THE INFLUENCE OF DISLOCATIONS ON ELECTRICAL-RESISTIVITY ANOMALIES IN PALLADIUM ALLOYS

Palladium-tungsten and palladium-molybdenum alloys are shown to have a higher electrical resistivity after annealing than in the cold-worked condition, an effect associated with the development of short-range o rder at elevated temperatures. Electrical resistance and microhardness measurements, together with transmission electron microscopy, are use d to investigate the evolution of dislocation structures and their rel ationship to resistance changes due to annealing. It is shown that alt hough the introduction of dislocations into annealed alloys has the ef fect of destroying the short-range order present, the presence of disl ocation structures after cold deformation enhances solute diffusion at low annealing temperatures sufficiently for short-range order to deve lop. It is concluded that short-range order is an energetically stable configuration, developing with relative ease in formerly cold-worked alloys both at high temperatures and at low temperatures in the presen ce of dislocations.