Some New Aspects in Developing TiAl Based Alloys as Competitive High Temperature Materials
In order to make the TiAl Intermetallics-based materials more competitive with conventional superalloys, further work on microstructure modification and alloying process has been carried out specific to the cast and wrought process, respectively. It is proved that directional lamellar microstructures can be formed in the cast TiAl. Those microstructures have demonstrated preponderant mechanical properties under unidirectional load after the cast porosity being removed by HIP at proper temperatures. This microstructure design specific to the rotating parts has benefited the endurance capacity of cast TiAl turbochargers. On the other hand, the additions of Gd have shown significant effect in refining the lamellar microstructures of forged TiAl alloys but do not bring out the detrimental influence to the tensile ductility. The reason is that the Gd-containing precipitates can greatly impede the growth of grains while themselves dispersing during the thermal process. Upon those technology advances, the further success of TiAl alloys’ applications is prospected.
J. Zhang et al., "Some New Aspects in Developing TiAl Based Alloys as Competitive High Temperature Materials", Advanced Materials Research, Vol. 278, pp. 557-562, 2011