Recrystallisation temperature of tungsten as a function of the heating ramp

The recrystallisation temperature of tungsten filaments as a function of the heating ramp is investigated. The Study is performed on a series of lamps with non-recrystallised filaments. The recrystallisation temperature is determined via two different analysing methods: (1) Micro-structure by analysing the cross sections of the filament. (2) Change in the resistance of the filament measured at room temperature (non-destructive). These analyses are performed as a function of the annealing temperature and as function of various ramps. The results for the recrystallisation temperature of the two methods are compared. The recrystallisation process of tungsten is described with a thermal activation process. We have found a relatively high activation energy of 800-1000 kJ/mole. The activation energy of the recrystallisation process of tungsten is discussed further. (C) 2005 Published by Elsevier Ltd.