NSUF 20-4200: Morphological Response of Spherical and Platelet MX-Type Precipitates to In-Situ Ion Irradiation in Novel Fe-Based Alloys
Nanoscale precipitation is an important microstructural feature that acts to trap point defects and to pin grain boundaries at high temperatures, thus providing necessary sink and creep strength. This feature has been shown to be tailorable through composition and processing optimization using Additive Manufacturing (AM). Novel alloys fabricated via AM and simulated AM heat treatment have been developed in order to create a high density of nanoscale MX precipitates. The two processing techniques were successful in increasing the number density of precipitates in two alloys of interest, ANA2 (from AM) and AM2 (from simulated AM heat treatment), both of which have the number densities of nanoscale MX-type precipitates comparable to oxide dispersion-strengthened steels. The objective of this work is to determine the stability of MX-type precipitates under dual-beam irradiation in the novel ANA2 and AM2 alloys as a function of irradiation temperature and dose. Our previous work demonstrated different precipitate morphologies from different processing techniques; platelet precipitates in ANA2 and spherical precipitates in AM2. Of particular interest is the stability of different precipitates under irradiation and their effective sink strength to radiation induced defects. This proposal will evaluate the evolution of the platelet precipitates in the ANA2 alloy and spherical precipitates in the AM2 alloy using in-situ ion irradiation. This includes the investigation of size, density, shape, and coherency of the precipitates as directly observed using the TEM during in-situ dual ion irradiation. In addition, the defect population from the irradiation will be quantified to qualitatively compare the effective sink strength from different precipitates, acknowledging that other microstructure features could affect the defect population, although the microstructure are similar for ANA2 and AM2. It is expected that the spherical and platelet precipitates will behave differently due to their different interfacial strain energies. The precipitates’ radiation responses will be investigated in-situ using the FEI Tecnai TF30 S/TEM at the Michigan Ion Beam Laboratory (MIBL) at University of Michigan. The in-situ irradiations would be completed up to 5 dpa at two temperatures (300°C and 500°C). The irradiation temperatures are expected to operate in two competing precipitate stability regimes: ballistic dissolution and back diffusion, allowing for the role of these mechanisms to be investigated. All experiments will use a Kr3+ beam to induce radiation damage, with co-injection of He++ to better simulate the damage mechanisms expected to occur in the candidate alloys under typical fast reactor conditions, or with co-injection of H in order to examine and compare the entrapping behavior at the different precipitate-matrix interfaces in the two alloys, which may provide an indication of chemical binding differences This proposed work allows us to direct compare the stability of MX precipitate with different morphology as a function of irradiation temperature and dose and provide fundamental information on the morphology effect on the precipitate stability. More importantly, the outcome of this proposal enables one to design alloys with optimal precipitate morphology.
Additional Info
| Field | Value |
|---|---|
| Abstract | Nanoscale precipitation is an important microstructural feature that acts to trap point defects and to pin grain boundaries at high temperatures, thus providing necessary sink and creep strength. This feature has been shown to be tailorable through composition and processing optimization using Additive Manufacturing (AM). Novel alloys fabricated via AM and simulated AM heat treatment have been developed in order to create a high density of nanoscale MX precipitates. The two processing techniques were successful in increasing the number density of precipitates in two alloys of interest, ANA2 (from AM) and AM2 (from simulated AM heat treatment), both of which have the number densities of nanoscale MX-type precipitates comparable to oxide dispersion-strengthened steels. The objective of this work is to determine the stability of MX-type precipitates under dual-beam irradiation in the novel ANA2 and AM2 alloys as a function of irradiation temperature and dose. Our previous work demonstrated different precipitate morphologies from different processing techniques; platelet precipitates in ANA2 and spherical precipitates in AM2. Of particular interest is the stability of different precipitates under irradiation and their effective sink strength to radiation induced defects. This proposal will evaluate the evolution of the platelet precipitates in the ANA2 alloy and spherical precipitates in the AM2 alloy using in-situ ion irradiation. This includes the investigation of size, density, shape, and coherency of the precipitates as directly observed using the TEM during in-situ dual ion irradiation. In addition, the defect population from the irradiation will be quantified to qualitatively compare the effective sink strength from different precipitates, acknowledging that other microstructure features could affect the defect population, although the microstructure are similar for ANA2 and AM2. It is expected that the spherical and platelet precipitates will behave differently due to their different interfacial strain energies. The precipitates’ radiation responses will be investigated in-situ using the FEI Tecnai TF30 S/TEM at the Michigan Ion Beam Laboratory (MIBL) at University of Michigan. The in-situ irradiations would be completed up to 5 dpa at two temperatures (300°C and 500°C). The irradiation temperatures are expected to operate in two competing precipitate stability regimes: ballistic dissolution and back diffusion, allowing for the role of these mechanisms to be investigated. All experiments will use a Kr3+ beam to induce radiation damage, with co-injection of He++ to better simulate the damage mechanisms expected to occur in the candidate alloys under typical fast reactor conditions, or with co-injection of H in order to examine and compare the entrapping behavior at the different precipitate-matrix interfaces in the two alloys, which may provide an indication of chemical binding differences This proposed work allows us to direct compare the stability of MX precipitate with different morphology as a function of irradiation temperature and dose and provide fundamental information on the morphology effect on the precipitate stability. More importantly, the outcome of this proposal enables one to design alloys with optimal precipitate morphology. |
| Award Announced Date | 2020-07-14T14:15:10.547 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Kevin Field |
| Irradiation Facility | None |
| PI | Lizhen Tan |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4200 |