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Quantitative prediction of yield strength of high-alloy complex steel using high-energy synchrotron X-ray diffractometry

By on November 14, 2022 0

Determining the strength of a piece of steel, especially stainless steel used in everything from automotive manufacturing to construction, is vitally important to keeping drivers and passengers safe during crashes and preventing the collapse of buildings. Accurately predicting the strength of a prototype steel, based on its microstructure and composition, would be extremely useful for the design and manufacture of new and improved types of this alloy. However, this capability has been unattainable – until now. Harishchandra Singh, Graham King, and associates used high-energy synchrotron X-ray diffraction (HE-SXRD) experiments and an analytical model to predict the yield strength of cerium-modified super duplex stainless steel (SDSS) subjected to various cold and cryo deformations. Spectroscopy recently had the opportunity to discuss the experiments and results with Singh and King.

Your paper (1) proposes a new high-energy synchrotron X-ray diffraction (HE-SXRD) method to predict the yield strength of high-alloy complex steels. Why do you think a “new way” was needed?

Ultra-fast methodology with precision is always beneficial. The yield strength of a steel is the result of many microstructural factors within it. The more complex the microstructure, the more complicated it is to know their individual contribution to the yield strength. Conventional approaches easily measure the yield strength, but not the reinforcement mechanism. HE-SXRD in combination with analytical models do the same job in precise time. This lightning-fast, accurate approach can help optimize high-strength steel faster.

Were you surprised that you could apply HE-SXRD to accurately predict the yield strength of deformed variants of Ce-modified stainless steel? Did your results meet your expectations?

Indeed, we expected it to work but not that precisely! Yes, since HE-SXRD provided all existing microstructural factors affecting yield strength, it helped prediction accurately.

Briefly describe the HE-SXRD method and how this method differs from what you or others have been doing before.

In short, HE-SXRD (High Energy Synchrotron X-ray Diffraction) probes the crystal structure of bulk materials even with a few mm thickness due to its high penetrating power. XRD in the laboratory mainly allows to obtain information from a few hundred micrometers. To the best of our knowledge, this methodology has never been performed before with such precision.

It was noted that the described process could also help in the design of new steels through a better understanding of the relationship between the microstructure of a steel and its mechanical properties. How could this be accomplished and why is it important?

Steel is made up of complex microstructures that must be studied to realize its strength. If you know the microstructure details, you can better design high strength steel. As stated, the microstructure of a steel strongly affects its mechanical properties and therefore it is necessary to know all the information about the existing microstructures in a bulk steel. Due to many limitations, conventional methods may be unable to provide all details in a time efficient manner. The same can be easily probed using advanced methods like HE-SXRD due to high photon flux and penetrating power. Full knowledge is important because the type of microstructures determine the strength of the steel.

What is the main advantage of using HE-SXRD to predict the yield strength of steels compared to other spectroscopic methods?

HE-SXRD can be applied in bulk whereas most spectroscopic methods deal with the surface and require dedicated sample preparation. Another concern is the scaling of information obtained from spectroscopic methods.

Did you encounter any challenges or obstacles in developing this method? How did you overcome them?

Yes, a lot actually, because of the paucity of literature on such methods. The experimental yield strength data already collected served as a reference point for this method. Following the complete microstructural information from HE-SXRD, we used an appropriate analytical model to predict the yield strength.

What kind of feedback have you received regarding this work?

Initially criticized by steel metallurgy experts, as it was a completely new discovery. However, they ultimately appreciated this unique approach to better steel design.

What are the next steps in this research?

We plan to generalize this concept to a variety of other steel alloys and complex metals such as carbon steel, high entropy alloy. Such tests with multiple batches of steel can be of great benefit to various steel and metallurgy experts, as they allow high-strength steel to be designed faster.

(1) S. Ghosh, S. Wang, H. Singh, G. King, Y. Xiong, T. Zhou, M. Huttula, J. Kömi and W. Cao,J. Mater. Res. Technology. 20,485-495 (2022).

Harishchandra Singh is Adjunct Professor at NANOMO, University of Oulu, Finland. His main research focuses on structural/construction materials and energy production/storage materials with the aim of explaining their physics via advanced synchrotron methods. Singh earned a Ph.D. in physical sciences from the Raja Ramanna Center for Advanced technology, India, on synchrotron-based structural and spectroscopic studies. After his PhD, Singh joined Stony Brook University/Brookhaven National Laboratory, USA as a postdoctoral researcher for the successful development of modulation excitation X-ray absorption spectroscopy on the line of ISS light from the NSLS-II synchrotron source.

Graham King received his BS in Chemistry from SUNY Buffalo in 2005 and his Ph.D. in Solid State Inorganic Chemistry from The Ohio State University in 2010 under the supervision of Patrick Woodward. He then spent 6 years at the Lujan Neutron Scattering Center of the Los Alamos National Lab, first as a post-doctoral fellow and then as a researcher. After briefly working as an independent consultant, he joined CLS in 2018 as Instrument Scientist for the Brockhouse beamlines. He specializes in advanced powder diffraction methods for the determination of crystal and local structures of materials, with a particular interest in cation-ordered perovskites.