CN109211903B - Method for carrying out quantitative analysis on in-situ observation result of phase change and application - Google Patents

Abstract

The invention discloses a method for carrying out quantitative analysis on an in-situ observation result of phase change, and belongs to the field of metal heat treatment. The method comprises the steps of carrying out contour extraction, coloring, superposition and re-extraction on microscopic structure images of a metal material to be detected, which are obtained in situ at different time periods, so as to obtain structure images which are formed in sequence according to time; and counting the number of pixels with different colors in the tissue map, accumulating the pixels according to time, and calculating the cooling phase change volume fraction. Compared with the conventional method, the method for determining the phase variable has the characteristics of intuition and accuracy, and can be used for calculating the relation between the phase change product and time/temperature.

Description

A method and application for quantitative analysis of in situ observations of phase transitions

technical field

The invention belongs to the field of metal heat treatment, and more particularly, relates to a method for quantitatively analyzing in-situ observation results in phase transition.

Background technique

The quantitative analysis methods of phase transition are commonly used quenching method, thermal expansion method, ultrasonic method, high temperature XRD method, DSC method, etc. These methods have their own advantages and disadvantages. For example, although the quenching method has high precision, the number of experiments is large, and the workload is extremely large when quantitatively analyzing the phase transformation process. The thermal expansion method greatly reduces the number of experiments, but if different structures are formed successively during cooling, it is extremely difficult to accurately obtain the phase transition point. The ultrasonic method device is difficult to obtain, and the high-temperature XRD method faces the problem that the scanning speed cannot keep up with the cooling speed. When DSC measures the phase transition, it is difficult to obtain the phase transition curve at a faster cooling rate due to the limitation of the maximum cooling rate of the equipment. Relevant published patents are: Chinese utility model patent specification CN1247978 discloses a high-pressure and high-temperature phase transition test method, which determines the phase transition process of the sample by plotting the dP/dT curve of the change rate of pressure with temperature. Chinese utility model patent specification CN103308546A discloses a method for measuring the phase change function of a shape-setting phase change material, which determines the phase change kinetics by measuring the thermal conductivity and the latent heat of the phase change during the heating process of the material.

The in-situ observation method is a method that has emerged in recent years, and has been gradually applied in many fields such as material solidification, phase transformation, and grain growth. The phase transition process can be observed in a wide range of cooling rates. However, quantitative analysis of the in situ observations of phase transitions is still lacking, so that the scientific significance of the in situ observations cannot be fully explored.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention provides an accurate quantitative analysis method, the purpose of which is to process the microstructure images taken in situ at different times, such as discoloration, superposition, extraction, etc. The in-situ observation results are accurately quantitatively analyzed, thereby solving the technical problem that the prior art lacks the quantitative analysis of the in-situ observation results.

In order to achieve the above object, according to one aspect of the present invention, a method for quantitatively analyzing the in-situ observation results of the phase transition is provided, comprising the following steps:

Step 1: Obtain in-situ microstructure diagrams of the metal material to be tested before, during, and after phase transformation;

Step 2: Extract the grain boundaries and newly generated phase contours in the microstructure images at different times. Except for the contours, other positions in the image are transparent;

Step 3: Change the contour photos at different times to different gradient colors, and superimpose them in chronological order. Among them, the contours in the picture taken first should be covered with the pictures taken later; The different colors of , indicate that the sequence of formation is different;

Step 4: On the basis of the color images obtained by superimposing in step 3, several images of different colors are sequentially extracted according to the gradient colors selected in step 3, and these images respectively represent the organizations formed in chronological order;

Step 5: Count the number of pixels with different colors in the image extracted in step 4, and accumulate these pixels by time to calculate the cooling phase change volume fraction.

Further, in step 2, the grain boundaries and newly generated phase contours in the photos at different times are extracted by adjusting the brightness and contrast of the image processing method.

Further, choose blue-green for the gradient color of step 3.

Further, in step 1, the in-situ image acquisition method is an in-situ photographing result of a high-temperature metallographic microscope, or an in-situ video recording of a high-temperature laser confocal microscope.

Further, the metal material to be tested is steel or nickel-based superalloy.

In order to achieve the above object, the present invention also provides the application of the above method, that is, the above method is used to calculate the relationship between phase change products and time/temperature.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

1. The present invention can achieve accurate quantitative analysis of the in-situ observation results by performing discoloration, stacking, extraction, and pixel accumulation on the microstructure images taken at different times in situ, and overcomes the inability to target phase transitions in the prior art. In situ observations of defects for precise quantitative analysis.

2. Compared with the conventional method, the phase variable determined according to the method of the present invention has the characteristics of intuition and accuracy.

3. By superimposing the color images first and then extracting them, it is possible to obtain the organizational charts that represent the chronological order, and realize the accurate classification of the in-situ measurement results, which is beneficial to the subsequent statistical operations.

Description of drawings

Fig. 1 is the quantitative analysis flow of the present invention.

Figure 2 is a schematic diagram of a quantitative analysis of tissue transition diagrams according to a preferred embodiment of the present invention.

FIG. 3 is a metallographic diagram observed in situ in an application example of the present invention.

