Atomic scale observation of FCC phase formed symmetrically in { $$10\overline{1 }2$$ } < $$\overline{1 }011$$ > twin in Zircaloy-4 subjected to cyclic deformation

Abstract

The formation mechanism of FCC phase on prismatic-basal (PB) interfaces in {\(10\overline{1 }2\)} < \(\overline{1 }011\)> twin in Zircaloy-4 under cyclic deformation at the strain level of 1.0% was systematically investigated by using transmission electron microscopy. Results showed that {\(10\overline{1 }2\)} < \(\overline{1 }011\)> twin was presented in α-Zr grain and PB interfaces can be introduced into the twin boundaries. Under cyclic stresses, the emission of 1/3[\(0\overline{1 }10\)] and 1/3 \([01\overline{1 }0]\) Shockley partial dislocations would be initiated on the PB interfaces of the twin and slipped symmetrically on every other (\(0001\)) planes of the twin, resulting in the HCP → FCC phase transformation. Moreover, when the shear stresses were large enough, 1/6 < \(\overline{1 }\overline{1 }2\)> Shockley partial dislocations were activated during cyclic deformation and the formation of {\(111\)} SFs in FCC phase was presented.