Evaluation of microstructure and mechanical properties of bulk nanostructured Ti۵Si۳ and Ti۵Si۳-Al۲O۳ nanocomposite

Mechanical alloying and vacuum sintering have been used to produce bulk nanostructured Ti۵Si۳ and Ti۵Si۳-۱۵Wt.% Al۲O۳ 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 Al۲O۳ through mechanochemical reaction has amorphous structure which crystallized during sintering process. Nanohardness, elastic modulus and fracture toughness of Ti۵Si۳-۱۵Wt.% Al۲O۳ nanocomposite were calculated as ۱۶۶۰ HV, ۲۳۸ GPa and ۵.۵ MPa.m۱/۲ that is higher than monolithic Ti۵Si۳ and other Ti۵Si۳-based nanocomposites. Toughening mechanisms based on crack deflection and crack bridging were suggested as responsible factors for fracture toughness increase Ti۵Si۳/Al۲O۳ nanocomposite.

Keywords:

Intermetallics , Composite , Nanoindentation , Fracture toughness , Powder processing