This is an album of SEM photographs for those interested in Metallurgy. One of the best tools for a metallurgist is a SEM (scanning electron microscope). With a SEM the engineer can identify various fracture modes when doing failure analysis.   The engineer can then take the data collected from the analysis and figure out a solution and/or improve upon the material characteristics.

Brittle Fracture, Cleavage

The best description I’ve heard of a brittle fracture is when the material does not stretch like taffy, and instead shatters like glass. When the material separates from each other they create crystalline facet planes which kind of resemble the surface of a leaf. To a metallurgist this type of brittle fracture is commonly known as cleavage.

MIC (Microbiological Induced Corrosion)

MIC is one of my favorite things to observe in a scanning electron microscope. MIC is basically microorganisms or bacteria. There are many types of MIC, and they can be very picky on what element they like to consume, but what is more interesting is what they leave behind. Using a scanning electron microscope I have found some very interesting crystal structure created by MIC.

Ductile Fracture

A good description of a ductile fracture is a material that stretches like taffy before it breaks apart quickly. Basically the material undergoes a plastic deformation and creates a dimpling on the surface that resembles a cup and cone. Most ductile fractures can be commonly found in the on the final fracture or shear lip of a fracture.

Fatigue Fracture

The best way to describe a fracture by fatigue is if you take a paperclip and bend it back and forth until it breaks. If you were to put the broken paperclip in a scanning electron microscope you would see fatigue lines running across the fracture surface. Fatigue can also happen thermally. The constant heat and cold can cause material to expand and contract until the material finally breaks.

Intergranular Fracture

Intergranular fractures kind of remind me of rock candy. An Intergranular fracture is a fracture that follows the grain boundaries of the material. Visually the surface will look really bumpy and may even be shiny. Intergranular fractures are usually caused by overheating the material or stress corrosion cracking. The material becomes super hard and very brittle.

Porosity, Shrinkage

Porosity is like the voids in swiss cheese, however porosity in metals can get a bit more interesting. Porosity is formed when gases are introduced into liquid molten metal. When the molten metals cool and turn solid it will begin to contract also known as shrinkage. The gasses in the molten metals cause the metals to pull apart during the shrinkage which form round nodules and dendrites in the void.

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