Journal Article

Investigation of Primary and Secondary Creep Deformation Mechanism of TiAl

Soo W . Nam, H . S . Cho, Sun Keun Hwang, Nack J . Kim

2000

Overview

Creep deformation behaviors in lamellar TiAl alloys have been investigated. As in the case with metals, the normal primary creep stage was observed. As creep strain increased within the primary regime, dislocation density decreased, and creep activation energy increased from 300kJ/mol, the activation energy of the self-diffusion of Ti in TiAl, to about 380kJ/mol, that of steady state creep deformation. During primary creep deformation of lamellar TiAl, as the initial dislocation density decreased, the α2 -phase was found to transform to a γ-phase, generating new dislocations which contributed to the creep deformation. In other words, this phase transformation is the source of the dislocation generation for continuous creep deformation. Therefore, we suggest that phase transformation is the rate controlling processes having an activation energy of about 400kJ/mol, which is higher than that of self-diffusion. A small amount of prestrain was found to be responsible for the reduction of initial dislocation density. In addition, this prestrained specimen showed significantly reduced primary creep strain, and the creep activation energy in the primary stage was measured to be about 380kJ/mol. These results clearly confirm the suggested creep deformation mechanism of lamellar TiAl alloys.

• Publisher: 대한금속재료학회
• Subject: creep / lamellar / phase transformation / TiAl