Influence of Mn content on the microstructure and mechanical properties of ultrafine grained C-Mn steels

The effect of Mn content on the microstructure and mechanical properties of two ultrafine grained 0.2%C-Mn steels has been investigated. The ultrafine grained microstructure was produced by use of large strain warm deformation and subsequent annealing. The final microstructure consists of fine cementite particles within an ultrafine grained ferrite matrix. The increase in the Mn content leads to a decrease in the average ferrite grain size (from 1.3 to 0.8 mu m for an increase in the Mn content from 0.74 to 1.52 mass%). This can be attributed to the enrichment of Mn in the cementite particles, which becomes finer in the steel with a higher Mn content. The increase in the Mn content results in an increase in strength at equal ductility and toughness.