Production and characterization of TiB2 – Al2O3 reinforced NiAl matrix composites using H3BO3 and TiO2

The aim of the thesis is to produce and characterize NiAl matrix composites containing TiB2, Al2O3 reinforcement particles by combustion synthesis using H3BO3, TiO2, Ni and Al powders as starting materials. For this purpose, NiAl matrix composites containing 5-40 vol% TiB2, Al2O3 reinforcement particles were produced and the effects of TiB2, Al2O3 reinforcement in different percentages on microstructure and mechanical properties were investigated. The samples were produced in 3 different groups. In the first group, NiAl powders reinforced with TiB2, Al2O3 were produced by self-propagating high temperature synthesis (SHS). In the second group, low percentange (5-10%) Ni and Al powders were added to the 40, 25, 10% TiB2, Al2O3 reinforced NiAl powders produced by volume combustion synthesis (VCS). In the third group, high percentage (80-90%) Ni and Al powders were added to the 100-90% TiB2, Al2O3 reinforced NiAl powders produced by VCS. The powders produced in the second and third groups were ground for 2 hours. After pressing, the samples were sintered for 1 hour at 1375 oC, 1375 oC and 1100 oC, respectively. Volume combustion synthesis is predicted to occur during the heating of the 3rd group samples. Thereafter, XRD analyses, microhardness measurements, optical and scanning electron microscopy examinations, EDS analyses and 3-point bending tests were performed. As a result of the experiments, it can be said that the third group samples were more successful. When the microstructure of the samples in the first and second groups was examined, it was observed that while TiB2 particles were generally formed in the NiAl matrix, Al2O3 particles were seen to accumulate in the pores at the NiAl grain boundaries. In the third group, 10% TiB2, Al2O3 reinforced NiAl matrix composites had the best hardness value of 371,3 ± 32,8 HV0.2 and the best flexural strength was found to be 329,5 MPa.