Microstructure and mechanical properties of spark plasma sintered AlCoFeMnNi high entropy alloy (HEA)-carbon nanotube (CNT) nanocomposite

Highlights: • The effects of minor additions of carbon nanotube (CNT) on the mechanical properties of AlCoFeMnNi are investigated. • Mechanical alloying and spark plasma sintering were used to synthesize composite samples. • Minor additions of CNT cause a significant improvement of mechanical properties. • The correlation between the microstructure and mechanical properties are discussed. -- Abstract: This paper investigates the concept and the possibility of synthesizing high entropy alloy (HEA)/carbon nanotube (CNT) nanocomposites. AlCoFeMnNi was chosen as the matrix and 1 wt% CNT was added as the reinforcement. HEAs have recently gained a lot of attentions as new class of alloys with unprecedented properties, such as superior high temperature corrosion/oxidation resistance, excellent high temperature strength, and perfect structural stability, making HEAs an emerging class of alloys for many demanding applications. AlCoFeMnNi/CNT nanocomposites in this study were produced by combination of mechanical alloying and spark plasma sintering. The microstructure and mechanical properties of produced HEA/CNT nanocomposites were evaluated, using electron microscopy, shear punch, and hardness tests. Results showed that mechanical alloying up to 40 h is enough to transform initial elemental powder mixture to HEA solid solution. Results also showed that CNT addition to the HEA matrix significantly enhances the maximum shear strength of the alloy. Implications of CNT additions to the HEA matrix for the mechanical properties and microstructure HEA/CNT nanocomposite samples were discussed in this paper.