Deformation behavior and strengthening mechanisms in a CNT-reinforced bimodal-grained aluminum matrix nanocomposite

The aim of this study was to identify deformation behavior and strengthening mechanisms of a carbon nanotube (CNT)-reinforced bimodal-grained Al-Cu-Mg nanocomposite and its base alloy fabricated by two-step ball milling, powder metallurgy and extrusion. A superior strength-ductility synergy stemming from the concurrent presence of ultrafine grains (UFGs) and coarse grains (CGs) was achieved. Singly-dispersed CNTs in UFGs and sound CNT/Al interfacial bond contributed to a significant improvement in the strength of the nanocomposite. The predominant strengthening mechanism in the CNT-reinforced nanocomposite was identified to be Orowan looping due to severe shearing of CNTs into nano-sized fragments during ball milling, along with load-transfer and thermal mismatch-induced dislocation strengthening mechanisms. The predicted yield strength of the nanocomposite was in agreement with the experimental value obtained. The findings in this study help pave the way for developing high-performance lightweight materials with a superior strength-ductility synergy via incorporating CNTs with novel bimodal grain structures.

Automated summary

This study identified the deformation behavior and strengthening mechanisms of a carbon nanotube (CNT)-reinforced bimodal-grained Al-Cu-Mg nanocomposite fabricated by two-step ball milling, powder metallurgy and extrusion. The synergy of superior strength-ductility was achieved due to the presence of ultrafine grains (UFGs) and coarse grains (CGs). The predominant strengthening mechanism was identified as Orowan looping, contributing to the significant improvement in strength of the nanocomposite. The findings help pave the way for developing high-performance lightweight materials with a superior strength-ductility synergy by incorporating CNTs with novel bimodal grain structures.