effect of cold rolling and first precipitates on the coarsening behavior ofγ″-phases in inconel 718 alloy.pdfVIP

International Journal of Minerals, Metallurgy and Materials Volume 23, Number 9, September 2016, Page 1087 DOI: 10.1007/s12613-016-1326-9 Effect of cold rolling and first precipitates on the coarsening behavior of γ″-phases in Inconel 718 alloy Jing-ling Zhang, Qian-ying Guo, Yong-chang Liu, Chong Li, Li-ming Yu, and Hui-jun Li State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science Engineering, Tianjin University, Tianjin 300354, China (Received: 1 April 2016; revised: 4 June 2016; accepted: 7 June 2016) Abstract: The coarsening behaviors of γ″-phase particles in Inconel 718 alloy aged at 750, 800, and 850°C were investigated by scanning electron microscopy (SEM). Detailed observations and quantitative measurements were conducted to characterize the coarsening behavior of the γ″-phase under various aging conditions. The experimental results indicate that the existence of the δ-phase retards the formation and coarsening of the γ″-phase, without influencing its final particle size or amount. Moreover, when cold rolled with a reduction of 50%, the dimensions of the γ″ particles in Inconel 718 alloy decrease with increasing aging time. Furthermore, the coarsening behavior of the γ″-phase in the Inconel 718 alloy after a normal aging treatment (sample A) and that of the primary δ-phase (sample B) follow the Lif- shitz–Slyozov–Wagner (LSW) diffusion-controlled growth theory; the thus-obtained activation energies for the γ″-phase are 292 kJ·mol−1 and 302 kJ·mol−1, respectively. Keywords: nickel base superalloys; cold rolling; precipitates; coarsening 1. Introduction The growth of precipitated particles strongly affects the long-term mechanical properties of precipitation-hardened Inconel 718, which is a nickel-ba