Deformation Mechanisms Coupled with Phase Field and Crystal Plasticity Modeling in a High‐Temperature Polycrystalline Ni‐Based Superalloy

Abstract

Physics-based modeling of disk superalloys is inherently complex due to the strong influence of microstructure on properties, as well as the multitude of deformation mechanisms operative at elevated temperatures. The present contribution will focus on the effects of monotonic and cyclic loading conditions, and the underlying deformation mechanisms will be discussed. Detailed substructure analysis of deformed specimens was conducted with scanning transmission electron microscopy diffraction-contrast methods. These characterization efforts have led to a series of phase field simulations in which the interaction of various deformation modes with experimentally measured precipitate configurations can be explored and critical parameters quantified. Additionally, these results have been incorporated into a novel, dislocation-densitybased crystal plasticity model that has been calibrated based on a single crystal response, and enables the computationally efficient modeling of polycrystalline behavior.

Stress orientation dependence for the propagation of stacking faults and superlattice stacking faults in nickel-based superalloys

“…The only exception are the extended faults with alternating character, which appear switched in Figure 12 because the athermal looping of precipitates requires a higher stress than the formation of the superlattice faults. In the case of larger channels, as those in this alloy, the boundaries from equations (20) and (24) shift these regions closer to φ ∼ 0 • , where both of these faults are found experimentally. This general picture of the superlattice faults in nickel-based superalloys offers an overview of how crystals find intricate ways to accommodate deformation in the direction of the shear stress.…”

“…analogous to equation (20). This mechanism would then be promoted in a region in Figure 14 similar to that of the extended SESF + ISF but mirrored along the τ S axis, for φ ∼ 0 • .…”

“…The analytical model for the athermal propagation of ISFs builds on a number of previous studies. Mechanistic maps like the one in Figure 7 have been generated before by simulations of individual partials for the case of Frank-Read sources [37], narrow channels [5,19] and precipitates arrays [5,20,21], but the current analytical approach encompasses these to give a comprehensive prediction of dislocation behaviour. Moreover, the infinitely long stacking fault regime has never been described.…”

“…Investigations on the stress orientation dependence for the formation and propagation of ISFs have been performed mainly via simulations of individual dislocations by Douin et al [19] and subsequent studies [5,20,21]. However, rationalising the effects of loading orientation on the propagation of superlattice faults is considerably more difficult due to the different Shockley partials involved.…”

A Stress Orientation Analysis Framework for Dislocation Glide in Face-Centred Cubic Metals

“…Note that the lines joining the point with the highest Schmid factor and the two coplanar slip directions have in the orientation map slopes of ± √ 3, as they share the same partials. Similarly, the polar coordinates (with radius m and angle ϕ) for each slip system can be easily observed; this description is also widely used in the literature [20][21][22]. Table 1 contains the conversion formulae between the variables from different nomenclatures.…”