Effects of tensile temperatures on phase transformations in zirconium by molecular dynamics simulations

The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed (HCP) zirconium were investigated by molecular dynamics simulations, which were combined with experimental observation under high resolution transmission electron microscopy. The results show that externally applied loading first induced the HCP to body-centered cubic (BCC) phase transition in the Pitsch-Schrader (PS) orientation relationship (OR). Then, the face-centered cubic (FCC) structure transformed from the BCC phase in the Bain path. However, the HCP-to-BCC transition was incomplete at 100 K and 300 K, resulting in a prismatic-type OR between the FCC and original HCP phase. Additionally, at the temperature ranging from 100 K to 600 K, the inverse BCC-to-HCP transition occurred locally following other variants of the PS OR, resulting in a basal-type relation between the newly generated HCP and FCC phases. A higher tensile temperature promoted the amount of FCC phase transforming into the BCC phase when the strain exceeded 45%. Besides, the crystal stretched at lower temperatures exhibits relatively higher strength but by the compromise of plasticity. This study reveals the deformation mechanisms in HCP-Zr at different temperatures, which may provide a better understanding of the deformation mechanism of zirconium alloys under different application environments.