Microstructure Evolution and Mechanical Properties of NiAl-TiB2 Nanocomposite Produced by Heat Treatment Post Mechanical Alloying

In the current study, NiAl-TiB2 nanocomposite was produced by mechanical alloying and subsequent heat treatment. For this purpose, mixtures of pure Ni, Al, Ti, and B powders were milled in a ball mill for 20 h to produce NiAl-TiB2 nanocomposites containing 10, 20, and 30 at% TiB2. The heat treatment temperature was selected at 850 degrees C for 30 min which was determined by differential thermal analysis. X-ray diffractometer (XRD) was used to identify the existing phases. The XRD results showed the completion of alloying after heat treatment. Furthermore, the morphology of the powders and microstructure of the sintered samples were investigated by optical microscopy and field emission scanning electron microscopy. Results showed that the NiAl-20% TiB2 sample had the most homogeneous morphology. Then the powder mixture was hot pressed at 800 degrees C under 300 MPa. The density of the sample reached 95% after hot pressing. The sample containing 20% TiB2 was subjected to wear test under 5, 7, 10, and 13N loads by pin on disk method. Examination of the morphology of the worn surface and wear debris showed that spalling was the dominant wear mechanism.