Microstructure evolution in a
large-grained TiAl alloy
large-grained TiAl alloy
(School of Materials Science and Engineering, Key Laboratory of
Ministry of Education for High Temperature Materials and Tests,
Shanghai Jiaotong University, Shanghai 200030, China)
Ministry of Education for High Temperature Materials and Tests,
Shanghai Jiaotong University, Shanghai 200030, China)
Abstract: Microstructure evolution during superplastic deformation of a large-grained TiAl alloys with near-γ microstructure was characterized by orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). In OIM, significant grain refinement is observed at different strain levels with an increase in the density of low angle grain boundaries and high angle grain boundaries. A direct evidence of dynamic formation of grain boundaries with misorientation of 15 °～30° during deformation is found, which is a result of subboundary evolution. The formation of subboundaries by intersecting dislocations, and the evidence of dislocation glide in the interior of grains are revealed by TEM observations. A continuous recovery and recrystallization process similar to that in FeAl and Fe3Al is proposed as superplastic deformation mechanism in the large-grained TiAl alloy.
Key words: TiAl alloy; superplasticity; microstructure evolution; large-grained; EBSP