Thermodynamic aspects of nanostructured Ti 5Si 3 formation during mechanical alloying and its characterization

Abstract

Mechanical alloying (MA) was used to produce Ti 5Si 3 intermetallic compound with nanocrystalline structure from elemental powders. The structural changes and characterization of powder particles during milling were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and microhardness measurements. MA resulted in gradual formation of disordered Ti 5Si 3 intermetallic compound with crystallite size of about 15 nm after 45 h of milling. Also a thermodynamic analysis of the process was carried out using Miedema model. The results showed that in the nominal composition of Ti 5Si 3 intermetallic phase (X Si = 0·375), formation of an intermetallic compound has the lowest Gibbs free energy rather than solid solution or amorphous phases. So the MA product is the most stable phase in nominal composition of Ti 5Si 3. This intermetallic compound exhibits high microhardness value of about 1235 HV. © Indian Academy of Sciences.