Zhang Xianguang, Pei Yiwu, Han Haoran, Feng Shouli, Zhang Yongjie
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
Materials (Basel). 2025 Mar 14;18(6):1292. doi: 10.3390/ma18061292.
Low-cost and low-alloy dual-phase (DP) steel with a tensile strength (TS) above 1000 MPa and high ductility is in great demand in the automobile industry. An approach to using a medium-carbon and fibrous DP structure for developing such new DP steel has been proposed. The microstructure and mechanical performance of fibrous DP steel obtained via partial reversion from martensite in Fe-C-Mn-Si low-alloy steel have been investigated. The TS of the as-quenched DP steel is above 1300 MPa, while the total elongation is less than 6%. The total elongation was increased to above 13%, with an acceptable loss in TS by performing additional tempering. The fibrous tempered-martensite/ferrite DP steel exhibits an excellent balance of strength and ductility, surpassing the current low-alloy DP steels with the same strength grade. Plate-like or quasi-spherical fine carbides were precipitated, and the relatively high-density dislocations were maintained due to the delay of lath recovery by the enrichment of Mn and C in martensite (austenite before quenching), contributing to the tempering softening resistance. In addition, nanotwins and a very small amount of retained austenite were present due to the martensite chemistry. High-density dislocations, fine carbide precipitation, and partially twinned structures strengthened the tempered martensite while maintaining relatively high ductility. Quantitative strengthening models and calculations were not included in the present work, which is an interesting topic and will be studied in the future.
抗拉强度（TS）高于1000MPa且具有高延展性的低成本低合金双相（DP）钢在汽车工业中需求量很大。已提出一种利用中碳纤维状双相组织来开发这种新型双相钢的方法。研究了通过Fe-C-Mn-Si低合金钢中马氏体的部分回复获得的纤维状双相钢的微观结构和力学性能。淬火态双相钢的抗拉强度高于1300MPa，而总伸长率小于6%。通过进行额外回火，总伸长率提高到13%以上，同时抗拉强度有可接受的损失。纤维状回火马氏体/铁素体双相钢在强度和延展性方面表现出优异的平衡，超过了目前相同强度等级的低合金双相钢。析出了板状或准球形的细小碳化物，由于马氏体（淬火前的奥氏体）中Mn和C的富集延迟了板条回复，从而保持了相对高密度的位错，这有助于提高回火软化抗力。此外，由于马氏体的化学成分，还存在纳米孪晶和极少量的残余奥氏体。高密度位错、细小碳化物析出和部分孪晶组织在保持较高延展性的同时强化了回火马氏体。本工作未包括定量强化模型和计算，这是一个有趣的课题，未来将进行研究。
