JPS5817425B2 - Etching method for copper-based alloys - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an etching process for specimens of copper-based alloys for microscopy, and includes an etching method for microscopy of α-human β brass containing lead, iron, etc. It is related to.

Metal structures of copper and copper-based alloys, such as pure copper crystal grains, α-brass crystal grains, the morphology and distribution of β-phase particles in α-β brass, and the morphology of γ-phase particles in bronze. Inspection of the distribution of α, β, and γ phases, iron,
This is done by coloring the tops of precipitated grains of lead, etc., and observing them with a metallurgical microscope.

For example, pure copper or (Cu-Z with very few impurities)
When preparing a sample for observing crystal grains W of an n-alloy (α single phase), etching solutions having the components shown in Table 1 have been used individually.

On the other hand, as an etching solution used for observing the beta phase of alpha and beta brass containing lead and iron, etching solutions having the components shown in Table 2 have been used individually.

In the case of pure copper, alpha brass, etc., by using one of the etching solutions mentioned above, the grain boundaries will be revealed very clearly, making it the best specimen for metallurgical microscopy. easily obtained.

However, when α+β brass containing lead, iron, etc. is treated with the conventional etching solution shown in Table 2, lead particles, iron particles, etc. are removed by the β phase darkened by etching.
Unsolved added elements and the like are interfered with, making it almost impossible to clearly identify them.

Figure 1 shows a sample (2) of a copper-based alloy having the components shown in Table 3, etched for about 20 seconds with the /I62 etching solution (mixed aqueous solution of ferric chloride and hydrochloric acid) shown in Table 2. Microstructure of the speculum surface after treatment.

This shows that.

As is clear from Fig. 1, the darkened β-phase 1 occupying a large area greatly obstructs the Pb particles 2 and other additive elements, especially the Pb particles 2 and β-phase 1 adjacent to the β-phase 1. It is almost impossible to identify other additive elements located within.

As a result, for example, when investigating the machinability of Cu-Zn-Pb alloy from the metallographic aspect, it is difficult to
The size of the particles and their distribution state are unclear, and furthermore, it is not possible to accurately determine in what form the other active ingredient elements added are dissolved in the base material, so accurate cutting using a metallurgical microscope is not possible. A major drawback is that it is not easy to investigate gender, etc.

The present invention eliminates the above-mentioned drawbacks in the etching treatment of α+β brass specimens containing lead, iron, etc., and
The object of the present invention is to provide an etching treatment method that can easily prepare specimens for microscopy that are extremely easy to identify by vividly coloring the precipitated particles of Pb, Fe, and the like.

The present invention involves immersing a puff-polished copper-based alloy sample in two-component diluted water consisting of ammonia and hydrogen peroxide for a short time and then rinsing it with water. The brown thin film was washed and peeled off with an aqueous acetic acid solution, washed with water, and then etched by immersing the sample in an aqueous sodium thiosulfate solution for several minutes.
It is characterized in that the α phase of the copper-based alloy is colored white, the β phase is colored yellowish brown, the Pb particles are colored black, and the Fe particles are colored blue.

Hereinafter, the details will be explained based on the embodiments of the present invention shown in FIGS. 2 to 23.

FIG. 2 shows the steps for processing a specimen for microscopy in order to carry out the etching method according to the present invention.

In the cutting process 5, the material to be inspected is cut to an appropriate size and size.
For example, it is cut into a size of about 20φ×20mm.

In collecting the sample, the location and direction of the sample should, of course, be selected so that the cut portion can retain a tissue that is completely representative of the material to be inspected.

The collected sample is polished in a preparatory polishing step 6 using emery abrasive paper of various grain sizes until the specular surface has a grain size suitable for polishing in the next step.

Next, the specimen is subjected to a polishing step 7, in which minute scratches and defective layers on the specimen surface are completely removed by polishing machine Q, and the specimen surface is completely finished.

The polished sample is etched 8 by the method described below, and after the prescribed etching is completed, it is thoroughly dried in a drying step 9 to prevent rust on the etched speculum surface and to remove metal. Subjected to observation using a microscope.

FIG. 3 shows the etching process for a speculum sample according to the present invention. The sample is targeted for etching.

In step 8a of the first treatment T, the polished sample (1) is first immersed for approximately 30 seconds in a first treatment solution (substrate) consisting of diluted water containing two components of ammonia and hydrogen peroxide, and then Wash thoroughly with water.

Note that the first treatment liquid. By immersing it in W, the surface of the speculum is colored yellowish brown.

Next, the sample (1) is transferred to the second treatment step 8b, where the yellow-brown thin film formed on the surface of the sample 1 in the first treatment step is removed using a second treatment solution consisting of an acetic acid aqueous solution. (B) for approximately 30 seconds, and then washed with water.

The microstructure of the speculum surface in this state is as shown in FIG. 4, in which the α phase 3 is white, the β phase 1 is pale yellow, the Pb particles 2 are black, and the Fe particles 4 are blue.

