Hierarchical Morphologies in Vapor and Laser Deposited Immiscible Alloys

An overview of the microstructure evolution in immiscible alloys processed via either physical vapor deposition (PVD) or laser direct metal deposition (DMD) will be presented. Model systems focused on face-centered cubic (FCC) and body-centered cubic (BCC) metals will be highlighted. Experimental results will be integrated with atomistic and phase-field modeling to develop microstructure morphology maps in terms of processing parameters. The hierarchical structures form during deposition via phase separation and self-organization processes across multiple length scales from a nanometer to a micrometer. In both PVD and DMD, hierarchical microstructure can form under certain processing window involving both equilibrium, e.g., fcc-Cu, bcc-Mo, bcc-Fe, and metastable phases, e.g., bcc-Cu, fcc-Mo, fcc-Fe. In some cases, up to four phases co-existed in far-from-equilibrium processed binary concentrated alloys. The hierarchical architecture in these microstructures is shown to produce unusual mechanical properties such as high strength and high plastic deformability.