Grain boundary segregation in UFG alloys processed by severe plastic deformation

TL;DR

This study investigates how severe plastic deformation affects grain boundary segregation in various alloys, revealing increased local enrichment of Mg and C at grain boundaries, linked to non-equilibrium structures.

Contribution

It provides new insights into the mechanisms of grain boundary segregation in ultrafine-grained alloys processed by SPD, highlighting differences between substitutional and interstitial solutes.

Findings

Mg enrichment up to 20 at.% in Al alloys after SPD

Large carbon concentrations along grain boundaries in Fe alloys after SPD

Segregation mechanisms differ between substitutional and interstitial solutes

Abstract

Grain boundary segregations were investigated by Atom Probe Tomography in an Al-Mg alloy, a carbon steel and Armco\trademark Fe processed by severe plastic deformation (SPD). In the non-deformed state, the GBs of the aluminium alloy are Mg depleted, but after SPD some local enrichment up to 20 at.% was detected. In the Fe-based alloys, large carbon concentrations were also exhibited along GBs after SPD. These experimental observations are attributed to the specific structure of GBs often described as "non-equilibrum" in ultra fine grained materials processed by SPD. The grain boundary segregation mechanisms are discussed and compared in the case of substitutional (Mg in fcc Al) and interstitial (C in bcc Fe) solute atoms.