Molecular dynamics simulation of fracture behaviors of á110？ tilt grain boundaries in γ-TiAl
(1. Key Laboratory of Materials Design and Preparation Technology of Hunan Province,
Xiangtan University, Xiangtan 411105, China;
2. School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China;
3. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;
4. School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522, Australia)
Xiangtan University, Xiangtan 411105, China;
2. School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China;
3. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;
4. School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522, Australia)
Abstract: Molecular dynamics (MD) simulations were carried out to study the fracture behaviors of several symmetric tilt grain boundaries in γ-TiAl bicrystals with á110？ misorientation axes. Tensile deformation along direction perpendicular to grain boundary was simulated under various strain rates and temperatures. The results indicate that the relative orientation of the grains and the presence of certain atom units are two critical factors of the interface structure affecting the stress required for dislocation nucleation. Dislocations nucleate and extend at or near the symmetric tilt grain boundaries during the tensile deformation of Σ3 (111) 109.5°, Σ9 (221) 141.1° and Σ27 (552) 148.4° interfaces. For Σ27 (115) 31.6° and Σ11 (113) 50.5° interfaces, the interfaces fractured directly in a cleavage manner due to no dislocation emitted from the boundary. The tensile fracture mechanisms of the bicrystals are that micro-cracks nucleate at the grain boundary and propagate along the interface. The variance of crack propagation is whether there is accommodation of plastic region at the crack tips.
Key words: gamma TiAl alloy; tilt grain boundary; molecular dynamics; tensile deformation; fracture