The effect of Nb solute and NbC precipitates on dynamic and metadynamic recrystallisation in Ni-30Fe-Nb-C model alloys

Dynamic and metadynamic recrystallisation behaviour of Ni-30Fe-Nb-C model alloys during plane strain compression was investigated by optical and electron microscopy. The dynamically recrystallised grains were primarily located at the pre-existing grain boundaries with few additional new recrystallised grains in the prior grain interior. A limited nucleation of recrystallised grains at >400 nm size NbC particles was also evident. On the other hand, smaller semi-coherent particles (~10-150 nm) severely inhibit the dislocations rearrangement and subgrain boundary mobility, thus leading to sluggish or even suppressed dynamic and metadynamic recrystallisation. These smaller NbC particles maintained cube-on-cube orientation relationship with austenite matrix (001)NbC||(001)γ, [001]NbC||[001]γ. The shape of the NbC particles changes from nearly ellipsoidal to octahedral followed by hexagonal and tetra-kai-decahedral by truncation of {111} facets by {001} ones.