Figure 3
In situ cooling rates, calculated for data collected at 500 Hz frame rate and 1 ms acquisition time per frame. (a) Time evolution of scale factors of the α-Ti (blue circles) and β-Ti (orange diamonds) crystalline phases for laser power of 225 W and speed 144 mm/s. The drop in the α-Ti peak intensity coincides with the laser indicated by the dashed black line. Also, shown in the figure is the time period (τβ) for which the phase fraction is mainly β-Ti. The solid lines are guides for the eye. (b) Lattice parameters of the α-Ti a- and c-parameters (blue diamonds and orange squares respectively) and β-Ti phase (green circles) as a function of time for same process parameters as (a). The c-lattice parameter of the α-Ti phase is divided by the approximate c/a ratio of 1.6 for the pristine material. The change in the lattice parameters of the β-Ti phase over τβ is indicated as Δaβ. The lattice parameters for the α-Ti phase are not shown during τβ because of the large uncertainties in this time range. (c) Cooling rates for a range of laser powers calculated from rate of lattice relaxation (blue circles), and β-Ti lifetime, τβ, (orange diamonds).
