Grain boundary diffusion in severely deformed Al-based alloy

TL;DR

This study investigates how severe plastic deformation and related microstructural changes affect grain boundary diffusion in an Al-based alloy, using isotope tracing and theoretical modeling to understand transport phenomena.

Contribution

It combines experimental diffusion measurements with theoretical modeling to analyze the effects of severe deformation and precipitates on grain boundary diffusion in Al alloys.

Findings

Deformation modifies grain boundary diffusion rates.

Nano-sized precipitates influence diffusion behavior.

Theoretical models elucidate stress effects around precipitates.

Abstract

Grain boundary diffusion in severely deformed Al-based AA5024 alloy is investigated. Different states are prepared by combination of equal channel angular processing and heat treatments, with the radioisotope $^{57}$Co being employed as a sensitive probe of a given grain boundary state. Its diffusion rates near room temperature (320~K) are utilized to quantify the effects of severe plastic deformation and a presumed formation of a previously reported deformation-modified state of grain boundaries, solute segregation at the interfaces, increased dislocation content after deformation and of the precipitation behavior on the transport phenomena along grain boundaries. The dominant effect of nano-sized Al$_3$Sc-based precipitates is evaluated using density functional theory and the Eshelby model for the determination of elastic stresses around the precipitates.