Abstract
High strength and high ductility are often mutually exclusive properties for structural metallic materials. This is particularly important for aluminum (Al)-based alloys which are widely commercially employed. Here, we introduce a hierarchical nanostructured Al alloy with a structure of Al nanograins surrounded by nano-sized metallic glass (MG) shells. It achieves an ultrahigh yield strength of 1.2 GPa in tension (1.7 GPa in compression) along with 15% plasticity in tension (over 70% in compression). The nano-sized MG phase facilitates such ultrahigh strength by impeding dislocation gliding from one nanograin to another, while continuous generation-movement-annihilation of dislocations in the Al nanograins and the flow behavior of the nano-sized MG phase result in increased plasticity. This plastic deformation mechanism is also an efficient way to decrease grain size to sub-10 nm size for low melting temperature metals like Al, making this structural design one solution to the strength-plasticity trade-off.
Highlights
High strength and high ductility are often mutually exclusive properties for structural metallic materials
If the size of the metallic glass (MG) is smaller than 100 nm, the shear banding event can be fully suppressed[18,19], which contributes to an ideal strength[20] and homogeneous plastic flow behavior of the MGs
To realize such a material, we develop a hierarchical nanostructured Al alloy composed of face-centered-cubic nanograins surrounding by nano-sized MG shells
Summary
High strength and high ductility are often mutually exclusive properties for structural metallic materials. The nano-sized MG phase facilitates such ultrahigh strength by impeding dislocation gliding from one nanograin to another, while continuous generation-movement-annihilation of dislocations in the Al nanograins and the flow behavior of the nano-sized MG phase result in increased plasticity This plastic deformation mechanism is an efficient way to decrease grain size to sub-10 nm size for low melting temperature metals like Al, making this structural design one solution to the strength-plasticity trade-off. We hypothesize that with an extremely thin MG phase surrounding the crystalline phase, strain hardening of the crystalline phase and plastic flow of the nano-sized MG phase will contribute to both high strength and large ductility To realize such a material, we develop a hierarchical nanostructured Al alloy composed of face-centered-cubic (fcc) nanograins surrounding by nano-sized MG shells.
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