Investigation on micromechanism involved in ferrite hardening after prestraining of dual-phase steel
Investigation on micromechanism involved in ferrite hardening after prestraining of dual-phase steel
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DOI：
10.1016/j.msea.2020.140387
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发表时间：
2021
期刊：
影响因子：
6.4
通讯作者：
Nan Wang;Yongnan Chen;Gang Wu;Zhen Zhang;Zhicheng Wu;Jinheng Luo
中科院分区：
文献类型：
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作者：
Nan Wang;Yongnan Chen;Gang Wu;Zhen Zhang;Zhicheng Wu;Jinheng Luo
为揭示双相钢在1%~ 5%预应变过程中铁素体强化的微观机制，采用EBSD分析方法研究了双相钢小角度晶界（LAGBs）和泰勒因子（TF）的演变。结果表明，在1%~ 3%的预应变范围内，塑性变形以软铁素体相为主，随后在3%~ 5%的预应变范围内，塑性变形转变为界面变形。由于LAGBs的演化，在预应变过程中产生了位错亚结构。硬化后TF~2-3范围内的软晶含量逐渐减少，表明铁素体内的滑移系较难激活。铁素体的硬化是由于稳定位错亚晶结构的形成和晶粒取向的硬化。当预应变量大于3%时，铁素体相可以完全硬化。铁素体强化后，双相钢的应变硬化能力降低，屈服强度提高，均匀延伸率降低。结果表明，在应变硬化完成后，应力-应变曲线上出现了应力降（最高可达10 MPa），塑性变形直接从界面处开始，表现为解理脆性断裂和韧窝韧性断裂的混合破坏模式。这项工作的目的是提供详细的见解和实验证据的铁素体硬化行为后，预应变，这有望作出重大贡献，更好地使用双相钢的管道的服务保护。
The evolution of low angle grain boundaries (LAGBs) and Taylor factor (TF) was investigated by EBSD analysis to reveal the micromechanism of ferrite hardening for dual-phase steel during prestraining from 1% to 5%. The results showed plastic deformation was dominated by soft ferrite phases during prestraining from 1% to 3%, and subsequently, transformed to interface deformation during prestraining from 3% to 5%. Due to the evolution of LAGBs, dislocation substructures were generated during prestraining. The fraction of soft grains within the range of TF~2–3 gradually decreased after the hardening, indicating the slip system was more difficult to be activated within ferrite. The hardening of ferrite was attributed to the formation of stable dislocation subgrain structures and the hardening of grain orientation as well. When the prestraining degree went above 3%, the ferrite phases can be completely hardened. After ferrite hardening, the strain hardening ability of the dual-phase steel was reduced, the yield strength was increased and the uniform elongation was decreased at the same time. It was noteworthy that the stress drop (up to 10 MPa) occurred on the stress-strain curve after the completion of strain hardening, and the plastic deformation was initiated directly at interface, exhibiting a mixed mode of failure involving both cleavage brittle and dimple ductile fracture. This work is aiming to provide detailed insights and experimental evidence for ferrite hardening behaviour after prestraining, which is expected to make great contribution for better service protection of the pipeline using dual-phase steel.