An assessment of uncommon titanium binary systems: Ti-Zn, Ti-Cu, and Ti-Sb.

摘要

The current study focuses on phase stability and evolution in the titanium-zinc titanium-copper and titanium-antimony systems. The study utilized the Laser Engineering Net Shaping(LENS(TM)) processing technique to deposit compositionally graded samples of three binary system in order to allow the assessment of phase stability and evolution as a function of composition and temperature the material is subjected to. Through LENS(TM) processing it was possible to create graded samples from Ti-xSb (up to 13wt%) and Ti-xCu (up to 16wt%). The LENS(TM) deposited gradient were solutionized, and step quenched to specific aging temperature, and the resulting microstructures and phase were characterized utilizing XRD, EDS,SEM, FIB and TEM. The Ti-Zn system proved incapable of being LENS(TM) deposited due to the low vaporization temperature of Zn; however, a novel processing approach was developed to drip liquid Zn onto Ti powder at temperatures above beta transus temperature of Ti(882 °C) and below the vaporization temperature of Zn (907 °C). The product of this processing technique was characterized in a similar way as the graded LENS(TM) depositions. From measurements performed on Ti-Sb it seems that Sb could be a potential ƒ¿ stabilizer in Ti due to the presence of a mostly homogeneous ƒ¿ grains throughout the gradient; however, from XRD it can be understood that a titanium antimonide phase is present. From results obtained from the Ti-Zn samples, it can be surmised that the eutectoid reaction seems to be active, i.e. The eutectoid reaction is kinetically fast, as concluded by the presence of pearlitic structures. Finally, for the Ti-Cu system this work has been attempted to prove or disprove the existence of the Ti3Cu through the use of XRD and TEM SAD patterns. From XRD spectra collected there are peaks belonging to the Ti3Cu orthorhombic phase along with Ti2Cu and a-Ti phase. In addition to the Ti-Cu system displayed structures associated with divorced eutectoid decomposition mechanism, and at low undercooling seems to be prone to forming solid state dendrites.