Next, in the third treatment step 8e, the sample 1 is immersed for approximately 5 minutes in a third treatment liquid (C) consisting of an aqueous sodium thiosulfate solution.

As a result, the β phase on the speculum surface is colored yellowish brown by the third treatment liquid (C), and the α phase and β phase can be more clearly distinguished.

FIG. 5 is a microstructure photograph of the speculum surface after the final treatment step in this example, showing α phase 3, β phase 1, lead particles 2,
Iron particles 4 are clearly visible.

The types of etching solutions used in this example and their blending ratios are shown in Table 4.

Moreover, FIG. 6 shows the microstructure of the speculum surface when a sample having the components shown in sample (2) in Table 3 was etched under exactly the same conditions as sample (1).
β phase 1, α phase 3, lead particles 2, etc. can be more clearly identified.

This Figure 6 and sample (2). When comparing FIG. 1 with a sample having the same components treated with the conventional etching solution indicated by /162 in Table 2, β phase 1, α phase 3,
It is clearly seen that the degree of discrimination of lead particles 2 is significantly improved.

Note that since the content of iron 4 is small, it is completely dissolved in solid solution.

In this example, the components of the first treatment liquid (A) and their blending ratios are selected as shown in Table 4. This was determined based on experimental results.

Figures 7, 8, 9, 10, and 11 show the results at the end of the second treatment step 8b when the proportions of each component of the first treatment liquid (A) were changed. This figure shows the microstructure of the speculum surface.

In addition, Fig. 12, Fig. 13, Fig. 14, Fig. 15, and Fig. 1
Figure 6 shows that the same sample as in Figures 7 to 11 above was immersed in the third treatment solution (C) for 5 minutes in the third treatment step 8c.
It shows the microstructure at the time when the etching process is completed.

Note that iron 4 is completely dissolved in solid solution.

When we examine Figures 7 to 16 in detail, we find that 1:
The higher the blending ratio of 1NH4OH, the stronger the corrosion of α phase 3 becomes, and it becomes extremely difficult to distinguish between α phase 3, β phase 1, Pb particles 2, etc.

Conversely, when the blending ratio of I20□ is high, it becomes almost impossible to distinguish between α phase 3 and β phase 1, and
Even when immersed in the treatment liquid (C), the β phase 1 is no longer colored yellowish brown.

FIGS. 17, 18, and 19 show the first treatment liquid (
It shows the microstructure after the completion of the second treatment step 8b when the blending ratio of I20 in A) was changed.

107 added in the first treatment liquid (5) at a ratio of
711 I20! t, for stabilizing corrosion.

If I20 is not added at all, corrosion will be too strong and α phase 3
, β phase 1, and P'b particles 2 become extremely difficult to distinguish.

On the other hand, if the proportion of I20 is increased, the corrosion becomes too weak, making identification extremely difficult as described above.

From the above test results, when using 30% I20 and 1:1 NH4OH and I20 as the first treatment liquid (5), it is optimal to select the mixing ratio of 20:15:10. I came to the conclusion that there is.

That is, the volume ratio of H2O2, NT-I40H and I20 at this time is approximately 6:8:32.

Incidentally, it goes without saying that the blending ratio of each component constituting the first treatment liquid is not limited to the above numerical values, but can vary over a considerable range.

On the other hand, if the second treatment liquid (B) is an acetic acid aqueous solution having a concentration in the range of about 25 to 90%, it is possible to remove the yellow-brown thin film produced in the first treatment step 8a.

However, considering the ease of formulation and economic efficiency, 10~
A concentration of about 30% is appropriate.

Further, the third treatment liquid (C), an aqueous sodium thiosulfate solution (Na202S3.5H20), exhibits substantially the same discoloration effect as long as it has a concentration of 20% or more.

FIGS. 20 to 23 show the state of discoloration of the β phase when the concentration of the sodium thiosulfate aqueous solution is changed.

The present invention enables the α phase, β phase, Pb particles, Fe particles, etc. to be clearly and clearly detected by etching a speculum sample such as α+β brass containing lead, iron, etc. using the etching method described above. This makes it possible to perform extremely detailed microscopic observation and microscopic investigation that could not be achieved with conventional etched microscopic specimens.

Furthermore, as mentioned above, the present invention is based on an extremely simple process, and there is no large difference in the degree of discrimination depending on the skill of the operator, and microscopic specimens can be prepared efficiently in a short time. .

. As mentioned above, the present invention has excellent practical utility.

