Effect of delta phase on the hot deformation behaviour and microstructural evolution of inconel 718

Lalvani, Himanshu M. and Rist, Martin A. and Brooks, Jeffery W. (2010) Effect of delta phase on the hot deformation behaviour and microstructural evolution of inconel 718. Advanced Materials Research, 89-91 (THERME). pp. 89-91. ISSN 1022-6680

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Abstract

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 solutiontreated 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.