CN111060554B - Rapid analysis method for determining content of supercooled hypoeutectic alloy phase - Google Patents

Abstract

The invention discloses a rapid analysis method for determining the phase content of supercooled hypoeutectic alloy, which utilizes a thermal analysis device to simultaneously calculate the supercooling degree and the phase proportion of the hypoeutectic alloy by measuring and analyzing a heating curve of the eutectic alloy and a heating and cooling curve of the hypoeutectic alloy, thereby achieving the purpose of conveniently and accurately predicting the alloy structure. The invention has the following advantages: (1) compared with the theoretical analysis of a lever law or a Charles equation, the method does not need to determine physical parameters such as solute segregation coefficients and liquidus slopes which are difficult to quantify, does not need to consider the diversity and complexity of actual solidification structures, has accurate calculation results, and has higher universality on engineering multi-element alloys. (2) Compared with metallographic observation and synchrotron radiation in-situ analysis methods, the method can obviously shorten the analysis period, reduce the test cost, effectively solve the difference between the two-dimensional tissue and the actual three-dimensional tissue, and has higher accuracy and popularization and application values.

Description

Rapid analysis method for determining content of supercooled hypoeutectic alloy phase

Technical Field

The invention relates to the field of material processing, in particular to a rapid analysis method for determining the content of a supercooled hypoeutectic alloy phase for analyzing the nonequilibrium solidification process of hypoeutectic alloy.

Background

The phase content of the alloy directly influences the mechanical and electrochemical properties of the material and needs to be accurately described. The existing lever law or summer equation for calculating the content of alloy phase is only suitable for the complete equilibrium or near equilibrium condition and cannot be used for analyzing the solidification process when the supercooling degree exists. For multi-element alloy, due to the obvious interaction effect among elements, key physical parameters such as solute segregation coefficient, liquidus slope and the like are difficult to quantify, and only the assumed treatment can be carried out according to a binary alloy system, so that the error between the theoretical calculation result of a lever law or a summer equation and the actual situation is larger. Even if a multi-element alloy phase diagram software calculation or computer numerical simulation method is adopted, as the structure in the alloy has the diversity of plate shape, spherical shape or cylindrical shape and the like, and the structure can be further evolved along with the solidification process, the description is more complicated, and the accurate calculation of the phase content can not be realized from a theoretical level.

If the metallographic observation method after the intermediate quenching or the solidification is adopted, the actual three-dimensional structure condition in the alloy is difficult to truly reflect by the two-dimensional picture under the microscope, and the final analysis result is influenced by the deviation of the sampling position, the limited observation visual field, the proportion of the corrosive liquid, the corrosion time and the professional experience difference of an operator, so that the phase content of the alloy cannot be accurately reflected from the experimental layer. Even if the in-situ visualization is carried out on the crystal growth process of the alloy by adopting a synchrotron radiation light source with high energy, high brightness and strong penetrability, the analysis of certain specific and limited alloy systems under the condition of near equilibrium can only be realized at present under the influence of the contrast ratio and the resolution ratio of a solid phase and the liquid phase, the operation period is long, the cost is high, and the rapid analysis of the supercooled alloy cannot be realized from the experimental level.

Disclosure of Invention

The invention aims to provide a rapid analysis method which can rapidly, efficiently and accurately determine the content of a supercooled hypoeutectic alloy phase and conveniently and accurately predict an alloy structure.

The purpose of the invention is realized as follows:

a rapid analysis method for determining the content of supercooled hypoeutectic alloy phase is characterized in that: the rapid analysis method comprises the following steps:

A. carrying out thermal analysis experiment of eutectic alloy: obtaining heat flow change in the alloy melting process according to the temperature rise curve of the eutectic alloy, and calculating the latent heat value Q when the complete eutectic reaction occurs by adopting an envelope curve method₀；

B. Carrying out thermal analysis experiment of Al-Cu hypoeutectic alloy: determining the liquidus temperature T of the alloy according to the temperature rise curve of the Al-Cu hypoeutectic alloy_LObtaining the nucleation temperature T in the alloy solidification process according to the temperature reduction curve of the Al-Cu hypoeutectic alloy_NAnd the heat flow change when the eutectic phase is solidified, and calculating the latent heat value Q when the eutectic reaction occurs by adopting an envelope method₁；

C. According to the determined Al-Cu hypoeutecticLiquidus temperature T of alloy_LAnd nucleation temperature T_NCalculating the actual supercooling degree delta T as T when the alloy is solidified_L-T_N；

