Fabrication,microstructures and mechanical properties of ZrO_2 dispersion-strengthened Q345 steel

ZrO_2粒子弥散强化Q345钢的制备、显微组织与力学性能（英文）

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.

采用中频感应熔炼炉熔化钢液和喂丝法相结合的技术,将ZrO_2粒子与铁粉混合物的预制棒加入到Q345钢熔液中,制备不同ZrO_2粒子含量(0%、5%和1.2%,质量分数)的弥散强化Q345钢。通过光学显微镜(OM)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察铸态、正火态和淬火态弥散强化钢的显微组织和拉伸断口形貌,并分析ZrO_2粒子弥散强化Q345钢的强化机理和断裂机理。结果显示,ZrO_2粒子弥散强化Q345钢的强度得到显著提高;ZrO_2粒子附近形成的位错胞以及ZrO_2粒子的钉轧作用是弥散强化钢力学性能提高的主要强化机理;另外,硬质马氏体相、晶粒细化和高含量ZrO_2粒子在强化过程中均起到重要作用。采用纳米压痕仪对弥散强化钢的硬度和变形能力进行研究。结果表明,ZrO_2粒子弥散强化Q345钢的硬度随ZrO_2粒子含量的增加而提高。