Microstructural Evolution and an Improved Dynamic Recrystallization Kinetic Model of a Ni-Cr-Mo Alloy in Hot Deformation

Abstract

Microstructural evolution and dynamic recrystallization (DRX) behaviors of a Ni-Cr-Mo alloy were researched utilizing hot compressive experiments. The changed features of dislocation, subgrain and grain structure correlating to forming parameters were examined by transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). Results illustrate that the consumption of dislocation and the coarsening of substructure/DRX grain are prominently enhanced with an increased forming temperature. However, the annihilation/interaction of dislocation and the expansion of subgrain/DRX grain boundary can be limited at a larger strain rate. Meanwhile, considering the discrepancy in DRX variation rates concerning the strain rate’s ranges, an improved DRX kinetic model was developed. Compared to the classical DRX kinetic model, the good consistency between the forecasted and tested results demonstrates that the established improved DRX kinetic model can precisely characterize the DRX features of the Ni-Cr-Mo alloy over a wide strain rate range. Additionally, the EBSD’s quantitative statistical results proved that the variation of DRX grain size can be supremely defined as the power formulation of the forming temperature and strain rate.

Hot Deformation Behavior of Hastelloy C276 Alloy: Microstructural Variation and Constitutive Models

“…For the researched Hastelloy C276 alloy in hot compression with constant strain rates, the can be defined as [ 22 ] where and are the critical strain and the strain when the reaches 50%, respectively; is the Zener–Hollomon parameter; R expresses a gas constant (8.314 Jmol −1 K −1 ).…”

“…where ε c and ε 0.5 are the critical strain and the strain when the X drx reaches 50%, respectively; Z is the Zener-Hollomon parameter; R expresses a gas constant (8.314 Jmol −1 K −1 ). Moreover, the d drx for the researched Hastelloy C276 alloy can be identified as [22] d drx = 431.54…”

“…For the researched Hastelloy C276 alloy in hot compression with constant strain rates, the X drx can be defined as [22]…”

“…Recently, some studies investigated the microstructure changes in alloys during hot deformation [ 16 , 17 , 18 , 19 ]. For example, the nucleation and coarsening features of dynamic recrystallization (DRX) were explored in numerous investigations [ 20 , 21 ], and multiple kinetic models were proposed for describing the DRX features of Ni-based superalloys, i.e., Hastelloy C276 alloy [ 22 ] and GH4169 alloy [ 23 ]. Moreover, the evolution mechanisms of substructures, including the dislocation clusters/loops and subgrains were explored, which impacted the DRX behaviors of Ni-based superalloys [ 24 , 25 , 26 ].…”

Investigation on Mechanism of Microstructure Evolution during Multi-Process Hot Forming of GH4169 Superalloy Forging

“…The high DRX degree is beneficial to the uniformity of the grain structure after thermal deformation [20,21]. Therefore, plenty of investigations on the DRX behavior in nickel-based alloys have been undertaken, such as Inconel X-750 [22], Alloy 690 [23], Alloy 617 [24], C276 [25], Incoloy 901 [26], XH55 [27] and Haynes 282 [28]. GH4169 superalloy is one of the most important superalloys in the aviation field.…”