The Scale of Devitrification in Bulk Metallic Glasses

摘要

Partial or complete devitrification can improve the properties of metallic glasses, but the microstructural scale is important. The crystals can be on the scale of nanometres to millimetres. This great range, useful for tailoring properties, is a challenge to explain. Factors favouring nm-scale crystallization include: amorphous phase separation, inoculation, low crystal-liquid interfacial energy, quenched-in nuclei, and linked-flux effects. Metallic glasses are compared with oxide glasses. While fragility is often used to compare different glass-forming systems, it has limited utility in interpreting the scale of devitrification. The focus is on the relative mobilities of different atomic species. A large spread in mobility, typical in early-late transition metal glasses but not in metal-metalloid glasses, favours nanocrystallization in bulk metallic glasses.