Improved strength-ductility-toughness balance of a precipitation-strengthened low-carbon medium-Mn steel by adopting intercritical annealing-tempering process
Improved strength-ductility-toughness balance of a precipitation-strengthened low-carbon medium-Mn steel by adopting intercritical annealing-tempering process
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DOI：
10.1016/j.msea.2020.140636
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发表时间：
2021-01
期刊：
影响因子：
6.4
通讯作者：
Y. Zou;Yunbo Xu;G. Wang;Y. Han;H. Teng;D. Han;M. Qiu;F. Yang;R. Misra
中科院分区：
文献类型：
--
作者：
Y. Zou;Yunbo Xu;G. Wang;Y. Han;H. Teng;D. Han;M. Qiu;F. Yang;R. Misra
对低碳中锰钢的研究表明，新提出的“亚温退火-回火”工艺通过同时优化奥氏体逆转变和Cu析出，导致了强度、塑性和冲击韧性的良好组合。高温亚温退火加速了铁素体颗粒的溶解，促进了逆转变奥氏体的形成，从而提高了总延伸率和冲击功。在500 °C下的额外回火促进了二次马氏体中富Cu沉淀物的强烈沉淀。析出相细小、尺寸均匀、密度高，具有显著的强化效果。纳米级富铜析出物的强化补偿了高温退火的软化，并使回火中锰钢的屈服强度提高了75 MPa。除了促进Cu沉淀之外，二次马氏体的引入还在回火期间促进了回复奥氏体的成核，其中具有足够的C和Mn浓度，其稳定了奥氏体并进一步改善了延展性。经645 °C亚温退火和500 °C × 2 h回火处理的沉淀强化低碳中锰钢具有优异的力学性能，屈服强度为960 MPa，抗拉强度为1010 MPa，总延伸率为29.2%，室温冲击功为150 J。
The present study on low-carbon medium-Mn steel demonstrates that the newly proposed “intercritical annealing-tempering” process led to good combination of strength, ductility and impact toughness, by simultaneously optimizing austenite reverted transformation and Cu precipitation. Intercritical annealing at high temperature accelerated the dissolution of cementite particles, promoted the formation of reverted austenite, and then increased the total elongation and impact energy. The additional tempering at 500 °C facilitated intensive precipitation of Cu-rich precipitates in secondary martensite. The precipitates were fine, uniform in size and high in density, which provided a significant strengthening effect. Strengthening by nano-scale Cu-rich precipitates compensated softening associated with high temperature annealing, and increased the yield strength of tempered medium-Mn steel by 75 MPa. In addition to facilitating Cu precipitation, the introduction of secondary martensite also promoted nucleation of reverted austenite during tempering with sufficient C and Mn concentration that stabilized austenite and further improved ductility. Excellent mechanical properties, 960 MPa yield strength, 1010 MPa tensile strength, 29.2% total elongation and 150 J impact energy at room temperature were obtained in the precipitation-strengthened low-carbon medium-Mn steel, on intercritical annealing at 645 °C, followed by tempering at 500 °C for 2 h.