"The major requirement on gamma-TiAl feedstock materials for subsequent forging operations (forging stocks) is a fine grained microstructure which decreases the flow stresses at elevated temperatures. Novel gamma-TiAl based TNM alloys have been developed from a consortium consisting of GfE, Böhler, MTU and University of Leoben in order to increase wrought processing capability by the addition of the bcc structured beta-Ti phase into the well known alpha2/gamma microstructure of Titanium Aluminides. As a side effect, the microstructure remains fine grained due to a different solidification path of the alloy which is characterized by a complete beta-solidification mechanism. It has been demonstrated that the as-cast TNM alloy can be subsequent wrought processed without primary ingot conversion via extrusion technology. Thus, the objective of the materials conversion technology is reduced to the generation of small size parts. There is a substantial interest in improved homogeneity, high reproducibility and low overall production costs including ingot manufacturing and ingot conversion.
In the project, different materials production technologies such as VAR and PAM are being evaluated. The conversion of the resulting ingots to small size forging stocks will be performed via VAR skull melting and VIM skull melting, both followed by casting in permanent moulds, HIP and machining. The objective of the project is the development of a low cost casting process for gamma-TiAl based TNM alloys which guarantees to meet all technical specifications of the products."
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