Dislocation structures in be₁₂nb after high-temperature deformation

Abstract

Dislocation structures and faults in vacuum-hot-pressed Be₁₂Nb have been examined after compressive deformation at 1200[ddot]C. Both perfect and partial dislocations were observed in the deformed polycrystalline material. Most dislocations were found to be partials bounding planar faults in the grains characterized. Slip systems for individual partial dislocations were identified as ½ (101]{121), ½⟨101]{101) and ½⟨100]{011). Several faults were bounded by identical ½⟨101] or ½⟨100] dislocations. Extended planar {101) faults created by emission of a single ½⟨101] partial from grain or twin boundaries were seen in both the vacuum-hot-pressed and deformed conditions. Perfect dislocations in the deformed microstructure were ½⟨101]{101) and ½⟨111]{121), with some evidence for ⟨001]{100] and ⟨101]{101) dislocations. The partial dislocations are related to a possible phase transformation from Be₁₂Nb to Be₁₇Nb₂ which may enhance dislocation mobility and promote high-temperature deformation.