EBSD Analysis of Relationship Between Microstructural Features and Toughness of a Medium-Carbon Quenching and Partitioning Bainitic Steel
EBSD Analysis of Relationship Between Microstructural Features and Toughness of a Medium-Carbon Quenching and Partitioning Bainitic Steel
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DOI：
10.1007/s11665-017-3052-5
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发表时间：
2017-11
影响因子：
2.3
通讯作者：
Qiangguo Li;Xuefei Huang;Weigang Huang
中科院分区：
文献类型：
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作者：
Qiangguo Li;Xuefei Huang;Weigang Huang
采用贝氏体等温转变+淬火配分（B-QP）新工艺，在0.3C贝氏体钢中获得了贝氏体、马氏体和残余奥氏体复相组织。利用电子背散射衍射（EBSD）研究了该合金的显微组织特征与韧性的关系，结果表明，含50%贝氏体的复相组织比全马氏体组织具有更高的强度（1617 MPa）、伸长率（18.6%）和冲击韧性（103 J）。EBSD分析表明，具有较小平均局部取向差（1.22°）的复相组织具有较低的内应力集中可能性，且复相组织中最先形成的贝氏体铁素体片能够细化后续生成的团和块。相应的包和块平均尺寸分别从11.9和2.3 μ m减小到8.4和1.6μm。边界取向差分析表明，多相显微组织具有较高的百分比的高角度边界（67.1%）比全马氏体（57.9%），因为更大的数量和更小的尺寸的包和块。包边界比块边界更有效地阻止裂纹扩展。
A multiphase microstructure of bainite, martensite and retained austenite in a 0.3C bainitic steel was obtained by a novel bainite isothermal transformation plus quenching and partitioning (B-QP) process. The correlations between microstructural features and toughness were investigated by electron backscatter diffraction (EBSD), and the results showed that the multiphase microstructure containing approximately 50% bainite exhibits higher strength (1617 MPa), greater elongation (18.6%) and greater impact toughness (103 J) than the full martensite. The EBSD analysis indicated that the multiphase microstructure with a smaller average local misorientation (1.22°) has a lower inner stress concentration possibility and that the first formed bainitic ferrite plates in the multiphase microstructure can refine subsequently generated packets and blocks. The corresponding packet and block average size decrease from 11.9 and 2.3 to 8.4 and 1.6μm, respectively. A boundary misorientation analysis indicated that the multiphase microstructure has a higher percentage of high-angle boundaries (67.1%) than the full martensite (57.9%) because of the larger numbers and smaller sizes of packets and blocks. The packet boundary obstructs crack propagation more effectively than the block boundary.