![]() It is reported that the presence of CNTs at GBs are effectively ensured the preserve of high density of tangled dislocations, dislocation walls and sub-boundaries. On one hand, mechanical properties especially flow stress and on the other hands the phenomena such as dynamic recovery (DR) and dynamic recrystallization (DRX) in CNT/Al composites largely affects the microstructure which in turn is influenced by processing parameters including temperature, strain rate and strain. In such fabricating approach, CNTs are mainly distributed at GBs, showing a strong pinning effect on aluminum grain growth phenomena during a series of high temperatures, such as sintering, forging and hot extrusion processes, ,, ,, , ]. Indeed, making flake Al powder by BM, provides a better geometric compatibility with the CNTs, a larger surface area than spherical powder as well as a homogenous CNT distribution in the resultant composites, , ]. Plus, the adsorptive capacity of CNTs does not depend only on the specific surface area of the powder, but also on the geometry of the Al particles. A strong flake aluminum powder thickness dependence in both strength and ductility is reported. Mechanical properties depend not only on the microstructure changes but also on the morphology changes of the as-milled powders. An important but rarely discussed issue about enhancing mechanical properties of CNT/Al composites is the relationship between BM conditions, microstructure, and mechanical properties of the resultant products, considering the morphology of the as-milled powders. However, very little attention has been paid to the pre-microstructure correlation influenced by BM conditions with mechanical properties. The significant influence of grain size induced by BM process on the strength improvement of UFG composites after consolidation has been widely investigated. Meanwhile, the average grain size decreases with the increase in milling time and rotating speed, , ]. During the BM process, the sequential occurrences, such as deforming, flattening, and then cold-welded of metallic powders, are accelerated with the increase of milling speed. Powder metallurgy (PM), which is generally achieved through ball milling (BM) process, has been highly developed for manufacturing ultrafine-grained (UFG) composites with improved microstructure and mechanical properties. This work strengthened the understanding of ball milling process on the microstructure and mechanical properties of metal matrix composites. The simulated results agreed well with experimental results, confirming a strain rate dependency of GBAZ thickness. The enhancing in tensile properties of CNT/Al composite mostly caused by grain refinement, dislocation strengthening, and back stress hardening, which last two terms are closely linked to GBAZ thickness. ![]() ![]() The results showed that the grain size of CNT/Al composite were significantly influenced by milling conditions, which caused obvious variations in mechanical properties. The ultrafine-grained (UFGed) architectures of the CNT/Al composites made from flake powders with the same thickness under different BM conditions, introduce different strain rates and vary dislocation density. The relationship between different ball milling (BM) conditions and mechanical properties of CNT/Al composites was studied through tailoring grain interior/grain boundary affected zone (GI/GBAZ).
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