FORMATION, STABILITY AND STRUCTURE OF PALLADIUM-SILICON BASED ALLOY GLASSES

Pd-Si based alloy glasses were formed by quenching melts to room temperature at various cooling rates. Certain ternary alloys of Pd-Au-Si, Pd-Ag-Si and Pd-Cu-Si formed glasses with thicknesses greater than 1 mm at cooling rates as low as 102 °C/sec. The glass-liquid transition was exhibited thermally by both binary and ternary alloys. The stability, ease of formation and glass transition temperature, Tg, of the glasses were all increased by the replacement of Pd with small concentrations of the noble metals. At a heating rate of 20°C/min, bulk glasses of certain ternary alloys could be heated 40°C above Tg without appreciable crystallization. The rheological manifestations of the glass transition was observed qualitatively for certain of the ternary alloys. When held at temperatures above 300°C but below Tg, the alloys crystallized to homogeneous f.c.c. solutions. Electron transmission microscopy of thin sections showed that when heated above Tg the amorphous alloys phase separated. An amorphous alloy of Pd0.78Au0.06Si0.16 phase separated into interconnected Pd-Au rich and Si rich amorphous phases in which the Si rich phase attained a high degree of order. An amorphous Pd0.80Si0.20 alloy phase separated into spherical Pd rich particles, which were crystalline at the time of observation, embedded in a silicon rich matrix. The electrical resistivity of the alloys in their various states were also measured. © 1969.