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Abstract
The deformation behaviour of an α + β Ti–6Al–4V (wt.%) alloy was investigated during in situ deformation inside a scanning electron microscopy (SEM). Tensile experiments were performed at 296 and 728 K (~0.4Tm), while a tensile-creep experiment was performed at 728 K and 310 MPa (σ/σys = 0.74). The active deformation systems were identified using electron backscattered diffraction-based slip-trace analysis and SEM images of the specimen surface. The distribution of the active deformation systems varied as a function of temperature. Basal slip deformation played a major role in the tensile deformation behaviour, and the relative activity of basal slip increased with increasing temperature. For the 296 K tension deformation, basal slip was less active than prismatic slip, whereas this was reversed at 728 K. Twinning was observed in both the 296 and 728 K tension experiments; however, no more than 4% of the total deformation systems observed was twins. The tension-creep experiment revealed no slip traces, however grain boundary ledge formation was observed, suggesting that grain boundary sliding was an active deformation mechanism. The results of this work were compared with those from previous studies on commercially pure Ti, Ti–5Al–2.5Sn (wt.%) and Ti–8Al–1Mo–1V (wt.%), and the effects of alloying on the deformation behaviour are discussed. The relative amount of basal slip activity increased with increasing Al content.
Acknowledgements
The authors are grateful to Professor Darren Mason of Albion College for his assistance in the development of the CRSS ratio methodology. The authors are grateful to Dr. Christopher Cowen, previously at National Energy Technology Laboratory, Albany, Oregon and currently at United States Mint, West Point, NY, who provided the alloy used in this study.