Fabrication of hierarchical layered structure in Zr/Ti composite via multi-step heat treatments and its effect on the mechanical properties

The strength and ductility of metallic structural materials are two pivotal properties generally considered mutually contradictory. In the past few decades, numerous heterogeneous materials have been designed and fabricated to overcome this trade-off. Biomimetic-designed hierarchical layered (HL) materials represent a promising approach. In the present study, HL Zr/Ti materials with three hierarchical levels were fabricated via multi-step heat treatments. Scanning Electron Microscopy (SEM), Transmission electron microscope (TEM), Electron Backscatter Diffraction (EBSD), Transmission Kikuchi Diffraction (TKD), and Energy Dispersive X-ray Spectroscopy (EDS) were employed to observe the evolution of the HL microstructure. The mechanical properties of the HL Zr/Ti materials were assessed through hardness and tensile tests, analyzing the influence of microstructural changes in the diffusion layer on the overall mechanical performance. Our results demonstrated that the HL structure could introduce extra strength beyond the rule of mixtures (ROM) due to multiple-scaled hetero-deformation induced (HDI) strengthening. Additionally, the refinement of the second-level layer thickness effectively inhibited crack propagation. This research provides new insights into developing multi-level HL materials with enhanced mechanical properties through cost-effective and scalable manufacturing processes.