Description
This thesis discusses the processing of Carbon nanotube (CNT)- Nickel Aluminide (Ni3Al) intermetallics with boron (B) additions using electrically activated Self-propagating high-temperature synthesis (SHS) process and post annealing. The effect of CNT content (0- 5 vol%) at the ambient and elevated temperature on the material properties (tensile and compressive) was investigated. Materials characterization was conducted to determine phase analysis pre- and post-annealing, together with fractography post mechanical testing induced fracture. Annealing was found to reduce porosity and improve homogeneity of the microstructure, however the presence of NiAl phase was noted in all composites. Addition of 1 vol% CNT produced best results in terms of hardness, tensile and compressive strength of the synthesized compact primarily due to good CNT dispersion. Also, lowest porosity was observed for 1 vol% CNT samples. Further addition of CNT decreased the hardness, tensile and compressive strength, and increased porosity of the material. Tensile strength generally increased with an increase in temperature from room temperature to 300oC, while compressive strength showed first a decline at 305oC then a slight increase at 500oC. These results are consistent with the mechanical behavior of NiAl with temperature in compression versus tension, and is believed to influence the mechanical behavior of the final product.
