Unraveling hot deformation behavior and microstructure evolution of nanolamellar TiAl/Ti3Al composites

Abstract

An in-depth understanding of the deformation behavior of a nanolamellar TiAl/Ti3Al composite is prerequisite to control the mechanical properties of this material. Nevertheless, to obtain the excellent performance, the role of microstructure evolution on the deformation mechanism maps at a wide temperature range is still required. To this end, the effect of temperature on the compressive response and deformation mechanism of a nanolamellar TiAl/Ti3Al composite is investigated using molecular dynamics simulations. The deformation-induced α2→γ phase transformation results in the softening, and the deformation twinning causes the strain hardening. The high temperature reduces the local shear strain along the interface, to enhance the deformation capacity of the γ phase. At a low strain, the dislocation slip on the single slip system is the dominant deformation mode; at a medium strain, the phase transformation controls the plastic deformation; at a high strain, the deformation twinning associated with the activation of the multi-slip systems is responsible for the late plastic stage. The phase interface bents towards the γ phase, and then the α2 phase grows up, resulting in the evolution of the dynamic complex microstructures. The origin of the nanoscale plasticity event depends upon the atomic-scale deformation gradient field and the atomic-scale microrotation field. The current temperature-dependent deformation mechanism maps provide an insight into the design and fabrication of the advanced nanolamellar TiAl/Ti3Al composites with outstanding strength and ductility.