Micro-mechanism of mechanical enhancement of NiTiAl amorphous-crystal nanomultilayers

Abstract

Amorphous-crystal nanomultilayers (ACNMs) exhibit outstanding mechanical properties, but the micro-mechanisms responsible for the enhancement of their mechanical performance remain incompletely understood. Molecular dynamics (MD) simulations were performed on the tensile processes of NiTiAl ACNMs to examine the microstructure evolutions during deformation in crystals, amorphous (MGs), and crystal-amorphous interfaces (CAIs). ACNMs increase in strength and decrease in plasticity with decreasing interface spacing. The MGs layer can accommodate larger strains. The intense competition among shear transformation zones (STZs) mitigates strain localization in MGs and boosts the plasticity of ACNMs. In the crystal layer, the main plastic deformation mechanism is that FCC clusters are disrupted and converted into other MGs clusters. As the interface spacing decreases, the geometrically constrained dispersion of STZs boosts material strength. The self-developed Largest Standard Cluster Analysis (LaSCA) method was employed to accurately depict the microstructure evolution of CAIs. The CAIs are responsible for strain transmission and induce dislocation accumulation in their vicinity, leading to localized strain. This study elucidates the microstructural changes in ACNMs during tensile deformation, offering insights for optimizing their mechanical properties through interface spacing design.