Interstitial and Substitutional Solution Hardening and Softening in BCC Metals( + )

Abstract

We have used the phenomenon of surface film softening of bcc metals to examine solid solution hardening and softening in bcc alloys which contain either a preponderance of edge dislocations (coated materials) or screw dislocations (uncoated materials). Experiments performed on Nb-base alloys illustrate that: (1) the difference in hardening by substitutional solutes in the presence of edge dislocations versus screw dislocations is smaller than can be accounted for by theories of solution hardening; (2) solid solution softening is observed in both the edge-containing and screw-containing ternary alloys; (3) interstitial solutes harden greater in the presence of edge dislocations than screw dislocations.