Recovery of hardness and resistivity during annealing of 16MeV proton irradiated 12Cr-1MoV Steel

Abstract

The 12Cr-1 MoV steel which is candidate material for fusion reactor``s first wall had been irradiated in cyclotron to a proton of 16MeV energy and $-10^18$ p/㎠ fluence at a temperature of about 200℃. After irradiation, the recovery of hardness and resistivity during annealing were observed. The hardness profile along specimen depth indicates that the damaged region was significantly broaden since radiation-induced point defects were thermally diffused along damage gradient. Maximum increase of hardness (35 DPH) and resistivity (4μΩcm) were observed at second-layered specimens. The recovery of resistivity was more rapidly occurred than hardness recovery. Isochronal annealing indicates that two stages of recovery were observed, i.e., 200 ~ 280℃ and 305 ~ 380℃. Based on the Meechan-Brinkman method of analysis, the recovery activation energy were found to be 1.4 eV and 1.52 eV for first and second recovery process, respectively. The recovery activation energy in the present work is very similar to the sum of carbon-vacancy binding energy and vacancy migration energy. Therefore, it seems that most of vacancies created by proton irradiation were attached by carbon or hydrogen atoms. When thermal annealing is begun, it is inferred that dissociation of carbon-vacancy complexes then migration of vacancy to sink occurred at the first recovery process and dissociation of carbon or hydrogen decorated vacancy cluster then vacancy migration was occurred at the second recovery process. The order of reaction by Meechan-Brinkman method were determined as 1.345 and 1.32 for the first and the second recovery stage, respectively. These values are nearly first order reaction. The order of reaction near to first order reaction and rapid recovery of resistivity well confirmed the above mentioned recovery mechanism.