Abstract
A cross-correlative precession electron diffraction – atom probe tomography investigation of Cr segregation in a Fe(Cr) nanocrystalline alloy was undertaken. Solute segregation was found to be dependent on grain boundary type. The results of which were compared to a hybrid Molecular Dynamics and Monte Carlo simulation that predicted the segregation for special character, low angle, and high angle grain boundaries, as well as the angle of inclination of the grain boundary. It was found that the highest segregation concentration was for the high angle grain boundaries and is explained in terms of clustering driven by the onset of phase separation. For special character boundaries, the highest Gibbsain interfacial excess was predicted at the incoherent ∑3 followed by ∑9 and ∑11 boundaries with negligible segregation to the twin and ∑5 boundaries. In addition, the low angle grain boundaries predicted negligible segregation. All of these trends matched well with the experiment. This solute-boundary segregation dependency for the special character grain boundaries is explained in terms of excess volume and the energetic distribution of the solute in the boundary.
Highlights
Though similar restrictions can exist in precession electron diffraction (PED) scans, recent work by Kiss et al.[25,26,27] has shown how the inclination angle can be estimated by a weight average from the overlapping transmission diffraction patterns across the boundary
The estimated inclination angle of the grain boundary using the PED was done following the procedure by Kiss et al.[25] with details specific to this work given in the supplementary material section
From the boundary map [Fig. 3(c)], we identified twenty-three grain boundaries with either LAGBs (2 GBs), high-angle grain boundary (HAGB) (9 GBs), or one of the five special character boundary types – ∑3(twin) (2 GBs), ∑3 (4 GBs), ∑5 (2 GBs), ∑9 (2 GBs), and ∑11 (2 GBs)
Summary
Xuyang Zhou[1], Xiao-xiang Yu1, Tyler Kaub[1], Richard L. In this paper we further those efforts by quantifying the solute segregation to specific nanocrystalline grains using precession electron diffraction (PED)[20,21,22] and APT Unlike these prior experimental studies, we have expanded the work to directly compare the findings to computational predictions for specific types of grain boundaries and their segregation. Atom probe results in that work revealed a range of Gibbsian interfacial excess values for the boundaries studied which suggested boundary specific segregation behavior. This was never confirmed and provided motivation for this new work. Others have reported how Cr can desegregate from the boundaries after irradiation[47,48]
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