Effect of partitioning procedure on microstructure and mechanical properties of a hot-rolled directly quenched and partitioned steel
Effect of partitioning procedure on microstructure and mechanical properties of a hot-rolled directly quenched and partitioned steel
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DOI：
10.1016/j.msea.2013.11.064
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发表时间：
2014-01
期刊：
影响因子：
6.4
通讯作者：
X. Tan;Yunbo Xu;Xiaoli Yang;Z. Liu;Di Wu
中科院分区：
文献类型：
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作者：
X. Tan;Yunbo Xu;Xiaoli Yang;Z. Liu;Di Wu
采用热轧直接淬火配分（HDQP）工艺对一种低碳钢进行了动态配分和等温配分，研究了两种工艺在组织和力学性能上的差异。用电子探针、电子背散射衍射、透射电镜和X射线衍射等手段对样品的微观结构进行了表征。通过单轴拉伸试验测量机械性能。结果表明，HDQP板材的显微组织为板条马氏体和板条间薄膜状残余奥氏体。与等温分配板相比，动态分配板具有更窄的马氏体板条和更高的位错密度。随着冷却速度的降低或配分时间的延长，马氏体板条展宽，位错密度降低，碳化物粗化。当析出时间超过5 min时，析出的粗大碳化物促进了奥氏体的分解。不同塑性应变试样的X射线衍射（XRD）检测结果表明，碳含量低于1.5wt%的残余奥氏体在塑性应变低于5%时具有较好的相变行为。等温配分工艺可以提高残余奥氏体中碳的平均浓度和均匀性，但会使部分残余奥氏体过于稳定。力学性能测试结果表明，动态分配板具有较高的强度（1500-1600 MPa）和相似的延伸率（14-16%），强伸积（PSE）为22,000-25,000 MPa%。得出的结论是，动态分配程序是优选的，以获得具有优异的力学性能的HDQP钢。
Hot-rolling direct quenching and partitioning (HDQP) processes distinguished by the dynamical partitioning procedures and the isothermal partitioning procedures were applied to a low-carbon steel to investigate the differences in the microstructure and the mechanical properties. Microstructures were characterized by means of EPMA, EBSD, TEM and XRD. Mechanical properties were measured by uniaxial tensile tests. Results show that the microstructures of the HDQP sheets are characterized by lath martensite and film-like inter-lath retained austenite. The dynamically partitioned sheets possess narrower martensite laths with higher dislocation densities, compared with the isothermally partitioned sheets. The martensite lath broadening, the dislocation density reduction and the carbide coarsening exist with decreased cooling rate or with prolonged partitioning time. The coarse carbides appearing in the sheet partitioned longer than 5 min promote the decomposition of austenite. X-ray diffraction (XRD) detection results of the specimens with different plastic strains indicate that the retained austenite with the carbon concentration below 1.5 wt% can perform a better transformation behavior with the plastic strain under 5%. The isothermal partitioning processes can improve the average concentration and homogeneity of carbon in the retained austenite but make up part of the retained austenite too stable. Mechanical property results show that the dynamically partitioned sheets possess higher strengths about 1500–1600 MPa and similar elongations about 14–16% with excellent products of strength and elongation (PSE) about 22,000–25,000 MPa%. It is concluded that a dynamical partitioning procedure is preferable for obtaining a HDQP steel with excellent mechanical properties.