Detection of phase separation of neutron-irradiated Fe–Cr binary alloys using positron annihilation spectroscopy

• Published in: Nuclear materials and energy Vol. 15; pp. 175 - 179
• Main Authors: Noshita, Y., Sato, K., Yamashita, H., Kasada, R., Xu, Q., Hatakeyama, M., Sunada, S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-05-2018; Elsevier
• Subjects: Fe–Cr binary alloys; Hardness; Neutron irradiation; Phase separation; Positron annihilation; Fe–Cr binary alloys; Neutron irradiation; Positron annihilation; Hardness; Phase separation
• ISSN: 2352-1791; 2352-1791
• DOI: 10.1016/j.nme.2018.04.007

•Using positron annihilation coincidence Doppler broadening measurements, phase separation progress was observed in neutron-irradiated Fe–Cr binary alloys.•Vacancy clusters were detected in Fe–xCr (x = 0, 9, 15, 30, 45, 50, and 100) after 473 K irradiation by positron annihilation lifetime measurements.•In Fe–xCr (x = 70, 85, and 91) irradiated at 473 K, vacancy clusters were not detected in Fe-rich phases.•Hardness increased due to irradiation-enhanced phase separation and irradiation-induced defects.
Phase separation in Fe–Cr binary alloys irradiated with neutrons at 473 K and 573 K was investigated using positron annihilation spectroscopy. Using positron annihilation coincidence Doppler broadening (CDB) measurements, the phase separation progress was observed in neutron-irradiated samples at 473 K and 573 K. Vacancy clusters were detected in Fe–xCr (x = 0, 9, 15, 30, 45, 50, and 100) during 473 K irradiation using positron annihilation lifetime measurements, but were not detected in Fe–xCr (x = 70, 85, and 91) irradiated at 473 K or in any samples irradiated at 573 K. Additionally, in Fe–xCr (x = 70, 85, and 91) irradiated at 473 K, all positrons were annihilated with core Fe electrons as determined from CDB ratio curves. Thus, vacancy clusters were not detected in the Fe-rich phase. There was a possibility that vacancy clusters are formed in the Cr-rich phase, but they were not detected by the PAS. Therefore, another method is necessary to investigate this further. Vickers hardness tests indicated that neutron-irradiated samples were harder than unirradiated samples. The contribution of phase separation and neutron-irradiation defects to increased hardness was dependent on the irradiation conditions including temperature and dose.