Alloy and process development of TiAl

The development of cast TiAl-based components for the automotive industry and the possibility of wrought components for applications in gas turbines are clear indications that these alloys are maturing as materials for engineering components. There are however problems in the cost of manufacture and in the properties of these alloys. In this paper it is argued that recent developments, which have resulted in a totally new microstructure, taken together with improved casting technology, open the way for wider application of these alloys. The new microstructure has been obtained by tempering massively transformed TiAl alloys so that a highly convoluted fine scale microstructure is obtained by simply heat treating cast samples. This fine microstructure can thus be obtained in cast components, without the need to add boron and problems associated with the extreme plastic anisotropy of fully lamellar samples are also eliminated.