Microstructure and mechanical properties of high niobium containing TiAl alloys elaborated by spark plasma sintering

Abstract

Spark Plasma Sintering (SPS) is used to process TNB alloys. Pre-alloyed powders (Ti–46Al–9Nb) were sintered between 975 °C and 1300 °C under 100 MPa. The microstructures of the products are determined by X-ray diffraction and by scanning and transmission electron microscopy. Their mechanical properties are evaluated by tensile tests performed at room temperature and creep experiments at 700 °C under 300 MPa stress. Depending on the sintering temperature, two-phased, duplex and lamellar microstructures have been obtained. A quasi-α2 phase has been observed, which is in fact an α2 phase in which Nb atoms have substituted Ti atoms. The TNB alloys consolidated by SPS are stronger than the alloys previously elaborated by SPS using Ti–47Al–2Cr–2Nb and Ti–44Al–2Cr–2Nb–1B powders but they exhibit a lower ductility. Moreover, some specimens broke prematurely due to Fe inclusions.