjusted so that the time and the equation (2-20) are satisfied. The solid-liquid coexisting alloy was cooled to the second order target temperature 2102 at-10 kelvin for 27.3 seconds.
Step six, adjusting heating power to enable the solid-liquid coexisting alloy to be stabilized at a second-order target temperature and implementing second-order trigger solidification:
The initial temperature is taken to be the second order target temperature 2102. The temperature coefficient dT/dT was taken to be 0 kelvin per second. The constant temperature time was t equ seconds 59.5. The as-formed phase solid state density ρ S,Primary, as-formed phase solid specific heat c P,S,Primary, the remaining liquid phase density ρ L,Residual, and the remaining liquid phase specific heat c P,L,Redidual are estimated from the results obtained in the step one. The alloy total mass m Total, the total emissivity epsilon Total and the total density rho L,Total are substituted into (2-18). The absorption power Q is 5.29 watts. By substituting the formula (2-8), the heating power q 4 was 44.+ -. 2 Watts.
The heating power was adjusted to be equal to the resulting q 4 and the liquid alloy stabilized at 2102 on for 59.5 seconds. And operating the trigger device to solidify the alloy residual liquid phase. And immediately turning off the heating laser after solidification occurs, so that the alloy is naturally cooled. The static suspension step triggers solidification to finish, and the alloy is completely solidified.
The step trigger temperature curve in the alloy preparation process can be obtained through the steps, and the step trigger temperature curve is shown in fig. 1. As can be seen from fig. 1, the results obtained by the calculation of the present invention can well control the solidification of the primary phase of the alloy at the first order target temperature 2375 and the solidification of the remaining liquid phase of the alloy at the second order target temperature 2102. Fig. 2 shows a solidification structure of an Nb 90Si10 alloy prepared by a conventional solidification method, in which a primary phase is a rod-like eutectic composed of a white phase and a gray phase. FIG. 3 shows the solidification structure obtained in example 1, wherein the primary interphase structure is completely different from the conventional solidification structure and is a black-white two-phase lamellar eutectic. Fig. 5 shows their X-ray diffraction patterns, whereas the conventional solidified niobium silicon alloy is composed of a brittle and unstable (Nb) +nb 3 Si phase, whereas example 1 is composed of a stable (Nb) +αnb 5Si3 phase. The electrostatic suspension step triggering solidification method provided by the invention can effectively regulate and control the composition and microstructure of the alloy phase.
Example 2
The present embodiment provides a niobium-silicon alloy, which has a chemical composition Nb 90Si10, and the preparation process is the same as that of embodiment 1, except that the values of the first-order target temperature T 1n, the second-order target temperature T 2n and the temperature coefficient dT/dT are the same in the third, fourth, fifth and sixth steps.
Step three, adjusting heating power to enable the liquid alloy to be cooled to a first-order target temperature at a constant speed:
The initial temperature was taken to be T start at 2515. The first order target temperature T 1n is 2325 on. The temperature coefficient dT/dT was taken to be-13 kelvin/sec. And (3) taking the results obtained in the step one from the liquid density ρ L and the liquid specific heat c P,L, substituting the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e into the formula (2-10), and obtaining the relation between the absorption power Q and the time, wherein the unit is W.
Q=10.76-0.23t+1.72×10-2t2 (3-1)
By substituting the formula (3-1) into the formula (2-8), the relation between the heating power q 1 and time can be obtained in watts.
q1＝89.67-1.96t+4.14×10-2t2 (3-2)
The electrostatic levitation-heating power q 1 is adjusted so as to satisfy the formula (3-2) with time. The liquid alloy is cooled to a first order target temperature 2325 at 13 kelvin per second over a period of 14.6 seconds.
Regulating heating power to stabilize the liquid alloy at the first-order target temperature and implementing first-order trigger solidification:
The initial temperature is taken to be the first order target temperature 2325. The temperature coefficient dT/dT was taken to be 0 kelvin per second. The constant temperature time was t equ and 7.7 seconds. The liquid density ρ L and the liquid specific heat c P,L are obtained in the first step. The absorption power Q is 8.04W by substituting the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e into the formula (2-10). By substituting the above formula (2-8), the heating power q 2 was 67.+ -. 3W.
The heating power was adjusted to be equal to the resulting q 2 and the liquid alloy was stable at 2325 over a period of 7.7 seconds. And operating the trigger device, and solidifying the primary phase of the alloy. And (3) finishing the first stage of static suspension step solidification, and changing the sample into a solid-liquid coexisting state.
