A metastable liquid state miscibility gap in undercooled Pd–Ni–P melts

Recently, phase separation was found to occur in Pd41.25Ni41.25P17.5 bulk metallic glasses (BMG), which have a negative heat of mixing among the constituent elements. In this work, Pd40 + 0.5xNi40 + 0.5xP20 − x BMG with x = 0 to 3.5, were studied for amorphous phase separation. It occurs for x ≳ 1, but absent for x ≲ 1. In addition, in phase-separated specimens, the characteristic sizes or wavelengths of the decomposed phases were measured. It was found that they obey the lever rule. The experimental results suggest the existence of a metastable liquid/amorphous miscibility gap. Its origin is attributed to unique short range orders in the undercooled Pd–Ni–P melts.