Irradiation-induced loss of coherency of precipitates can serve as a ‘diagnostic monitor’ providing an indicator of point-defect (PD) cluster migration behavior due to the interaction between mobile PDs and coherent precipitates may induce precipitate coherency loss [1-3]. The precipitate coherency will be judged from the “no contrast line” appears in normal direction to the g vectors under dynamical diffraction condition . Our previous ex situ TEM observations have shown that ion irradiations with 1MeV Ni ions at 25 and 350°C with doses of 1 to 10dpa result in the coherency loss for lower sink strengths (5.9×1013m-2) of matrix precipitates. The extent of the loss of coherency regimes are closer to the calculated 1-D migration mean free path ("λ" ~ (6𝛑2r4N2)-1/2)  of 2286nm for the initial precipitate size (r) and density (N), indicating that most of the radiation-produced clusters exhibit 1-D motion.
However, precipitate coherency loss was not observed below 1dpa at 25 or 350°C, neither for the higher sink strength (>3×1014m-2). Thus, an innovative study is proposed by using in situ ion irradiation experiments to explore the threshold concentration of absorbed self-interstitial atoms to induce coherency loss as a function of precipitate size or sink strength.
TEM foils of fcc-structured model binary alloys (Cu-1at.%Co, Cu-1at.%Fe and Cu-0.4at.%Cr) with similar sink strengths will be irradiated at 25 and 350°C with 1MeV Kr ions to midrange doses of 1-10dpa (corresponding fluences: 6E14-6E15 ions/cm2). TEM samples will be prepared through jet-polish technique to produce an electron-transparent region. Based on SRIM calculation results, the midrange dose region will start from 60nm from the surface, and the free surface effects will be avoided minimized in this condition. Considering the precipitate number density in each of the binary alloys, tens of precipitates should be visible in the irradiated thin foil at the same time through certain two beam conditions. This project will need 10 days of IVEM facility access. Three days for irradiation temperature at 25°C and 6 days at 350°C. These two different temperatures will be used to investigate the effect of immobile vacancy clusters as matrix sink in the irradiated regions. We are expecting to see the coherency loss of the precipitates at high temperatures above specific threshold dose conditions whereas precipitates may remain coherent up to high doses at room temperature. The extra one day will be used to conduct cryo irradiation at 30K where interstitial and vacancy are immobile after the cascade, then anneal the sample with increasing temperature to find out the recovery stage III temperature for dilute binary alloy system. The corresponding dislocation loops coming out from the precipitate/matrix interface should also be observed as the result of misfit relaxation of the initially coherent interface.
The result will be a guidance in improving coherent oxide particles in oxide dispersion strengthened ferritic steels [6,7] or super high strength austenitic stainless steels with fcc precipitates  by exploring the stability behavior of coherent precipitates in model fcc-base binary alloys and the different responses to the in situ ion irradiation experiments compared to ex situ ion irradiation experiments.
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 P. Dou, A. Kimura, R. Kasada, T. Okuda, M. Inoue, S. Ukai, S. Ohnuki, T. Fujisawa, F. Abe, S. Jiang, Z. Yang, TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition. Journal of Nuclear Materials, 485 (2017) 189-201.
 T. Chen, J.G. Gigax, L. Price, D. Chen, S. Ukai, E. Aydogan, S.A. Maloy, F.A. Garner, L. Shao, Temperature dependent dispersoid stability in ion-irradiated ferritic-martensitic dual-phase oxide-dispersion-strengthened alloy: Coherent interfaces vs. incoherent interfaces, Acta Materialia 116 (2016) 29-42.
 P. Ou, L. Li, et. al., Steady-state creep behavior of super304H Austenitic steel at elevated temperatures. Acta Metallergy, 28 (2015), 1336-1343.