During the past contract year, new results have been obtained in two major project areas:(I) surface oxide softening and solute gradients in niobium and tantalum, and (2) mechanical properties of Nb-H and Nb-D alloys. The important results include:(a) observation and characterization of an extremely large softening and ductilizing effect of body-centered cubic metals (niobium and tantalum) by application of thin (500-1000Å) oxide films coupled with injection of a high density of mobile dislocations;(b) determination of the relative strengthening and ductility changes caused by hydrogen and deuterium in niobium.
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