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Improvement of mechanical properties for low carbon ultra-high strength steel strengthened by Cu-rich multistructured precipitation via modification to bainite
Materials Science and Engineering: A ( IF 6.4 ) Pub Date : 2021-05-04 , DOI: 10.1016/j.msea.2021.141337
Chengning Li , Ran Duan , Wen Fu , Heshan Gao , Dongpo Wang , Xinjie Di

This work focused on ultra-high strength steel strengthened by Cu-rich multistructured precipitates and toughened by bainite. A Cr–Mo bearing bainitic steel was designed and contrasted with a ferritic steel to examine the effects of Cr and Mo on microstructural transformation and precipitation evolution as well as the corresponding mechanical properties. By adding Cr and Mo elements, bainitic steel was obtained by an air cooling process after hot rolling, thus omitting controlled cooling and off-line quenching. Cr and Mo decreased the γ/α transformation temperature, such that the ferritic matrix was modified to fine bainite. Cu-rich multistructured particles and (Nb,Ti)C particles were found to be the two main precipitation phases in this bainitic steel. Cu-rich multistructured particles contained B2-ordered structure and transition-state structure between B2-ordered and 9R structure. Notably, this Cr–Mo bearing bainitic steel had better strength and toughness compared with ferritic steel. Its yield strength reached 1155 MPa, owing to precipitation and grain boundary strengthening, which were estimated to be 596 and 311 MPa, respectively. The impact absorbed energy of this steel at −40 °C was ~55.3 J and its fracture mode a brittle-ductile mixed mode, compared with the cleavage fracture mode of ferritic steel. The small grain size of this steel compensated for toughness deterioration caused by precipitation and contributed to high impact toughness.



中文翻译:

富铜多结构沉淀强化贝氏体改善低碳超高强度钢的力学性能

这项工作的重点是通过富含铜的多结构析出物增强并由贝氏体增韧的超高强度钢。设计了Cr-Mo轴承贝氏体钢,并与铁素体钢进行对比,以检验Cr和Mo对显微组织转变和析出以及相应力学性能的影响。通过添加Cr和Mo元素,在热轧后通过空冷工艺获得贝氏体钢,从而省去了受控的冷却和离线淬火。Cr和Mo降低了γ/α相变温度,从而使铁素体基体改性为细贝氏体。富铜的多结构颗粒和(Nb,Ti)C颗粒被发现是该贝氏体钢中的两个主要析出相。富铜多结构颗粒包含B2有序结构和B2有序与9R结构之间的过渡态结构。值得注意的是,与铁素体钢相比,这种含Cr-Mo的贝氏体钢具有更好的强度和韧性。由于沉淀和晶界强化,其屈服强度达到1155 MPa,估计分别为596和311 MPa。与铁素体钢的分裂断裂模式相比,该钢在−40°C时的冲击吸收能为〜55.3 J,其断裂模式为脆性-韧性混合模式。这种钢的小晶粒尺寸弥补了因沉淀而导致的韧性下降,并提高了冲击韧性。由于沉淀和晶界强化,其屈服强度达到1155 MPa,估计分别为596和311 MPa。与铁素体钢的分裂断裂模式相比,该钢在−40°C时的冲击吸收能为〜55.3 J,其断裂模式为脆性-韧性混合模式。这种钢的小晶粒尺寸弥补了因沉淀而导致的韧性下降,并提高了冲击韧性。由于沉淀和晶界强化,其屈服强度达到1155 MPa,估计分别为596和311 MPa。与铁素体钢的分裂断裂模式相比,该钢在−40°C时的冲击吸收能为〜55.3 J,其断裂模式为脆性-韧性混合模式。这种钢的小晶粒尺寸弥补了因沉淀而导致的韧性下降,并提高了冲击韧性。

更新日期:2021-05-11
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