Surface damage of a TiAl-based alloy during high temperature annealing

On the role of thermal exposure on the stress controlled fatigue behaviour of an intermediate strength γ-TiAl based alloy

“…7c were accumulated to form a white layer at surface. They might form Mn-, Nb-containing oxides or even precipitated to form small sized α 2 and B2 (with ω) phases [34]. Between this bright layer and the loose dark layer is a narrow grey layer, which could be a transition region between the Al-Ti-O rich loose layer and Mn-Nb rich white layer.…”

Influence of alloying elements on the kinetics of massive transformation in gamma titanium aluminides

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] It was also suggested by Jones and Kaufman [27] that massive transformation does not take place in the binary Ti-45Al alloy and is favored when the overall alloy composition is close to the equilibrium composition of the gamma phase. pct Al, with and without the presence of alloying elements.…”

Oxidation kinetics of the pack siliconized TiAl-based alloy and microstructure evolution of the coating

“…Beneath the Ti 5 Si 3 layer, a Ti-rich [27] or an Al-rich zone [28,29] will be formed according to the siliconizing medium and siliconizing temperature. Prasad et al [30] showed that the surface of TiAl alloy would be damaged with the formation of an Aldepleted layer with thickness ranging from several microns to about 100 mm due to the loss of aluminum by evaporation during heating in argon at approximately 160 Torr and 180 Torr at 1000 C and 1200 C. Thus if the Al atoms evaporate much faster than the input of Si atoms, a Ti-rich zone will be formed. This is the case we studied previously [27], where siliconizing medium of Si powder with addition of Mo and NH 4 Cl was used and siliconization was performed in vacuum at 1250 C. On the other hand, if the Si atoms input is faster, then a Ti 5 Si 3 layer will be formed and thicken quickly which will prohibit the further evaporation of Al.…”