Fig. 1 a Experimental equipment and sample preparation in a custom-built HPT device, b assembling scheme of Al (brown) and Zn (blue) foils in a stack and HPT-processing of the disk-shaped specimen, c physical photos of 10 mm diameter Al and Zn discs

Fig.2 a Representative TEM image, as well as SEM image b and the corresponding EDX mapping from the 50 turns HPT-processed Al50Zn50 alloy. In b, the red dots denote the Al while the green one is Zn. The HRTEM images from two regions in one grain are presented in c and e, where the corresponding FFT patterns are displayed in the insets. An XRD profile of HPT-processed Al50Zn50 alloy is shown in d

Fig. 3 Evolution of a potential energy per atom, crystal structure fraction, as well as b the dislocation length and pressure in Z direction with the time, based on MD simulation of polycrystalline Al-Zn alloy

Fig. 4 Comparison of the dislocation distribution in HCP a, d and FCC b, e phases at 20 and 60 ps. The snapshots of atomic configuration at 20 and 60 ps are presented in c and f, respectively

Fig.5 MD simulation results in bicrystal Al-Zn alloy. a Snapshots showing the microstructure evolution at 60, 70, 210 and 2370 ps during shearing. The evolutions of phase fractions b, dislocation density c and dislocation length d

Fig. 6 Snapshots in the bicrystal simulation showing the nucleation and growth processes during the HCP → FCC phase transformation viewed along the direction perpendicular to (0001)HCP at 70 ps a, b, c and 80 ps (d, e, f. g Structural evolution in the polycrystalline simulation from 22 to 30 ps. h A HRTEM image showing the ${(0002)}_{{{\text{HCP}}}} /{{(\overline{1}\overline{1}1)}}_{{{\text{FCC}}}}$ interface between the remaining HCP and the transformed FCC Zn. i A close-up of the region enclosed by the red rectangle in e

Fig. 7 FFT-filtered HRTEM image of HCP/FCC interface perpendicular to the basal plane, viewed from [$2\overline{1 }\overline{1 }0$] // [$01\overline{1 }$]

Fig. 8 Schematic diagram for the glides directions of three Shockley dislocations

Fig. 9 a Schematic illustration of the atomic motion during HCP →FCC phase transformation. Snapshots in the bicrystal simulation at 24 ps (b) and 26 ps (c), viewed from [$2\overline{1 }\overline{1 }0$] // [$01\overline{1 }$]