Evaluation of microstructure and mechanical properties of bulk nanostructured Ti5Si3 and Ti5Si3-Al2O3 nanocomposite

Mechanical alloying and vacuum sintering have been used to produce bulk nanostructured Ti5Si3 and Ti5Si3-15Wt.% Al2O3 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 Al2O3 through mechanochemical reaction has amorphous structure which crystallized during sintering process. Nanohardness, elastic modulus and fracture toughness of Ti5Si3-15Wt.% Al2O3 nanocomposite were calculated as 1660 HV, 238 GPa and 5.5 MPa.m1/2 that is higher than monolithic Ti5Si3 and other Ti5Si3-based nanocomposites. Toughening mechanisms based on crack deflection and crack bridging were suggested as responsible factors for fracture toughness increase Ti5Si3/Al2O3 nanocomposite.