Homogenization of Ingot Metallurgy Near-Gamma Titanium Aluminides

Abstract

The elimination of microsegregation and subsequent breakdown of the lamellar structure in near-gamma titanium aluminides was investigated through a series of high temperature homogenization heat treatments and isothermal hot compression tests. The homogenization heat treatment studies revealed that microsegregation could be eliminated after approximately five hours or one and one-half hours at temperatures either 15 C or 40 C, respectively, above the transus in the single phase alpha field. Subsequent attempts to breakdown the coarse prior alpha grain, lamellar structure were successful at low strain rates (∼ 10−3 s−1) and temperatures low in the alpha + gamma phase field, but led to wedge cracking and gross fracture at high strain rates (∼ 1 s−1) high in the alpha + gamma phase field. Subsequent annealing treatments to globularize the hot-worked structure in order to obtain a uniform, fine, and stable grain structure were also identified.

Mechanical performance of extruded Ti–46Al–5Nb–1W titanium aluminide

“…This alloy composition has been evaluated previously following production from either a cast 6 or a forging route. 7 Therefore, the work here provides a further commercial production route that can be compared with this composition. In addition, the mechanical performance of the extruded Ti-46Al-5Nb-1W (at-%) (Ti-46-5-1) alloy has been compared with other competing c-TiAl compositions and the opportunity has also been taken to re-evaluate these materials in comparison with other materials systems (e.g.…”

Workability and microstructure evolution of Ti–47Al–2Cr–1Nb alloy during isothermal deformation

“…These reports on hot workability have focused on ingot metallurgy (I/M) processing and typically have emphasized on material starting condition [19][20][21][22][23][24]. The purpose of this paper was to study the whole process of a single alloy composition by isothermal forging, that is, the processing window and stress-strain curves were set up, and grain refining method as well as refining mechanism were discussed.…”

Local variations of the chemistry in as‐cast γ‐TiAl (TiBx) alloys and its consequence for thermomechanical treatments

“…Additionally, technical alloys can also contain several alloying elements as well as titanium borides. However, depending on ingot size, composition and cooling rate a highly inhomogeneous microstructure can form during solidification (Semiatin et al, 1991). TiAl alloys solidify mainly under the formation of primary aor b-Ti dendrites with interdendritic g-TiAl regions (Laakman et al, 1996).…”