Investigation of the main strengthening mechanism of carbon nanotube reinforced aluminum composites

Highlights: • CNT aspect ratio has only small effects on the strength of CNT/Al. • Reinforcement of CNT/Al is dominated by dispersion strengthening. • CNT addition within 0.5 wt% increases strength markedly without plasticity loss. • The calculated CNTs diameters are close to the experimental used ones. The effects of carbon nanotube aspect ratio (R) on mechanical properties of CNT/Al composites containing 0–2.0 wt% CNTs are studied. The optimum carbon nanotube (CNT) reinforced aluminum (Al) composites are fabricated at 580 °C for 1 h under 60 MPa, and subsequently hot extruded at 480 °C. CNT addition within 0.5 wt% can increase the strength significantly without plasticity loss, which overcomes the dilemma of strength and toughness. Strength and hardness increase significantly due to the uniformly distributed CNTs in Al matrix within a content of 1.0 wt%. Quantitatively fitting results also show that the main strengthening mechanism of CNT/Al composites should be dispersion strengthening rather than load transfer. The R, which is very crucial for load transfer theory, has only small effects on the mechanical properties of CNT/Al composites. The calculated CNTs diameters are close to the experimental used ones.