CN106645249A - Method for representing stereo-morphology of solidified dendritic crystal - Google Patents

Abstract

The invention provides a method for characterizing the three-dimensional morphology of solidified dendrites. The method is characterized by its applicability to materials that can be analyzed using SEM. Cut the metal material sample with the maximum diameter <25mm, polish the surface and keep it dry, grind and polish the sample and corrode it, after blowing dry, use conductive glue to stick the sample on the sample stage, and put the sample with the sample The stage is placed on the stage to evacuate, the parameters of the scanning electron microscope are set, the debugging is clear, and the electronic image of the dendrite is taken, and the three-dimensional surface reconstruction function of the dendrite is used to obtain a clear three-dimensional image of the dendrite. The 3D reconstructed picture of the solidified dendrites was again obtained by grinding and polishing the sample without etching. The invention realizes the clear characterization of the three-dimensional morphology of the solidified dendrites, and provides a new method for analyzing and characterizing the solidified dendrites.

Description

A method for characterizing the three-dimensional morphology of solidified dendrites

technical field

The invention relates to a method for characterizing the three-dimensional shape of solidified dendrites, which is a method for analyzing and characterizing the three-dimensional shape of solidified dendrites by using the three-dimensional surface reconstruction function carried by a scanning electron microscope, and belongs to the field of metal materials.

Background technique

During the solidification process, when the temperature at the interface increases due to the release of latent heat of crystallization, and the liquid phase is under a supercooled condition, a negative temperature gradient may be generated. At this time, the latent heat of crystallization generated on the phase interface can pass through the solid phase. It can also be lost through the liquid phase. The transition of the phase interface is not only controlled by the heat transfer rate of the solid phase. In this case, if part of the phase interface growth protrudes into the previous liquid phase, it can be in a liquid with a lower temperature, that is, a greater subcooling degree. In the phase, the growth rate of the protruding part increases and extends further into the liquid. In this case, it is impossible for the liquid-solid interface to maintain a planar shape, and many branches extending toward the liquid (along a certain crystal axis) will be formed. At the same time, secondary dendrites may grow on these dendrites, Three dendrites grow out of the secondary dendrites, as shown in Figure 1 of the accompanying drawings. This growth pattern of crystals is called dendritic growth or dendrites. Even if there is a positive temperature gradient at the front of the solid-liquid interface during the solidification process, due to the segregation of solute components caused by non-equilibrium solidification, component supercooling will occur and dendrites will also form.

Solidified dendrites can be displayed by grinding, polishing and corroding the sample. In addition, dendrites sometimes appear without corrosion. This is because the holes formed by the sample when the metal solidifies and shrinks cannot get enough metal. The replenishment of liquid directly preserves the dendrite morphology during solidification.

3D surface reconstruction technology (3D roughness reconstruction) is to reconstruct a 3D model from an electronic image obtained from a view obtained by a scanning electron microscope. The feature of this method is based on the three-dimensional reconstruction of the image, the three-dimensional depth information of the object is calculated and extracted from the scanned image, and the three-dimensional model object with a strong sense of three-dimensional reality is reconstructed according to the obtained three-dimensional depth information. The images obtained by the 3D roughness reconstruction technology can clearly and vividly display the three-dimensional shape of the solidified dendrites, and the size of the dendrite arms can also be measured by the 3D surface reconstruction technology. This technique provides a new method to characterize the three-dimensional shape of solidified dendrites, which is beneficial to quantitatively determine the geometric size characteristics of dendrites, so as to study the solidification behavior of different systems more deeply.

The applicant of the present invention uses dendrite + three-dimensional surface reconstruction (3D roughness reconstruction) as a keyword in "Engineering Abstracts Index" (EI) in the United States, Sciencedirect scientific paper database, ISI Web of Science and other foreign scientific and technological databases, my country's "Chinese Journal "Net" and "VIP Chinese Periodical Database" and other scientific and technological literature indexes, but no complete relevant literature was found. The applicant also searched the United States Patent and Trademark Office (USPTO), the European Patent Office (EPO), the World Intellectual Property Organization (WIPO), "China Patent Information Network" and "Patent Search of the State Intellectual Property Office of the People's Republic of China", and found no Similar patents.

