β-type (with bcc structure) titanium alloys have been widely used as artificial implants in the medical field due to their favorable properties. Among them, Ti-Mo alloy attracted numerous interests as metallic biomaterials. Understanding of kinetic characteristics of Ti alloys is critical to understand and manipulate the phase transformation and microstructure evolution during homogenization and precipitation. In this work, diffusion couple technique was employed to investigate the diffusion behaviors in bcc Ti-Mo-Zr alloys. The diffusion couples were prepared and annealed at 1373 K for 72 h and 1473 K for 48 h, respectively. The composition-distance profiles were obtained via electron probe micro-analysis (EPMA). The chemical diffusion coefficients and impurity diffusion coefficients were extracted via the Whittle-Green method and Hall method. The obtained diffusion coefficients were assessed to develop a self-consistent atomic mobility database of bcc phase in Ti-Mo-Zr system. The calculated diffusion coefficients were compared with the experimental results. They showed good agreement. Simulations were implemented by Dictra Module in Thermo-Calc software. The predicted composition-distance profiles, inter-diffusion flux, and diffusion paths are consistent with experimental data, confirming the accuracy of the database.

Selective laser melting (SLM) is an advanced additive manufacturing technique that can produce complex and accurate metal samples. Since the process performs local high heat input during a very short interaction time, the physical parameters in the solidification are difficult to measure experimentally. In this work, the microstructure evolution of Ti-6Al-4V alloy in additive manufacturing was studied. With the increase of scanning speed, the cooling rate and the temperature gradient of molten pool position increased, which was attributed to the gradual decrease of energy density. The phase-field simulation resulted in the overall microstructure morphology of columnar crystals owing to the very large temperature gradient and cooling rate obtained from the temperature field. Microsegregation was observed during dendritic formation, and the solute was enriched in the liquid phase near the dendritic tip and between the dendritic arms due to the lower equilibrium distribution coefficient. The scanning speed had an effect on the dendrite spacing.

The microstructure and mechanical properties of a newly developed Fe-microalloyed Ti–6Al–4V titanium alloy were investigated after different heat treatments. The volume fraction and the morphological features of the lamellar α phase had significant effects on the alloy’s mechanical performance. A dataset showing the relationship between microstructural features and tensile strength, elongation, and fracture toughness was developed. A high aging temperature resulted in high plasticity and fracture toughness, but relatively low strength. The high strength favored the fine α and the slender β. The high aspect ratio of lamellar α led to high strength but low fracture toughness. The alloy with ~84 vol % α exhibited the highest strength and lowest fracture toughness because the area of its α/β-phase interface was the highest. Optimal comprehensive mechanical performance and heat-treatment procedures were thus obtained from the dataset. Optimal tensile strength, yield strength, elongation, and fracture toughness were 999 and 919 MPa, 10.4%, and 94.4 MPa·m^1/2, respectively.

The interdiffusion behavior of BCC alloys of Ti-Sn binary and Ti-Al-Sn ternary was investigated at 1473 K (1200 °C) by the diffusion-couple technique. The extracted interdiffusion coefficients of Ti-Sn binary was found to gradually increase with increasing the Sn content, whereas those of Ti-Al-Sn ternary, either main or cross, greatly enhance as the content of diffusing species increases. By a way of comparison, Sn diffusion in Ti-Al-Sn ternary was discerned to occur by the vacancy mechanism.