Atomic scale investigation of FCC → HCP reverse phase transformation in face-centered cubic zirconium

Mechanism of FCC -> HCP reverse phase transformation in face-centered cubic zirconium (FCC-Zr) along with a concomitant 70.5 degrees rotation of alpha-Zr matrix were investigated in zircaloy-4 (Zr-4) cladding tube by using transmission electron microscopy (TEM). Results showed that the interaction among a secondary phase particle (SPP) and three FCC-Zr grains resulted in the formation of cross stacking faults in SPP and exerted a drag force on minor axis of the adjacent FCC-Zr phase. Moreover, when the shear stress along [1 1 2](FCC-Zr) direction was large enough to initiate the emission of 1/6 [1 1 2] Shockley partial dislocation on every other ( 111)FCC-Zr close-packed plane, the stacking sequence would change from ABCABCA to ABABABA viz. (0 0 01) planes of the daughter HCP phase. Thus, FCC -> HCP reverse phase transformation in FCC-Zr was presented. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The mechanism of the FCC to HCP reverse phase transformation in FCC-Zr, along with a 70.5 degrees rotation of the alpha-Zr matrix, was investigated using transmission electron microscopy. The findings suggest that the interaction between secondary phase particles and FCC-Zr grains leads to the formation of cross stacking faults, exerting a drag force on the adjacent FCC-Zr phase. Furthermore, under certain shear stress conditions, the stacking sequence changes, resulting in the reverse phase transformation from FCC to HCP in FCC-Zr.