CN111778507A

CN111778507A - Metallographic corrosive liquid and preparation method thereof

Info

Publication number: CN111778507A
Application number: CN202010645325.0A
Authority: CN
Inventors: 谭元标; 杨亚; 向嵩; 杨秋月; 张文玮
Original assignee: Guizhou University
Current assignee: Guizhou University
Priority date: 2020-07-07
Filing date: 2020-07-07
Publication date: 2020-10-16

Abstract

The application discloses a metallographic etchant and a preparation method thereof, wherein the metallographic etchant comprises 8-12% of hydrofluoric acid solution, 40-50% of nitric acid solution, 4-8% of hydrochloric acid solution and the balance of water according to a percentage by volume. The metallographic etchant has the advantages that the grain boundary of grains which are not recrystallized in thermal deformation can be clear, the grains can be easily identified, and the grain size measurement is facilitated.

Description

Metallographic corrosive liquid and preparation method thereof

Technical Field

The application belongs to the technical field of metallographic corrosion of metal materials, and particularly relates to a metallographic corrosive liquid and a preparation method thereof.

Background

Zirconium alloys have properties such as high strength, high corrosion resistance, high melting point, and good plasticity, and are therefore used in important fields such as aerospace, nuclear reactions, military industry, atomic energy, and the like. In these fields, the mechanical properties of zirconium alloys are required to be high, and the mechanical properties of zirconium alloys significantly depend on the microstructure formed by the hot working process of zirconium alloys. Therefore, the research on the hot working behavior of the zirconium alloy is of great significance. In the process of researching the thermal deformation of the zirconium alloy, different microstructure structures are often formed due to different components and thermal deformation processes of the alloy, and the different microstructure structures determine that the alloy has different physical, chemical and mechanical properties. Therefore, in order to obtain a zirconium alloy with good mechanical properties, the optical metallographic structure of the microstructure of the zirconium alloy after thermal deformation needs to be observed so as to adjust the thermal processing parameters of the zirconium alloy in time to obtain the required microstructure.

Generally, the metallographic etchant for zirconium alloy consists of hydrofluoric acid, nitric acid, water and the like, and the volume percentage ratio of the metallographic etchant to the hydrofluoric acid is HF: HNO₃：H₂O is 10%: 45%: 45 percent. The metallographic corrosive liquid is adopted to corrode zirconium alloy, particularly, a zirconium alloy sample which is not recrystallized in thermal deformation often forms a white thin film pollution layer which is difficult to remove on the surface of the metallographic sample, when the structure on the surface of the sample is observed under a metallographic microscope, the surface is blackened, the grain boundary is blurred, adverse effects are generated on the observation and the identification of the metallographic structure, and the measurement of the grain size is not facilitated.

Therefore, there is a need for an improved metallographic etchant.

Disclosure of Invention

An object of the application is to provide a new technical scheme of a metallographic etchant.

According to one aspect of the application, the application provides a metallographic etchant which comprises 8-12% of hydrofluoric acid solution, 40-50% of nitric acid solution, 4-8% of hydrochloric acid solution and the balance of water in percentage by volume.

Optionally, the hydrofluoric acid solution has a concentration of hydrofluoric acid of 40% by mass.

Optionally, the mass percentage concentration of the nitric acid in the nitric acid solution is 65%.

Optionally, the mass percentage concentration of the hydrochloric acid in the hydrochloric acid solution is 36-38%.

According to another aspect of the application, the application also provides a preparation method of the metallographic etchant, which comprises the following steps:

provided in volume fractions: 8-12% of hydrofluoric acid solution, 40-50% of nitric acid solution, 4-8% of hydrochloric acid solution and the balance of water;

putting water into a plastic container, sequentially adding hydrofluoric acid solution, nitric acid solution and hydrochloric acid solution, and uniformly mixing.

The metallographic etchant has the advantages that the grain boundary of grains which are not recrystallized in thermal deformation can be clear, the grains can be easily identified, and the grain size measurement is facilitated.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a schematic diagram of the use effect of embodiment 1 of the present application;

FIG. 2 is a schematic diagram of the application effect of embodiment 2 of the present application;

FIG. 3 is a schematic diagram of the application effect of embodiment 3 of the present application;

fig. 4 is a schematic diagram showing the effect of comparative example 1 of the present application.

Detailed Description

Embodiments of the present application will be described in detail with reference to the drawings and examples, so that how to implement technical means to solve technical problems and achieve technical effects of the present application can be fully understood and implemented.

