Microstructure manipulation mechanism and mechanical properties improvement of H13 steel via trace nano-(TiC + TiB2) particles

In this study, an innovative method, wherein trace in situ synthesized nano-(TiC+TiB2) particles are added forged H13 steel, was designed and used to manipulate its microstructure. This refined the grains and laths martensite, increased the retained austenite and carbides, and controlled the carbide segregation. Thus, the strength, plasticity, and toughness of the steel were simultaneously improved. Among the samples, the H13 steel, manipulated by 0.02 wt% nano-(TiC+TiB2) particles, exhibited the best mechanical properties. Its yield strength, tensile strength, elongation, unnotched impact toughness and U-notch impact toughness increased by 11.6%, 7.6%, 14.2%, 35.0% and 33.8%, respectively, and reached 1142 MPa, 1426 MPa, 16.9%, 449.3 J/cm2, and 41.39 J/cm2, respectively. The main strengthening mechanisms were grain boundary strengthening, dislocation strengthening and dispersion strengthening. This study provides a new method for the bonding between ceramic nanoparticles and steel and provides a novel idea for the development of high-performance and low-cost steel.