Metallographic analysis is a very important technique for the quality testing of metal materials that will be used for a wide variety of commercial and scientific applications. By understanding what a metal is made of, experts can figure out how it will react to a wide range of outside stimuli and, therefore, whether or not it is suited for any number of practical applications.

This is what you should know about metallographic analysis, including how it works, why it’s so important, and how you could benefit from it. 

What is metallographic analysis?

Every type of metal has a complex and unique physical composition. Depending on the nature of the microstructure, different metals will react to stimuli in different ways. For example, metals like copper, silver, and aluminum have very high electrical conductivity, while bismuth hardly conducts electricity at all under normal temperatures.

Metallographic analysis involves using microscopic equipment and techniques to study the physical structure and components of metals to understand their properties. 

Why is metallographic analysis important?

By using metallographic analysis to understand the mechanical properties of metallic materials, experts can determine how they will meet specific performance objectives. 

This is essential for understanding whether a given metal material would be suitable and safe for building a part or product, such as a part of a car, plane, machine, or electronic device.

For example, a metal with a large grain structure is typically preferred when considering performance at high temperatures, whereas fine grain materials are better for resisting fatigue crack initiation.

Metallographic analysis is also commonly applied as a form of quality assurance. By characterizing the components and properties of a metal substance, metallographic experts can make sure it’s appropriate for whatever use it’s intended for or identify why it fails to meet specifications. 

Advanced metallographic analysis techniques like the ones used by Secat’s experts can even take this form of quality assurance further, using it to assist with manufacturing defect remediation and process optimization. Secat experts do this by identifying specific defects in a metal sample and then reverse-engineering what could have introduced those defects into the metallic product during the manufacturing process. 

How does metallographic analysis work?

Secat uses three metallographic analysis techniques:

Optical Microscopy (OM)

OM is the type of microscopic magnification most people are most familiar with. Optical microscopes, sometimes also called light microscopes, transmit light through a series of lenses to magnify the surface of the object being studied.

Standard optical microscopes are capable of 10 to 100x magnification, making it possible to see microstructural features on the surface of a metallic sample that are as small as 0.2 micrometers. This makes it most useful for analyzing larger microstructural features.

OM is typically the first step in metallographic analysis. It’s used to determine whether more powerful magnification techniques such as SEM and TEM will be necessary to fully understand the metal’s structure and composition.

Scanning Electron Microscopy (SEM)

SEM microscopes work by passing an accelerated electron beam over the surface of the metallic sample analysts want to study. As the beam’s electrons collide with the sample’s surface, they bounce or reflect off of it. 

When the electrons bounce off the sample, atoms on the sample’s surface interact with them to produce secondary electrons. The particular energy levels required to produce these secondary electrons differ from element to element, allowing analysts to understand which elements are present on the surface of the sample.

SEM provides a great deal of information about the surface and outer composition of metallic structures. It’s most commonly applied to analyze metallic structures with mid-sized microstructural features that are nevertheless too small to analyze with OM alone accurately.

Transmission Electron Microscopy (TEM)

TEM works similarly to SEM. The big difference between the two forms of microscopy is that, where SEM bounces or reflects electrons off of the sample, TEM passes electrons directly through the sample to create its image on the other side. 

After passing through the sample, the electrons hit a phosphor screen and produce an image that is magnified and projected for analysts to see. Where the sample has less density, more electrons pass through and the image is brighter, and a darker image is produced instead when the sample is more dense and lets fewer electrons through.

TEM offers greater resolution than SEM. TEM even allows experts to see and analyze details of the metal’s composition as minute as its nanoscale strengthening participates and their crystal structures. 

TEM is the most specialized and least commonly used form of metallographic analysis Secat applies. It is useful for analyzing even finer and smaller microstructural features in metals than OM or SEM can see in detail. 

By using these three metallographic analysis techniques in coordination, Secat’s analysts can comprehensively characterize the composition of metals to understand how they will react to outside stimuli. 

If you need metallographic analysis, Secat’s team has the tools and expertise to help. Get in touch for a quote today and we can get started.