Reconstruction and quantitative characterization of the three dimensional microstructure model of TC6 titanium alloy based on dual-energy X-ray microtomography

In the present study, dual-energy micro-computed tomography (Micro-CT) imaging was employed to overcome the difficulty of low absorption contrast due to the low difference in density among the primary α phase, secondary α phase, and β phase of the annealed microstructure (annealing at 800 °C for 2 h followed by air cooling) of TC6 titanium alloy. The three dimensional microstructure model of TC6 titanium alloy was first achieved by laboratory X-ray microtomography, and then analyzed quantitatively. It is found that the volume fractions of the primary α phase, secondary α phase and β phase are 28.32%, 47.78% and 23.90%, respectively. Some complex microstructural features of TC6 titanium alloy such as spatial distribution, shapes, and interconnectivities that can hardly be described by the conventional two dimensional microscopy technique were successfully captured. In three dimensional space, the primary α phase is composed of discrete equiaxed grains and interconnected grains, and the fraction of the individual equiaxed grains is up to 50% and the average diameter is about 10 µm; the secondary α phase interconnects with β phase forming a completely interconnected network.