Abstract:To study deformation banding in β working of TA15 titanium alloy, hot simulation compression experiments were carried out on a Gleeble 3500 thermal simulator, and the microstructure was investigated by optical microscopy (OM) and electron back- scattered diffraction (EBSD). It is found that in β working of TA15 titanium alloy, deformation banding is still an important grain refinement mechanism up to temperature as high as 0.7Tm (Tm is the melting temperature). Boundaries of deformation bands (DBBs) may be sharp or diffusive. Sharp DBBs retard discontinuous dynamic recrystallization (DDRX) by prohibiting nucleation, while the diffusive ones are sources of continuous dynamic recrystallization (CDRX). Deformation banding is more significant at high strain rate and large initial grain size. The average width of grain subdivisions is sensitive to strain rate but less affected by temperature and initial grain size. Multi-directional forging which produces crossing DDBs is potential to refine microstructure of small-size forgings.

Key words: TA15 titanium alloy; β working; deformation banding; grain refinement; dynamic recrystallization