Abstract
Five TiAl–Ti3AlC2 composite samples containing (10, 15, 20, 25 and 30 wt% Ti3AlC2 MAX phase) were prepared by spark plasma sintering technique at 900 °C for 7 min under 40 MPa. For this purpose, metallic titanium and aluminum powders (aiming at the in-situ formation of the TiAl matrix phase) were ball-milled with predetermined contents of Ti3AlC2 MAX phase, which already was synthesized using the same metallic powders as well as graphite flakes. Displacement-time-temperature variations during the heating and sintering steps, displacement rate versus temperature, displacement rate versus time, and densification behavior were studied. Two sharp changes were detected in the diagrams: the first one, ~16 min after the start of the heating process due to the melting of Al, and the second one, after ~35 min because of the sintering progression and the applied final pressure. The highest relative densities were measured for the samples doped with 20 and 25 wt% Ti3AlC2 additives. More Ti3AlC2 addition resulted in decreased relative density because of the agglomeration of MAX phase particles.
Highlights
Titanium aluminides are excellent materials for structural applications such as automobile and aerospace industries because of their exceptional combination of characteristics [1,2,3]
TiAl material with enhanced compression properties was obtained by spark plasma sintering using excessive yttrium additive, which led to the formation and dispersion of fine strip-like YAl2 particles [18]
Increased densification and mechanical performance in TiAl materials was reported through TiB2 reinforcing that in-situ synthesized by self-propagating hightemperature synthesis methodology [22]
Summary
Titanium aluminides are excellent materials for structural applications such as automobile and aerospace industries because of their exceptional combination of characteristics [1,2,3]. TiAl has low density, high melting point, good corrosion resistance, excellent oxidation performance, and creep resistance [4,5,6] Anyway, this intermetallic material suffers from low-temperature ductility and poor formability [7,8,9,10]. Low wear and good self-lubricity were achieved for TiAl materials by the addition of Cu-coated graphite Such a superior tribological characteristic was related to the synergetic influences of formation of soft tribo-film and hard TiC reinforcement [20]. Addition of nano-sized Y2O3 led to enhanced tensile strength and elongation in spark plasma sintered high-Nb containing TiAl intermetallics, due to the activation of secondphase strengthening and fine-grain strengthening mechanisms [23]. The TiAl–Ti2AlC composites were fabricated by self-propagating high-temperature synthesis [26] and vacuum arc melting [27] using the elemental powders of Ti, Al and C, as well as reactive hot pressing of TiC, Ti and Al powders [28] and spark plasma sintering of mechanically alloyed Al–Ti powders with carbon nanotubes [29]
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