Microstructure and mechanical properties of gamma TiAl based alloys produced by combustion synthesis + compaction route

Microstructure and mechanical properties of γ-TiAl alloy with the chemical composition Ti-48Al-2Cr-2Nb (at.%) have been investigated. The alloy was prepared in one step using a combustion synthesis + compaction process, where the synthesis and the shaping take place at the same time. Two different combustion routes were used: forced self-propagating high-temperature synthesis + compaction (FSHS + C) and thermal explosion + compaction (TE + C). Fully lamellar microstructure was obtained in both processing routes after the appropriate homogenisation thermal treatment. Nevertheless, TE + C route showed coarser lamellar colonies. A remarkable oxygen content reduction was achieved in samples synthesised by FSHS + C route. Tensile properties (especially UTS) were found to be in the same range as other alloys obtained by conventional processing routes, however, low ductility was achieved. Good creep and fatigue properties were obtained. All fracture surfaces showed a brittle fracture mechanism. Finally, it was found out that the studied processing routes showed promising results as an alternative manufacturing technology for γ-TiAl based alloys.