Pseudoelasticity in twinned alpha-Fe nanowires under bending

Y Yang and SZ Li and XD Ding and J Sun, COMPUTATIONAL MATERIALS SCIENCE, 188, 110128 (2021).

DOI: 10.1016/j.commatsci.2020.110128

The pre-existing twin boundaries play an important role in the mechanical behaviors of metals. In the present work, we studied the bending deformation of 100-oriented alpha-Fe nanowires seeded with (111)/112 twin boundaries using atomistic simulations. Bending behaviors along two different orientations were investigated. The initially flat twin boundaries become curved with a high density of 1/6 (111)/112 partial dislocations under bending when the neutral plane intersects with twin plane along 0 (1) over bar1 direction, whereas could transform to the nonconventional 110 interfaces under bending when the neutral plane intersects with twin plane along 111 direction. The bent alpha-Fe nanowires could recover to the original state upon unloading, leading to a unique pseudoelasticity. The driving force for shape recovery primarily arises from the high interfacial energy, i.e. curved 112 twin boundaries or the transformed 110 interfaces. We further characterized the recoverability by the ratio eta of the nanowire size (external length scale) to twin boundary spacing (internal length scale). This eta-dependent recoverability matches well with the experimental data at large length scale. The present work may help understand the unique mechanical properties associated with twin boundaries in metals.

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