Abstract
The objective of this work is to evaluate practically the potential of TiAl type P/M alloys for higher temperature structural applications. TiAl alloys mainly containing 1.4%Si (0.06%B), previously reported to have a good oxidation resistance, were investigated in the light of mechanical properties and plastic deformation (processing) at higher temperature.
The results were summarized as follows:
(1) TiAl type alloys investigated here have a ductile-brittle transition temperature in the vicinity of 800°C. The tensile behavior of TiAl specimens with and without Si content are much the same in the strength but fairly different in the strain for fracture at higher temperature.
(2) Flow stress (deformation) appears to be controlled superplastically (strain rate sensitivity m≥0.3) at lower strain rate in the refined grain size of a few μm, in both tension and compression, where its dependence on strain rate is influenced by Si additive, besides powder particle size and temperature as usual.
(3) Siliconizing TiAl P/M parts using the pack-cementation process may be recommended for almost no Si-in-fluence on mechanical properties, though Si alloyed to TiAl (B) lowers its tensile elongation at 1000°C or more. (Received January 18, 1990)
