CN115537904A - A method for obtaining the metallographic structure of aluminum alloy by electrolysis of two-stage electrolyte - Google Patents

Abstract

The invention relates to a method for polishing and corroding aluminum alloy by using a two-stage electrolyte, which aims at aluminum alloy with a metallographic structure, such as wrought aluminum alloy and heat-treated aluminum alloy, which is difficult to obtain by using a common treatment method. The proportion of the two-stage electrolyte is as follows: first-stage: perchloric acid 20% -25% methanol 75% -80%, second stage: 10-15% of perchloric acid and 85-90% of ethanol alcohol. According to the invention, the pretreated aluminum alloy is electrolyzed, and the pretreated aluminum alloy is sequentially put into the secondary electrolyte for electrolysis, so that a metallographic phase suitable for observation through OM is obtained. Each electrolyte can be used independently, and the electrolyte of the first grade can be used for removing larger scratches on the surface of the aluminum alloy so as to make the surface smoother. The second stage electrolyte may be used for the electrolyte of a general as-cast aluminum alloy, and the aluminum alloy treated with the second stage electrolyte may be used for an EBSD pattern.

Description

A method for obtaining the metallographic structure of aluminum alloy by electrolysis of two-stage electrolyte

technical field

A new proportion of aluminum alloy electrolyte and method for obtaining metallographic structure by electrolysis

Background technique

Aluminum alloy has the characteristics of high specific strength and high cost performance, and is widely used in various fields, including some high-tech fields such as aviation, aerospace, and military. It has a great impact on people's production and life, so the research on aluminum alloys has become extremely important. In the daily research on aluminum alloys, we need to observe the microstructure of its structure, which requires us to study the surface of aluminum alloys. Polishing and etching are carried out, and electrolytic polishing and etching is a better method, which has the advantages of simplicity, speed and outstanding effect. However, some aluminum alloys often have grain boundaries that become fine due to deformation or heat treatment, making it difficult to corrode the crystal phase. And the appropriate proportion of electrolyte and corrosion method will help to corrode the crystal phase structure suitable for observation.

Contents of the invention

The invention is a method for electrolytically polishing and corroding aluminum alloys that are extremely difficult to polish and corrode by using a double-stage electrolyte, and obtaining a metallographic structure.

The ratio of the primary electrolyte is 20%-25% perchloric acid and 75%-80% methanol, and the voltage is 20-25v. Its function is to remove the scratches that still exist after the aluminum alloy surface is polished, and make the surface brighter and smoother, creating conditions for subsequent further electrolytic corrosion.

The ratio of the secondary electrolysis is perchloric acid 10% methanol 90%, voltage 20-25v. Its function is equivalent to a corrosive solution, in order to make the surface of the aluminum alloy show a metallographic morphology, so as to better observe the metallographic structure.

Gradual polishing and corrosion with the above electrolyte requires rotating and stirring with the rotor, so as to take away the bubbles on the surface of the aluminum alloy and reduce the black spots and pores on the surface. The rotational speed in the primary electrolyte is 4-5r/s, and in the secondary electrolyte it is 3r/s.

The electrolyte occupies 2/3-3/4 of the container, and the beaker with a capacity of 500ml is used as the container of the electrolyte so that the rotor can fully exert its effect.

The size of the lead block selected is 50mm×50mm, and the electrolyte is submerged in 1/2 of the lead block.

The current can reach 1.5A in the primary electrolyte and 0.2A in the secondary electrolyte, both at room temperature.

The electrolysis time in the primary electrolyte is 5-20s, and the electrolysis time in the secondary electrolyte is 10-15s.

The electrolyte does not contain nitric acid, which is beneficial to environmental protection.

The electrolyte should be stored in a dark environment.

The primary and secondary electrolytes can be used for multiple purposes, and each electrolyte can be used independently. The primary electrolyte can be used to remove large scratches on the aluminum alloy surface to make the surface smoother. The secondary electrolyte can be used as an electrolytic polishing solution for aluminum alloys that are easy to corrode metal phases, and the electrolytic aluminum alloys can be used as EBSD patterns.

Description of drawings

Figure 1 is a schematic diagram of aluminum alloy electrolysis

FIG. 2 is a metallographic diagram of an aluminum alloy electrolyzed with the two-stage aluminum alloy electrolytic polishing solution of Example 1. FIG.

FIG. 3 is a metallographic diagram of an aluminum alloy electrolyzed with the two-stage aluminum alloy electrolytic polishing solution of Example 2. FIG.

FIG. 4 is a metallographic diagram of an aluminum alloy electrolytically polished with the aluminum alloy electrolytic polishing solution of Example 7. FIG.

detailed description

Next, set forth my invention by several concrete examples.

