A novel strengthening effect of in-situ nano Al2O3w on CNTs reinforced aluminum matrix nanocomposites and the matched strengthening mechanisms

Abstract Nano alumina whiskers (Al 2 O 3 w) were in-situ synthesized in carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites (AMNCs) which were fabricated by flake powder metallurgy (P/M). To study the strengthening effect of nano Al 2 O 3 w on CNTs reinforced AMNCs and clarify the strengthening mechanisms, the microstructures and mechanical properties of AMNCs are investigated. It is found that CNTs-Al 2 O 3 w reinforcements have a significant hybrid strengthening effect on tensile strength due to their uniform dispersion and good interfacial bonding with Al matrix. The strengthening mechanisms of CNTs-Al 2 O 3 w reinforcements are considered as a sum of load transfer, grain refinement, thermal mismatch and Orowan looping theory. The experimental strengths of AMNCs containing 0.25 and 0.5 vol% CNTs are well matched with the theoretical values calculated by the strengthening mechanisms. And the differences between them are less than 2.9%, which is highly effective for predicting the mechanical properties of CNTs-Al 2 O 3 w reinforced AMNCs. The predicted values indicate that load transfer mechanism from both CNTs and Al 2 O 3 w is dominant, improving UTS of 0.5CNTs reinforced flake AMNCs (228 MPa) by more than 79.5% in comparison with pure Al.