Fifthly, adjusting heating power to enable the solid-liquid coexisting alloy to be cooled to a second-order target temperature at a constant rate:
The initial temperature was recorded as 2325 on. The second order target temperature T 2n is noted as 2117. The temperature coefficient dT/dT was-13 kelvin per second. The cool down time t cool is 16.0 seconds. The relation between the absorption power Q and the time t can be obtained by substituting the total mass M Total, the total emissivity epsilon Total, the primary phase solid specific heat c P,S,Primary, the primary phase solid density rho S,Primary, the residual liquid phase corresponding alloy liquid density rho L,Residual, the relative atomic mass M L,Residual and the liquid specific heat c P,L,Redidual into the formula (2-18).
Q=7.68-0.18t+1.43×10-3t2 (3-3)
Where t is time and the units are seconds. By substituting the formula (3-3) into the formula (2-8), the relation between the heating power q 3 and the time t can be obtained in watts.
q3＝64.01-1.51t+1.19×10-2t2 (3-4)
Where t is time and the units are seconds.
The electrostatic levitation-heating power q 3 is adjusted so as to satisfy the formula (3-4) with time. The solid-liquid coexisting alloy was cooled to the second order target temperature 2117 at 13 kelvin per second over 16.0 seconds.
Step six, adjusting heating power to enable the solid-liquid coexisting alloy to be stabilized at a second-order target temperature and implementing second-order trigger solidification:
the initial temperature is taken as the second order target temperature 2117. The temperature coefficient dT/dT was taken to be 0 kelvin per second. The constant temperature time was t equ to 12.9 seconds. The as-formed phase solid state density ρ S,Primary, as-formed phase solid specific heat c P,S,Primary, the remaining liquid phase density ρ L,Residual, and the remaining liquid phase specific heat c P,L,Redidual are estimated from the results obtained in the step one. The alloy total mass m Total, the total emissivity epsilon Total and the total density rho L,Total are substituted into (2-18). The absorption power Q is 5.45 watts. By substituting the formula (2-8), the heating power q 4 is 45.+ -. 2 Watts.
The heating power was adjusted to be equal to the resulting q 4 and the liquid alloy stabilized at 2117 over a period of 12.9 seconds. And operating the trigger device to solidify the alloy residual liquid phase. And immediately turning off the heating laser after solidification occurs, so that the alloy is naturally cooled. The static suspension step triggers solidification to finish, and the alloy is completely solidified.
FIG. 4 shows the solidification structure obtained in example 1, wherein the primary interphase structure is completely different from the conventional solidification structure and is a black-white two-phase lamellar eutectic. Fig. 5 shows the X-ray diffraction patterns of the alloys obtained by the different preparation methods, whereas the conventional solidified niobium silicon alloy is composed of (Nb) +nb 3 Si phase, whereas example 2 is composed of (Nb) +βnb 5Si3 phase. The electrostatic suspension step triggering solidification method provided by the invention can effectively regulate and control the composition and microstructure of the alloy phase.

Claims (4)

1. An electrostatic suspension step triggering solidification method for regulating and controlling alloy phase selection is characterized by comprising the following steps:
Step 1, determining the density and specific heat related data of the prepared alloy, wherein the data comprise the liquid density rho L and the solid density rho S of the alloy, the unit is kilogram per cubic meter, the solid density rho S,Primary of the alloy corresponding to a primary phase and the liquid density rho L,Residual of the alloy corresponding to a residual liquid phase;
Determining the liquid specific heat of the alloy c P,L in joules per kelvin per mole, hereinafter abbreviated as coke per mole, determining the solid specific heat of the alloy corresponding to the primary phase as c P,S,Primary, and the liquid specific heat of the alloy corresponding to the remaining liquid phase as c P,L,Residual in joules per mole;
step 2, suspension melting of alloy:
Placing spherical alloy with mass of m kg into an electrostatic suspension device, heating the alloy in suspension until the alloy is melted to be in a complete liquid state above a liquidus line, and controlling the temperature T start to be above the liquidus line, wherein the unit is Kelvin, which is called open for short;
step 3, adjusting heating power to enable the liquid alloy to be cooled to a first-order target temperature T 1n at a constant speed:
The electrostatic levitation heating power q 1 is adjusted to be:
Wherein M, M, c P,L,、ε、ρL and a are respectively the mass, relative atomic mass, specific heat at constant pressure, emissivity, density and temperature absorption efficiency of the liquid alloy, T e, pi and sigma are respectively the ambient temperature, the circumferential rate and the Stefan-Boltzmann constant, and T 1、t1、dT1/dt1 is respectively the temperature, the time and the temperature rate;
the sample is cooled from the temperature T start to the temperature T 1n at the speed of dT 1/dt1;
