| Abstract Scope |
Solute segregation to grain boundaries in nanocrystalline alloys can direct disordering transitions and the development of a confined amorphous phase, with pronounced implications for thermal stability, mechanical behavior, and sintering. While the property benefits that these amorphous phases can confer has been established, the kinetics of ordering and crystallization from these confined defect phases are not understood. Here, we study segregation-engineered nanocrystalline binary and ternary alloys within the Al-X-Z (X=Ni, Z=Y, Ce) system that host amorphous defect phase transitions, and assess the evolution of microstructure and resulting mechanical behavior. We demonstrate that exceptional thermal stability and mechanical strength arise by promoting pre-melting events at sub-solidus temperatures followed by subsequent cooling to the glassy state. Ultrafast differential scanning nanocalorimetry combined with electron microscopy reveals the role of cooling rate on the solidification products from the interface disordered state, a path-independence of the subsequent disordering temperatures, and critical cooling rates. |