Phase Equilibria in an Ordering Alloy System

Abstract

The equilibria between phases in platinum alloys containing 42, 48, and 54 atomic percent cobalt were determined at temperatures below 1000°C. This system of alloys exhibits an order-disorder transition analogous to that for CuAu. A temperature range in which ordered and disordered phases coexist in equilibrium was determined for each alloy. These data were incorporated in the phase diagram. The Co-Pt system is the first ordering alloy system in which it has been shown that this reaction is a true phase transformation contrary to the prevalent concepts of the phenomena.