Atomic scale insights into the rapid crystallization and precipitation behaviors in FeCu binary alloys

Molecular dynamics (MD) simulations are employed to probe the crystallization and precipitation behaviors in FeCu alloys. The alloys will undergo liquid phase separation at high temperature, after which α-Fe nucleates preferentially, then metastable Cu solid solutions in BCC lattice (ε` phase) nucleate and transform into FCC structure (ε-Cu) via martensite phase transformation immediately. Reversible order-disorder transformation behavior is observed during time-consuming crystallization process of ε-Cu. Interestingly, the ε`-Cu with only approximately three atomic layers in thickness exists stably near BCC/FCC α/ε interface at room temperature, following the Kurdjumov–Sachs (K–S) orientation relationship. The lower nucleation energy and interface energy are the reasons for the existence of abnormal ε`-Cu at the interface. It is also found that the composition and cooling rate play key roles on the final phase structure. The alloys can be fully crystallized upon cooling down at a rate of 0.1 K/ps.