Densification behaviour and microstructural evolution of Ti-48Al consolidated by spark plasma sintering

Spark plasma sintering (SPS) is a fairly novel powder metallurgy (PM)-based process. Compared with more traditional PM processes, SPS technology provides greater sintering efficiency for the Ti-48Al alloy, due to its fast heating and cooling rates, combined with an applied pressure and electric field during the process. In this study, three fundamental processing parameters (i.e. sintering temperature, time and particle size) are investigated, and their effects on densification, hardness and phase transformations are studied. Three grain morphologies were found in the microstructures, present in different ratios in the samples, depending on the sintering parameters. A model is proposed to explain the (α₂) grain-phase growth and the transformation of two types (fine and coarse) of lamellar structural development. The pore configurations (i.e. size and quantity) are examined, and their interactions with the phases, which suggest the phase-formation sequence and sintering state, are also discussed.