[Brief explanation of drawings]

FIG. 1 is an Ij1ga mirror photograph showing the microstructure of the specimen surface when sample (1) in Table 3 was treated with the 7162 etching solution in Table 2 (conventional example). FIG. 2 shows the processing steps for a specimen for microscopy used to carry out the etching method according to the present invention. Figure 3 shows an outline of the etching process according to the present invention. Figure 4 shows the process of treating sample (1) by the method according to the present invention, and the second treatment process. Fig. 5 is a micrograph showing the microstructure of the inspection surface at the time of completion of the etching process. Fig. 5 is a photomicrograph showing the microstructure of the inspection surface of sample (1) after the etching process of the present invention has been completed. The figure is a micrograph showing the microstructure of the microscopic surface of sample (2) when sample (2) in Table 3 was etched according to the present invention. FIG. 7 is a micrograph showing the microstructure of the speculum surface of sample (2) at the end of the second treatment step when the proportions of each component of treatment solution (a) are changed; (A) Liquid mixture ratio 30% I20□10m1 ] : I NH4OH25m1 H2010m1 (B) Liquid mixture ratio 30% CH3COOH This is a microscopic photograph of the speculum surface. Figure 8 is (5) Liquid mixture ratio 30% I20 ° 15m1 1 : I NH4OH20rnl H2010m1 (B) Liquid 20% CH3CO0H This is a microscopic photograph of the transverse mirror surface. B) This is a microscopic photograph of the speculum surface when the liquid is 20% CH3COOH. Figure 10 is a micrograph of the speculum surface when the liquid is 20% CH3CO0H. This is a microscopic photograph. Fig. 11 is a microscopic photograph of the speculum surface in the case of (5) liquid blending ratio 30% CH202301TLl ]:I NH4OH5rIll H2010ml (B) liquid 20% CH3COOH ( ). Fig. 12 ( The sample in Figure 7 above was treated with the third treatment solution in Table 4 (
(') is a micrograph showing the microstructure of the speculum surface at the time when the etching process was completed after being immersed in water for 5 minutes. FIG. 13 is a microscopic photograph of the speculum surface obtained when the sample shown in FIG. 8 was treated in the same manner as in FIG. 12. FIG. 14 is a microscopic photograph of the microscopic surface obtained when the sample shown in FIG. 9 was treated in the same manner as in FIG. 12. FIG. 15 is a microscopic photograph of a microscopic surface obtained by processing the sample shown in FIG. 10 in the same manner as in FIG. 12. FIG. 16 is a microscopic photograph of the microscopic surface of the sample shown in FIG. 11 treated in the same manner as in FIG. 12. Figures 17 to 19 show the specular surface of sample (2) at the end of the second treatment step when the blending ratio of H2O in the first treatment liquid (5) in Table 4 was changed. FIG. 17 is a microscopic photograph showing the microstructure. (A) Solution 30% H2O220ml 1: I NH4OH15ml H200, ml! (B) A microscopic photograph of the speculum surface when the liquid was 20% CH3CO0H. Fig. 18 is a microscopic photograph of the speculum surface in the case of (5) liquid 30% 1120220m1 1 2 1 NH4OH15m1 H2010m1 (B) liquid 20% CH3CO0I-(. :I NH4OH15ml 112020ml (B) Liquid 20% CH3CO0T-IT These are microscopic photographs of the speculum surface.
FIG. 20 is a micrograph showing the microstructure of the speculum surface of sample (2) when the concentration of sodium thiosulfate is changed. B) Liquid 20% CH3CO0H (C) Liquid 10% Na2S2O3.5H20 This is a microscopic photograph of the speculum surface. In Fig. 21, liquid (5) and liquid (B) are the same as in Fig. 20, and liquid (C) is 20% Na 2 S 203 ・5.
It is a micrograph of the speculum surface in the case of H20. In Fig. 22, the (N solution and (B) solution are the same as in Fig. 20, and the (C) solution is 30% Na 2 S 203.5H2.
This is a microscopic photograph of the speculum surface in the case of 0. FIG. 23 is a microscopic photograph of the speculum surface when the liquid (5) and the liquid CB are the same as those in FIG. 20, and the liquid (C) is 40% Na2S2O3.5H20. 1...β phase, 2...lead particles, 3...
...α phase, 4... Iron particles, 5... Cutting process, 6... Preparation polishing process, 7...
Polishing process, 8... Etching process, 8a.
...First treatment step, 8b...Lower second treatment, 8c...Third treatment step, 9...Drying step, (3)... ...First treatment liquid, (B)...
...Second treatment liquid, (C)...Third treatment liquid.

Claims (1)

[Claims] 1. A copper base metal sample pretreated by buffing or the like is immersed for a short time in the first treatment solution A, which is an aqueous solution of hydrogen peroxide and ammonia. The sample was immersed in a second treatment solution consisting of an acetic acid aqueous solution to remove the yellow-brown thin film formed on the sample speculum surface, and then the sample was immersed in a third treatment solution (') consisting of a thorium thiosulfate aqueous solution to remove the yellowish brown thin film formed on the sample specimen surface. A method for etching a copper-based alloy, characterized in that alpha phase, beta phase, etc. on a specular surface and precipitated particles of lead, iron, etc. contained therein can be clearly colored and visualized.