In-Situ Proton Irradiation Creep of FM Steel T91.

[摘要] The objective of this study was to determine the irradiation creep mechanism of FM steel T91 using low dose proton irradiations. An irradiation creep apparatus was developed for in-situ straining of steel samples under high stress and high temperatures. Proton irradiation provided the unique capability to precisely monitor the temperature, dose rate, and stress states of a single irradiated sample. Post irradiation analysis on proton irradiation creep samples allowed for comparisons of microstructure between irradiation conditions without the effects of different reactor history or heat to heat variation. T91 creep behavior under proton irradiations were analyzed by their parametric dependencies. The temperature dependence was found to be negligible between 400oC – 500oC, and the dose rate dependence was found to be linear. The large exponent power law stress dependence of the proton irradiation creep experiments under high stress suggested dislocation glide. Transmission electron microscopy (TEM) analysis were conducted to determine the nature of the loops and to quantify the edge-on dislocation loop density as a function of their orientation to the tensile axis. Loops were determined to be interstitial in nature of the type ao<100>. The distribution of ao<100> loops was found to be strongly anisotropic in which loops preferentially formed with their normal in the tensile direction. An empirical correlation was developed to describe the relationship between the orientation of the loop normal to the tensile axis and the local dislocation loop density. Loop anisotropy was found to contribute between 4-11% of the total creep strain. Results from this study provide a means for quantifying empirically measured anisotropic microstructure and including it in irradiation creep mechanisms for FM steels.Anisotropic dislocation loops contribution to the total creep strain was calculated and subtracted from the total measured strain. After subtracting the power law creep and anisotropic dislocation loop contributions, irradiation creep strain measurements fit well with strain rate predictions from preferential absorption glide (PAG) and stress induced preferential absorption (SIPA). Irradiation creep of low dose proton irradiation creep of FM alloys was determined to be most consistent with the combination of PAG and SIPA operating within an anisotropic dislocation microstructure.

[发布机构] University of Michigan

[效力级别] Nuclear Engineering and Radiological Sciences

[关键词] Proton Irradiation Creep;Nuclear Engineering and Radiological Sciences;Engineering;Nuclear Engineering and Radiological Sciences