Twin hopping in nanolayered Zr-2.5Nb

Twinning in coarse-grained Zr is ubiquitous but not in nanostructured Zr due to the strong nano- confinement. Here we show that hexagonal close-packed (hcp) twins can proliferate in a nanolayered Zr-Nb as a result of the introduction of ductile body centered cubic (bcc) nanolayers. Both common {102} twins and less common {21} twins are found to propagate across the nanolayers by a novel twin hopping mechanism from one hcp layer to another. The fine ductile bcc nanolayers act as buffers that lower the back stress at the hcp/bcc interface far below that which usually constrains twinning. [GRAPHICS] . Impact statement We report a twin hopping mechanism by which hcp twins are facilitated by the introduction of ductile bcc nanolayers that lessen the back stress and enable the twin to bypass.