Evaluation of Microstructure and Mechanical Properties of Bulk Nanostructured Ti_5Si_3 and Ti_5Si_3-Al_2O_3 Nanocomposites

Mechanical alloying and pressure less sintering in vacuum have been used to produce bulk nanostructured ti_5si_3 and ti_5si_3-15 wt.% al_2o_3 nanocomposite. x-ray diffraction (xrd), scanning electron microscopy (sem) and transmission electron microscopy (tem) were used to study the microstructural characteristics of the samples. indentation method was used to calculate hardness, elastic modulus and fracture toughness of bulk samples. the results showed that the nanometric grains were obtained through mechanical alloying and remained in nanometric scale after subsequent sintering. it was also observed that the in-situ produced al_2o_3 through mechanochemical reaction has amorphous structure which was crystallized during sintering process. nanohardness, elastic modulus and fracture toughness of ti_5si_3-15 wt.% al_2o_3 nanocomposite were calculated as 1660 hv, 238 gpa and 5.5 mpa.m^1/2 ,respectively, that are higher than those of the monolithic ti_5si_3. toughening mechanisms based on crack deflection and crack bridging were suggested as responsible factors for fracture toughness increase of the ti_5si_3/al_2o_3 nanocomposite.