Composition and growth rate effects in directionally solidified TiAl alloys

Study of microstructure and solute partitioning in a cast Ti-48Al-2Cr-2Nb alloy by quenching during directional solidification technique

“…Nevertheless, in the present work, QDS experiments gave evidence that in the Ti-48Al-2Cr-2Nb alloy the ␣-hcp phase is the primary phase during directional solidification at a growth rate of 72 mm/h and with an average thermal gradient of 4°C/mm. Therefore, at this growth rate value, which is similar to the growth rate used by Kim et al [8] (V ϭ 90 mm/h), our results indicate that conclusions obtained from ternary alloys cannot be trivially extended to quaternary alloys. The ␤-stabilizer effects might not be superposed when considering coupled influences of Cr and Nb.…”

“…[7] However, intensive work has been carried out in the field of polysynthetically twinned (PST) crystal production and, more recently, directional solidification using a seeding technique, in order to achieve a better control of the lamellar microstructure and thus partly improve the roomtemperature tensile properties and high-temperature creep strength of TiAl-based alloys. [8][9][10][11] The latter works [8][9][10][11] showed that the selection of ␤ or ␣ primary phase during directional solidification of binary and ternary TiAl alloys depends strongly on the Al content in the case of binary alloys, on the ␤-stabilizing element content (i.e., Mo, Nb, or Cr) in the case of ternary additions, and on the growth and solidification rate.…”

Microstructure evolution of Ti-47Al-2Cr-2Nb alloy in the liquid-metal-cooling (LMC) directional-solidification process

“…If the two variants have the same orientations, they will turn into oneα grain; or the two variants will intersect at the β dendritic trunk, leaving grain boundaries of the two α grains behind. Further [15,16] 110 / / 0001 , 111 / / 1120 β α α β cooling, the new γ-phase lamella starts to grow from α grain boundaries, following the Burgers relationship:…”

“…Research on polysynthetically twinned (PST) crystals of TiAl-based alloys showed that a good combination of strength and ductility can be achieved when the lamellar plates aligned parallel to the loading axis [5,6] . Therefore, lamellar orientation control through seeding technique [6][7][8][9][10][11][12] or modifying the composition and processing conditions [13][14][15][16] during directional solidification (DS) process has been a promising method to enhance the performance of TiAl-based alloys recently.…”

Dependency of microstructure and microhardness on withdrawal rate of Ti-43Al-2Cr-2Nb alloy prepared by electromagnetic cold crucible directional solidification

“…Generally, directional solidification experiments were performed in ceramic mould materials, such as Al 2 O 3 , Y 2 O 3 or CaO [10][11][12] . To the best of our knowledge, no refractory materials completely resistant to molten titanium alloy have been developed so far.…”