CN107219105A - A kind of observational technique to AZ31 magnesium alloy internal shear bands - Google Patents

Abstract

The invention discloses a method for observing the internal shear band of an AZ31 magnesium alloy, which comprises the following steps: 1. Using sliding friction to make the AZ31 magnesium alloy undergo plastic deformation; 2. Sampling the plastically deformed AZ31 magnesium alloy for annealing treatment; 3. Grinding the annealed AZ31 magnesium alloy sample step by step to obtain the observation plane of the AZ31 magnesium alloy sample; 4. Corroding the observation plane of the AZ31 magnesium alloy sample; 5. Using an optical microscope to observe the inside of the corroded AZ31 magnesium alloy sample Morphology of the shear bands. The present invention improves the contrast difference between the internal shear band area and the non-shear band area of the AZ31 magnesium alloy sample through annealing treatment, and can clearly observe the shape and distribution of the internal shear band of the AZ31 magnesium alloy sample after deformation, and the process is simple , low cost and easy to promote.

Description

A Method for Observing Internal Shear Bands of AZ31 Magnesium Alloy

technical field

The invention belongs to the technical field of metal material microstructure observation, and in particular relates to an observation method for an internal shear band of an AZ31 magnesium alloy.

Background technique

Magnesium alloy is the metal structure material with the lowest density in the world, has high specific strength and specific modulus, and has broad application prospects in the fields of electronics, communications, aerospace and other fields. Magnesium alloy has a close-packed hexagonal crystal structure, so there are few independent slip systems and low plasticity at room temperature. According to different deformation conditions, the plastic deformation mechanisms of magnesium alloys are mainly divided into three types: (1) dislocation slip at high temperature; (2) twinning at low temperature; (3) shear at high strain rate. bring. Under the first two mechanisms, magnesium alloys usually exhibit continuous plastic deformation that is slow and predictable. Under the third shear band mechanism, magnesium alloys will break suddenly and cause serious consequences, so the study of shear band is particularly important. AZ31 magnesium alloy is the most widely used magnesium alloy at present, with good room temperature strength, good ductility and excellent corrosion resistance. Therefore, it is necessary to study the morphology and distribution of the shear bands inside the AZ31 magnesium alloy.

The shear band is a deformation structure formed by the localized plastic deformation. The heat generated by plastic deformation causes the temperature inside the shear zone to rise rapidly, so that the material strength inside the shear zone is significantly lower than that of the surrounding non-shear zone region. This weakening of the strength makes the shear zone region become the crack initiation zone and Rapid expansion zone. Therefore, studying the spatial distribution of shear bands is the key to studying the plastic deformation and fracture mechanism of AZ31 magnesium alloy under high strain rate conditions. At present, the research on shear bands is mainly directly observed through the contrast difference between the shear band area and the non-shear band area after corrosion of the plastically deformed AZ31 magnesium alloy. The contrast of the band area is relatively similar and difficult to distinguish, which makes it difficult to accurately reflect the spatial distribution of the shear band. Observation of shear bands in AZ31 magnesium alloy by scanning electron microscope also has the problem of small contrast difference and difficult determination of shear bands, while the scope of observation of shear bands by transmission electron microscope is small, and it is difficult to achieve accurate detection in a large range. Determine the morphology and distribution of shear bands.

Contents of the invention

The technical problem to be solved by the present invention is to provide an observation method for the internal shear band of the AZ31 magnesium alloy in view of the above-mentioned deficiencies in the prior art. In this method, the AZ31 magnesium alloy sample plastically deformed by sliding friction is annealed, so that the shear band region of the AZ31 magnesium alloy sample is completely recrystallized, and an obvious contrast difference is formed with the surrounding non-shear band region after the action of the corrosive agent, thereby The morphology and distribution of the shear bands are highlighted. The method is simple in process, low in cost and easy to popularize.

