What is it? ODS alloys consist of a combination of metals interspersed with small, nanometer-sized oxide particles and are known for their high creep resistance. This means that as temperatures rise, the materials keep their shape instead of deforming. Many ODS alloys can withstand temperatures up to 1000 °C and are typically used in power generation and engines within aerospace engineering, as well as cutlery.
The nuclear community has a high need for reliable and durable materials to make up the core components of nuclear reactors. The material must be high strength, radiation–tolerant, and resistant to void swelling (materials develop cavities when subjected to neutron radiation, leading to mechanical failures).
Ferritic failure: Nuclear researchers like Shao are consistently seeking to identify quality creep-resistant and swelling-resistant materials for use in high-temperature reactors.
“In general, ODS alloys should be resistant to swelling when exposed to extreme neutron irradiation,” Shao said. “However, the majority of commercial ODS alloys are problematic from the beginning.”
This is because almost all commercial ODS alloys are based on the ferritic phase. Ferritic alloys, classified by their crystalline structure and metallurgical behavior, have good ductility and reasonable high-temperature strength. The ferritic phase, however, is the weakest phase when judged by its swelling resistance, therefore making the majority of commercial ODS alloys fail in the first line of defense.
New developments: Shao, known internationally for his work in radiation materials science, directs the accelerator laboratory for testing alloys under extreme irradiation conditions. Shao and his research team collaborated with the Japanese research group at Hokkaido University led by Shigeharu Ukai to develop various new ODS alloys.
“We decided to explore a new design principle in which oxide particles are embedded in the martensitic phase, which is best to reduce void swelling, rather than the ferritic phase,” Shao said.
The resulting ODS alloys can survive up to 400 displacements per atom and are some of the most successful alloys developed in the field, both in terms of high-temperature strength and superior swelling resistance.
The team has conducted multiple studies, and the project has resulted in 18 journal papers and two doctoral degree dissertations.
Laura Simmons is a communications specialist at Texas A&M University.
