Various annealing on nickel coated tungsten wires have been performed
and have determined a critical annealing temperature of 1000 degrees C
. Above this temperature a phenomenon of recrystallization is produced
by an intergranular diffusion of nickel in the fibrous microstructure
of the tungsten. Tensile tests have shown the brittle feature of this
microstructural transformation and also the effect of the doping with
potassium on tungsten wires. This recrystallisation is related to a p
henomenon called D.I.G.M. (Diffusion Induced Grain boundary Migration)
but our system seems to be a particular case because it needs to find
another hypothesis with respect to the driving forces and mechanisms
to explain this phenomenon of recrystallization.