SOME OBSERVATIONS ON THE COLD-DRAWING AND ANNEALING BEHAVIOUR OF NICKEL CONTAINING A DISPERSED PHASE OF THORIA *

Abstract

Consideration is given to the effects of cold drawing and subsequent heat-treatment on the mechanical properties of extruded nickel-2·5 vol.-% thoria rod, prepared from mechanically mixed nickel and thoria powders. It is shown that the extruded alloy may be reduced > 80% in area using no intermediate annealing treatments, with significant beneficial effect on the room-temperature tensile strength and on the stress-rupture properties at 815°C. The cold-drawn alloy has marked resistance to annealing at temperatures in excess of 1000°C. Comparative data are given for pure nickel. The effects of cold drawing and subsequent heat-treatment on the structure of the alloy are then discussed with reference to changes in the dispersed phase and in the matrix revealed by electron microscopy and by X-ray diffraction studies.

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