Dislocation substructure in Ta-Re-N alloys deformed at 77 K

Abstract

High purity Ta, Ta-Re, and Ta-Re-N alloy single crystals were deformed in tension at 77 K, and the resulting dislocation arrangements were studied by transmission electron microscopy. Re and N have similar effects on the dislocation substructure. Alloying increases the fraction of primary screw dislocations at the expense of debris, tangling, and secondary dislocations. For a given increment in yield stress, Re causes much larger changes in the substructure than N. The substructures observed in Ta-Re-N alloys are similar to those in Ta-Re alloys, even though ternary alloys exhibit alloy softening and binary alloys exhibit alloy hardening. These observations can be explained in terms of the different intrinsic mobilities of edge and screw dislocations, the different interactions which substitutionals and interstitials have with edge and screw dislocations, and the large differences in concentration of substitutional and interstitial solutes.