C-COMPONENT DISLOCATIONS IN SUBBOUNDARIES IN A ZR-2.5 WT-PERCENT NB ALLOY

The nature of α-α sub-boundaries containing 〈c〉-component dislocations in Zr-Nb alloys has been studied by electron microscopy. The character of the sub-boundaries is thought to be established by the extrusion operation. The boundaries are composed of 〈a〉 and 〈c〉 dislocations forming a variety of tilt, twist and mixed boundaries. The α-α boundaries are closely linked with the α-β interface structure in extruded or β-quenched alloys and are only formed during dissolution of the β particles. Rotation of 〈a〉-tilt boundaries is localized around 〈c〉 dislocations forming a step structure. The configuration of 〈c〉-dislocation steps is believed to be a fault bounded by two 1 2〈c〉partial dislocations. The importance of these dislocation arrays in understanding the strengthening mechanisms and irradiation growth behaviour of the alloy is emphasized. © 1990.