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

The constant strain rate deformation behavior of individual alpha-beta 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-Burger's orientation relationship (OR) has been observed for the alpha (hcp) and beta (bcc) phases in these colonies. grown utilizing a vertical float zone technique. The Burger's OR is believed to be responsible for the observed anisotropy in the critical resolved shear stress for the three alpha/3<11-20>{10-10} prism slip systems. A more pronounced anisotropy was observed in the critical resolved shear stress (CRSS) for the three alpha/3<11-20>1{0001} hcp basal slip systems. Scanning Electron Microscopy (SEM) investigations of the slip line morphology of the deformed samples indicates an inhibition of beta-lath shearing for colonies oriented for basal slip, while frequent shear offsets of the beta phase by slip lines were observed in the samples oriented for prism slip. The effects of the Burger's OR, slip line spacing and elastic interactions stresses arising from the alpha-beta interface are considered in explaining the observed anisotropy in CRSS. (C) 2001 Elsevier Science B.V. All rights reserved.