Temperature dependence of the flow stress in Ir3Nb with the L12 structure

The temperature dependence of the strength of Ir3Nb with the L12 structure has been investigated using compression tests between -196 and 1200 degrees C. Below room temperature, the strength decreased with increasing temperature. An anomalous temperature dependence of the strength was observed between room temperature and 800 degrees C; the strength increased with increasing temperature. Above 800 degrees C, the strength again decreased with increasing temperature. The Burgers vectors of the dislocations in samples deformed at room temperature, 600 degrees C and 1200 degrees C were investigated using both dark-field weak-beam imaging techniques and the equithickness fringe method with a transmission electron microscope. The a<110>-type superdislocations dissociated into (a/3)<211>-type super partial dislocations bounding a superlattice intrinsic stacking fault in the samples deformed at 600 and 1200 degrees C. Dissociation of the antiphase boundary bounding dislocation was not observed at any of the deformation temperatures.