Deformation Mechanisms in Be₁₂X Compounds

Abstract

Dislocation structures have been examined, and active slip systems identified, in Be₁₂Nb after compressive deformation at 20, 800, 900,1000 and 1200°C. A large number of slip systems are active at 1200°C, but these decrease significantly at temperatures below 1000°C. Dislocation structures at low temperatures are limited to 1/2<101]{101) partial dislocations either paired or creating isolated planar faults. Significant ductility is not observed until 1200°C when a second type of partial dislocation, 1/2<100]{011) is present. Dislocations observed in the body-centered tetragonal Be₁₂X compounds (where X can be Nb, Ta, Mo, V, Fe etc.) have been modelled atomistically using molecular dynamics. Simulations corroborate the stability of these dislocation systems and indicate that the stacking faults associated with these partial dislocations have very low fault energy.