TENSILE TEST ON TUNGSTEN
How does fracture occur when tungsten is subjected to tensile test ?
The deformation behaviour and fracture modes of tungsten single crystals have been studied as a function of orientation. The orientation of the crystals was varied systematically around the edge of the unit stereographic triangle, and tensile tests were carried out at 77° and 295°K. The stress-strain curves showed considerable variation with orientation and only crystals of orientation close to [110] showed discontinuous yield behaviour. Deformation occurred purely by slip but the proportional limit did not obey a critical resolved shear stress criterion. The tensile behaviour has been rationalised in terms of the number of operative slip vectors. Specimens of orientation [100] were tested over a temperature range from 20° to 465°K. The proportional limit increased rapidly at temperatures below 250°K. The specimens always necked before fracture, even at 20°K, indicating that tungsten single crystals are not inherently brittle
Equipment and Methods :
- Fracture mechanical tests are conducted in three-point bending over a wide temperature range of 150°C to 1000°C at varied loading rates
- High temperature experiments are performed in a universal testing machine equipped wit a vacuum furnace
- Fractographic investigations by SEM and EBSD to gain insight into the responsible fracture mechanisms and the influence of the microstructure on the fracture process
GRAPHS SHOWING TENSILE TESTS:
MICROSCOPIC IMAGES OF FRACTURE OF TUNGSTUN:
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