Strain-induced solid-state coating of TWIP steel sheets with zinc

We propose the strain-induced solid-state coating process of twinning-induced plasticity (TWIP) steel with zinc, achieved through concurrent rolling of TWIP steel and zinc sheets. Our study explores the effects of strain, strain rate, and rolling temperature on the morphology and intermixing at the Zn-TWIP steel interface. We found that two simultaneous mechanisms are responsible for the formation of a joint interface between the sheets in the rolling temperature range of 100–380 °C, namely mechanical intermixing at the interface and accelerated diffusion along moving dislocations and other defects introduced during rolling. Since it is impossible to deconvolute these mechanisms, we introduced the concept of an ‘apparent diffusion coefficient’ to represent the diffusion-like mass transfer resulting from mechanical intermixing and diffusion. These diffusion coefficients were determined by primary electron energy variation method in scanning electron microscope and by energy-dispersive X-ray spectroscopy in transmission electron microscope. Notably, these diffusion coefficients were found to be higher than the grain boundary diffusion coefficients of Zn in γ-Fe, primarily due to the dynamic nature of interface microstructure formation during rolling.