Multiscale phase transitions of Cu and Fe in an additively manufactured Cu-Fe Alloy under high-Pressure.*

A state of the art custom-built direct-metal deposition (DMD) based additive manufacturing (AM) system at the University of Michigan was used to manufacture 50Cu-50Fe alloy with tailored properties for use in high strain/deformation environments. Subsequently, we performed the first high-pressure compression experiments to investigate the structural stability and deformation of this material. Our work shows that the alpha (BCC) phase of Fe is stable up to ~16 GPa before reversibly transforming to HCP, which is at least a few GPa higher than pure bulk Fe material. Furthermore, we observed evidence of the transition of Cu nano-precipitates in Fe from a well-known FCC structure to a metastable BCC phase, which has only been predicted via density functional calculations. Finally, the metastable FCC Fe nano-precipitates within the Cu grains show a modulated nano-twinned structure induced by high-pressure deformation. The results from this work demonstrate the opportunity in AM application for tailored functional materials and extreme stress/deformation applications.