A tungsten rhenium filament for an operation temperature is between 2900 and 3200° K. The filament comprises an aluminum-potassium-silicon (AKS) additive. The filament has a grain microstructure comprising substantially exclusively elongated interlocking grains with a Grain Aspect Ratio (GAR) not less than 12. The rhenium content of the filament is between 0.2-0.4percent by weight.
A method for manufacturing a rhenium-tungsten filament comprises the following steps. An AKS doped tungsten-rhenium alloy powder is prepared with a rhenium content of 0.2-0.4% by weight. The alloy powder is pressed and presintered, and thereafter sintered with direct current. A rhenium-tungsten filament is formed, which has a metalstable crystal structure. The filament is annealed below the recrystallisation temperature, and recrystallised above the crystallization temperature.
Tungsten rhenium filament can be used in lamps, such as halogen bulb.