Size-Dependent Power Laws for Edge Dislocations in Nickel Superalloys: A Molecular Dynamics Study

• Main Authors: Mistry, Divyeshkumar A, Ramabathiran, Amuthan A
• Format: Journal Article
• Language: English
• Published: 14.07.2025
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.2504.16409

We present computational evidence using MD simulations of a size effect for the critical resolved shear stress (CRSS) of edge dislocation motion in nickel superalloys. We model the superalloy as periodically spaced cubic $γ'$ precipitates inside a uniform $γ$ matrix. We then analyze the motion of paired edge dislocations in the $γ$ phase when subject to an external shear stress for various volume fractions of the $γ'$ precipitate for temperatures in the range 300 K to 700 K. The CRSS is found to exhibit a power law dependence on the volume fraction of the $γ'$ precipitate with two distinct regimes which have similar exponent but markedly different prefactors across a wide range of temperatures. We present a detailed analysis of this behavior and reduce it to a linear dependence of the CRSS on the length of the $γ'$ precipitate along the direction of dislocation motion. We further identify the critical length scale underlying the transition between the two observed regimes as the total core width of the paired dislocations in a pure $γ'$ system, which includes in addition to the complex stacking fault separating the partials of the paired dislocations the width of the anti-phase boundary that is formed between the super-dislocations. We present auxillary results using spherical precipitates that exhibit the same trend, but a full analysis of the interplay between size of the precipitate, volume fraction, and other related factors is not pursued in this work. Despite the special configurations considered in this work, the results presented here highlights non-trivial size-dependent effects, provides new details on the strengthening effect of $γ'$ precipitates in nickel superalloys, and has important implications for larger scale dislocation dynamics studies for nickel superalloys.