Applicability of JMAK-type model for predicting microstructural evolution in nickel-based superalloys

The question of the prediction of microstructural transformation over a wide range of temperatures and strain rates is important for the simulation of industrial hot forging processes, especially those focused on net-shape forging. A large spectrum of microstructural models, from the simplest empirical and phenomenological forms to more complex physics-based ones were developed during last century; some of them were embedded into commercial software. However, in spite of some successful implementations, the problem of the robust prediction of microstructure development in the real multi -operational industrial processes remains in general unsolved. Complex models often suffer due to high computational cost, possible mathematical instability and ill-defined calibration techniques. Simple models are easier for practical use but, due to the nature of the simplifying assumptions, have a limited range of validity, which is almost never specified. JMAK-type models are one of the examples of the relatively simple mathematical model forms popular for the description a number of metallurgical processes. One of them is recrystallisation, which is one of the dominating mechanisms in the hot working of metals. In this paper, the wellknown family of 718 nickel-base superalloys and a range of forging trials of different levels of complexity were used to analyse the applicability of the JMAK-type models. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on the Technology of Plasticity.