Hot deformation behaviour and microstructure evolution of ultra-fine grained carbon nanotube/2024Al matrix composite

Abstract Objectives The influence of reinforcements on the hot deformation behaviour of carbon nanotube (CNT)-reinforced 2024Al composite is investigated in this work. Methods The CNT-reinforced 2024Al composite was fabricated by ball milling and sintering. The fabricated CNT/2024Al composite was compressed at 350–500°C and 0.001–1 s−1. Results The composite exhibits the highest flow stress at 350°C/1 s−1, and the lowest stress at 500°C/0.001 s−1. Because of the addition of reinforcements in composites, the conventional Arrhenius equation yields relatively large errors in stress prediction. By introducing a correction factor, the modified Arrhenius model demonstrates improved accuracy in predicting stress. Processing maps reveal that the region of highest η is observed within the 350–400°C and 0.1–1 s−1. Conversely, lower efficiency coincides with the instability region at 400–500°C and 0.01–0.001 s−1. The composite deformed at 350°C/1 s−1 exhibits a fine and uniform grain size, while the microstructure of the composite deformed at 500°C/0.001 s−1 exhibits a bigger grain size. Conclusion The reinforcements distributed at grain boundaries play a pinning role on boundary migration, thereby suppressing grain growth within the composite. Moreover, the reinforcements enhance the deformation stress and energy required for microstructure evolution, resulting in an increase in deformation activation energy.