In-Situ Scanning Electron Microscopy/Electron Backscattered Diffraction Observation of Microstructural Evolution during α → γ Phase Transformation in Deformed Fe-Ni Alloy

This article presents in-situ observation of ferrite (alpha)/austenite (gamma) phase transformation in an Fe-8.5 at. pct Ni alloy deformed by rolling using an automated scanning electron microscopy/energy backscattered diffraction (SEM/EBSD) system. During heating, recrystallization in alpha phase and alpha -> gamma phase transformation independently occurred. The gamma grains nucleated in unrecrystallized alpha grains were most probably incorporated into the grain interior of recrystallized alpha grains. They did not have any specific orientation relation (OR) with recrystallized alpha grains and grew in an isotropic manner. On the other hand, the intragranular gamma grains nucleated in recrystallized alpha grains had a Kurdjumov-Sachs (K-S) OR with the alpha grains and grew in a considerably anisotropic manner. They preferentially grew along the common direction of surface traces of {110} (alpha) /{111} (gamma) . Approximately half of grain boundary (GB) allotriomorphs had either the K-S OR or the Nishiyama-Wasserman (N-W) OR with the parent alpha grains. The gamma allotriomorphs predominantly grew into the alpha grain having the special OR with themselves. The GB character distribution of gamma phase at high temperatures was measured. The fraction of CSL boundaries was as high as 63 pct, particularly that of I 3 pound grain boundaries (GBs) was 54 pct.