Radiation behavior of high-entropy alloys for advanced reactors. Final report

Technical Report · Thu Apr 30 00:00:00 EDT 2015

DOI:https://doi.org/10.2172/1214790· OSTI ID:1214790

Liaw, Peter K. ^[1]; Egami, Takeshi ^[1]; Zhang, Chuan ^[2]; Zhang, Fan ^[2]; Zhang, Yanwen ^[1]

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1. Univ. of Tennessee, Knoxville, TN (United States)
2. CompuTherm, LLC, Madison, WI (United States)

In the first task, we have demonstrated the radiation damage and the recrystallization behaviors in multicomponent alloys through molecular-dynamics simulations. It is found that by alloying with atoms of different sizes, the atomic-level strain increases, and the propensity of the radiation-induced crystalline to amorphous transition increases as the defects cluster in the cascade body. Recrystallization of the radiation induced supercooled or glass regions show that by tuning the composition and the equilibrium temperature, the multicomponent alloys can be healed. The crystalline-amorphous-crystalline transitions predict the potential high radiation resistance in multicomponent alloys. In the second task, three types of high-entropy alloys (HEAs) were fabricated from AlCoCrFeNi and AlCuCrFeNi quinary alloys. Hardness and reduced contact modulus were measured using nanoindentation tests. Heavy ion irradiation were performed using 10 MeV gold and 5 MeV nickel to study radiation effects. Al_0.5CrCuFeNi₂ shows phase separation upon the presence of copper. Both hardness and contact modulus exhibit the same trend as increasing the applied load, and it indicates that excessive free volume may alter the growth rate of the plastic zone. The as-cast Al_0.1CoCrFeNi specimen undergone the hot isostatic pressing (HIP) process and steady cooling rate which mitigate the quenching effect. The swelling behavior was characterized by the atomic force microscopy (AFM), and the swelling rate is approximately 0.02% dpa. Selected area diffraction (SAD) patters show irradiation-induced amorphization throughout the ion projected range. Within the peak damage region, an amorpous ring is observed, and a mixture of amorphous/ crystalline structure at deeper depth is found. The Al_0.3CoCrFeNi HEAs shows good radiation resistance up to 60 peak dpa. No voids or dislocations are observed. The crystal structures remain face-centered-cubic (FCC) before and after 5 MeV Ni irradiation. Higher dpa might be required to study defects formation mechanisms. In the third task, all the constituent binary and ternary systems of the Al-Co-Cr-Fe-Ni system were thermodynamically modeled within the whole composition range. Comparisons between the calculated phase diagrams and literature data are in good agreement. The multi-component thermodynamic database of the Al-Co-Cr-Fe-Ni system was then obtained via extrapolation. The current Al-Co-Cr-Fe-Ni thermodynamic database enables us to carry out the calculations of phase diagrams, which can be used as useful guidelines to identify the Al-Co-Cr-Fe-Ni HEAs with desirable microstructures. In the fourth task, we discuss how as-cast and homogenized phases can be identified, what phases are usually found in the as-cast and homogenized conditions, and what the thermodynamics and kinetics of phase transformations are in the AlCoCrFeNi HEA. The microstructure and phase composition were studied in as-cast and homogenized conditions. It showed the dendritrical structure in the as-cast condition consisting primarily of a nano-lamellar mixture of A2 [disorder body-centered-cubic (BCC)] and B2 (ordered BCC) phases, in addition to a very small amount of A1 [disorder face-centered-cubic (FCC)] phases. The homogenization heat treatment resulted in an increase in the volume fraction of the A1 phase and formation of a Sigma phase. Tensile properties in as-cast and homogenized conditions are reported at 700 °C. Thermodynamic modeling of non-equilibrium and equilibrium phase diagrams for the AlCoCrFeNi HEA gave good agreement with the experimental observations of the phase contents. The reasons for the improvement of ductility after the heat treatment are discussed.

• Research Organization: Univ. of Tennessee, Knoxville, TN (United States); CompuTherm, LLC, Madison, WI (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE). Nuclear Energy University Programs (NEUP)
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1214790
• Report Number(s): DOE/NEUP-11-3196; 11-3196; TRN: US1500412
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
FCC LATTICES
BCC LATTICES
ATOMIC DISPLACEMENTS
DISLOCATIONS
DUCTILITY
PHASE DIAGRAMS
MEV RANGE 01-10
ALUMINIUM ALLOYS
COBALT ALLOYS
COPPER ALLOYS
CHROMIUM ALLOYS
IRON ALLOYS
NICKEL ALLOYS
HOT PRESSING
COPPER
GOLD IONS
NICKEL IONS
HARDNESS
MIXTURES
SWELLING
DIFFRACTION
EQUILIBRIUM
EXTRAPOLATION
IRRADIATION
MOLECULAR DYNAMICS METHOD
COMPARATIVE EVALUATIONS
HEAT TREATMENTS
CRYSTAL DEFECTS
DEPTH
MICROSTRUCTURE
RECRYSTALLIZATION
AMORPHOUS STATE
PHASE TRANSFORMATIONS
COOLING
GLASS
SUPERCOOLING
KINETICS
QUENCHING
RINGS
COMPUTERIZED SIMULATION
STRAINS
THERMODYNAMICS
VOIDS
PHYSICAL RADIATION EFFECTS
SIZE
CHEMICAL COMPOSITION
TEMPERATURE DEPENDENCE
STATIC LOADS
CRYSTAL STRUCTURE
BINARY ALLOY SYSTEMS
TERNARY ALLOY SYSTEMS
PHASE STUDIES
LAMELLAE
TEMPERATURE RANGE 0400-1000 K