- For the first time, researchers develop a technique to capture 3D images of microscopic cracks in nickel-base alloys caused by hydrogen or water exposure.
- It will help engineer develop microstructures with extended material life, saving costs on repairs and replacements.
Microfractures in metal alloys cannot be seen with the naked eye, but they can extend to other regions when exposed to hydrogen or water, leading to serious problems in nuclear plants, electrochemical, hydrogen storage technologies and structures like bridges and tall buildings.
Usually, hydrogen embrittlement (HE) of alloys is denoted by unexpected fractures and loss of ductility that cause an ever-widening spectrum of material failures. Since the intensity of HE increases with metal strength, advanced alloys (like nickel base alloy) are more susceptible to HE. To predict and prevent HE, one needs to have a detailed knowledge of its physical origins.
Recently, researchers at MIT and LLNL (Lawrence Livermore National Laboratory) developed a technique to capture three-dimensional images of microscopic cracks in alloys caused by hydrogen embrittlement. These images can be used to detect different grain boundaries or orientations of microscopic structures that can divert fractures and prevent hydrogen- or water-assisted damage.
How Did They Do It?
The new technique– 3D microstructure mapping — relies on synchrotron-based X-ray diffraction and tomography methods for analyzing nickel alloy cracks caused by hydrogen/water.
If you want to precisely analyze how metal cracks propagate, you need to simulate the problem in three dimensions. Also, you need to have enough data about crack’s morphology and its relation to microstructure.
To carry out a nondestructive evaluation, authors shined high-intensity X-ray beams on cracked nickel alloys. They placed a camera to capture all transmitted and diffracted beams. Then they tested hundreds of thousands of orientations of microscopic structure and examined millions of spots.
Image credit: Dharmesh Patel / Texas A&M University
By aligning data with physical models, they transformed the diffraction points into a three-dimensional microstructure picture. This 3D image shows what types of boundary grains could deflect cracks, and outcomes suggest that BLIPS (boundaries with low index plains) are resistant to damage.
How It Is Useful?
The technology can bring advancements to metal processing techniques aimed at halting further propagation of cracks in nickel alloys. This would strengthen materials and increase their lifespans for components and structures.
More specifically, it could improve predictions of mechanical responses of HE alloys. Detrimental grain boundaries can be processed out while engineering alloys to add hurdles for fractures and stop them from growing.
Furthermore, data obtained from 3D images will help engineer develop effective microstructures with extended material life, saving costs on repairs/replacements. To increase the lifespan, microstructure should be processed with large amounts of BLIPS, which would deflect or blunt cracks in a better way.