Research On Deformation-driven Metallurgy Preparation Of GNPs/Al Composites And Their Strengthening-toughening And Anti-corrosion Mechanisms

Lightweight and high-performance structural/functional materials are one of the most effective approaches to improving the energy-to-mass ratio of vehicles and reducing carbon emissions.However,the performances of high-performance alloys guided by the classical metallurgical theory are approaching their theoretical limit.Aluminum matrix composites can realize the synergy of each component in the materials,and can even overcome the inherence shortcomings of its single component to achieve a breakthrough in the structural/functional demands.In this paper,a novel method,deformation-driven metallurgy(DDM),was proposed to break the equilibrium metallurgical thermal activation barriers via solid-liquid-solid state and build the severe deformation-driven fast diffusion metallurgical technologies directly via solid-solid state.Ultra-homogeneous composites considering strength,toughness,and functionality were obtained based on carbonaceous nanomaterials and aluminum,which achieved breakthroughs in higher strength-ductility balance and high anticorrosion performance.It has important guiding significance for the preparation of novel carbonaceous nanomaterial-reinforced aluminum matrix composites.In response to strengthening and toughening requirements,aluminum matrix composites were obtained through the combination of aluminum and low-cost graphene nanoplatelets(GNPs).With the addition of only 1.5 wt.%,the ultimate tensile strength and elongation reached 497 MPa and 15.2%,respectively,which showed an increase of 317% and a decrease of 27.0% compared to the 1060 pure aluminum.The aluminum matrix composites were further prepared by the combination of aluminum and few-layer GNPs.With the determined rotational velocity of 1000 rpm and dwelling time of 60 s,the optimized ultimate tensile strength and elongation reached 470 MPa and 19.8%,respectively.The strength-ductilit y product reached 9.31 GPa%,reaching the highest strengthening-toughening level of aluminum matrix composites and surpassing 2xxx and 7xxx series high-strength aluminum alloys.Their strengthening and toughening mechanisms could be attributed to the following five points: Ultra homogeneous dispersion of GNPs,highperformance interfacial bonding,nanocrystalline strengthening and toughening,limited interfacial embrittlement,and spatial self-compensation mechanism.Aiming at anti-corrosion performance,ultra homogeneous dispersion of GNPs was obtained via severe plastic deformation,and the GNP-reinforced aluminum matrix composites with high density and without hydrolyzable intermetallic compounds were preparaed via the adjustment of processing parameters.These composites could form a protective passivation layer composites of GNPs and carbondoped oxide film in the initial stage of corrosion in a chlorine-cotaining aqueous solution,thereby greatly improving the corrosion resistance.The polarization resistance reached 3 to 4 times of pure aluminum.The lower electron donor densit y in the carbon-doped passivation layer was seen to provide significant resistance to chloride ion corrosion and change transfer.The carbon doping provided by the ultra homogeneous dispersion of GNPs made the oxide film obtain high vacancy formation energy,chlorine diffusion energy barrier,and work function,showing obvious corrosion inhibitor characteristics.DDM composites were then prepared by co-doping fluorinated GNPs(F-GNPs)and magnesium alloying.The homogeneous dispersed magnesium-alloyed F-GNPs in the composites made them soaked in a chlorine-containing aqueous solution for 2months with the polarization resistance maintaining 89% of the initial state.They also had excellent ultimate tensile strength and elongation of 532±39 MPa and 17.3±1.2%,respectively.The heterogeneous doped F-GNP-reinforced and magnesium-alloyed aluminum matrix composites could form a protective passivation layer structure by F-GNPs and fluorine-doped oxide film under long-term immersion instead of a carbon-doped oxide film.The magnesium oxide layer ensured the high-performance bonding between the passivation layer and the matrix.This greatly improved the energy barrier and diffusion distance required for chloride ion ingress,thereby realizing a long-term corrosion resistance mechanism with extended shelf life.Facing the typical applications of anti-corrosion anodes for aqueous aluminumair batteries,F-GNP-reinforced and magnesium-alloyed aluminum matrix composites with homogeneous dispersion of F-GNPs induced by severe plastic deformation exhibited excellent corrosion resistance under static immersion in alkaline solutions.Their F-GNPs core-magnesium shell-aluminum matrix self-assembly structure ensured the formation of static nanosphere passivation on the corroded surface to resist the hydrogen evolution corrosion.The strong bonding of magnesium-doped aluminum hydroxides and F-GNPs ensured the integrity and stability of the passivation layer.The dense passivation layer exhibited rapid peeling-off abilit y induced by the flush ion impact via discharge current.The passivation layer on the composite surface could be completely peeled off and resumed normal discharge in only 30 seconds,and the passivation layer took less than 1 min to totally recover,showing a highly efficient reversible passivation behavior.The effective energy density of F-GNP-reinforced and magesium-alloyed aluminum matrix composites during intermittent discharge was increased by 424%,and the intermittent discharge efficiency was 95.3±3.1%.It had a more stable anti-polarization voltage plateau with a working voltage 0.2～0.4 higher than the 5N pure aluminum.