Description
This study analyzes the processing and mechanical behavior of carbon nanotube (CNT) reinforced nickel aluminides (Ni3Al) synthesized through electrically activated reactive synthesis and post-reaction homogenization annealing. The effect of temperature and CNT content on the flexural strength is investigated with a four-point bending test designed according to ASTM standards C1161-18 and C1211-18. Tests were conducted on four different material compositions (Ni3Al-0wt% CNT, Ni3Al-1wt% CNT, Ni3Al-3wt% CNT, and Ni3Al-5wt% CNT) and at three different temperatures (20°C, 300°C, and 500°C). Homogenization annealing was found to increase Ni3Al homogeneity and reduce porosity. An addition of 1wt% CNT gave the best combustion synthesis parameters; however, it also produced the highest porosity. Etching followed by microscopy analysis showed nickel confinement on the grain boundaries. A new type of loading profile was observed consistently on the Ni3Al-5wt% CNT. At 20°C, Ni3Al 5wt% CNT showed the best results by achieving a flexural strength of 1.19 (GPa) compared to the 0.43 GPa of Ni3Al-0wt% CNT. At 300°C, the flexural strength showed an improvement for all the compositions with the exception of Ni3Al-3wt% CNT. However, Ni3Al-5wt% CNT still showed the best results with a flexural strength of 1.45 GPa compared to the 0.45 GPa of Ni3Al-0wt% CNT. At 500°C, flexural strength values were low throughout all the compositions, showing signs of embrittlement and intergranular fracture.