D. According to the determined latent heat value Q of the eutectic alloy₀Eutectic reaction latent heat value Q with Al-Cu hypoeutectic alloy₁Calculating eutectic phase ratio f in the Al-Cu hypoeutectic alloy under the condition of supercooling degree₁＝Q₁/Q₀；

E. By the determined ratio f of eutectic phases₁Calculating the proportion f of the first phase₂＝1-f₁＝1-Q₁/Q₀；

F. From this, the actual supercooling degree DeltaT is determined_L-T_NWhen the eutectic phase proportion and the primary phase proportion of the Al-Cu hypoeutectic alloy are respectively Q₁/Q₀And 1-Q₁/Q₀I.e. f₁And f₂。

The method comprises the steps of firstly developing a thermal analysis experiment of the eutectic alloy by using a thermal analysis device, and determining the latent heat value when the eutectic reaction occurs according to a temperature rise curve; then carrying out a thermal analysis experiment of hypoeutectic alloy, determining the liquidus temperature of the alloy according to a temperature rise curve, and obtaining the nucleation temperature in the solidification process of the alloy and the latent heat value when eutectic reaction occurs according to a temperature drop curve; determining the actual supercooling degree of the alloy during solidification according to the liquidus temperature and the nucleation temperature; and finally, determining the proportion of eutectic phases in the hypoeutectic alloy under the supercooling degree condition according to the latent heat value when the eutectic reaction of the two alloys occurs, and determining the proportion of primary phases according to the proportion of the eutectic phases. Namely, the supercooling degree and the phase proportion in the hypoeutectic alloy are simultaneously calculated by measuring and analyzing the temperature rise curve of the eutectic alloy and the temperature rise and temperature fall curve of the hypoeutectic alloy, and subsequent metallographic structure analysis is not needed, so that the aim of conveniently and accurately predicting the alloy structure is fulfilled.

Compared with the traditional metallographic analysis and theoretical calculation method, the method has the following advantages:

(1) compared with the theoretical analysis of the lever law or the Charles equation, the method does not need to determine physical parameters such as solute segregation coefficient, liquidus slope and the like which are difficult to quantify, does not need to consider the diversity and complexity of an actual solidification structure, can quickly, efficiently and accurately obtain a calculation result, is not limited by an alloy system and supercooling degree, and has higher universality and popularization and application values for engineering multi-element alloys;

(2) compared with metallographic observation and synchrotron radiation in-situ analysis methods, the method can obviously shorten the analysis period, reduce the test cost and effectively solve the difference between the two-dimensional structure and the actual three-dimensional structure. Meanwhile, the device is not required by sampling position deviation, limited observation visual field, corrosion liquid proportion, corrosion time difference and professional experience requirements of operators, and has higher accuracy and popularization and application values.

The method solves the problem that the lever law or the Charles equation can only theoretically predict the phase content when the solidification is completely balanced or nearly balanced without supercooling, and simultaneously effectively overcomes the defects of high cost, long period and large error of microscopic metallographic analysis experiment in synchrotron radiation in-situ analysis.

Drawings

FIG. 1 is a schematic thermal analysis curve of an Al-32 wt% Cu eutectic alloy;

FIG. 2 is a schematic thermal analysis curve of an Al-5 wt% Cu hypoeutectic alloy;

FIG. 3 is a schematic optical microstructure of an Al-5 wt% Cu hypoeutectic alloy;

FIG. 4 is a schematic thermal analysis curve of an Al-10 wt% Cu hypoeutectic alloy;

FIG. 5 is a schematic representation of the optical microstructure of an Al-10 wt% Cu hypoeutectic alloy.

Detailed Description

The invention is further described with reference to the following examples and with reference to the accompanying drawings.

Example 1

The content of primary and eutectic phases in the undercooled Al-5 wt% Cu hypoeutectic alloy was determined. The basic operation steps are as follows:

1) the alloy smelting experiment process comprises the following steps:

respectively preparing Al-5 wt% Cu hypoeutectic alloy and Al-32 wt% Cu eutectic alloy by using a vacuum high-frequency induction smelting furnace, wherein the highest smelting temperature is 800 ℃, and keeping the temperature for 10 min;

2) thermal analysis experimental process:

respectively carrying out heating and cooling experiments on Al-32 wt% Cu eutectic alloy and Al-5 wt% Cu hypoeutectic alloy sheets by adopting a thermal analyzer with double platinum-rhodium thermocouples, wherein the mass of a sample is 50-60 mg, the thickness is 1mm, the whole thermal analysis process is carried out under the protection of high-purity flowing argon, and the heating and cooling rates are both 10K/min;

