Atomic-scale Nucleation and Growth Pathway of Complex Plate-like Precipitates in Aluminum Alloys

TL;DR

This study uncovers the atomic-scale mechanisms behind the nucleation and growth of complex nano-plate precipitates in aluminum alloys, revealing structural transition pathways that align with experimental data.

Contribution

It introduces a detailed atomic-level model of nano-plate formation in Al alloys, based on theoretical calculations of structural transitions involving dislocation and atomic shuffling.

Findings

Identified inter-layer-sliding+shuffling mode as key to nano-plate formation

Proposed structural evolution pathways consistent with experiments

Enabled evaluation of critical nuclei for nano-plate growth

Abstract

Aluminum alloys, the most widely utilized lightweight structural materials, predominantly depend on coherent complex-structured nano-plates to enhance their mechanical properties. Despite several decades of research, the atomic-scale nucleation and growth pathways for these complex-structured nano-plates remain elusive, as probing and simulating atomic events like solid nucleation is prohibitively challenging. Here, using theoretical calculations and focus on three representative complex-structured nano-plates in commercial Al alloys, we explicitly demonstrate their associated structural transitions follow an inter-layer-sliding+shuffling mode. Specifically, partial dislocations complete the inter-layer-sliding stage, while atomic shuffling occurs upon forming the unstable basic structural transformation unit of the nano-plates. By identifying these basic structural transformation units, we propose structural evolution pathways for these nano-plates within the Al matrix, which align well with experimental observations and enable the evaluation of critical nuclei. These findings provide long-sought mechanistic details into how coherent nano-plates nucleate and grow, facilitating the rational design of higher-performance Al alloys and other structural materials.