Effect of processing parameters on grain boundary modifications to alloy Inconel 718

The fraction of special low Σ CSL grain boundaries, hardness, and grain size were determined for thermo-mechanically processed alloy 718 1 samples. Processing consisted of sequential cycles of straining by cold rolling under 2.5%, 5%, 7.5% strain, followed by annealing at 1020 °C for 10 min. Several interesting relationships between processing parameters and grain boundary character distribution were observed. It was established that it was possible to at least double the fraction of special boundaries, Fsp, depending on the strain and number of cycles combinations used. The highest Fsp values appeared to be associated with a higher number of cycles as the strain values increased from 2.5% to 7.5%.