3) analysis of thermal analysis results:

the heat absorption capacity of melting, namely the total heat Q when the complete eutectic reaction occurs is determined by integral calculation of a thermal analysis curve of the Al-32 wt% Cu eutectic alloy₀336.7J/g (FIG. 1);

determining the liquidus temperature T of the alloy according to the alloy melting curve by analyzing the thermal analysis curve of the Al-5 wt% Cu hypoeutectic alloy_LThe temperature was 664.51 ℃. According to the alloy cooling curve, the nucleation temperature T can be determined_NThe temperature was 643.82 ℃ and hence the actual supercooling degree DeltaT was 20.69 ℃. According to integral calculation, the solidification process corresponding to the eutectic reaction releases latent heat Q₁It was 19.71J/g (FIG. 2). Thus, the eutectic ratio f can be calculated₁5.85%, primary phase ratio f₂94.15%, which is substantially consistent with 5.54% metallographic observation in fig. 3.

Example 2

The content of primary and eutectic phases in the supercooled Al-10 wt% Cu hypoeutectic alloy was determined. The basic operation steps are as follows:

1) the alloy smelting experiment process comprises the following steps:

respectively preparing Al-10 wt% Cu hypoeutectic alloy and Al-32 wt% Cu eutectic alloy by using a vacuum high-frequency induction smelting furnace, wherein the highest smelting temperature is 800 ℃, and keeping the temperature for 10 min;

2) thermal analysis experimental process:

respectively carrying out heating and cooling experiments on Al-32 wt% Cu eutectic alloy and Al-10 wt% Cu hypoeutectic alloy sheets by adopting a thermal analyzer with double platinum-rhodium thermocouples, wherein the mass of a sample is 50-60 mg, the thickness of the sample is 1mm, the whole thermal analysis process is carried out under the protection of high-purity flowing argon, and the heating and cooling rates are both 10K/min;

3) analysis of thermal analysis results:

the heat absorption capacity of melting, namely the total heat Q when the complete eutectic reaction occurs is determined by integral calculation of a thermal analysis curve of the Al-32 wt% Cu eutectic alloy₀336.7J/g (FIG. 1);

determining the liquidus temperature T according to the alloy melting curve by analyzing the thermal analysis curve of the Al-10 wt% Cu hypoeutectic alloy_LThe temperature was 647.17 ℃. According to the alloy cooling curve, the nucleation temperature T can be determined_NThe temperature was 627.28 ℃. The actual supercooling degree Δ T was therefore 19.89 ℃. According to integral calculation, the solidification process corresponding to the eutectic reaction releases latent heat Q₁It was 60.49J/g (FIG. 4). Therefore, the actual eutectic ratio f can be calculated₁17.96%, primary phase ratio f₂82.04%, which is substantially consistent with the metallographic observation of FIG. 5 of 18.1%.

Claims (1)

1. A rapid analysis method for determining the content of supercooled hypoeutectic alloy phases is characterized in that: the rapid analysis method comprises the following steps:

A. carrying out thermal analysis experiment of eutectic alloy: obtaining heat flow change in the alloy melting process according to the temperature rise curve of the eutectic alloy, and calculating the latent heat value Q when the complete eutectic reaction occurs by adopting an envelope curve method₀；

B. Carrying out thermal analysis experiment of Al-Cu hypoeutectic alloy: determining the liquidus temperature T of the alloy according to the temperature rise curve of the Al-Cu hypoeutectic alloy_LObtaining the nucleation temperature T in the alloy solidification process according to the temperature reduction curve of the Al-Cu hypoeutectic alloy_NAnd the heat flow change when the eutectic phase is solidified, and calculating the latent heat value Q when the eutectic reaction occurs by adopting an envelope method₁；

C. According to the determined liquidus temperature T of the Al-Cu hypoeutectic alloy_LAnd nucleation temperature T_NCalculating the actual supercooling degree delta T as T when the alloy is solidified_L-T_N；

D. According to the determined latent heat value Q of the eutectic alloy₀Eutectic reaction latent heat value Q with Al-Cu hypoeutectic alloy₁Calculating A under the supercooling degree conditionEutectic phase ratio f in l-Cu hypoeutectic alloy₁＝Q₁/Q₀；

E. By the determined ratio f of eutectic phases₁Calculating the proportion f of the first phase₂＝1-f₁＝1-Q₁/Q₀；

F. From this, the actual supercooling degree DeltaT is determined_L-T_NWhen the eutectic phase proportion and the primary phase proportion of the Al-Cu hypoeutectic alloy are respectively Q₁/Q₀And 1-Q₁/Q₀I.e. f₁And f₂。

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