Improvement of Cu-rich precipitation strengthening for high-strength low carbon steel strengthened via Ti-microalloying

Abstract

This present work aims to improve the precipitation strengthening of nanoscale Cu-rich particles in high-strength low carbon steel by Ti microalloying. Ti microalloying increased the density of small-angle boundaries and dislocations, which increased the nucleation sites and refined the dimension of Cu-rich particles. By adding 0.05 wt% Ti, the size of Cu-rich particles were refined from 22 nm to 7 nm. The structure of Cu-rich particles in Ti-free steel was incoherent FCC-Cu, whose mismatch degree with α-Fe matrix was 0.28. By adding 0.02 wt% and 0.05 wt% Ti, the structure of Cu-rich particles transformed into semi-coherent 3R-Cu and 9R-Cu, respectively. Meanwhile, the mismatch degrees between Cu-rich particle and α-Fe matrix decreased to 0.24 and 0.21, respectively. The refinement of Cu-rich particles increased the precipitation strengthening from 46 MPa to 248 MPa.