Strain induced epsilon-martensite in a Co-Cr-Mo alloy: grain size effects

In this work, compressive plastic straining was applied to a fine and a coa rse grain sized (d = 10 and 117 mu m, respectively) cobalt alloy. Although a strain induced (SIT) martensitic transformation occurred at both grain si zes, volume fractions of SIT epsilon-martensite reached values of 0.5 in th e fine grained alloy in contrast with only 0.05 in the alloy with a d = 117 mu m In addition, the alloy strength and ductility were influenced by grai n size. In particular, the alloy compressive strength increased from 2141 t o 2424 MPa whereas the alloy ductility increased from 0.295 to 0.41. It was found that the exhibited increase in alloy ductility was directly related to the alloy ability to remove the build-up of stress incompatibilities thr ough the SIT martensitic transformation. (C) 1999 Elsevier Science B.V. All rights reserved.