Atomic-scale understanding of stress-induced phase transformation in cold-rolled Hf

Identifying the character and the source of partial dislocations associated phase transformation from a hexagonal close-packed (HCP) structure to a face-centered cubic (FCC) structure is essential for understanding phase transformation mechanisms, but was rarely done using microscopy. Here, we report a stress-induced HCP to FCC phase transformation in pure hafnium during cold rolling. Detailed transmission electron microscopy investigations revealed that transformation-related partials stemmed from the dissociation of -type dislocations. Successive gliding of partials on every other basal plane resulted in the orientation relationship between the two phases of <1120>(hcp)//<110 >(fcc), <1010>(hcp)// <112 >(fcc), and [0001](hcp)//<111 >(fcc).Besides, a new way to form a twin relationship in the FCC structure was discovered. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.