Effect of Tempering Temperature on Microstructure and Mechanical Properties in New-Type Ultrahigh Strength Steel

The effect of tempering temperature on the microstructure and mechanical properties of new-type ultrahigh strength steel was explored. The maximum ultimate tensile strength 2230 MPa was reached after tempering at 470°C due to the precipitation of coherent zones of fine carbides. Upon tempering at 400°C∼470°C, the martensite decomposed to form a high of density of cementite particles at platelets and twin boundaries concomitant with a significant drop in impact toughness and fracture toughness.