In order to solve the above-mentioned technical problems, the present invention provides a method for observing the internal shear band of AZ31 magnesium alloy, which is characterized in that the method comprises the following steps:

Step 1, using sliding friction to make the surface of the AZ31 magnesium alloy plastically deformed;

Step 2. Sampling the plastically deformed AZ31 magnesium alloy in step 1 to obtain an AZ31 magnesium alloy sample, and then annealing the AZ31 magnesium alloy sample;

Step 3: Use 600 ^# , 1000 ^# , 2000 ^# , 5000 ^# silicon carbide sandpaper to grind the surface of the AZ31 magnesium alloy sample after the annealing treatment in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed;

Step 4, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 3, so that the shear band inside the AZ31 magnesium alloy sample appears;

Step five, using an optical microscope to observe the morphology and distribution of the internal shear bands of the AZ31 magnesium alloy sample that appeared in step four.

The above method is characterized in that the strain rate of the sliding friction in step 1 is 10 ² s ^-1 to 10 ³ s ^-1 .

The above method is characterized in that the temperature of the annealing treatment in step 2 is 160° C. to 200° C., and the holding time is 20 minutes.

The above method is characterized in that the corrosive agent in step 4 is prepared by mixing oxalic acid, nitric acid and water according to the ratio of 5g: 10ml: 0.5ml, and the oxalic acid and nitric acid are analytical reagents.

The above-mentioned method is characterized in that the corrosion treatment time in step 4 is 30s.

The specific method for plastically deforming AZ31 magnesium alloy by sliding friction in step 1 is the method disclosed in the invention patent entitled "A Method for Realizing the Surface Nanoscale of Metal Materials by Using Sliding Friction" with the authorized announcement number CN102321791B.

The principle of the present invention is: after the AZ31 magnesium alloy is plastically deformed by sliding friction, a shear band area is generated inside the AZ31 magnesium alloy, and the defect density in this area is much higher than that of the surrounding non-shear band area, resulting in a shear band The region has a higher deformation storage energy, which makes the shear band region have a higher recrystallization ability under appropriate conditions. After plastically deformed AZ31 magnesium alloy samples were annealed, complete recrystallization occurred in the shear band area, and the defect density in the shear band area after complete recrystallization was lower than that in the surrounding non-shear band area, so that the shear band Areas with high corrosion resistance. After treatment with etchant, the shear zone area and the surrounding non-shear zone area appear bright white and gray black, respectively, and the contrast difference is obvious, thereby highlighting the shape and distribution of the shear zone.

Compared with the prior art, the present invention has the following advantages:

1. The present invention completely recrystallizes the internal shear band area of the AZ31 magnesium alloy sample through the annealing process, thereby improving the contrast difference between the internal shear band area and the non-shear band area of the AZ31 magnesium alloy sample, and clearly showing plasticity The shape and distribution of shear bands inside the AZ31 magnesium alloy sample after deformation, the process is simple and the cost is low.

2. The present invention uses an optical microscope to directly observe the internal shear bands of the AZ31 magnesium alloy sample, and can accurately determine the distribution of the shear bands in a wide range without using scanning electron microscopes and electronic lenses. The equipment requirements are low and easy to popularize.

The technical solutions of the present invention will be described in further detail below with reference to the drawings and embodiments.

Description of drawings

Fig. 1 is a topography diagram of the internal shear band of the AZ31 magnesium alloy sample in Example 1 of the present invention.

Fig. 2 is a topography diagram of the internal shear band of the AZ31 magnesium alloy sample in Comparative Example 1 of the present invention.

Fig. 3 is a topography diagram of the internal shear band of the AZ31 magnesium alloy sample in Example 2 of the present invention.

Fig. 4 is a topography diagram of the internal shear band of the AZ31 magnesium alloy sample in Example 3 of the present invention.

Fig. 5 is a topography diagram of the internal shear band of the AZ31 magnesium alloy sample in Comparative Example 2 of the present invention.

