OBSERVATIONS OF STATIC STRAIN-AGING IN POLYCRYSTALLINE NIAL

Static strain-aging has been investigated in eight polycrystalline NiA l alloys. After annealing at 1100 K for 7200 a followed by furnace coo ling, high-purity, nitrogen-doped, and titanium-doped alloys exhibited continuous yielding, while conventional-purity and carbon-doped alloy s exhibited distinct upper yield points and Luders strains. Either wat er quenching from 1100 K or prestraining via hydrostatic pressurizatio n suppressed the yield points in the latter alloys, but they could be reintroduced by further annealing treatments. Yield points could be re -introduced more rapidly if the specimens were prestrained uniaxially rather than hydrostatically, owing to the arrangement of dislocations into cell structures during uniaxial deformation. Chemical analysis su ggests that the species responsible for strain-aging is interstitial c arbon. Copyright (C) 1996 Elsevier Science Limited