[SY-E10] Symposium E-10

[SY-E10] Atomic structure of gamma/alpha2 interface and its influence on plastic deformation of lamellar TiAl alloys

^○Hao Wang¹, Aidong Tu¹, Yanxia Liu², Dongsheng Xu¹, Rui Yang¹ (1.Institute of Metal Research, CAS, China, 2.Dept. of Physics, Liaoning University, China)

TiAl alloys with the γ-TiAl/α₂-Ti₃Al lamellar structure exhibit excellent high temperature performance. However, the strong anisotropy of the lamellae leads to the strong dependence of mechanical properties, in particular the fatigue behavior, on lamella orientation, thickness, volume fraction, etc. In the present work, molecular dynamics with the embedded-atom potential is employed to investigate the energy of both the coherent and incoherent γ/α₂ interfaces. The interface coherency is found to depend on the volume ratio of the γ lamellae over the α₂lamellae, resulting in a critical volume ratio, below/above which the interface is coherent/incoherent. Loading perpendicular and parallel to the lamella interface indicates that the yield strength of coherent interface is higher than that of the incoherent interface. Plastic deformation mostly occurs first in the γ region and transmits to the α₂ region via dislocations or twinning across the γ/α₂ interface. Subsequent fracture behavior also depends on the γ/α₂ volume ratio. With the coherency and incoherency interfaces, crack nucleates within the γ region and at the γ/α₂ interface, respectively. The present result thus contribute to the evaluation of the structural stability and the improvement of mechanical performance of TiAl alloys.