Fig. 6 is a topography diagram of the internal shear band of the AZ31 magnesium alloy sample in Comparative Example 3 of the present invention.

detailed description

Example 1

Step 1. Plastic deformation occurs on the surface of the AZ31 magnesium alloy by sliding friction, and the strain rate of the sliding friction on the surface of the AZ31 magnesium alloy is controlled to be 10 ² s ^-1 ;

Step 2: Sampling the plastically deformed AZ31 magnesium alloy in step 1 to obtain an AZ31 magnesium alloy sample, and then annealing the AZ31 magnesium alloy sample; the temperature of the annealing treatment is 180° C., and the holding time is 20 minutes;

Step 3: Use 600 ^# , 1000 ^# , 2000 ^# , 5000 ^# silicon carbide sandpaper to grind the surface of the AZ31 magnesium alloy sample after the annealing treatment in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed;

Step 4, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 3, so that the shear band inside the AZ31 magnesium alloy sample appears; Proportionally mixed, the oxalic acid and nitric acid are analytical reagents; the corrosion treatment time is 30s;

Step five, using an optical microscope to observe the morphology and distribution of the internal shear bands of the AZ31 magnesium alloy sample that appeared in step four.

Fig. 1 is a morphological view of the internal shear bands of the AZ31 magnesium alloy sample in this example, and the arrows in the figure indicate the shear bands. In Figure 1, the internal shear band of the AZ31 magnesium alloy sample is bright white, and the non-shear band area is gray-black. The contrast difference between the shear band area and the surrounding non-shear band area is very obvious. The shape and distribution of the shear band Clear and easy to observe.

Comparative example 1

Step 1. Plastic deformation occurs on the surface of the AZ31 magnesium alloy by sliding friction, and the strain rate of the sliding friction on the surface of the AZ31 magnesium alloy is controlled to be 10 ² s ^-1 ;

Step 2: Use 600 ^# , 1000 ^# , 2000 ^# , and 5000 ^# silicon carbide sandpaper to grind the surface of the plastically deformed AZ31 magnesium alloy sample in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed;

Step 3, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 2, so that the shear band inside the AZ31 magnesium alloy sample appears; Proportionally mixed, the oxalic acid and nitric acid are analytical reagents; the corrosion treatment time is 30s;

Step 4, using an optical microscope to observe the morphology and distribution of the shear bands inside the AZ31 magnesium alloy sample that appeared in Step 3.

Fig. 2 is a morphological view of the internal shear bands of the AZ31 magnesium alloy sample in this example, and the arrows in the figure indicate the shear bands. In Fig. 2, the internal shear band of the unannealed AZ31 magnesium alloy sample is gray-black, and the non-shear band area is gray. The contrast difference between the shear band area and the surrounding non-shear band area is not obvious, and the shear band The shape and distribution are fuzzy and difficult to observe.

Comparing Example 1 with Comparative Example 1, it can be seen that the contrast difference between the internal shear band area and the surrounding non-shear band area of the annealed AZ31 magnesium alloy sample is more obvious than that of the AZ31 magnesium alloy that has not been annealed. The morphology and distribution of the shear bands are more clearly visible and easier to observe, indicating that the annealing treatment is helpful for the observation of the internal shear bands of the AZ31 magnesium alloy. By adopting the method of the invention, it is very convenient to observe the morphology and distribution of shear bands inside the AZ31 magnesium alloy sample in a large range.

Example 2

Step 1. Plastic deformation occurs on the surface of the AZ31 magnesium alloy by sliding friction, and the strain rate of the sliding friction on the surface of the AZ31 magnesium alloy is controlled to be 5.5×10 ² s ^-1 ;

Step 2. Sampling the plastically deformed AZ31 magnesium alloy in step 1 to obtain an AZ31 magnesium alloy sample, and then annealing the AZ31 magnesium alloy sample; the temperature of the annealing treatment is 160° C., and the holding time is 20 minutes;

Step 3: Use 600 ^# , 1000 ^# , 2000 ^# , 5000 ^# silicon carbide sandpaper to grind the surface of the AZ31 magnesium alloy sample after the annealing treatment in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed;

Step 4, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 3, so that the shear band inside the AZ31 magnesium alloy sample appears; Proportionally mixed, the oxalic acid and nitric acid are analytical reagents; the corrosion treatment time is 30s;

Step five, using an optical microscope to observe the morphology and distribution of the internal shear bands of the AZ31 magnesium alloy sample that appeared in step four.

