Enhancement of mechanical and corrosion properties of Al-Cu-Mg-Li alloy by high-pressure torsion processing

Abstract

Nanostructured metallic materials often possess extraordinary mechanical properties, and can be fabricated using two different approaches, bottom-up (i.e. electrodeposition, physical and chemical vapor deposition) and top-down approaches. The top-down approach (i.e. severe plastic deformation techniques) focuses on refining grain size of the existing coarse-grained materials through large straining to produce large bulk nanostructured solids. High-pressure torsion (HPT) has recently been proven as an effective technique to produce bulk materials with ultrafine-grained microstructures.

In this study, a modified aluminum 2024 alloy (Al-Cu-Mg-Li alloy) was processed at first time by HPT under an applied pressure of 6.0 GPa for a range of torsional revolutions from 1/4, 1/2, 1, 5 and 10 turns, and then exposed to a 3.5 wt.% NaCl solution for open-circuit potential (OCP) measurements followed by electrochemical impedance spectroscopy and potentiodynamic polarization tests. The electrochemical results exhibit that corrosion resistance of Al-Cu-Mg-Li alloy in NaCl solution is significantly enhanced by 8 times upon high torsion strains of HPT processing compared with that of the as-received coarse-grained sample. Microhardness measurements also reveal a two-fold improvement in hardness for the Al-Cu-Mg-Li alloy after HPT processing. The enhancement of microhardness and corrosion resistance was elucidated by examining the effect of HPT processing on surface topography and microstructure as observed by SEM, EDX, EBSD and TEM characterization.

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Identifiers

ORCID for Mengyan Nie: orcid.org/0000-0002-7758-760X

ORCID for N. Gao: orcid.org/0000-0002-7430-0319

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