Plastic deformation in Ti-46at.%Al alloy of cellular-lamellar structure

The influence of structure changes in the Ti-46 at.% Al alloy on effects of deformation has been assessed at high temperatures ranging from 1023 K to 1273 K upon compression by 3% at strain rate 25 x 10(-5) s(-1). The initial morphology differed by the fractions of eutectoidal lamellar structure and fragmented, coarsened lamellas of the TiAl phase in the Ti,AI matrix. As a result of structural investigation of the deformed alloy by means of TEM a nd texture analysis it was established that the lowest compression strength of approx. 500 MPa was attained while deforming the alloy which reveals fi ne lamellar structure formed in eutectoidal transformation. The effects of deformation show then the highest contribution of superplastic deformation defined as diffusional creep by crystallographic slip and twinning in the g rain. Such effects can be observed at 1173 K. Above this temperature the co mpression strength increases and the contribution of diffusional creep on t he grain boundaries decreases probably on the expense of growth of the recr ystallisation nuclei.