Spark plasma sintering of Ti-48Al intermetallic using elemental powder

Sintered compacts without further heat treatment were fabricated at 540 °C, 570 °C, 600 °C and 650 °C (below the melting temperature of aluminium) via spark plasma sintering (SPS). Ti and Al in a proportion of 52% (at.) and 48% (at.) respectively were used as the starting powders. Powder mixture without mechanical alloying was prepared in a turbula mixer for a period of 8 h. The microstructure and phases present in the elemental and mixed powders were investigated. The microstructure, phase transformation and mechanical properties of the sintered samples were investigated. The density of sintered compacts increased from 3.32 to 3.39 g/cm³ as the sintering temperature increased from 540 to 600 °C, and it shot beyond the theoretical density of 3.41 g/cm³ to a value of 3.91 g/cm³ due to loss of aluminium melt from the reaction zone during sintering. XRD analysis shows the formation of Ti, TiAl₂ and Ti₂Al₅ as the major phases, and TiAl and Ti₃Al as the minor phases. There was an indication that the powder mixture has undergone a complex reaction with the evolution of unordered (non-equilibrium) phases retained during SPS. An average microhardness value of 89.87 HV was obtained for temperature 540 to 600 °C, which increased abruptly to a value of 276.63 HV for temperature of 650 °C. This study gives insight to the discussion of the synthesis of Ti-Al intermetallic without mechanical alloying of elemental powders and no further heat treatment of consolidated powder. [Figure not available: see fulltext.].