Detection of new co phase morphologies in β-III Ti using transmission electron microscopy
The to phase transformation in titanium and other alloys has been extensively studied1. This phase has an hep structure with three atoms per cell located at (000), (1/3, 2/3, 1/2) and (2/3, 1/3, 1/2). ‘Isothermal’ ω phase precipitates are oriented in the bec β matrix such that [lll]β ‖ [0001]ω and [110]β ‖ω. In fact four varients of such an ω phase exist oriented in all four [111] directions. Isothermal ω phase has been studied as a displacement controlled growth as distinct from another type of ω phase (as quenched) which is produced by a dif fusionless transformation resulting from a very rapid cooling rate.Using transmission electron microscopy (TEM) and small angle neutron scattering (SANS) we have detected and identified two previously unreported morphologies in β-III Ti (Ti-11.0 Mo-6.0 Zr-4.5 Sn-0.15 O2). Fig. 1 shows a TEM micrograph of a conventional ‘isothermal’ ω precipitate (obtained by annealing β-III Ti 20 hours at 400°C) imaged in bright field with its diffraction pattern showing hep spots as well as the brighter spots of the bec matrix. The long axis of the precipitates is oriented along a [111] direction.