Quantitative Prediction of Yield Strength of Highly Alloyed Complex Steel Using High Energy Synchrotron X-Ray Diffractometry

Determining the strength of a piece of steel, especially the stainless steel used in everything from car manufacturing to construction, is vitally important in keeping drivers and passengers safe during crashes and preventing the collapse of buildings. Predicting the strength of a steel prototype accurately, based on its microstructure and composition, would be extremely helpful in the design and manufacturing of new and improved types of that alloy. However, that ability has been impossible to achieve—until now. Harishchandra Singh, Graham King and associates have employed high energy synchrotron X-ray diffraction (HE-SXRD) experiments and an analytical model in order to predict the yield strength of cerium-modified super duplex stainless steel (SDSS) subjected to various cold- and cryo-deformation. Spectroscopy recently had the opportunity to discuss the experiments and the findings with Singh and King.

Your paper (1) offers a new high energy synchrotron X-ray diffraction (HE-SXRD) method to predict the yield strength for highly alloyed complex steel. Why do you feel a “new way” was needed?

An ultra-fast methodology with accuracy is always beneficial. The yield strength of a steel is a result of many microstructural factors inside. The more complex the microstructure the more complicated is to know their individual contribution to yield strength. Conventional approaches measure yield strength easily but not the mechanism of strengthening. HE-SXRD in combination with analytical models do the same job in an hour precisely. This ultra-fast precise approach can help to optimize the high strength steel in a faster way.

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

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

Briefly describe the HE-SXRD method, and how this method differs from what was previously done by yourself or others.

Briefly, HE-SXRD (high energy synchrotron X-ray diffraction) probes the crystalline structure of bulk materials even with a few mm thickness because of its high penetration power. Lab based XRD mostly allows information from a few hundred of micrometers. To the best of our knowledge, this methodology has not been realized before to this accurate extent.

It was noted that the process described could also help to engineer novel steels through a better understanding of the relationship between a steel’s microstructure and its mechanical properties. How could this be accomplished and why is this important?

Steel consists of complex microstructures which need to be investigated to realize its strength. If you know the microstructure details, you can design high strength steel in a better way. As pointed out, a steel’s microstructure highly affects its mechanical properties, and therefore one needs to know the full information about existing microstructures within a bulk steel. Due to many limitations, conventional methods may be unable to provide the full details in a time effective manner. The same can be easily probed using advanced methods such as HE-SXRD due to high photon flux and penetration power. Full knowledge is important because the type of microstructures decides the strength of steel.

What is the main benefit in using HE-SXRD to predict the yield strength of steels as opposed to other spectroscopic methods?

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

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

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

What sort of feedback did you receive regarding this work?

Initially critical from steel metallurgy experts, as this was a completely new finding. However, they finally appreciated this unique approach towards better steel design.

What are the next steps in this research?

We plan to generalize this concept to a variety of other complex steel and metal alloys such as carbon steel, high entropy alloy. Such tests with several batches of steel may be highly beneficial to various steel and metallurgy experts the faster way to design the high strength steel.

(1) S. Ghosh, S. Wang, H. Singh, G. King, Y. Xiong, T. Zhou, M. Huttula, J. Kömi, and W. Cao,J. Mater. Res. Technol. 20,485-495 (2022). https://doi.org/10.1016/j.jmrt.2022.07.066.

Harishchandra Singh is an Adjunct Professor at NANOMO, University of Oulu, Finland. His main research includes structural / building materials and energy production / storage materials with the goal to explain their physics via advanced synchrotron methods. Singh received Ph.D. in Physical Sciences from Raja Ramanna Centre for Advanced technology, India on synchrotron-based structural and spectroscopic studies. After Ph.D., Singh joined Stony Brook University/Brookhaven National laboratory, USA as a postdoctoral researcher for the successful development of modulation excitation X-ray absorption Spectroscopy at ISS beamline of NSLS-II synchrotron source.

Graham King received his B.S. in Chemistry from SUNY Buffalo in 2005 and his PhD in inorganic solid state chemistry from The Ohio State University in 2010 under the guidance of Patrick Woodward. He then spent 6 years at the Lujan Neutron Scattering Center at Los Alamos National Lab, first as a postdoc and then as a staff scientist. After briefly working as an independent consultant he came to CLS in 2018 as an instrument scientist for the Brockhouse Beamlines. He specializes in advanced powder diffraction methods for determination of the crystal and local structures of materials, with a special interest in cation ordered perovskites.