Step 4, adjusting heating power to enable the liquid alloy to be stabilized at a first-order target temperature and implementing first-order trigger solidification:
The electrostatic levitation heating power q 2 is adjusted to be:
Wherein T 1n、Te, pi and sigma are first-order target temperature and environment temperature respectively;
the sample is stabilized at a first-order target temperature T 1n, a trigger device is operated, and an alloy primary phase is solidified;
step 5, adjusting heating power to enable the solid-liquid coexisting alloy to be cooled to a second-order target temperature at a constant rate:
the electrostatic levitation heating power q 3 is adjusted to be:
Wherein T 3、t3、dT3/dt3 is the temperature, time and temperature rate of the stage respectively, f Primary、MPrimary、cP,S,Primary、ρS,Primary is the volume fraction, relative atomic mass, specific heat and density of the primary phase respectively, ρ L,Residual、ML,Residual、cP,L,Redidual is the density, relative atomic mass and specific heat of the residual liquid phase respectively, and V Total、εTotal、mTotal、ρTotal is the total volume, total emissivity, mass and total average density of the alloy respectively;
The sample is cooled from the temperature T 1n to a second-order target temperature T 2n at the speed of dT 3/dt3;
And 6, adjusting heating power to enable the solid-liquid coexisting alloy to be stabilized at a second-order target temperature and implementing second-order trigger solidification, wherein the adjusting electrostatic suspension heating power q 4 is as follows:
Wherein T 2n is the second-order target temperature, epsilon Total、mTotal、ρTotal is the total emissivity, mass and total average density of the alloy respectively;
The sample is stabilized at a second-order target temperature T 2n, a trigger device is operated, the alloy residual liquid phase is solidified, and heating laser is immediately turned off after solidification occurs, so that the alloy is naturally cooled.
2. The method for controlling the electrostatic suspension step triggering solidification of alloy phase selection according to claim 1, wherein the density and specific heat data of the alloy are not given in the literature in the step 1, refer to "C.H.zheng, P.F.
Zou,L.Hu,H.P.Wang,B.Wei,Composition dependence of thermophysical propertiesfor liquid Zr-V alloys determined at electrostatic levitation state,J.Appl.Phys.,131(2022)165104." The method disclosed in (a) is used for measurement.
3. The method for triggering and solidifying an electrostatic suspension step for regulating and controlling alloy phase selection according to claim 1, wherein the electrostatic suspension device is described in the literature "P.F.Zou,H.P.Wang,S.J.Yang,L.Hu,B.Wei,DensityMeasurement and Atomic Structure Simulation of Metastable Liquid Ti-Ni Alloys,Metall.Mater.Trans.A,49A(2018)5488-5496.".
4. The method for controlling the electrostatic suspension step triggering solidification of alloy phase selection according to claim 1, wherein q 1、q2、q3 and q 4 in the step 3, the step 4, the step 5 and the step 6 are all electrostatic suspension heating power q in different stages, and the calculation according to q 1 is based on the relation q 1＝q1 (t) between the heating power q 1 and time, wherein the electrostatic suspension alloy satisfies a heat balance equation:
Wherein M is the mass, M is the relative atomic mass of the liquid alloy in kilograms per mole, c P,L is the constant pressure specific heat of the liquid alloy in grams per mole, T is the temperature in grams per mole, T is the time in seconds, ε is the emissivity of the liquid alloy, σ is the Stefan-Boltzmann constant, 5.67 x 10 -8 watts per square meter, T e is the ambient temperature, A is the surface area of the liquid alloy in square meter, Q is the absorbed power in watts, and the absorbed power and the heating power Q 1 satisfy:
aq1=Q
wherein a is absorption efficiency, a heat balance equation is arranged to obtain absorption power Q, and the unit is watt:
Wherein pi is the circumferential rate, ρ L is the alloy liquid density, and the unit is kilogram per cubic meter;
The initial temperature is recorded as T start, the first-order target temperature is recorded as T 1n, the first-order target temperature is recorded as on, the temperature coefficient dT/dT is recorded as a constant R, the unit is Kelvin per second, the cooling time is recorded as T cool, the unit is seconds, the liquid density rho L and the liquid specific heat c P,L, the mass M, the relative atomic mass M, the emissivity epsilon, the Stefan-Boltzmann constant sigma and the ambient temperature T e are substituted into the above to obtain the relation between the absorption power Q and the time, and the unit is W
Q=Q(t)
Substituting the above formula into the formula aq 1 =q, the relationship between the heating power Q 1 and time is obtained in watts.
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CN1578846A (en) * 2001-10-03 2005-02-09 液态金属技术公司 Process for improving bulk solidifying amorphous alloy compositions and cast articles made therefrom
CN114334016A (en) * 2021-10-26 2022-04-12 兰州大学 Method for predicting concentration of magnesium-lithium alloy directional solidification starting liquid phase

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