The deformation of 2-phase samples was investigated at 450 to 750K. The observed deformation behaviours included discontinuous yielding and a negative strain-rate sensitivity; indicating the operation of a Portevin¯LeChatelier effect. The pinning processes which occurred at the dislocations were studied by performing static strain-aging experiments. Wide ranges of alloy compositions and microstructures were investigated in order to identify the relevant defect species. Dislocation pinning was characterized by a relatively small activation energy (0.7eV); inconsistent with a conventional diffusion process. Strain-aging phenomena were most marked in Ti-rich alloys; thus suggesting that antisite defects were involved in the pinning process.

Strain Aging in γ(TiAl)-Based Titanium Aluminides due to Antisite Atoms. U.Fröbel, F.Appel: Acta Materialia, 2002, 50[14], 3693-707