Mechanical tests contribute to a better understanding of the deformation behaviour of tungsten
Special mechanical experiments have shown that the differences in deformation behaviour between cold and hot worked or unworked tungsten are due to a change in microstructure during working.
The deformation behaviour of tungsten (W), intended for use in highly stressed components of a fusion reactor, is highly temperature dependent. Below a transition temperature, W fails brittle and unpredictably under load. Above this transition temperature, W is plastically deformable and its failure can be predicted in advance. The more a W-based material is deformed during manufacture, the lower its transition temperature will be. A possible reason for this behaviour could be differences in the so-called rate-controlling deformation mechanism. This refers to the mechanism, which is slowest during plastic deformation and therefore controls the speed of the overall process. Special mechanical experiments (see Figure) have shown that the so-called kink pair mechanism determines the rate of plastic deformation at temperatures above the transition temperature in both strongly and weakly deformed materials. This result suggests that the shift in transition temperature is due to the change in microstructure of W during manufacture. The related work has recently been published in the prestigious Philosophical Magazine [1].