NSUF 23-1847: High-Resolution Characterization of Neutron-Irradiated Cr-Fe-Mn-Ni-(Al,Ti) High-Entropy Alloys
Many advanced reactor concepts demand pushing in-core materials to higher temperatures and higher irradiation doses that current code-qualified materials are rated for, which has motivated researchers to pursue more out-of-the-box alloy designs to bring such reactor concepts to fruition. High-entropy alloys (HEAs) have garnered interest as potential material candidates for next-generation reactor claddings, following numerous modeling efforts and ion irradiation studies which have demonstrated that HEAs are often more resistant to the effects of irradiation damage than their less compositionally complex counterparts. However, while these results from ion irradiation experiments and modeling are promising, as of this writing, there have been no experimental studies published which examine HEAs that have been irradiated by neutrons at reactor-relevant doses and temperatures. Recently, test capsules containing HEA samples, among other alloys, have been irradiated with neutrons in the Advanced Test Reactor (ATR) to doses >6 displacements per atom (dpa) at temperatures ranging from ~400-600 °C. The proposed work is to perform high-resolution microstructural characterization on these neutron-irradiated HEAs, specifically, Cr10Fe30Mn30Ni30 and Al4Cr9Fe28Mn28Ni28Ti2 irradiated at two different temperatures, 395 °C and 579 °C. Of interest is the presence of voids and chemical redistribution resulting from neutron irradiation at elevated temperatures and whether pre-existing precipitates from minor alloying additions of aluminum (Al) and titanium (Ti), which may serve as sufficient defect sinks to mitigate extended defect formation (e.g., voids, network dislocations), are altered during neutron irradiation. The irradiated samples, which are in the form of 3-mm transmission electron microscopy (TEM) disks, will be characterized at the Irradiated Materials Characterization Laboratory (IMCL) at the Idaho National Laboratory (INL) using the Titan scanning transmission electron microscope (S/TEM), with TEM lamellae produced using a focused-ion beam (FIB), to image the irradiated microsctructures, identify any radiation-induced changes in the pre-existing precipitates, radiation-induced segregation, voids, and to quantify dislocation loop densities and size distributions. In addition to the TEM lamellae, atom probe tomography (APT) needles will also be produced using the FIB and examined using the LEAP 5000, both at IMCL, to measure chemical redistribution within the matrix and the precipitates and to identify any chemical clustering or short-range ordering within the matrix. If awarded, all work will be performed within nine months of the award date. The proposed study represents the first opportunity to observe the irradiation response of multiple HEAs irradiated with neutrons at temperatures and doses relevant to advanced reactor designs, including sodium-cooled reactors (SFRs), lead-cooled fast reactors (LFRs), and molten-salt reactors (MSRs). In addition to aligning well with several DOE-NE programs, this work will provide insight into the radiation damage mechanisms which are predominant in HEAs and how significantly radiation damage evolution is impacted by the presence of pre-existing precipitates intentionally added to the microstructure.
Additional Info
| Field | Value |
|---|---|
| Abstract | Many advanced reactor concepts demand pushing in-core materials to higher temperatures and higher irradiation doses that current code-qualified materials are rated for, which has motivated researchers to pursue more out-of-the-box alloy designs to bring such reactor concepts to fruition. High-entropy alloys (HEAs) have garnered interest as potential material candidates for next-generation reactor claddings, following numerous modeling efforts and ion irradiation studies which have demonstrated that HEAs are often more resistant to the effects of irradiation damage than their less compositionally complex counterparts. However, while these results from ion irradiation experiments and modeling are promising, as of this writing, there have been no experimental studies published which examine HEAs that have been irradiated by neutrons at reactor-relevant doses and temperatures. Recently, test capsules containing HEA samples, among other alloys, have been irradiated with neutrons in the Advanced Test Reactor (ATR) to doses >6 displacements per atom (dpa) at temperatures ranging from ~400-600 °C. The proposed work is to perform high-resolution microstructural characterization on these neutron-irradiated HEAs, specifically, Cr10Fe30Mn30Ni30 and Al4Cr9Fe28Mn28Ni28Ti2 irradiated at two different temperatures, 395 °C and 579 °C. Of interest is the presence of voids and chemical redistribution resulting from neutron irradiation at elevated temperatures and whether pre-existing precipitates from minor alloying additions of aluminum (Al) and titanium (Ti), which may serve as sufficient defect sinks to mitigate extended defect formation (e.g., voids, network dislocations), are altered during neutron irradiation. The irradiated samples, which are in the form of 3-mm transmission electron microscopy (TEM) disks, will be characterized at the Irradiated Materials Characterization Laboratory (IMCL) at the Idaho National Laboratory (INL) using the Titan scanning transmission electron microscope (S/TEM), with TEM lamellae produced using a focused-ion beam (FIB), to image the irradiated microsctructures, identify any radiation-induced changes in the pre-existing precipitates, radiation-induced segregation, voids, and to quantify dislocation loop densities and size distributions. In addition to the TEM lamellae, atom probe tomography (APT) needles will also be produced using the FIB and examined using the LEAP 5000, both at IMCL, to measure chemical redistribution within the matrix and the precipitates and to identify any chemical clustering or short-range ordering within the matrix. If awarded, all work will be performed within nine months of the award date. The proposed study represents the first opportunity to observe the irradiation response of multiple HEAs irradiated with neutrons at temperatures and doses relevant to advanced reactor designs, including sodium-cooled reactors (SFRs), lead-cooled fast reactors (LFRs), and molten-salt reactors (MSRs). In addition to aligning well with several DOE-NE programs, this work will provide insight into the radiation damage mechanisms which are predominant in HEAs and how significantly radiation damage evolution is impacted by the presence of pre-existing precipitates intentionally added to the microstructure. |
| Award Announced Date | 2023-02-08T10:50:41.777 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Alina Zackrone |
| Irradiation Facility | None |
| PI | Michael Moorehead |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4521 |