Effect of Original Microstructure on the Hot Compression Behavior of Superalloy 718
Hot compression tests at different temperatures and strain rates were performed on superalloy 718 annealed at 1100 °C for 30 min as well as 950 °C for 30 min in order to investigate the effect of the original microstructure on the hot deformation behavior. The results show that the δ phase precipitated on the grain boundaries of superalloy 718 prior to hot deformation leads to a decrease of the flow stress, which can be attributed to the drop of the matrix strength. The activation energy (Q) for hot deformation of the fine-grained material with δ phase on the grain boundaries is determined to be 381 kJ/mol, which is much lower than that of the coarse-grained material without δ phase (472 kJ/mol). It is suggested that the initial δ phase precipitated on the grain boundaries of the annealed material affect the thermal activation process of hot deformation for superalloy 718, resulting in the decrease of activation energy.
Yu Zhou, Shan-Tung Tu and Xishan Xie
Y. Wang et al., "Effect of Original Microstructure on the Hot Compression Behavior of Superalloy 718", Key Engineering Materials, Vols. 353-358, pp. 515-518, 2007