Fig. 3 is a morphological view of the internal shear bands of the AZ31 magnesium alloy sample in this example, and the arrows in the figure indicate the shear bands. In Figure 3, the internal shear band of the AZ31 magnesium alloy sample is bright white, and the non-shear band area is gray-black. The contrast difference between the shear band area and the surrounding non-shear band area is obvious, and the shape and distribution of the shear band are clear. , which is easy to observe.

Example 3

Step 1. Plastic deformation occurs on the surface of the AZ31 magnesium alloy by sliding friction, and the strain rate of the sliding friction on the surface of the AZ31 magnesium alloy is controlled to be 10 ³ s ^-1 ;

Step 2. Sampling the plastically deformed AZ31 magnesium alloy in step 1 to obtain an AZ31 magnesium alloy sample, and then annealing the AZ31 magnesium alloy sample; the temperature of the annealing treatment is 200° C., and the holding time is 20 minutes;

Step 3: Use 600 ^# , 1000 ^# , 2000 ^# , 5000 ^# silicon carbide sandpaper to grind the surface of the AZ31 magnesium alloy sample after the annealing treatment in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed;

Step 4, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 3, so that the shear band inside the AZ31 magnesium alloy sample appears; Proportionally mixed, the oxalic acid and nitric acid are analytical reagents; the corrosion treatment time is 30s;

Step five, using an optical microscope to observe the morphology and distribution of the internal shear bands of the AZ31 magnesium alloy sample that appeared in step four.

Fig. 4 is a morphological view of the internal shear bands of the AZ31 magnesium alloy sample in this example, and the arrows in the figure indicate the shear bands. In Fig. 4, the internal shear band of the AZ31 magnesium alloy sample is bright white, and the non-shear band area is gray-black. The contrast difference between the shear band area and the surrounding non-shear band area is obvious, and the shape and distribution of the shear band are relatively Clear and easy to observe.

In Example 1, Example 2 and Example 3, the contrast difference between the internal shear band area and the surrounding non-shear band area of the annealed AZ31 magnesium alloy samples is obvious, and the shape and distribution of the shear bands are very obvious. Clearly; when the annealing temperature increased from 160°C to 200°C, the density of the shear bands did not change significantly, indicating that all shear band regions were completely recrystallized after annealing.

Comparative example 2

Step 1. Plastic deformation occurs on the surface of the AZ31 magnesium alloy by sliding friction, and the strain rate of the sliding friction on the surface of the AZ31 magnesium alloy is controlled to be 10 ³ s ^-1 ;

Step 2. Sampling the plastically deformed AZ31 magnesium alloy in step 1 to obtain an AZ31 magnesium alloy sample, and then annealing the AZ31 magnesium alloy sample; the temperature of the annealing treatment is 120° C., and the holding time is 20 minutes;

Step 3: Use 600 ^# , 1000 ^# , 2000 ^# , 5000 ^# silicon carbide sandpaper to grind the surface of the AZ31 magnesium alloy sample after the annealing treatment in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed;

Step 4, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 3, so that the shear band inside the AZ31 magnesium alloy sample appears; Proportionally mixed, the oxalic acid and nitric acid are analytical reagents; the corrosion treatment time is 30s;

Step five, using an optical microscope to observe the morphology and distribution of the internal shear bands of the AZ31 magnesium alloy sample that appeared in step four.

Fig. 5 is a morphological view of the internal shear bands of the AZ31 magnesium alloy sample in this example, and the arrows in the figure indicate the shear bands. In Figure 5, the internal shear band of the AZ31 magnesium alloy sample is white, and the non-shear band area is gray. The contrast difference between the shear band area and the surrounding non-shear band area is not obvious enough, and the shape and distribution of the shear band are not clear enough. , it is more difficult to observe.

