Investigation on microstructure and properties of 0.17% carbon steel with dispersed cementite particles

Using “ultra fast cooling (UFC) + thermo-mechanical treatment (TMT)” process, nanoscale cementite particles were obtained while the matrix varied from “proeutectoid ferrite + degenerated pearlite” to complete lath-like bainitic matrix by controlling the UFC stop temperature. Microstructures were examined by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that TMT process promoted cementite precipitation in proeutectoid ferrite, leading to more uniformly distributed cementite particles. The tensile properties and Charpy V-notch (CVN) impact toughness were evaluated. The correlation with the microstructural features is then discussed in details.