Nonlinear diffusion, bonding, and mechanics of the interface between austenitic steel and iron

We investigate the atomic diffusivity and mechanics of the interface between bulk austenitic steel (fcc structure) and bcc iron at various temperatures and strain rates using molecular dynamics simulations. We adopt the system of Fe₇₄Cr₁₆Ni₁₀ corresponding to 316L steel as a representative model of austenitic steels, denoted as FeCrNi. We find that the compressive strength of the FeCrNi/Fe system decreases by 44.3% and the corresponding strain decreases by 7.2% when the temperature increases from 1500 K to 1800 K. The temperature enhances nonlinearly the diffusion of interfacial atoms and improves the cohesion of FeCrNi/Fe by forming a thicker diffusion layer, of which the thickness increases by 56.3% when the temperature increases from 1600 K to 1700 K, and by nearly 48% when the temperature increases from 1700 K to 1800 K. However, the thickness of the diffusion layer decreases by 33.3% when the compressive strain rate increases from 1 × 10⁹ s^-1 to 4 × 10⁹ s^-1. Our study sheds light on the atomistic mechanism of the interfaces of bimetals and might be helpful in optimizing the process of the fabrication of bimetal composites.