Abstract
The room‐temperature tensile strength, toughness, and high‐temperature creep strength of 2000, 6000, and 7000 series aluminum alloys can be improved significantly by dispersing up to 1 wt% carbon nanotubes (CNTs) into the alloys without sacrificing tensile ductility, electrical conductivity, or thermal conductivity. CNTs act like forest dislocations, except mobile dislocations cannot annihilate with them. Dislocations cannot climb over 1D CNTs unlike 0D dispersoids/precipitates. Also, unlike 2D grain boundaries, even if some debonding happens along 1D CNT/alloy interface, it will be less damaging because fracture intrinsically favors 2D percolating flaws. Good intragranular dispersion of these 1D strengtheners is critical for comprehensive enhancement of composite properties, which entails change of wetting properties and encapsulation of CNTs inside Al grains via surface diffusion‐driven cold welding. In situ transmission electron microscopy demonstrates liquid‐like envelopment of CNTs into Al nanoparticles by cold welding.
Highlights
The MIT Faculty has made this article openly available
The consolidated Al + carbon nanotubes (CNTs) was further shaped by milling, extrusion, and rolling
The quantitative contribution of CNTs to mechanical strength enhancement can be analyzed using the strengthening efficiency (R), R ≡ (σ c − σ m )/υcσ m, where σc and σm are the tensile strengths of the composite and matrix, respectively, and υc is the volume fraction of CNTs to metal, is the change in strength by adding unit volume of CNTs.[32]
Summary
The MIT Faculty has made this article openly available. Please share how this access benefits you. Creep strength of 2000, 6000, and 7000 series aluminum alloys can be and becomes very soft at 500 K or so. This improved significantly by dispersing up to 1 wt% carbon nanotubes (CNTs) into the alloys without sacrificing tensile ductility, electrical conductivity, or thermal conductivity. CNTs act like forest dislocations, except mobile dislocations cannot annihilate with them. The gist is that well-dispersed CNTs act like forest dislocations. It can harden the metal pretty much like stored dislocation line density in the traditional
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