Atomic diffusion kinetics in IMC formation: A molecular dynamic insight into a novel friction stir backward extrusion cladding process

Abstract

Bimetallic are in high demand due to their capability to economically integrate two distinct material properties. Bimetallic tubular components composed of stainless steel and aluminum (Al) have gained significant attention in the automobile and aerospace industries for their lightweight advantage. However, fabricating this could be challenging with conventional approaches due to the formation of brittle intermetallic compounds (IMCs) at the interface and the lack of control over the formation of non-favorable IMCs, which reduces joint strength. Mitigating the concern, this study presents a novel friction stir backward extrusion (FSBE) process. This study provides a thorough understanding of IMCs formation through molecular dynamics (MD) simulation and precise temperature prediction through finite element analyses. This work provides a fundamental understanding of diffusion kinetics between Al and iron (Fe) atoms, revealing that Al atoms exhibit significantly higher mean square displacements and intricate trajectory pathways than Fe atoms, signifying a higher diffusion coefficient. MD simulation results reveal that grain boundaries facilitate the infiltration of Al atoms into the Fe lattice. Further insights into the dislocation generation were gained by electron back scattered diffraction analysis, which reveals dislocation density influences the diffusion behavior. This study contributes towards a scalable framework for optimizing the FSBE process and similar thermomechanical processes for different sets of material combinations and providing a foundation for comprehending the process of diffusion and the IMCs formation at the atomistic scale.