Bulk ultrafine grained microstructures with high thermal stability via intragranular precipitation of coherent particles

Abstract

Producing ultrafine-grained (UFG) microstructures with enhanced thermal stability is an important yet challenging route to further improve mechanical properties of structural materials. Here, a high-performance bulk UFG copper that can stabilize even at temperatures up to 750 °C (∼ 0.75Tm, Tm is the melting point) was fabricated by manipulating its recrystallization behavior via low alloying of Co. Addition of 1 wt.%–1.5 wt.% of Co can trigger quick and copious intragranular clustering of Co atoms, which offers high Zener pinning pressure and pins the grain boundaries (GBs) of freshly recrystallized ultrafine grains. Due to the fact that the subsequent growth of the coherent Co-enriched nanoclusters was slow, sufficient particles adjacent to GBs remained to inhibit the migration of GBs, giving rise to the UFG microstructure with prominently high thermal stability. This work manifests that the strategy for producing UFGs with coherent precipitates can be applied in many alloy systems such as Fe- and Cu-based, which paves the pathway for designing advanced strain-hardenable UFGs with plain compositions.