Contents of the invention

The present invention proposes a method for characterizing the three-dimensional morphology of solidified dendrites, that is, a method for analyzing and characterizing the three-dimensional morphology of solidified dendrites by using the three-dimensional surface reconstruction function of a scanning electron microscope. The specific operation steps are as follows:

1. Cut out a metal sample suitable for the size of the scanning electron microscope. The surface of the metal sample is polished and kept dry;

2. Grinding, polishing and corrosion of the sample;

3. Use conductive glue to stick the sample on the sample stage of the scanning electron microscope, and then put the sample stage with the sample on the stage;

4. Use the electronic image of the scanning electron microscope to take a photo of the surface of the dendrite, and then use the three-dimensional surface reconstruction function to obtain a clear three-dimensional shape of the dendrite;

5. Re-grind and polish the sample to obtain a corresponding smooth surface without corrosion, and repeat steps 3 and 4 to obtain the results in Figure 2.

In the method for characterizing the three-dimensional morphology of solidified dendrites, the surface of the metal material needs to be clean and dry, and the maximum diameter of the metal sample should not exceed 25 mm.

The beneficial effect of the invention is that the clear characterization of the three-dimensional shape of the solidified dendrite is realized, and a new method for characterizing the three-dimensional shape of the solidified dendrite is provided. Applicable to all kinds of solidified material systems that can produce dendrite morphology. The three-dimensional morphology of solidified dendrites can be displayed, providing a method for characterizing the three-dimensional morphology of dendrites.

Description of drawings

Figure 1 is a schematic diagram of dendrite growth.

Figure 2 shows the scanned and reconstructed pictures obtained after grinding, polishing and corrosion: (a) is the scanned picture, and (b) is the three-dimensional surface reconstruction picture.

Figure 3 is the scanned and reconstructed images after grinding and polishing but not corroded: (a) is the scanned image, (b) is the three-dimensional surface reconstruction image. Comparing with the obtained Figure 2 shows that the dendrites are not corroded, but formed when the metal solidifies.

Figure 4 is a partially enlarged dendrite morphology using the three-dimensional surface reconstruction function.

detailed description

The present invention will be described in detail below by taking spot welding of medium manganese steel as an example.

Example

1. Intercept the medium manganese steel spot welding sample suitable for scanning electron microscope size, the surface of the sample is polished and kept dry;

2. The corresponding solidified dendrite structure is obtained by corroding the sample after grinding and polishing;

3. Use conductive glue to stick the sample on the sample stage of the scanning electron microscope, and then put the sample stage with the sample on the stage;

4. Use the electronic image of the scanning electron microscope to take a photo of the surface of the dendrite, and then use the three-dimensional surface reconstruction function to obtain a clear three-dimensional shape of the dendrite, as shown in Figure 2;

5. Then re-grind and polish the medium manganese steel spot welding sample to obtain a corresponding smooth surface without corrosion, and repeat steps 3 and 4 to obtain the results in Figure 3.

Claims (2)

1. A method for characterizing the solidified dendrite three-dimensional morphology, characterized in that the method has the following steps: a. Cut out a metal sample suitable for the size of the scanning electron microscope. The surface of the metal sample is polished and kept dry; b. Use conductive glue to stick the metal sample on the sample stage of the scanning electron microscope, and then put the sample stage with the metal sample on the stage; c. Use the electronic image of the scanning electron microscope to take a photo of the surface of the dendrite, and then use the three-dimensional surface reconstruction function to perform three-dimensional reconstruction of the shape of the dendrite to obtain a clear three-dimensional reconstruction picture, thus showing the primary branch of the dendrite Microstructure information related to crystal arms and secondary dendrite arms. 2. The method for characterizing the three-dimensional morphology of solidified dendrites according to claim 1, wherein the surface of the metal material needs to be clean and dry, and the maximum diameter of the metal sample is no more than 25 mm.