The investigation of deformation behaviors and mechanisms of carbon reinforced TiAl alloys during the tensile in combination with microstructure characterization and molecular dynamics

The effects of carbon addition on the deformation mechanisms and the evolution of phases and related interfaces of as-cast TiAl alloys have been investigated in combination with microstructure characterization and molecular dynamics (MD) simulation. It has been found that the ordinary dislocations 1/2<110>, partial dislocations 1/6<112>, sessile dislocations 1/6<110> and 1/3<100> within γ phases and the dislocations 1/3<1 1‾ 00> and 1/3<12‾ 10> within α₂ phases were activated in the carbon reinforced TiAl alloys during the tensile loading at room temperature. Except for the dislocations, super dislocations with Burgers vector b = 1/2<112> within γ phases and <2a+c< dislocations with Burgers vector b = 1/3<11 2‾ 6> within α₂ phases have been activated in the carbon reinforced TiAl alloys with the temperature increasing to 900°C. Carbon solid solution triggered off increased dislocation densities and decreased critical tensile strains of dislocation activation, which led to the better coordinated deformation of α₂ and γ phases at various temperatures. Meanwhile, the layered atoms on the (0001) crystal plane of Ti₂AlC transformed to atomic ripplocations which resulted in the fracture during the tensile loading at room temperature, while the atomic vibrations at the layers caused atomic clusters and broken Ti₂AlC crystals at elevated temperatures. Additionally, most of dislocations that were activated in γ phases tended to pile up in γ phases as sessile dislocations and along the interfaces between γ and Ti₂AlC phases rather than slip into Ti₂AlC phases during the tensile loading, which were conducive to the enhanced strengths of carbon reinforced TiAl alloys.