Effects of Si and C additions on the thermal stability of directionally solidified TiAl–Nb alloys

Directional solidification of Ti-45Al-8Nb-(W,B,Y) alloy

“…PST crystal growth with high Nb containing TiAl alloy is different from that with other TiAl-based alloys reported by Johnson [11], Lee [12], Kim [13], and so on. Most of them achieved preferred lamellar orientation by controlling the primary solidification α-(Ti) phase or by means of a seeding technique.…”

Stability of lamellar microstructures in a Ti–48Al–2Nb–2Cr alloy during heat treatment and its application to lamellae alignment as a quasi-seed

“…By comparing the characteristics of the general seed (such as Tie43Ale3Si seed) and the quasi-seed, a significant difference is that the lamellae within the former will be retained well after general heat treatments [18], whereas the lamellae within the latter will maintain unchanged only if the heating rate is higher than 61 C/min. And one fact is confirmed that the quasi-seed can be used to align the lamellar microstructure as long as the lamellae orientation is retained well upon rapid heating.…”

Effects of β-Dendrite Growth Velocity on β → α Transformation of Hypoperitectic Ti–46Al–7Nb Alloy

“…where DT t is the thermal undercooling; DT c is the solutal undercooling; DT r is the curvature undercooling; DT k is the kinetic undercooling; C is the Gibbs-Thomson coefficient; P t = VR/2a 1 is the thermal Peclet number; a 1 is the thermal diffusivity in liquid; P c = VR/2D is the solute Peclet number; I v (P c ) = P c exp(P c )E I (P c ) is the Ivantsov function of solute Peclet number; m 0 is the actual liquidus slope under non-equilibrium conditions; m is the slope of the liquidus line; k is the actual solute partition coefficient; k 0 is the equilibrium solute partition coefficient; l is the actual kinetic coefficient; R is the radius at the dendrite tip; r is the interface energy; DS is the entropy of fusion; r* = 1/(4p) 2 , r* is a stability constant; DH f is the heat of fusion; C p is the specific heat of the undercooled melt, V 0 is the velocity of sound in the liquid, and R g is the gas constant; T L is the liquidus temperature of the alloy; n c is the solute stability function; n t is the thermal stability function; D is the atomic diffusive coefficient; a 0 is the atomic distance; C 0 is the alloy composition. According to Kim et al [26], 1 at% of Nb addition to Ti-Al binary alloy is known to shift the phase boundaries to the Al-rich side by 0.3%. The alloy composition of Ti-46Al-7Nb approximately corresponds to the binary Ti-48Al alloy.…”