Nitrogen-induced dynamic strain aging in a biomedical-grade Co–Cr–Mo alloy

The present study examined plastic deformation behavior of a biomedical-grade Co–29Cr–6Mo (wt.%) alloy at intermediate temperatures, focusing on dynamic strain aging (DSA) induced by nitrogen doping (0.2 wt.%). The compression tests were performed at strain rates in the range of 10−4 to 10−1 s−1 at temperatures between room temperature and 1073 K. Gliding of Shockley partial dislocations bounding stacking faults played a dominant role in the plastic deformation over a wide temperature range. The nitrogen-associated DSA resulted in enhanced in-grain lattice distortions even when there was little macroscopic serrated flow. Shear band formation was identified after the lamellar structures developed, in spite of quite small macroscopic strain (5% in height reduction). Cr–N short-range ordering can be responsible for the observed DSA.