Phase transition in yttrium under shock compression by atomistic simulations

BB Liu and YC Chen and L Guo and XF Li and K Wang and HQ Deng and Z Tian and WY Hu and SF Xiao and DW Yuan, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 250, 108330 (2023).

DOI: 10.1016/j.ijmecsci.2023.108330

The insightful understanding of phase transition in rare earth elements under shock compression is significant to the future development of materials science. In this work, a new reliable Finnis-Sinclair interatomic potential for hexagonal close-packed (HCP) single crystal yttrium (Y) is developed and validated. The potential reproduces the phase transition sequence of HCP-+ Sm-type (samarium-type)-+ DHCP (double hexagonal-close-packed)-+ FCC (face-centered-cubic) of Y observed in high-pressure experiments. Further, large-scale NEMD simulations are conducted to study shock compression behaviors of Y. For the 10-10HCP shock direction, the HCP-+ Sm-type phase transition occurs via an intermediate metastable BCC structure, which is accomplished by atomic shuffles and shear. Then, a pure-shear along the 10-10Sm-type direction transforms the Sm-type to DHCP structure. Besides, we find FCC phase can be generated by shifting the atoms at two layers in opposite < 10-10 > directions on 0001 planes in the DHCP lattice. Combined with the transition state theory, we confirm these transition pathways follow the minimum energy path. For shock along the 0001HCP and - 12-10HCP directions, the HCP-+ FCC phase transition is mediated by the amorphization which subsequently annihilates and turns to recrystallize to be FCC lattice. The results suggest that the uniaxial compression strain along the 0001HCP and - 12-10HCP directions hinders the formation of Sm-type and DHCP phases. Our findings provide essential insights into the phase transition behavior of Y under shock loading.

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