Deformation mechanisms and microtensile behavior of single colony Ti–6242Si

The constant strain rate deformation behavior of individual α–β colonies of the titanium aeroengine alloy Ti–6Al–2Sn–4Zr–2Mo–0.1Si (compositions in wt.%) has been investigated through microsample tensile testing techniques. The mechanical behavior and deformation mechanisms observed were found to depend strongly on colony orientation. A near-Burgerʹs orientation relationship (OR) has been observed for the α (hcp) and β (bcc) phases in these colonies, grown utilizing a vertical float zone technique. The Burgerʹs OR is believed to be responsible for the observed anisotropy in the critical resolved shear stress for the three a/3〈11-20〉{10-10} prism slip systems. A more pronounced anisotropy was observed in the critical resolved shear stress (CRSS) for the three a/3〈11-20〉{0001} hcp basal slip systems. Scanning Electron Microscopy (SEM) investigations of the slip line morphology of the deformed samples indicates an inhibition of β-lath shearing for colonies oriented for basal slip, while frequent shear offsets of the β phase by slip lines were observed in the samples oriented for prism slip. The effects of the Burgerʹs OR, slip line spacing and elastic interactions stresses arising from the α–β interface are considered in explaining the observed anisotropy in CRSS.