The influence of processing and texture on the grain boundary character distribution of an austenitic Ni-30Fe alloy

The effect of processing route (casting versus iterative recrystallisation) on the texture and grain boundary network characteristics (i.e., population, plane orientation and connectivity) of an austenitic Ni-30Fe alloy has been determined. The processing route determined the mechanism of microstructure evolution (i.e., nucleation and growth), and this influenced the overall texture and grain boundary network characteristics. In material processed by iterative recrystallisation, the microstructure was dominated by a well-connected network of E3 and E9 boundaries with minimum energy grain boundary plane orientations. However, in the cast material, the E3 and E9 boundaries had lower relative areas and were more isolated, suggesting they formed through the accidental impingement of randomly oriented nuclei during solidification. As a result, the E3 and E9 boundaries were less likely to be terminated on the lowest energy planes and more incoherent E3 and E9{221} symmetric tilt grain boundaries were formed due to the change in the arrangement of triple junctions. In the two cast microstructures, the grain boundary misorientation angle distribution was strongly correlated with the texture. For the material with a strong theta-fibre (i.e., 001//ND), the misorientation angle distribution was flat and had a maximum at 45 degrees, an expected result of limiting the grain boundary misorientations the [100] axis.