HYPERCOOLING OF COMPLETELY MISCIBLE ALLOYS

Calorimetric measurements and undercooling investigations were perform ed on the high-melting, completely miscible binary systems (Go, Ni, Fe )-Pd. The alloys, characterized by phase diagrams with concavous liqui dus and solidus lines, exhibit heat-of-fusion values considerably lowe r than calculated assuming ideal solution behavior. As a consequence, these metallic systems offer the possibility to achieve the hypercooli ng regime at a reduced extent of undercooling. Investigations on the u ndercoolability of the liquid alloys indicate the surmounting of the c alculated hypercooling limit. Time-resolved radiation thermometry expe rimentally proved the appearance of complete isenthalpic solidificatio n. Metallographic investigations of samples solidified from different levels of undercooling revealed the corresponding stages of microstruc tural evolution. (C) 1996 American Institute of Physics.