Understanding the atomistic deformation mechanisms of polycrystalline gamma-TiAl under nanoindentation: Effect of lamellar structure

摘要

Molecular dynamics (MD) simulations have been performed to study the deformation behavior of polycrystalline gamma-TiAl under nanoindentation. Effect of three different lamellar structure patterns is investigated respectively. Simulation results reveal that the lamellar samples are soft due to a dislocation-nucleation-controlled softening mechanism. Dislocations propagate along lamellar interface and experience no obstacle. Moreover, not only grain boundary (GB) but also lamellar interfaces can act as sliding interfaces, the additional sliding interface can also assist softening of lamellar samples. In addition, the different evolution processes of the three gamma/gamma interface variants are also investigated. Lamellar coarsening can be observed in the true-twin (TT) sample due to the direct migration and annihilation of TT interfaces. While the pseudo-twin (PT) and rotational-boundary (RB) interfaces cannot migrate directly but transform to each other at the origin interface planes, thus the origin lamellar spacing remains. (C) 2020 Elsevier B.V. All rights reserved.