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Title: Radiation-Damage in Molybdenum-Rhenium Alloys for Space Reactor Applications

Abstract

Various Mo-Re alloys are attractive candidates for use as fuel cladding and core structural materials in spacecraft reactor applications. Molybdenum alloys with rhenium contents of 41% to 47.5% (wt%), in particular, have good creep resistance and ductility in both base metal and weldments. However, irradiation-induced changes such as transmutation and radiation-induced segregation could lead to precipitation and, ultimately, radiation-induced embrittlement. The objective of this work is to evaluate the mechanical properties of Mo-41Re and Mo-47.5Re after irradiation at space reactor relevant temperatures. Tensile specimens of Mo-41Re and Mo-47.5Re alloys were irradiated to ~ 0.7 dpa at 1073, 1223, and 1373 K and ~1.4 dpa at 1073 K in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Following irradiation, the specimens were strained to failure at a rate of 1 x 10-3 s-1 in vacuum at the irradiation temperature. In addition, unirradiated specimens and specimens aged for 1100 hours at each irradiation temperature were also tested. Fracture mode of the tensile specimens was determined.

Authors:
 [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Flux Isotope Reactor
Sponsoring Org.:
Work for Others (WFO)
OSTI Identifier:
931931
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Journal Volume: 366; Journal Issue: 3; Conference: TMS 2006 Spring Conference: Space Reactor Fuels and Materials: Refractory Alloy Properties and Welding, San Antonio, TX, USA, 20060313, 20060316
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; ALLOYS; BUILDING MATERIALS; HEAT RESISTING ALLOYS; HFIR REACTOR; IRRADIATION; MECHANICAL PROPERTIES; MOLYBDENUM ALLOYS; NUCLEAR FUELS; RHENIUM ALLOYS; WELDING; NESDPS Office of Nuclear Energy Space and Defense Power Systems

Citation Formats

Busby, Jeremy T, Leonard, Keith J, and Zinkle, Steven J. Radiation-Damage in Molybdenum-Rhenium Alloys for Space Reactor Applications. United States: N. p., 2007. Web. doi:10.1016/j.jnucmat.2007.03.028.
Busby, Jeremy T, Leonard, Keith J, & Zinkle, Steven J. Radiation-Damage in Molybdenum-Rhenium Alloys for Space Reactor Applications. United States. doi:10.1016/j.jnucmat.2007.03.028.
Busby, Jeremy T, Leonard, Keith J, and Zinkle, Steven J. Mon . "Radiation-Damage in Molybdenum-Rhenium Alloys for Space Reactor Applications". United States. doi:10.1016/j.jnucmat.2007.03.028.
@article{osti_931931,
title = {Radiation-Damage in Molybdenum-Rhenium Alloys for Space Reactor Applications},
author = {Busby, Jeremy T and Leonard, Keith J and Zinkle, Steven J},
abstractNote = {Various Mo-Re alloys are attractive candidates for use as fuel cladding and core structural materials in spacecraft reactor applications. Molybdenum alloys with rhenium contents of 41% to 47.5% (wt%), in particular, have good creep resistance and ductility in both base metal and weldments. However, irradiation-induced changes such as transmutation and radiation-induced segregation could lead to precipitation and, ultimately, radiation-induced embrittlement. The objective of this work is to evaluate the mechanical properties of Mo-41Re and Mo-47.5Re after irradiation at space reactor relevant temperatures. Tensile specimens of Mo-41Re and Mo-47.5Re alloys were irradiated to ~ 0.7 dpa at 1073, 1223, and 1373 K and ~1.4 dpa at 1073 K in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Following irradiation, the specimens were strained to failure at a rate of 1 x 10-3 s-1 in vacuum at the irradiation temperature. In addition, unirradiated specimens and specimens aged for 1100 hours at each irradiation temperature were also tested. Fracture mode of the tensile specimens was determined.},
doi = {10.1016/j.jnucmat.2007.03.028},
journal = {},
number = 3,
volume = 366,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Specimens of Mo-7 at. % Re and Mo-30 at. % Re were irradiated with 1.8 MeV /sup 4/He/sup +/ ions at elevated temperatures. Radiation-induced segregation of Re was measured during irradiation by in situ Rutherford backscattering spectrometry. Segregation of the undersized Re atoms in the same direction as the defect fluxes, i.e., toward the external surface, was observed. The amount of Re enrichment in the near-surface region was measured as a function of temperature and of dose at a calculated near-surface displacement rate near 1 x 10/sup -4/dpa/s. Segregation was observed at temperatures from 800 to 1500/sup 0/C in Mo-7Re,more » and from 850 to 1225/sup 0/C in Mo-30Re. Irradiated disks were examined by transmission electron microscopy. Precipitates of Chi phase were observed on grain boundaries, or in a thin layer at the irradiated surface in Mo-30Re after irradiation at temperatures from 750 to 1075/sup 0/C. Frequently, Chi precipitates formed with a crystallographic twin orientation with respect to the host matrix. No voids were observed for doses up to 1.6 dpa.« less
  • Vacuum arc-cast (VAC) alloys with 2.5 to 9.6 at.% Re were produced, converted to plate, and experiments were performed to determine properties and fabricability as a function of rhenium content. Tensile mechanical behavior was determined between 155 K and room temperature for the VAC alloy plate and Mo-7 at.% Re alloy round bar produced by powder metallurgical (PM) methods. Optimum room temperature mechanical behavior was indicated for alloys containing 5.4 to 7.6 at.% rhenium, while the optimum rhenium content increased with decreasing test temperature. Creep tests on VAC Mo-3.9Re, Mo-6.2Re, and Mo-7.4Re + 0.04C in the temperature range 1,400 tomore » 1,600 K and the stress range 13.7 to 27.6 MPa indicated creep rates were affected by thermomechanical history. Ductile GTA welds were made in relatively thick plates of Mo-6.2 and -7.4at.% Re with Mo-11 at.% Re filler metal. High quality electron beam fusion weld joints were made in both VAC and PM alloys containing approximately 7 at.% Re. Thermal expansion data were obtained over the temperature range 295 to 1,373 K as a function of rhenium content with the alloys having higher thermal expansion than pure molybdenum.« less
  • Oxide dispersion strengthened (ODS) molybdenum alloys being developed for high temperature applications possess excellent high temperature strength and creep resistance. In addition they exhibit a ductile-to-brittle transition temperature (DBIT) in the worked and stress-relieved condition under longitudinal tensile load well below room temperature. However, in the recrystallized condition, the DBTT maybe near or above room temperature, depending on the volume fraction of oxide dispersion and the amount of prior work. Dilute rhenium additions (7 and 14 wt.%) to ODS molybdenum were evaluated to determine their effect on low temperature ductility. The addition of 7 wt.% rhenium to the ODS molybdenummore » did not significantly enhance the mechanical properties. However, the addition of 14 wt.% rhenium to the ODS molybdenum resulted in a DBTT well below room temperature in both the stress-relieved and recrystallized condition. Additionally, the tensile strength of ODS Mo-14Re is greater than the base ODS molybdenum at 1,000 to 1,250 C.« less
  • Several Mo- and Ta-base alloys have been selected as candidate materials for space reactor heat transfer applications. The initial phase of this investigation has compared the effects of inert and oxidizing atmospheres on tensile and bend properties of these alloys. Microstructural variables include texture and degree of recrystallization. Results are discussed with implications for future elevated temperature testing.