Fig. 4 is the processing method of Fig. 3 , wherein a-f are the structure diagrams of different colors, g is the superimposed diagram, and h is the relationship curve of the phase change product and temperature.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

As shown in Figure 1, a method for quantitatively analyzing the in-situ observation results of the phase transition of the present invention mainly includes the following steps:

Step 1: Obtain in-situ microstructure images of the metal material to be tested before, during, and after phase transformation; in-situ images are obtained by in-situ photographing results of a high-temperature metallographic microscope, or high-temperature laser confocal Microscope in situ video. The metal material to be tested is steel or nickel-based superalloy.

Step 2: Extract the grain boundaries and newly generated phase contours in the microstructure map at different times. Except for the contours, other positions in the image are transparent; preferably, the images at different times are extracted by adjusting the brightness and contrast of the image processing method. Grain boundaries and newly generated phase contours in .

Step 3: Change the contour photos at different times to different gradient colors, and superimpose them in chronological order. Among them, the contours in the picture taken first should be covered with the pictures taken later; The different colors of , indicate that the sequence of formation is different; preferably, the gradient color is selected from blue to green.

Step 4: On the basis of the color images obtained by superimposing in step 3, several images of different colors are sequentially extracted according to the gradient colors selected in step 3, and these images respectively represent the organizations formed in chronological order;

Step 5: Count the number of pixels of different colors in the image extracted in step 4 in the image processing software, accumulate these pixels by time, and calculate the cooling phase change volume fraction.

Below in conjunction with Fig. 2, the schematic diagram of the above bainite formation process is taken as an example to explain the specific implementation steps of the present invention:

1. Obtain the in-situ observation pictures of the upper bainite before, during and after the formation.

2. Adjust the pictures to different colors.

3. Overlay these pictures in turn.

4. Respectively extract the regions where different colors of the superimposed image are located.

5. Count the pixels of these regions separately to obtain the tissue transformation value.

It should be noted that Figure 2 is only the idea and method of realization. Due to limitations such as photographing and contrast, the perfect process of tissue transformation may not be accurately extracted in the specific implementation. Image processing methods are not limited to adjusting contrast and brightness, but can also adjust hue, saturation, etc.

Below in conjunction with an application example of Fig. 3 and Fig. 4, the specific application of the present invention in the quantitative analysis of 300M steel continuous cooling microstructure transformation is described:

1. Record the metal cooling phase transformation process in situ on a high temperature laser confocal microscope, and obtain the microstructure pictures before, during and after phase transformation. FIG. 3 is a metallographic diagram of the metal cooling phase transformation process obtained by in-situ observation at two cooling rates.

2. By adjusting the brightness, contrast and other image processing methods, the grain boundaries and newly generated phase contours in the photo at different times are extracted. Except for the contour, other positions in the image are transparent.

3. Change the contour photos at different times to different colors that gradually change, such as blue-green, and superimpose them in chronological order. The contours in the pictures taken first should cover the pictures taken later. After superimposing, a color map is obtained, and the different colors of the phases in the figure indicate different sequences of formation. In Fig. 4, a-f are tissue maps of different colors, and g is the superimposed image. Figure 4 replaces the actual color image with a grayscale image.

4. Count the number of pixels of different colors in these pictures in the picture processing software.

5. Accumulate these pixels according to time, calculate the tissue transformation amount, and draw a relationship curve with temperature as shown in h in Figure 4.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (6)

1. a method for carrying out quantitative analysis to the in-situ observation result of phase transition, is characterized in that, comprises the steps: Step 1: Obtain in-situ microstructure diagrams of the metal material to be tested before, during, and after phase transformation; Step 2: Extract the grain boundaries and newly generated phase contours in the microstructure images at different times. Except for the contours, other positions in the image are transparent; Step 3: Change the contour photos at different times to different gradient colors, and superimpose them in chronological order. Among them, the contours in the pictures taken first should be covered with the pictures taken later; after the superposition, a color image is obtained, and the corresponding images in the color image are Different colors indicate different sequences of formation; Step 4: On the basis of the color images obtained by superimposing in step 3, several images of different colors are sequentially extracted according to the gradient colors selected in step 3, and these images respectively represent the organizations formed in chronological order; Step 5: Count the number of pixels with different colors in the image extracted in step 4, and accumulate these pixels by time to calculate the cooling phase change volume fraction. 2. a kind of method for carrying out quantitative analysis to the in-situ observation result of phase change as claimed in claim 1, is characterized in that, in step 2, extracts crystals in different moment photos by the image processing method of adjusting brightness, contrast. bounds and newly generated phase contours. 3. The method for quantitatively analyzing the in-situ observation results of the phase transition according to claim 1 or 2, wherein the gradient color in step 3 is selected from blue to green. 4. a kind of method for carrying out quantitative analysis to the in-situ observation result of phase transition as claimed in claim 1 or 2, it is characterized in that, in step 1, the mode of in-situ acquisition of image is high-temperature metallographic microscope in-situ photographing result , or high-temperature laser confocal microscopy in situ video. 5. The method for quantitatively analyzing the in-situ observation results of phase transformation according to claim 1 or 2, wherein the metal material to be tested is steel or a nickel-based superalloy. 6. Use of the method according to any one of claims 1 to 5 for calculating the relationship between phase change products and time/temperature.

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