Plasticity and structure evolution of ferrite and martensite in DP 1180 during tension and cyclic bending under tension to large strains
Plasticity and structure evolution of ferrite and martensite in DP 1180 during tension and cyclic bending under tension to large strains
复制标题
DOI：
10.1016/j.msea.2021.141536
复制
发表时间：
2021-07
期刊：
影响因子：
--
通讯作者：
Krishna Yaddanapudi;M. Knezevic;S. Mahajan;I. Beyerlein
中科院分区：
文献类型：
--
作者：
Krishna Yaddanapudi;M. Knezevic;S. Mahajan;I. Beyerlein
本文介绍了从一个详细的实验研究中获得的主要结果的位错和孪晶结构，发展双相（DP）钢板。特别地，使用透射电子显微镜（TEM）检查具有55%铁素体和45%马氏体的DP 1180钢中存在的形态和缺陷结构。DP 1180的显微组织由板条和岛状的无孪晶马氏体相和位错含量相对较低（3.41 × 108 cm −2）的铁素体相组成。该钢在简单拉伸（ST）中变形至断裂，并在拉伸下连续弯曲（CBT）中变形至六个循环。由于CBT测试促进片材的拉伸显著超过颈缩点，因此强度增加并且显著超过ST在断裂时所实现的强度。作为塑性变形的结果，在岛状马氏体中发现纳米孪晶，而板条状马氏体保持无孪晶。此外，一些马氏体区域在CBT之后形成针状形态。随着铁素体基体中的位错密度随着塑性应变的增加而增加，铁素体中铁素体/马氏体界面附近的位错结构和位错的积累发展。与接收态和ST变形的DP 1180样品不同，在CBT处理的样品的铁素体区域中观察到高密度的位错（1.47 × 109 cm −2）和位错缠结。我们建议，主要机制，使实现高强度，同时保持剩余的延展性后CBT是强烈的塑性滑移的铁素体和丰富的纳米孪晶的马氏体区域。
This paper describes the main results obtained from a detailed experimental investigation into the dislocation and twinned structures that develop in dual phase (DP) steel sheets. In particular, the morphology and defect-structures present in DP 1180 steel having 55% ferrite and 45% martensite, were examined using transmission electron microscopy (TEM). Microstructure of the as-received DP 1180 consists of a twin-free martensite phase in the form of lath and island morphologies and a ferrite phase exhibiting a relatively low dislocation content (3.41 × 108cm−2). The steel was deformed in simple tension (ST) to fracture and in continuous-bending-under-tension (CBT) to six cycles. As the CBT test facilitates stretching of the sheet considerably beyond the point of necking, strength increases and substantially exceeds that achieved in ST at fracture. As a consequence of plastic deformation, nano-twins are found in the island-shaped martensite, while the lath-shaped martensite remains twin-free. Additionally, some martensite regions develop a needle-like morphology after CBT. As dislocation density in the ferrite matrix increases with plastic strain, dislocation structures and accumulations of dislocations near the ferrite/martensite interface develop in the ferrite. Unlike in the as-received and ST-deformed DP 1180 samples, high density of dislocations (1.47 × 109cm−2) and dislocation tangles are observed in ferrite regions of the CBT processed sample. We propose that the primary mechanisms enabling the achievement of high strength, while maintaining residual ductility upon CBT are intense plastic slip in the ferrite and profuse nano-twinning in the martensite regions.