TRANSFORMATION TEXTURES IN TI-15V-3CR-3SN-3AL ALLOY SHEETS

Cold rolling and recrystallization textures of the metastable beta-phase (bcc) and transformation textures of the alpha-phase (hcp) precipitated during aging from the beta-matrices having these textures in a Ti-15V-3Cr-3Sn-3Al alloy were investigated in conjunction with their microstructures. Furthermore, the measured transformation textures were compared with the alpha-phase textures predicted theoretically from the parent beta-phase textures using the crystallite orientation distribution function to discuss the mechanism of texture formation caused by the beta to alpha-transformation. In the sheets cold rolled after solution treatment, a <110>//RD partial fiber texture showing the maximum intensity at {001}<110> was developed at high reductions. The recrystallization textures obtained by annealing from this rolling texture consisted mainly of the {554}<225> orientation. Aging at 773 K after recrystallization resulted in the formation of somewhat coarse plate-like alpha-precipitates at grain boundaries rather than inside grains. In this case, the quantitative agreement between the measured and predicted transformation textures were found except for the basal orientation, indicating that all variants obeying Burgers' orientation relationship appeared with nearly the same probability. On the other hand, fine needle-like alpha-precipitates were observed in materials aged at 773 K directly from the cold rolled state. The texture of the precipitated alpha-phase was composed nearly of orientations derived from the beta-phase rolling texture through Burgers' relationship. However, the results of quantitative texture analysis suggested that the variants which formed the (1210BAR)[1010]BAR orientation from the main orientation {001}<110> in the rolling texture were preferentially selected in the precipitation from the deformed matrix. This variant selection can be explained by taking active slip systems operating during cold rolling into account.