||Heat Treatment of Gamma Titanium Aluminides
||Maegaard, Morten Lyck
||Horsewell, Andy (Materials Science and Engineering, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Mortensen, Andreas (Laboratory of Mechanical Metallurgy, Swiss Federal Institute of Technology in Lausanne)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||Since the early 1950s, research on the high temperature capabilities of intermetallics has steadily increased. Among todays most promising intermetallic compounds are
the titanium aluminides, primarily consisting of titanium and aluminum, with other minor alloying additions.
These materials exhibit a unique combination of low density and good high temperature mechanical properties, making them potentially applicable as structural materials for high performance, elevated temperature applications. Partly replacing superalloys in jet engines and other gas turbines, is seen as one of the important future applications.
As the alloys based on the particular gamma titanium aluminum (-TiAl) com-pound, have shown the most promising features, they are subject to much current research. The most severe of the limiting factors for future application of these in-termetallics, have been their low room temperature ductility. Thus, attempts have been and are made, to overcome this obstacle, within all parts of the alloy production chain.
The heat treatment represents a crucial part of the alloy production chain. It is therefore very important to understand the correlation between heat treatments,
microstructures and the properties induced by various microstructures. After a review of the current state of
-TiAl research and development, this study examines two
-TiAl alloys, referred to as the XD alloy and the IMPRESS alloy. Their compositions in at.% are given below.
XD alloy Ti-45Al-2Mn-2Nb-0.8vol.% TiB2 IMPRESS alloy Ti-45Al-8Nb + X
Whereas research on the XD alloy type has been conducted for the last two decades, the IMPRESS alloy type represents a rather new trend in the -TiAl alloy research, that is, relatively high niobium content and minor additions of other
Three di¤erent heat treatments are performed on each of the alloys and their resulting microstructures are examined using optical and scanning electron microscopy.
Hardness measurements are made on the XD alloy as a way of relating microstructures to a mechanical property.
Creation date: 2007-07-26
Update date: 2011-09-27