Example 1

48ml of water is firstly put into a plastic container, then 8ml of hydrofluoric acid (with the mass percentage concentration of 40%) and 40ml of nitric acid (with the mass percentage concentration of 65%) are added, and finally 4ml of hydrochloric acid (with the mass percentage concentration of 38%) are added and mixed evenly.

After the corrosive liquid is prepared, a cotton ball with a proper size is immersed into the corrosive liquid, and then the soaked cotton ball is clamped by a pair of tweezers to lightly wipe the metallographic observation surface of the polished zirconium alloy sample for 25-30 times. And after the wiping, repeatedly washing the sample by using water, lightly wiping the metallographic observation surface of the sample by using a cotton ball dipped in alcohol, and drying the surface of the sample by using an electric blower, thereby obtaining the required metallographic structure observation sample.

As shown in FIG. 1, it is a photograph of a metallographic structure of a zirconium alloy showing no recrystallization during thermal deformation, which was prepared by using the etching solution prepared in example 1. The grain boundaries of the individual grains are clearly shown in the figure, which is very advantageous for the measurement of the grain size.

Example 2

39ml of water is firstly put into a plastic container, then 10ml of hydrofluoric acid (with mass percent concentration of 40%) and 45ml of nitric acid (with mass percent concentration of 65%) are added, and finally 6ml of hydrochloric acid (with mass percent concentration of 38%) are added and mixed evenly.

As shown in FIG. 2, the metallographic structure of a zirconium alloy was photographed without recrystallization in the thermal deformation by using the etching solution prepared in example 2, and the preparation method was the same as in example 1. The grain boundaries of the individual grains are clearly shown in the figure to facilitate measurement of the grain size of the individual grains.

Example 3

Firstly, 30ml of water is put into a plastic container, then 12ml of hydrofluoric acid (with the mass percentage concentration of 40%) and 50ml of nitric acid (with the mass percentage concentration of 65%) are added, and finally 8ml of hydrochloric acid (with the mass percentage concentration of 36%) are added and uniformly mixed.

As shown in FIG. 3, the metallographic structure of a zirconium alloy was photographed without recrystallization in the thermal deformation by using the etching solution prepared in example 2, and the preparation method was the same as in example 1. The grain boundaries of the individual grains are clearly shown in the figure to facilitate measurement of the grain size of the individual grains.

Comparative example 1

The method is characterized in that a common zirconium alloy metallographic corrosive liquid is used, and the volume percentage ratio of each component in the corrosive liquid is HF: HNO₃：H₂O is 10%: 45%: 45% by mass, and no recrystallization occurred during heating deformation. As shown in FIG. 4, the photograph of the metallographic structure showing no recrystallization in the case of the thermal deformation of the zirconium alloy was black, and the grain boundary was hardly visible from the photograph, and therefore, the grain boundary could not be observedMeasurement of grain size is performed.

By comparing fig. 1 and fig. 4, the metallographic etchant prepared by the invention can clearly display the grain boundary of each grain, which is beneficial to the measurement of the grain size. Can prevent white film-shaped pollutants from being formed on the surface of a metallographic specimen of the zirconium alloy which is not recrystallized in the thermal deformation.

As used in the specification and claims, certain terms are used to refer to particular components or methods. As one skilled in the art will appreciate, different regions may refer to a component by different names. The present specification and claims do not intend to distinguish between components that differ in name but not in name. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect. The description which follows is a preferred embodiment of the present application, but is made for the purpose of illustrating the general principles of the application and not for the purpose of limiting the scope of the application. The protection scope of the present application shall be subject to the definitions of the appended claims.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a good or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such good or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a commodity or system that includes the element.

While the foregoing description shows and describes several preferred embodiments of the invention, it is to be understood, as noted above, that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The metallographic etchant is characterized by comprising, by volume percentage, 8-12% of hydrofluoric acid solution, 40-50% of nitric acid solution, 4-8% of hydrochloric acid solution and the balance of water.

2. The metallographic etchant according to claim 1, wherein the hydrofluoric acid solution has a concentration of 40% by mass of hydrofluoric acid.

3. The metallographic etchant according to claim 1, wherein the nitric acid solution has a concentration of 65% by mass of nitric acid.

4. The metallographic etchant according to claim 1, wherein the hydrochloric acid solution contains hydrochloric acid in an amount of 36 to 38% by mass.

5. A method for preparing a metallographic etchant according to any one of claims 1 to 4, comprising the steps of: