HEA 2023: Performance in Extreme Environments II
Program Organizers: Andrew Detor, DARPA/DSO; Amy Clarke, Los Alamos National Laboratory
Wednesday 1:40 PM
November 15, 2023
Room: Three Rivers
Location: Omni William Penn
Session Chair: Stephen Giles, CFD Research Corporation
1:40 PM Introductory Comments
1:45 PM
A First-principles Study on the Structural-thermodynamics Properties of Tungsten-based High Entropy Alloys: Jie Peng1; David Cerecedar1; Yichen Qian1; 1Villanova University
High entropy alloys (HEAs) are a class of materials promising for plasma-facing applications in fusion energy devices. Among them, Tungsten (W-) based HEAs have been considered as leading candidates due to remarkable properties including superior mechanical properties, a superior melting point (above 2873 K), enhanced radiation resistance to heavy ion irradiation, and negligible radiation hardening compared to pure W. However, there is a lack of understanding of how mechanical and thermodynamics properties of W-based HEAs are affected by temperature. In this work, we present a study on the temperature-dependent thermal properties of W-based HEAs. The first-principles density-functional-theory (DFT) calculations combined with quasi-harmonic approximation (QHA) theory is used to investigate electronic, structural, and thermal properties of HEAs in different chemical compositions as a function of temperature. Our work advances understanding of structural-mechanical-thermal relations in HEAs, thus providing insights on inverse design of candidate HEAs in fusion energy devices.
2:05 PM
Radiation-induced Segregation in FCC Multi-principal Element Alloys: Daniele Fatto Offidani1; Emmanuelle Marquis1; 1University Of Michigan - Ann Arbor
Multi-principal element alloys (MPEAs) have been proposed as potential structural material candidates for next-generation nuclear reactors because of their notable mechanical properties and environmental resistance. However, the effects of irradiation on the microstructural and chemical evolution of these alloys are still not fully understood. Grain boundaries are of particular interest due to their susceptibility to radiation-induced segregation (RIS), which by altering their chemistries can negatively impact the resistance of the materials to stress-corrosion. Focusing on the impact of alloy chemistry and the role of single elements on RIS, we systematically characterized the RIS behavior at grain boundaries in three ion-irradiated single-phase FCC Fe-Ni-Cr-Co-Mn based alloys. The results provide insights into the effects of dose, temperature, and alloy composition on RIS.
2:25 PM
Irradiation Effects in a Precipitation-hardened AlCuCrFeNi High Entropy Alloy: Nathan Curtis1; Bao-Phong Nguyen1; Junliang Liu1; Nate Eklof1; Adrien Couet1; 1University Of Wisconsin - Madison
Interest in the nuclear industry surrounding high entropy alloys (HEAs) is fueled by their observed resistance to microstructural damage under irradiation. HEA compositions of interest were compiled and downselected by comparing their mechanical properties to current structural nuclear materials. An AlCuCrFeNi HEA has reported nanoscale L12 precipitate growth with thermal aging, resulting in a 70% increase in yield strength and an elastic limit an order of magnitude greater than code-certified materials. The presence of nano-precipitates also increases defect-absorbing sinks which, while employed in conventional alloys to increase irradiation resistance, have not been thoroughly explored in HEAs. To better understand the influence of these nano-precipitates, this work presents heavy-ion irradiation results in aged AlCuCrFeNi HEAs. Transmission electron microscopy and nano-indentation techniques were used to characterize the irradiation-induced changes in microstructure and mechanical properties.
2:45 PM Cancelled
Effect of Local Chemical Order on the Irradiation-induced Defect Evolution in Multi-principal Element Alloys: Jun Ding1; Zhen Zhang1; Chenyang Lu1; Robert Ritchie2; Evan Ma1; 1Xi'an Jiaotong University; 2University of California Berkeley
Multi-principal element alloys (MPEAs) have emerged as potentially suitable structural materials for nuclear applications, particularly as they appear to show promising irradiation resistance. However, the influence of local chemical order (LCO) on the irradiation response of MPEAs has remained uncertain thus far. In this work, we combine ion irradiation experiments with large-scale atomistic simulations to reveal that the presence of LCO, slows down the formation and evolution of point defects in MPEAs during irradiation. In particular, the irradiation-induced vacancies and interstitials exhibit a smaller difference in their mobility, arising from a stronger effect of LCO in localizing interstitial diffusion. This effect promotes their recombination as the LCO serves to tune the migration energy barriers of these point defects, thereby delaying the initiation of damage. These findings imply that local chemical ordering may provide a new variable in the design space to enhance the resistance of MPEAs to irradiation damage.
3:05 PM Cancelled
Characterization and Comparison of Radiation Damage in HfMoNbTaTi and HfMoNbTaZr Refractory High Entropy Alloys by Multi-energy Helium Ion Irradiation: Pin-Haung Chiu1; Jenq-Horng Liang1; Der-Sheng Chao1; Che-Wei Tsai1; Jien-Wei Yeh1; Peng-Wei Chu1; 1National Tsing-Hua University
Refractory HEAs (RHEAs), which consist of high melting point metallic elements, demonstrate exceptional mechanical properties even in extremely high-temperature conditions. However, it remains unclear whether these superior mechanical properties are still true in high-radiation environments. To address this issue, two RHEAs, HfMoNbTaTi and HfMoNbTaZr, were selected and multiple energy helium ion irradiation was adopted to introduce radiation damage within the alloy in this study. The mechanical properties and microstructures of RHEAs samples were examed by several characterization methods, such as nanoindentation and GIXRD method, etc. The results showed that the hardness of both compositions decreases after He+ irradiation. The lattice parameter of HfMoNbTaTi remains almost unchanged, while that of HfMoNbTaZr slightly declines by a ratio of 0.74%. It can be expected that this study would be useful to evaluate the feasibility of RHEAs utilized in high-radiation environments and gain insights into the effects of alloy elemental components on radiation resistance.