CMU Tech Takes 3D Photo of Metal Microstructure
Using a technology developed by Carnegie Mellon University and the Argonne National Laboratory, a multi-institution collaboration of researchers has for the first time taken a 3D image of a microscopic crack as it spreads through metal damaged by hydrogen.
The research was initiated by a team at MIT that was assisted by Carnegie Mellon and Argonne scientists. Members of that team are currently at Texas A&M and Johns Hopkins universities, and Lawrence Livermore National Laboratory.
The picture demonstrates an improved methodology for studying how metal can fail in the presence of a stressor. The results of this work can be used to inform the creation of new materials and increase the durability and reliability of most things made out of metal, including bridges and airplanes.
Most materials are made up of aggregates of crystals or “grains” that have different sizes, shapes and orientations. They are tied together by a network of grain boundaries. When the material is exposed to heat, water or other stressors, the grain boundaries can shift and have altered properties. One example is when hydrogen, which is omnipresent, becomes bound to the boundaries. Such exposure has long been known to cause embrittlement that weakens the material and can lead to catastrophic fractures.
Until recently, these fractures could only be seen after the material failed, and researchers could only guess at what led to the fracture.
Carnegie Mellon physicist Robert M. Suter and colleagues at Argonne developed a new way to study the microstructure of materials. Their technique combines high-energy diffraction microscopy and X-ray absorption tomography with high-performance computing and allows researchers to view grain orientations, grain boundaries and cracks within a material. This level of resolution makes it possible to see a crack when it forms and follow its progression.
In Nature Communications, the researchers reported that they were able to image cracks along the grain boundaries of a nickel alloy that was exposed to hydrogen. From these pictures, they were able to identify a class of boundaries that resist embrittlement and therefore the associated cracking. The finding can help materials scientists and engineers as they make new materials for commercial and industrial use in hostile environments.
Suter commented that, “It is extremely gratifying to see our new microscopy yield results that are directly relevant for applications.”
