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Title: Reduced Activity Complex Concentrated Alloys for Generation IV Reactor Systems

Abstract

Successful launch of next generation nuclear reactors demands availability of radiation-resistant alloys that have long creep life and can sustain liquid or gas-cooled environments at 400-850°C. The overarching goal of clean energy source and reduced environmental impacts of nuclear reactors can be realized only when material discard from nuclear reactors do not become a source of nuclear hazard. This translates to materials taken out from the reactor to be easily disposable or recyclable without any induced radioactivity contaminating the environment. State of the art reduced activity materials for nuclear reactors have major drawbacks including poor high temperature strength, swelling, hot corrosion, and deterioration in microstructure during welding. In this Phase I project, high entropy complex concentrated alloys (CCAs) were developed to overcome these challenges for longer service life in Generation IV reactor environments. Complex concentrated high entropy type alloys represent a new paradigm in structural alloy development resulting in materials with a combination of exceptional properties and processing ability. Three different refractory complex concentrated alloys were developed, namely Ti-V-Zr-Cr-Fe, Ti-V-Zr-Ta-W and Ti-V-Zr-Ta-Hf. All three alloys showed BCC single-phase microstructure. Stabilization of the desired phase was achieved by taking advantage of the high configurational entropy in complex concentrated alloys, arising frommore » near equimolar proportions of constituent elements. This gives access to the central region of multi-component phase diagrams rather than the vertices and makes the system highly tunable. The three alloys showed high room temperature and elevated-temperature hardness. Detailed microstructural characterization was done for the three alloys and it was observed that all the alloys had dendritic structure in the cast condition or produced by fusion additive manufacturing. Based on the preliminary microstructure and mechanical properties, the Ti-V-Zr-Ta-Hf alloy was chosen for irradiation studies. The alloy was irradiated using 50 MeV Ni2+ heavy ions to cause an equivalent damage of 50 DPA on SS304. Transmission electron microscopy (TEM) analysis was performed on the irradiated sample to assess the damage mechanism. Nano-indentation was performed at gradually increasing loads to measure indentation size effect (ISE) for quantifying the change in hardness at increasing depths from the material surface. The complex concentrated alloy showed hardness decrease after irradiation while reference SS304 steel and pure vanadium samples showed a significant increase in hardness after irradiation indicating greater degree of material damage. The radiation experiments and modeling results obtained during this Phase I demonstrate that the developed refractory complex concentrated alloys are very promising for next generation nuclear reactors. The decrease in hardness after radiation provides a significant breakthrough that identifies an alloy system meeting multiple types of nuclear reactor demands.« less

Authors:
 [1]
  1. ATS-MER, LLC, Tucson, AZ (United States)
Publication Date:
Research Org.:
ATS-MER, LLC, Tucson, AZ (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
Contributing Org.:
University of North Texas
OSTI Identifier:
1410433
Report Number(s):
DOE-ATS-MER-17138-F
DOE Contract Number:  
SC0017138
Type / Phase:
STTR (Phase I)
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Nuclear Reactors; Complex Concentrated Alloys; Radiation Resistance; Low Activity; Creep Strength

Citation Formats

Withers, James C. Reduced Activity Complex Concentrated Alloys for Generation IV Reactor Systems. United States: N. p., 2017. Web.
Withers, James C. Reduced Activity Complex Concentrated Alloys for Generation IV Reactor Systems. United States.
Withers, James C. Tue . "Reduced Activity Complex Concentrated Alloys for Generation IV Reactor Systems". United States.
@article{osti_1410433,
title = {Reduced Activity Complex Concentrated Alloys for Generation IV Reactor Systems},
author = {Withers, James C.},
abstractNote = {Successful launch of next generation nuclear reactors demands availability of radiation-resistant alloys that have long creep life and can sustain liquid or gas-cooled environments at 400-850°C. The overarching goal of clean energy source and reduced environmental impacts of nuclear reactors can be realized only when material discard from nuclear reactors do not become a source of nuclear hazard. This translates to materials taken out from the reactor to be easily disposable or recyclable without any induced radioactivity contaminating the environment. State of the art reduced activity materials for nuclear reactors have major drawbacks including poor high temperature strength, swelling, hot corrosion, and deterioration in microstructure during welding. In this Phase I project, high entropy complex concentrated alloys (CCAs) were developed to overcome these challenges for longer service life in Generation IV reactor environments. Complex concentrated high entropy type alloys represent a new paradigm in structural alloy development resulting in materials with a combination of exceptional properties and processing ability. Three different refractory complex concentrated alloys were developed, namely Ti-V-Zr-Cr-Fe, Ti-V-Zr-Ta-W and Ti-V-Zr-Ta-Hf. All three alloys showed BCC single-phase microstructure. Stabilization of the desired phase was achieved by taking advantage of the high configurational entropy in complex concentrated alloys, arising from near equimolar proportions of constituent elements. This gives access to the central region of multi-component phase diagrams rather than the vertices and makes the system highly tunable. The three alloys showed high room temperature and elevated-temperature hardness. Detailed microstructural characterization was done for the three alloys and it was observed that all the alloys had dendritic structure in the cast condition or produced by fusion additive manufacturing. Based on the preliminary microstructure and mechanical properties, the Ti-V-Zr-Ta-Hf alloy was chosen for irradiation studies. The alloy was irradiated using 50 MeV Ni2+ heavy ions to cause an equivalent damage of 50 DPA on SS304. Transmission electron microscopy (TEM) analysis was performed on the irradiated sample to assess the damage mechanism. Nano-indentation was performed at gradually increasing loads to measure indentation size effect (ISE) for quantifying the change in hardness at increasing depths from the material surface. The complex concentrated alloy showed hardness decrease after irradiation while reference SS304 steel and pure vanadium samples showed a significant increase in hardness after irradiation indicating greater degree of material damage. The radiation experiments and modeling results obtained during this Phase I demonstrate that the developed refractory complex concentrated alloys are very promising for next generation nuclear reactors. The decrease in hardness after radiation provides a significant breakthrough that identifies an alloy system meeting multiple types of nuclear reactor demands.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {11}
}

Technical Report:
This technical report may be released as soon as November 28, 2021
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