Abstract: High strength and high plasticity have been achieved recently in crystalline-amorphous dual-phase composites with size optimization. However, the effect of phase space distribution has not been revealed. This work investigates the mechanical behaviors of Fe-SiOC dual-phase nanocomposites, focusing on understanding how amorphous continuity affects plasticity. The co-sputtered Fe-SiOC nanocomposite is comprised of nanocolumnar Fe and interconnected amorphous SiOC grain boundaries (GBs), and the 800 °C annealed nanocomposite displays nano-equiaxed Fe embedded with dispersed amorphous SiOC nanoparticles at GBs. Both the as-deposited and annealed Fe-SiOC nanocomposites show typical heterostructure and high yield strength, which are ∼2.7 GPa and ∼2.6 GPa respectively, but obviously different plasticity. The as-deposited sample displays homogeneous plastic deformation up to a strain of 23% and a slight strain-hardening capability, which should be attributed to heterostructure and the strong geometry constraint effect of interconnected amorphous GBs on adjacent columnar, promoting the co-deformation between amorphous SiOC and nanocolumnar Fe. In contrast, although the annealed sample shows uniform plastic at the initial stage of deformation because dispersed amorphous nanoparticles act as plastic flow units, the discontinuous amorphous nanoparticles have limited geometry constraints to adjacent nanograins, resulting in the nucleation and propagation of shear band in nanocrystalline Fe with the increase of strain. Our work shows that the continuous amorphous phase has a more significant improvement in the plasticity of nanocrystalline metals compared to the dispersed amorphous phase.

Key words: Plasticity, Crystalline-amorphous, Dual-phase, Nanocrystalline