| As the most important candidate materials for IV reactor and fusion reactor, austenite stainless steel has been investigated in the work. In this work, the micro-defects introduced by quenched and ions implanted in the Fe17Cr12Ni model alloys. The addition of Mo element was used to research the irradiation effect in the Fe17Crl2Ni.The effect of isochronal annealing on vacancy-type defects has been investigated by positron annihilation techniques, in quenched Fe17Cr12Ni alloys and SUS316, vacancy-type defects gather and grow with the annealing temperature increasing from room temperature to 523 K. And the vacancy-type defects annihilated gradually at the annealing temperature increasing in the Fe17Cr12Ni alloys. This results show that the addition of Mo and nonmetal elements is not the key reasons that determined the annihilated temperature of vacancy micro-defects. It’s worth noting that the vacancy-type defects annihilated and dislocation-type defects formed in all sample alloys after 673 K annealing treatment. In addition, the density of defects in Mo diluted Fe17Cr12Ni model alloy is lower than that in Fe17Cr12Ni model alloy due to the Mo-vacancy complexes formed in Mo diluted Fe17Cr12Ni model alloy. The long lifetime of vacancy-type defects in commercial stainless steel 316 is smaller than that in Fe17Cr12Ni model alloys because the mobility of vacancy-type defects changed by nonmetal elements. In addition, vacancy-type and dislocation defects detected contribute to the S and W parameters of positron annihilation in the whole annealing treatment.The micro-structural features and the effect of Mo addition during incubation period in Fe17Cr12Ni austenitic alloy have been investigated using positron annihilation technique and Vickers Hardness. The electron irradiation (8 MeV) was performed at room temperature up to the dose of 1.7×10-4 dpa and 5×10-4 dpa, respectively. The electron irradiation was performed at room temperature. An amount of vacancy micro-defects generated after electron irradiation. The defect concentration was estimated 10-5-10-7 during electron irradiation. The added Mo could prevent the generation of micro-defects, while no precipitates or solute clusters formed in Mo-diluted alloy. The micro-structural evolution during electron irradiation resulted in hardening and Mo addition might prevent the radiation hardening process.In order to study the evolution that the irradiation-induced defects under different irradiation fluencies, the austenite model steel Fe17Cr12Ni was irradiated by 2.0 MeV Fe-ion at room temperature. The irradiation fluence was 2.09×1013 ions/cm2, 1.62×1014 ions/cm2,4.85×1014 ions/cm2 and 1.46×1015 ions/cm2. After irradiation, the irradiation-induced defects have been investigated by variable-energy positron beam Doppler broadening spectroscopy. The S parameter of irradiated evidently higher than un-irradiation sample owing to energetic Fe-ions produced a large number of defects in the Fe17Cr12Ni model steel. S parameter decreases with dose level increasing after Fe ions irradiation in Fe17Cr12Ni model alloy. The enhanced recombination between vacancies and interstitial atoms especially for the excess Fe atoms from deeper layers, and high diffusion rate of self-interstitial atoms further improved by diffusion via grain boundary and dislocations at room temperature, are thought to be the main reasons for the reversed trend of vacancy-type defects between the samples irradiated at RT. Besides, much Cr-cluster formed in the Fe17Cr12Ni model steel result in the S parameters decrease. S-W plots suggest that more than one type of defect (open-volume defect) is present in irradiated alloys. Notably, a number of vacancy-type defects migrated and annihilated in the grain boundary and dislocation-type defects. All these arguments can account for the decline of the S parameters in irradiation samples with the irradiation level increasing. |
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