Measuring the brittle-to-ductile transition temperature of tungsten-tantalum alloy using chevron-notched micro-cantilevers

EBSD mapping of cantilever samples

An Oxford based research team has conducted a series of high temperature micro-fracture tests of an industrial grade W-1%Ta alloy, from room temperature up to 700 degrees celsius, utilising chevron-notched micro-cantilevers.

As the temperature rose, the gradual increase of conditional fracture toughness was measured.  A microscale brittle-to-ductile transition temperature (BDTT) was found at ~600 degrees celsius, being slightly higher than macroscopic three-point bending tests from the same materials.  This contradicts most literatures for pure tungsten, which show a much lower micro-BDTT. 

The results suggest the BDTT is independent of the specimen size, and the higher micro-BDTT is due to the tantalum in the alloy.