Ti, Nb, Mo, Ta, V) that promote their formation. In body-centered cubic (bcc) alloys, strengthening via dispersion of an ultrahigh number density of NPs can be achieved by adding small quantities (≤2 wt.%) of elements (e.g. These precipitates act as nanoparticles (NPs) dispersed in a solid metallic matrix and provide effective obstacles for dislocation motion, thereby increasing yield strength, high-temperature strength, and creep resistance of numerous engineering alloys 11, 12, 13, 14. Also, most nanomaterials cannot be readily synthesized at large quantities.Īn alternative approach is to exploit the formation of nanometer-sized precipitates through a simple heat treatment. However, nanocystalline alloys are metastable, and the driving force for grain growth at moderate temperatures can be sufficient to trigger a drastic modification of their fine-scale substructure and a loss of the material’s properties of interest. This strategy has been widely used to produce nanocystalline metallic materials, in which a high number density of grain boundaries (GBs) impedes lattice dislocation motion, thereby providing strength to materials used in manufacturing, construction, energy supply and transportation 7, 8, 9, 10. Nanostructuring is a successful strategy to manipulate the internal defect landscape of metallic alloys for improving their strength while maintaining ductility 1, 2, 3, 4, 5, 6. Amongst those defects, dislocations that are linear irregularities in the crystal lattice, are the primary carriers of shear, enabling the well-known formability of metallic materials 2. Mechanical properties of materials are directly linked to their internal structural defects, and how easily they can move. Very strong materials often lack ductility, and ductile materials are usually not strong this is known as the strength-ductility trade-off 1. Designing such highly organized metallic core-shell nanoparticle arrays provides a new pathway for developing a wide range of stable nano-architectured engineering metallic alloys with drastically enhanced properties. The core-shell structure hampers particle coarsening, enhancing the material’s strength. We observe MoC and TiC nanoparticles at early precipitation stages as well as core-shell nanoparticles with a Ti-C rich core and a Mo-V rich shell at later precipitation stages. The nanoparticles form at moving heterophase interfaces during cooling from the high-temperature face-centered cubic austenite to the body-centered cubic ferrite phase. Here, by combining advanced microscopy techniques, we unveil how formation of highly regular nano-arrays of nanoparticles doubles the strength of an Fe-based alloy, doped with Ti, Mo, and V, from 500 MPa to 1 GPa, upon prolonged heat treatment. Manipulating structure, defects and composition of a material at the atomic scale for enhancing its physical or mechanical properties is referred to as nanostructuring.
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