Comparative example 3

Step 1. Plastic deformation occurs on the surface of the AZ31 magnesium alloy by sliding friction, and the strain rate of the sliding friction on the surface of the AZ31 magnesium alloy is controlled to be 10 ³ s ^-1 ;

Step 2. Sampling the plastically deformed AZ31 magnesium alloy in step 1 to obtain an AZ31 magnesium alloy sample, and then annealing the AZ31 magnesium alloy sample; the temperature of the annealing treatment is 150° C., and the holding time is 20 minutes;

Step 3: Use 600 ^# , 1000 ^# , 2000 ^# , 5000 ^# silicon carbide sandpaper to grind the surface of the AZ31 magnesium alloy sample after the annealing treatment in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed;

Step 4, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 3, so that the shear band inside the AZ31 magnesium alloy sample appears; Proportionally mixed, the oxalic acid and nitric acid are analytical reagents; the corrosion treatment time is 30s;

Step five, using an optical microscope to observe the morphology and distribution of the internal shear bands of the AZ31 magnesium alloy sample that appeared in step four.

Fig. 6 is a morphological view of the internal shear bands of the AZ31 magnesium alloy sample in this example, and the arrows in the figure indicate the shear bands. In Fig. 6, the internal shear band of the AZ31 magnesium alloy sample is bright white, and the non-shear band area is off-white. The contrast difference between the shear band area and the surrounding non-shear band area is slightly obvious, and the shape and distribution of the shear band can be see clearly.

Comparing Example 2, Example 3, Comparative Example 2 and Comparative Example 3, it can be known that when the annealing temperature is less than 160°C, the contrast between the internal shear band area and the surrounding non-shear band area of the AZ31 magnesium alloy sample The difference is not obvious enough, and the shape and distribution of the shear bands are not clear enough; when the annealing temperature is 200 ° C, a small part of the shear bands inside the AZ31 magnesium alloy sample becomes wider and the brightness increases. If the annealing temperature exceeds 200 At ℃, more shear bands become wider and even become one piece, which will make the shape and distribution of shear bands difficult to see clearly. Therefore, the temperature of the annealing treatment is selected to be 160° C. to 200° C.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the invention still belong to the technical solution of the present invention. within the scope of protection.

Claims (5)

1. an observation method to AZ31 magnesium alloy internal shear band, it is characterized in that, the method may further comprise the steps: Step 1, using sliding friction to make the surface of the AZ31 magnesium alloy plastically deformed; Step 2. Sampling the plastically deformed AZ31 magnesium alloy in step 1 to obtain an AZ31 magnesium alloy sample, and then annealing the AZ31 magnesium alloy sample; Step 3: Use 600 ^# , 1000 ^# , 2000 ^# , 5000 ^# silicon carbide sandpaper to grind the surface of the AZ31 magnesium alloy sample after the annealing treatment in step 2 step by step to obtain a flat, finely scratched AZ31 magnesium alloy sample Observe the plane; after each replacement of the silicon carbide sandpaper, rotate the observation plane of the AZ31 magnesium alloy sample horizontally by 90° and then grind until the scratches from the previous grinding are removed; Step 4, using a corrosive agent to corrode the observation plane of the AZ31 magnesium alloy sample obtained in step 3, so that the shear band inside the AZ31 magnesium alloy sample appears; Step five, using an optical microscope to observe the morphology and distribution of the internal shear bands of the AZ31 magnesium alloy sample that appeared in step four. 2 . The method for observing the internal shear band of the AZ31 magnesium alloy according to claim 1 , wherein the sliding friction strain rate in step 1 is 10 ² s ^-1 to 10 ³ s ^-1 . 3. A method for observing the internal shear band of the AZ31 magnesium alloy according to claim 1, characterized in that the temperature of the annealing treatment in step 2 is 160° C. to 200° C., and the holding time is 20 minutes. 4. A method for observing the internal shear band of AZ31 magnesium alloy according to claim 1, wherein the corrosive agent in step 4 is prepared by mixing oxalic acid, nitric acid and water according to the ratio of 5g: 10ml: 0.5ml Into, the oxalic acid and nitric acid are analytical reagents. 5. A method for observing the internal shear band of the AZ31 magnesium alloy according to claim 1, characterized in that the corrosion treatment time in step 4 is 30s.