Cyclic transformation between nanocrystalline and amorphous phases in Zr based intermetallic alloys during ARB

By applying a simple room temperature accumulative roll bonding (ARB) process, the multilayered Zr/Ni and Zr/Ti elemental foils can be mixed and transformed into nanocrystalline and eventually amorphous bulk materials. The latest stage of the transformation from the nanocrystalline elemental phase measuring ∼2 nm to the amorphous alloying phase via gradual atomic mixing is examined, using high resolution transmission electron microscopy, Fourier transformation, and molecular dynamics simulation. Closer examination is focused on the following evolution during the subsequent ARB cycles after amorphization. Transformation from the amorphous phase back to the nanocrystalline elemental phase occurs during the next 3 ARB cycles. Upon further ARB cycles, the nanocrystalline Ni phase is again transformed into the complete amorphous state, exhibiting the cyclic transformation behavior between the nanocrystalline and amorphous phases.