Characterization and mechanical properties of in situ synthesized Ti5Si3/TiAl composites

A series of composites of Ti5Si3/TiAl were synthesized by combination of mechanical alloying (MA) and hot isostatic pressing (HIPing). 20 h-milled powders of 65Ti–17Al–18Si (at.%) and 58Ti–21Al–21Si (at.%) were used as precursors incorporated into elemental 50Ti–50Al (at.%) powder matrices, followed by HIPing at 1100 °C and 150 MPa. Analyses by X-ray diffraction (XRD) as well as energy dispersive spectrometer (EDS) revealed the presence of three phases, namely, TiAl, Ti3Al and Ti5Si3. Observations by optical microscopy (OM) and scanning electron microscopy (SEM) showed features of equiaxed grain matrix (TiAl) with a number of distributed large clusters and small particles of Ti5Si3. The size of scattered distributed particles was estimated to be less than 1 μm while the large clusters and matrix grains are in the range of 10–50 μm. The mechanical properties of composites were evaluated by micro- and nano-hardness measurements and compression tests at ambient temperature. The alloys exhibited significant compressive deformability (10–20%) and pronounced strain hardening. While the matrices exhibited hardness of 4–7 GPa, the distributed Ti5Si3 particles indicated hardness of 10–12 GPa.