ALLOY BEHAVIOR AND THE PHASE-EQUILIBRIUM DIAGRAM FOR THE SC-RU-RH SYSTEM .2. MELTING DIAGRAM FOR THE RU-SCRU-SCRH-RH PARTIAL SYSTEM

Microstructure, x-ray phase, and microprobe analyses have been used to gether with temperatures for the start Of melting determined by the Pi rani-Alterthum method in deriving the projection of the liquidus surfa ce and crystallization scheme for the Ru-ScRu-ScRh-Rh partial system. The liquidus surface is made up of five surfaces for the primary cryst allization of solid solutions based on ruthenium and rhodium, phases b ased on the compounds ScRu2, ScRh3, and the delta phase (a continuous solid-solution series between isostructural phases of CsCl type based on ScRu and ScRh). There are the three nonvariant four-phase equilibri a involving the liquid: L + [Rh] reversible arrow [Ru] + [ScRh3] (1640 degrees C) and L reversible arrow delta + [ScRh3] + [Ru] (1520 degree s C), which involve separate monovariant processes.