Due to its excellent thermal-mechanical properties,F/M steels are considered as the candidate structural materials for Gen-Ⅳreactors and fusion reactors.Thermal and irradiation would result in the formation of Cr enrichedα′phase in ferritic steels.The Cr precipitates can impede the mobile of dislocation,causing material hardening and embrittlement.Knowing the Due to its excellent thermal-mechanical properties, F / M steels are considered as the candidate structural materials for Gen-IV reactors and fusion reactors. Thermal and irradiation would result in the formation of Cr enriched alpha’phase in ferritic steels. The Cr precipitates can impede the mobile of dislocation, causing material hardening and embrittlement .Knowing the