Atomic scale observation of FCC phase formed symmetrically in {101¯2} < 1¯011> twin in Zircaloy-4 subjected to cyclic deformation.

The formation mechanism of FCC phase on prismatic-basal (PB) interfaces in { 10 1 ¯ 2 } < 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 1 ¯ 2 } < 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 1 ¯ 10 ] and 1/3 [ 01 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 < 1 ¯ 1 ¯ 2 > Shockley partial dislocations were activated during cyclic deformation and the formation of { 111 } SFs in FCC phase was presented. [ABSTRACT FROM AUTHOR]