Sample Preparation Techniques for Microscopic Analysis in Metallurgy

Embedding and polishing are commonly used flat sample preparation techniques for microscopic analysis. Embedding protects fragile or coated materials during preparation and provides good edge retention. It is also used to prepare samples of a consistent size such as clay, minerals, or other particles. Additionally, embedding enables sectioning samples for further interior analysis. The specimens are often embedded in a resin with a standard diameter of 1” (Figure 1).

Figure 1. Samples embedded in a resin BSE Mode of β-processed Ti-6-4

The Phenom™ is equipped with a special metallurgical mount holder that can securely hold 1¼” (~32mm) samples (Figure 2).

Figure 2. Special holder to support the polished metallurgical mounts up to 1¼”

Sample Preparation

Mechanical preparation is a commonly used technique for preparing metallographic samples for microscopic analysis. It involves using abrasive particles in successively finer steps to strip material from the surface until achieving the desired result.

Preparing materialographic/metallographic samples for light microscopy or SEM for hardness testing or image analysis is a challenging task. Nevertheless, the availability of more sophisticated and fully automatic systems makes things easier. However, it is a time-intensive process for sectioning, grinding, mounting, and polishing samples.

Grinding and Polishing

With grinding, saw marks and levels are removed and the sample surface is cleaned. The artifacts of grinding are eliminated with very little material removal through polishing. Fixed abrasives composed of abrasive particles bonded to the paper or plates are used in the grinding process for fast material removal. Abrasive particles in a liquid that are suspended on a cloth are used for polishing.

Depending on the hardness, it will take up to one hour for sectioning sample. The grinding and polishing process may require roughly 2 - 2½ hrs.

Microscopic Analysis

Image of a polished surface of glass in contact with glass furnace construction material (ZAC) is shown in Figure 3. The image is captured at 1000x in compositional mode, showing different phases with different grey levels.

Figure 3. Image of a polished surface of glass (left) in contact with glass furnace construction material (right)

Glass-furnace diffusion zone is shown in Figure 4, wherein white portions represent the zirconium particles and dark grey portions represent the aluminum granules. As can be seen, the glass phase (on the left side) is diffusing into the granules.

Figure 4. Glass-furnace diffusion zone

Figure 5 shows a picture captured in topographical mode, revealing the height variations between the phases after polishing.

Figure 5. Topographical image showing the difference in height between the phases after polishing

About Phenom-World

Phenom™, world’s fastest Desktop Scanning Electron Microscope takes your imaging performance to a higher level. The Phenom desktop scanning electron microscope (SEM) helps customers stay competitive in a world where critical dimensions are continuously getting smaller.

The Phenom desktop SEM combines superb imaging power up to 100,000x and outstanding technical performance with better depth of focus and chemical contrast. It is the smart, affordable and market’s fastest solution that enables engineers, technicians, researchers and educational professionals to investigate micron and submicron structures.

With the Phenom proX we offer integrated, powerful EDS microanalysis to complete the optical performance of our SEM-range. Any Phenom system can be tailored to suit application and sample needs by choosing one of the many Pro Suite-based software solutions or specially designed hardware accessories.

Phenom-World helps you to stay competitive in a world where critical dimensions are continuously getting smaller. The Phenom desktop SEM offers direct access to the high-resolution and high-quality imaging necessary in a large variety of applications. It is an affordable solution that enables engineers, technicians, researchers and educational professionals to visualize micron and submicron structures.

This information has been sourced, reviewed and adapted from materials provided by Phenom-World BV.

For more information on this source, please visit Phenom-World BV.