Dynamic recrystallization behaviors of typical solution-treated and aged Ni-based superalloy under stepped strain rates

Dynamic recrystallization (DRX) behaviors of solution-treated Ni-based and aged superalloys under stepped strain rates were investigated by hot compressive tests and metallographic technique. The stepped strain rate means that the strain rate of specimen includes two stages, I and II. Moreover, the strain rate of stage I is larger than that of stage II for this study. The experimental results show that: (1) for the solution-treated Ni-based superalloy, the DRX fraction of deformed specimen at stepped strain rate is in between those of two specimens deformed at the constant strain rates of stages I and II; (2) however, for aged Ni-based superalloy, the DRX fraction of deformed specimen at stepped strain rate is larger those of two specimens deformed at the constant strain rates of stages I and II. It indicates that the stepped strain rate cannot accelerate the DRX behaviors of solutiontreated Ni-based superalloy, but can accelerate the DRX behaviors of aged one. The reason is that the number of likely nucleation positions for the aged Ni-based superalloy is more than that for solution-treated one when the strain rate is abruptly decreased. The law can be applied in the hot working of the studied superalloy. (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.