Molecular dynamics simulations of nano-indentation in lamellar γ-γ' microstructures of TiAl
Master Thesis, Ruhr-Universität Bochum (2016)
Different misorientations of γ phase in TiAl- at γ-γ interfaces are investigated by rotat- ing the reference γ phase by 60° around [1 1 1]. Three possible orientations, Pseudo-twin (PT), Rotational-boundary (RB) and True-Twin (TT) where created in adjacent to the reference γ phase. After preparing bi-crystals and 4-lamellae models and applying nano- indentation on them, it is observed that in bi-crystals, the PT interface model presents a sudden drop in hardness during loading and the TT has more stable potential en- ergy behavior than the two others. The formation of superlattice intrinsic stacking faults(SISFs) and anti-phase boundaries(APBs) as dominant origins of events for defect nucleation and growth in the models under loading is discussed. Moreover, when the thickness of lamellae are reduced by 50% while the number of interfaces is increased, an increase in hardness is observed in all the models. Finally, it is concluded that RB and PT models have lower stability in comparison to TT model due to the higher level of their potential. In addition, by increasing in the number of interfaces, the hardness deviation values between bi-crystal and 4-lamellae models for PT and RB models are higher than TT models.