The influence of heating rate on the microstructural evolutions and mechanical properties of spark plasma sintered multi-walled carbon nanotubes reinforced NiAl intermetallic matrix composites

The effect of heating rate on the mechanical characteristics and microstructures of multi-walled carbon nanotubes (MWCNTs) reinforced nickel aluminide (NiAl) was studied. Powder synthesis was carried out by the use of the planetary ball milling and the admixed powders were fabricated by spark plasma sintering (SPS) technique to promote homogeneity. Three values of the heating rate was used namely 50, 100 and 150 °C/min to evaluate the effect of heating rate on the resulting microstructures and mechanical properties of the sintered composites. The microstructures of the sintered composites revealed the presence of porosity as the heating rate was higher, due to lack of contact area between particles. The densifications of the composites were observed to decrease as the heating rate was increased. Furthermore, results showed that a heating rate of 50 °C/min gave the best combination of properties among the composite batches with nanohardness of 9.6 GPa, microhardness of 371.2 HV, elastic modulus of 107.7 GPa, and relative density of 95.7%.