Fabrication, microstructures and mechanical properties of ZrO2 dispersion-strengthened Q345 steel
(1. State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China;
2. CNOOC Research Institute of Oil and Petrochemicals (CRI), Qingdao 266500, China)
2. CNOOC Research Institute of Oil and Petrochemicals (CRI), Qingdao 266500, China)
Abstract: ZrO2 dispersion-strengthened Q345 steel with different ZrO2 contents (0%, 0.5% and 1.2%, mass fraction) was fabricated through combining middle frequency induction furnace melting and cored-wire injection technologies. The microstructure and fracture surface morphology of ZrO2 dispersion-strengthened Q345 steel in casting, normalizing and quenching states were observed using optical microscopy, scanning electron microscopy and transmission electron microscopy. Also, strengthening and fracture mechanisms of the alloys were analyzed. Results showed that the dispersed ZrO2 particles added into Q345 matrix significantly enhanced its strength, and the main strengthening mechanism was the formation of dislocation cells and pinning effect caused by the addition of ZrO2 particles. Apart from that, the hard martensite phase, grain refinement and high ZrO2 particles content also played important roles in strengthening effect. Furthermore, the nanoindentation was also performed to further reveal the strengthening effect and mechanism of dispersed ZrO2 particles in Q345 steel. Results showed that the hardness of ZrO2 dispersion-strengthened Q345 steel increased with the increase of ZrO2 content.
Key words: Q345 steel; ZrO2 particles; dispersion strengthening; microstructure; mechanical properties