Lalvani, Himanshu; Rist, Martin and Brooks, Jeffery W.
Effect of Delta Phase on the Hot Deformation Behaviour and Microstructural Evolution of Inconel 718.
Advanced Materials Research, 89-91 pp. 313–318.
In order to investigate the influence of δ-phase precipitation during high temperature forging of Inconel 718, hot axi-symmetric compression tests have been performed on specimens with two distinct initial microstructures: i) as-received material containing a dense population of δ precipates at grain boundaries and along intragranular slip planes, and ii) material solution-treated
to dissolve the δ phase. Results indicate that the presence of δ leads to a slight increase in peak stress and a proportionately greater post-peak reduction in flow stress, as compared to solution-treated material. For both types of microstructure flow softening is associated with grain
refinement, but in different ways: in δ-free material conventional dynamic recrystallisation leads to the formation of new grains, whereas the presence of plate-like δ appears to cause the mechanical break-up and segmentation of prior grains.
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