Strength-ductility materials by engineering a coherent interface at incoherent precipitates.

In the quest for excellent light-structural materials that can withstand mechanical extremes for advanced applications, design and control of microstructures beyond current material design strategies have become paramount. Herein, we design a coherent shell at incoherent precipitates in the 2195 aluminum alloy with multi-step metastable phase transitions. A high local strain rate via a neoteric deformation-driven metallurgy method facilitated the diffusion of Li. The original T1 (Al2CuLi) phases were transformed into coherent-shell (Li-rich) irregular-coated incoherent-core (Al2Cu) precipitates. The ultimate tensile strength and elongation reached 620 ± 18 MPa and 22.3 ± 2.2%, exhibiting excellent strength-ductility synergy. Grain boundaries, dislocation, solid solution atoms, and precipitates all contributed to the yield strength of the materials, among which precipitates occupied a dominant position, contributing approximately 56.07%. A new "incoherent-coherent interact" strain-hardening mechanism was also clarified, which was believed to be promoted in other heat-treatable alloy systems, especially with multi-step metastable phase transitions.

Grain Boundary Engineering in Ta-Doped Garnet-Type Electrolyte for Lithium Dendrite Suppression.

Solid-state lithium batteries (SSLBs) based on Ta-doped Li6.5La3Zr1.5Ta0.5O12 (LLZTO) suffer from lithium dendrite growth, which hinders their practical application. Herein, first principles simulations indicate that the Ta element prefers to segregate along grain boundaries in the form of Ta2O5 precipitates due to a high energy difference induced by Ta doping. Grain boundary engineering is employed to regulate the distribution of the Ta element and enhance the density of LLZTO by introducing the La2O3 additive. The sufficient La2O3 additive reacts with the Ta2O5 precipitates, while the residual La2O3 nanoparticles fill up void defects, promoting the homogeneous distribution of the Ta element and improving the relative density to ∼98%. Critical current density of the symmetric Li battery reaches 2.12 mA·cm-2 at room temperature with the solid-state electrolyte (LLZTO + 5 wt % La2O3), which increases by 41% compared to pure LLZTO. SSLBs with the LiFePO4 cathode achieve a stable cycling performance with a discharge capacity of 138.6 mA·h·g-1 after 400 cycles at 0.2 C. This work provides theoretical insights into the distribution of Ta-doped LLZTO and inhibits lithium dendrite growth through grain boundary engineering.

Heteroatom Modification Enhances Corrosion Durability in High-Mechanical-Performance Graphene-Reinforced Aluminum Matrix Composites.

The antagonism between strength and corrosion resistance in graphene-reinforced aluminum matrix composites is an inherent challenge to designing reliable structural components. Heteroatom microstructural modification is highly appreciated to conquer the obstacle. Here, a bottom-up strategy to exploit the heterogeneous phase interface to enable high corrosion durability is proposed. Deformation-driven metallurgy derived from severe plastic deformation is developed to produce Mg-alloyed fluorinated graphene structures with homogeneous dispersion. These structures allow for absorbing corrosion products, forming a dense protective layer against corrosion, and local micro-tuning of the suppression of charge transfer. This results in superior corrosion resistance with an outstanding strength-ductility balance of the composites via ultrafine-grained and precipitation strengthening. The anti-corrosion polarization resistance remains 89% of the initial state after 2-month immersion in chloride-containing environment, while the ultra-tensile strength and elongation of 532 ± 39 MPa and 17.3 ± 1.2% are obtained. The economical strategy of heteroatom modification broadens the horizon for anti-corrosion engineering in aluminum matrix composites, which is critical for the design of carbonaceous nanomaterial-reinforced composites to realize desired performances for practical applications.

Homogeneously Dispersed Graphene Nanoplatelets as Long-Term Corrosion Inhibitors for Aluminum Matrix Composites.

Deformation-driven metallurgy was implemented to prepare graphene nanoplatelet (GNP)-reinforced aluminum matrix composites with a time-dependent self-enhancement in corrosion resistance. Severe plastic deformation contributed to the sufficient brokenness, thinning, enfolding, and redispersion of GNPs, as well as grain refinement. The homogeneously dispersed GNPs showed a great corrosion inhibition mechanism in a chloride-containing environment, ascribed to the formation of a carbon-doped protective film via diffusion and chemical bonding between GNPs and the surface oxide film. Electrochemical and intergranular corrosion tests were conducted to show the enhancement of long-term corrosion resistance. First-principles calculations were performed to explore the high corrosion resistance of the carbon-doped protective film. The energy barriers of vacancy formation, Cl ingress, and charge transfer were synchronously enhanced with the addition of GNPs into aluminum matrix composites as long-term corrosion inhibitors.