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.