On the mechanisms of nanoparticle mediated thermal stability in a lamellar-nanostructured Al–1.0%Si alloy

Adding alloying elements has long been known to improve the thermal stability of nanostructured metals via atoms segregation or/and precipitated particles. Despite this, questions regarding the effect of particles on microstructure and their synergic impacts on structural coarsening remain nebulous. Here, we demonstrate the interactions between nanoparticles and microstructural coarsening by Y-junction motion during recovery of lamellar-nanostructured Al–1.0%Si that exhibit good thermal stability. In-situ annealing experiments in a transmission electron microscope reveal three ways for particles to pin moving Y-junctions: (1) direct pinning from particles precipitated at lamellar boundaries or/and inside lamella; (2) synergic pinning from a neighbouring interconnecting dislocation boundary and the particles located at the junction of interconnecting and lamellar boundaries; (3) indirect pinning caused by the particles located at interconnecting dislocation boundaries inside neighbouring lamellae. These pinning mechanisms originating from Si nanoparticles enable high thermal stability in the lamellarnanostructured Al–1.0%Si alloy. The findings enrich the current understanding on the specific role of particles related to structural coarsening resistance in lamellar-nanostructured Al alloys.