Editorial Feature

Chemical Alteration of Solid-Solution Alloys

As Material Science Researchers continue to move away from their previous focus on working with traditional alloys, recent success and advantages associated with the use of single-phase concentrated solid-solution alloys (SP-CSAs) have pulled them in another direction.

As a result of their rising use in applications that expose the alloys to consistent corrosive and high radiation environments, such as those that exist within nuclear power applications, there is a need to determine how these chemical alterations could potentially affect the nature of these alloys.

A group of Researchers funded by the U.S. Department of Energy’s Energy Frontier Research Center in conjunction with the University of Tennessee Oak Ridge National Laboratory Ion Beam Materials Laboratory (IBML) have recently determined that the ability of SP-CSAs to resist radiation damage is a property that is found at the atomic level of these alloys.

This provides an additional insight into how future energy systems can be constructed to enhance radiation tolerant alloys for such applications.

Tradition metal alloys, which are often comprised of a single primary element, differs greatly from SP-CSAs which will contain two to five, or even more elements, that will be present at a concentration that is equal or near-equal in comparison to the other principle elements that are present within the solution.

The presence of such highly abundant and various elemental species within the crystal lattice results in a disordered chemical environment to exist within the solution. Such unique chemical characteristics allows SP-CSAs to exhibit enhanced mechanical and chemical properties as a result of the improved electron scattering within the solution, thereby increasing the thermal conductivity and energy production of these alloys as well.

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In addition to these added beneficial properties, SP-CSAs have been found to exhibit greater damage resistance, such as that which has been proven by comparing molecular dynamic (MD) simulation results on single-phase NiFe and NiCoCr alloys as compared to pure Ni, which were shown to demonstrate a much greater damage reduction.

Furthermore, the irradiation resistance of solid-solution alloys to prevent defect formation and further microstructural changes within the metal compositions has been found to be a beneficial and desirable property of SP-CSAs.

To understand the complex chemical nature that allows for such defect resistance properties to be present in SP-CSAs, the Researchers led by William Weber and Yanwen Zhang included pure Ni, Ni80Fe20 and Ni50Fe50 as their experimental model, which closely resemble solid-solution alloys that are currently being looked at for their potential use in nuclear power applications.

As a result of the varying resistivity properties associated with different types of elements, different concentrations of both Fe and Cr content within the alloys were utilized in this study in order to fully understand the atomic-level irradiation response. To study the irradiation resistance of these models, 1.5 MeV Ni or Mn ions irradiated the metals of interest, while MD simulations involving overlapping cascades of 25 keV recoils were utilized to understand metal resistivity to accumulated damage.

The results of the study determined that further reduction of accumulated damage was found in both Ni50Fe50 and Ni40Fe40Cr20 alloys, of which both metal compositions exhibited and increased randomly arranged atomic structure.

By adjusting the atomic complexity of the concentrated solid solution alloys, the Researchers determined that they were able to manipulate the defect accumulation that was found as a result of extended exposure to irradiation environments. The coupling nature of the elements, as well as the amount of the elements present with the SP-CSAs was found to strongly affect the damage accumulation and irradiation resistance found in the alloying metals used in this study.

The information gathered from this study allows industrial Researchers to understand the affect that their material designs have on the way in which alloy materials are capable of resisting both physical and radiation damage when present in such exposing environments.

References:

“Effects of chemical alteration on damage accumulation in concentrated solid-solution alloys” M. Ullah, H. Xue, et al. Scientific Reports. (2017). DOI: 10.1038/s41598-017-0451-8.

Image Credit:

Shutterstock.com/ HQuality

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