On low temperature plastic instability in pure niobium single crystals

Abstract

Niobium single crystals of good purity and of various orientations were tested in tension between 2·17 and 17°K. At temperatures below about 12°K. heterogeneous deformation takes place. It seems possible to explain this behaviour by the local heating due to moving dislocations.

The thermal origin of this instability is deduced by comparing stress–strain curves performed at 2·17°K in the normal and superconductive states. The influence of purity and temperature on thermal softening is discussed.