Example 1

In this example, the ratio of the two-stage electrolyte is adopted: the primary electrolyte perchloric acid 20% methanol 80%; the secondary electrolyte perchloric acid 10% ethanol 90%.

Connect the aluminum alloy that has been pre-ground (sanded to 2000 mesh, and then polished to a bright surface) to the anode, and the cathode is a lead block.

First put the beaker with the rotor on the magnetic stirring device, adjust the voltage to 25v and rotate at 4r/s, and then turn on the magnetic stirring device. Put the lead block and aluminum alloy into the first-level electrolyte for 10 seconds, take it out and rinse the surface with alcohol, then soak in alcohol for 1 minute, pick it up with tweezers, dry the surface with a hair dryer, and observe it on an optical microscope. If there are scratches, black spots or air bubbles on the surface, you need to continue to repeat the above operations until no scratches, black spots or air bubbles appear.

Then immerse the aluminum alloy treated with the first-level electrolyte in the second-level electrolyte in the same way for 5s, the voltage is 25v, the rotational speed of the rotor is 3r/s, and the electrolysis time is 15s.

Example 2

The proportioning and operation of the electrolyte in the process and Example 1 are basically the same, the only difference is that the time of electrolysis in the primary electrolyte is changed to 15s.

Example 3

The proportioning and operation of the electrolyte of the process and Example 1 are basically the same, the only difference is that the time of electrolysis in the secondary electrolyte is changed to 10s.

Example 4

The proportioning of electrolyte is set as: primary electrolyte is perchloric acid 20% methanol 80%, secondary electrolyte is perchloric acid 15% ethanol 85%, other operations are identical with example 1.

Example 5

The ratio of the electrolyte is the same as that of Example 4. Electrolyze in the primary electrolyte for 15s, the rotor speed is 4r/s, and the voltage is 20V; in the secondary electrolyte, it is electrolyzed for 5s, the rotor speed is 3r/s, and the voltage is 25v. Other operations are the same as Example 1.

Example 6

Electrolyze 10s in the secondary electrolyte, other operation and the proportioning of electrolyte are identical with example 5.

Example 7

The electrolyte solution is chloric acid 20% methanol 80%, the rotor speed is 4r/s, the voltage is 25v, the current is 1.5A, and the temperature is room temperature.

Example 8

The electrolyte is configured as perchloric acid 10% ethanol 90%, the rotor speed is 3r/s, the voltage is 25v, the current can reach 0.2A-0.4A, and the temperature is room temperature.

Electrolyze for 10s with a smooth and easily corroded aluminum alloy after mechanical polishing.

The above experiments show that for aluminum alloys that are difficult to corrode grain boundaries (various deformed aluminum alloys, heat-treated aluminum alloys), the above-mentioned two-stage electrolyte is very suitable, and the electrolyte of each stage can be used alone to achieve different Effect.

Claims (3)

1. An aluminum alloy electrolyte is characterized by being a two-stage electrolyte. And each electrolyte can be independently used to exert different effects, the primary electrolyte can remove deep scratches on the surface of the pretreated aluminum alloy, and the secondary electrolyte can be used as an electrolytic polishing solution for common cast aluminum alloys.

2. The formula is as follows: first-stage: perchloric acid 20-25% and methanol 75-80%; and (2) second stage: 10-15% of perchloric acid and 85-90% of ethanol. The surface of the aluminum alloy is pretreated before electrolysis (sand paper is ground to 2000 meshes, and then mechanical polishing is carried out until the surface presents a mirror surface). The area of the aluminum alloy polished surface is 16mm2-40mm2. The method is mainly used for metallographic corrosion of the aluminum-copper alloy and the aluminum-silicon alloy in the deformation state and the heat treatment state. Connecting an aluminum alloy with a positive electrode, connecting a negative electrode with a lead block, placing electrolyte put into a rotor on a magnetic stirrer, opening the magnetic stirrer to rotate the rotor so as to fully eliminate a large number of bubbles on the surface of the aluminum alloy, wherein the voltage in the first-stage electrolyte is 20-25v, the electrolysis time is 10-20s, immediately washing the rotor with alcohol after taking out, drying the washed bubbles after 1-2 minutes in the alcohol by using a blower, observing whether bubbles or black spots exist on the surface, continuously carrying out electrolysis if bubbles and black spots exist until the surface is bright and no bubbles exist, and then carrying out second-stage electrolysis, wherein the voltage in the second-stage electrolyte is 20-25v, and the electrolysis time is 5-15s.

3. According to the patent claim 2, the rotor speed in the primary electrolyte is 4-5r/s, the rotor speed in the secondary electrolyte is 3-4r/s, and the requirement for the electrolyte is that the shelf life is one month (or when the solution becomes red), and the electrolyte should be re-proportioned after the solution becomes red.

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