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

► Amorphous phase separation was found in Pd40 + 0.5xNi40 + 0.5xP20 − x BMG with x = 1 to 3.5. ► Amorphous phase separation was absent in Pd40 + 0.5xNi40 + 0.5xP20 − x BMG with x = 0 to 1. ► The phase-separated Pd40 + 0.5xNi40 + 0.5xP20 − x BMG with x = 1 to 3.5 obey the lever rule. ► The experimental results suggest the existence of a metastable liquid/amorphous miscibility gap in undercooled Pd-Ni-P melts.