Investigation of the Peculiar Stress Flow Behavior of a Novel TiAl Alloy under High Strain Rate Conditions

초록

In this study, we investigated the peculiar flow behavior during the isothermal deformation of a novel TiAl composition at 1200 degrees C and 1300 degrees C under high strain rate conditions using Gleeble (R) Thermal-Mechanical Simulators. The initial yield-point phenomenon, resembling strain hardening at both temperatures, is attributed to the remnant lamellar microstructure. Secondary hardening at 1200 degrees C is caused by dislocation accumulation at the grain boundaries of the alpha phase, without the formation of dynamically recrystallized gamma lamellar grains. In-grain misorientation axes analysis revealed a shift in the dominant deformation slip mode of the alpha phase from the prismatic slip system to a combined prismatic and basal slip system. The disappearance of gamma lamellar laths after the first strain hardening and during secondary hardening is likely initiated by a deformation-induced gamma ->alpha phase transition within the gamma phase matrix by the extended dislocation with intrinsic stacking faults and occurred simultaneously in the whole gamma lamellae.

키워드