Leica EM TIC3X application: high-ductivity oxygen-free copper grain refinement under high strain rate

By ion beam cutting of the sample by Leica EM TIC3X , the resolution of the sample EBSD mapping is significantly improved, up to 80%-90%, and the results are stable and repeatable, better characterizing the deformation of the grain, and the grain size of the grain. The transformation.

Experimental sample

High-conductivity oxygen-free copper (OFHC) under high strain rate

Purpose

The grain refinement and recrystallization behavior of the materials obtained under high strain rate, high temperature and large deformation conditions were characterized by electron backscatter diffraction (EBSD) in order to achieve the purpose of characterizing the mechanical properties of the materials.

experiment procedure

1. Preparation of the original sample

High-speed cutting is a complex material forming condition that combines high strain rate, high temperature and large deformation. By changing the cutting speed to change the above-mentioned deformation boundary conditions, the high-speed cutting process is as follows:

(Figure 1 Schematic diagram of high-speed cutting process)

The obtained samples after metallographic inlaying and corrosion are shown in the figure:

(Fig. 2 Chips after inlaying and etching)

It can be seen from Fig. 2 that the crystal grains have been severely deformed, the light microscope has been indistinguishable, and the light mirror cannot be characterized for any change in the crystal grains, so it is necessary for the EBSD characterization of the material.

2. Preparation of experimental samples

EBSD sample preparation is the most important part of this experiment. The difficulty of this experiment is mainly reflected in three aspects: First, because there is a certain residual stress inside the grain of the material itself that has undergone severe deformation deformation, There is a certain difficulty in characterization; second, high-conductivity oxygen-free copper is a particularly soft material, which is very easy to bring in stress during the sample preparation, or scratch the test surface; third, the sample width obtained by high-speed cutting is very wide. Slender, not a traditional block, the process of making samples is more difficult.

At present, there are four main solutions: mechanical polishing, electrolytic polishing, vibration polishing, and ion polishing. These methods are currently tried, and the resolution is not too high. The reason is mainly because my sample is slender and curved. The reason is that after the inlay, the electropolishing cannot be satisfied, the mechanical polishing is easy to bring in the scratches, and the effect of the sample after the ion polishing inlay is not very satisfactory, and many methods are not suitable.

By communicating with Leica electron microscopy sample technicians, it is believed that the ion cutting method can solve the existing problems better . The resolution of the sample after Leica EM TIC 3X ion cutting exceeds 80%, and some areas can even reach more than 90%. The most important thing is that this method of sample preparation is very stable, and the results of the experiment can be reproduced more conveniently , which can better meet my research needs.

3. Experimental observation

Through the EBSD test, the resolution of the obtained mapping graph has been significantly improved. The higher resolution rate means that the deformation of the grain and the transformation of the grain boundary of the large and small angles can be better characterized.

Figure 3 EBSD angular orientation distribution obtained after vibration polishing

Figure 4 EBSD angular orientation distribution obtained after ion cutting

to sum up

From the results of the above experiments, it can be concluded that compared with the current mainstream vibration polishing, electrolytic polishing and ion polishing, the ion cutting method is not subject to the sample when preparing the EBSD samples of some special shape samples. Self-shape limitation, high efficiency, good stability, high repeatability, etc. are not commonly used in the current sample preparation methods, so ion cutting has made a very important expansion for the EBSD sample preparation method!

Acknowledgement: School of Mechanical Engineering, Xi'an Jiaotong University, Xu Xiang

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