length Texture evolution and temperature-dependent deformation modes in ambient- and cryogenic-rolled nanolayered Zr-2.5Nb

Interface-dominate properties can be strengthened when the interface spacing is further reduced to nanoscale dimensions. To analyze the dominant deformation modes in alpha-Zr sandwiched by alpha/beta interfaces, a nanolayered Zr-2.5Nb alloy was rolled to various reductions at room temperature (RT) and near-liquid-nitrogen temperature (LNT). The alpha/beta lamellar structures are refined significantly when rolling reduction exceeds 25% at both RT and LNT rolling. We show that the alloy is remarkably formable at both RT and LNT, as indicated by homogeneous deformation with no shear banding detected. Based on a combination of microstructural analysis, texture measurements and multi-scale polycrystal model simulations, two types of tensile {1 (1) over bar 02} <<(1)over bar>101> and {(1) over bar1 (1) over bar 21} <11<(2)over bar>6> twins were found to form at LNT rolling and expand until they reoriented all alpha-Zr lamellae in the same colony to the twin orientation. In addition, the high density of alpha/beta interfaces substantially enhances the activity of pyramidal < c+a > dislocations in alpha-Zr during both RT and LNT rolling, eventually tilting the < c > axis of alpha-Zr nearly parallel to the normal direction of the as-rolled sample. The higher fraction slip activity of < c+a > dislocations and deformation twins accommodate deformation along < c > direction in alpha-Zr, increasing the formability of this ultra-strong nanolayered Zr-2.5Nb alloy. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.