A solid-state diffusion bonding steel-titanium interface is designed, revealing the formation of continuous micro–nano-sized FCC-TiC grains at the interface. Carbon atoms occupying the octahedral interstice in the FCC-TiC lattice are directly observed. The study shows that FCC-TiC formation is driven by carbon diffusion and titanium phase transformation, providing new insights into atomic-scale regulation of titanium carbide.
Abstract
Titanium carbide (TiC), which typically forms at the solid-state diffusion interface in steel–titanium (Ti) composite structures, significantly influences steel–Ti interface bonding. However, the atomic-level formation mechanism of this carbide remains unclear. Herein, the TiC crystal structure and formation mechanism are investigated through experiments involving TA2 pure Ti and 45# carbon steel under solid-state diffusion conditions. Analysis of the solid-state diffusion behavior between the steel and Ti, based on selected area electron diffraction, reveals the formation of a continuous micro–nano TiC layer with a balanced (FCC) crystal structure on the substrate near the Ti side of the interface. Using the integrated differential phase contrast technique, occupation of the octahedral interstices in the FCC-TiC lattice by carbon (C) atoms is confirmed for the first time. Additionally, it is suggested that C diffusion and phase transformation jointly induce the FCC-TiC crystal phase transformation under hot-pressing conditions. Finally, the atomic-scale TiC formation mechanism is elucidated. The findings of this study may guide the design and development of high-performance materials with unique properties for aerospace equipment manufacturing.
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