Dynamic precipitation during high-pressure torsion of a magnesium-manganese alloy

TL;DR

This study investigates how dynamic precipitation of manganese particles during high-pressure torsion refines and stabilizes the grain structure of a magnesium alloy, enhancing its mechanical properties.

Contribution

It reveals the formation and role of nanometer-scale Mn precipitates during HPT, which pin grain boundaries and prevent grain growth, a novel insight into alloy strengthening mechanisms.

Findings

Nanometer-scale Mn particles precipitate during deformation.

Precipitates pin grain boundaries, maintaining ultrafine grains.

Grain size stabilizes at 230 nm after 10 rotations.

Abstract

An ultrafine grained magnesium alloy has been produced through room temperature high-pressure torsion (HPT) of solutionised Mg-1.35 wt.%Mn. Dynamic precipitation of nanometer-scale Mn particles occurred during deformation. These particles populated the grain boundaries, acting as pinning sites which allowed the alloy to develop a grain size of 140 nm after 0.5 rotations. Further HPT deformation resulted in a gradual increase in grain size with no increase in precipitate size. Despite the extensive deformation applied, the alloy did not develop a bimodal grain structure and retained a grain size of 230 nm after 10 complete rotations, demonstrating the stability and effectiveness of these pinning particles.