Atomistic Insights into Gradient Architecture Driven Strengthening in Additively Manufactured Cu–Ni Stepwise Graded Structures

ABSTRACT In this study, Molecular Dynamics (MD) simulations are employed to compare the mechanical behavior of additively manufactured Cu‐Ni Functionally Graded Materials (FGMs) as a function of the functional gradient design. Two gradient architectures, a stepwise graded architecture and a layer‐by‐layer gradient, are explicitly modeled to analyze their influence on deformation and strengthening mechanisms. The stepwise graded architecture exhibits approximately 30% higher tensile strength compared to the alternate‐layer deposition approach. This improvement is attributed to repeated thermal cycling during layer deposition, which enhances atomic diffusion and promotes more uniform Ni redistribution across layers. Radial Distribution Function (RDF) analysis confirms atomic‐scale mobility at interlayer interfaces, leading to improved metallurgical bonding. Layer‐specific tensile simulations reveal that increasing Ni content progressively enhances tensile strength, reaching a maximum of approximately 900 MPa, accompanied by reduced ductility, consistent with experimental trends. Dislocation analysis identifies the formation of sessile dislocations, including stair‐rod, hirth, and Frank dislocations, whose increased density with higher Ni content restricts atomic mobility and contributes to strengthening. The present work provides a comparative and qualitative atomistic analysis of gradient architecture effects and offers mechanistic insights into strengthening behavior.