Room temperature strengthening mechanisms in a Co-Cr-Mo-C alloy

The various contributions to the flow stress at room temperature of a cast Co-Cr-Mo-C alloy were identified using transmission electron microscopy. These alloys are used as surgical implant materials. It was concluded that stacking fault intersections and twins make the largest contribution to the work hardening behaviour of the as-cast Co-Cr-Mo-C alloy. The stacking fault intersection was modelled as a form of dislocation dipole, from which the stress interaction with slip dislocations was estimated. In the case of twin-slip interactions, it is suggested that the incorporation of the slip dislocation into the twin is governed by the reaction 1/2[110](_-11-1)→1/6[141](_-1-15)+1/6[2-1-1]_{coherent Twin Boundary (111)} A nucleation model for twinning in alloys with very low stacking fault energy is also proposed.