The concealed solid-solid structural phase transition of Fe70Ni10Cr20 under high pressure

The structural evolution of melts during solidification under high pressure is important for understanding their properties. In this paper, the phase transition of Fe70Ni10Cr20 during rapid cooling under high pressures ranging from 50 to 100 GPa was investigated by molecular dynamics simulation. The structural evolution was quantified in terms of the average potential energy, the pair distribution function, and the Largest Standard Cluster Analysis (LaSCA). A potential energy curve can only reveal a liquid-solid transition (LST), but LaSCA unveils that LST always results in a meta-stable bcc state that then converts to fcc/hcp crystals through a concealed solid-solid structural transition (SST). The crystallization of Fe70Ni10Cr20 melts can be a multi-intermediate-state transition (MisT) or a single-intermediate-state transition (SisT). The selection of SisT and MisT is discussed based on structure and energy. In addition, identified by our software a double hexagonal close-packed phase can be observed in a probability ∼25% of all simulated samples. These findings will enrich the solidification theory.