中国百年钢轨钢的微观组织

回顾中国百年钢轨钢微观组织的演变，能够了解过去100多年来中国钢轨钢在材料设计、生产技术、应用性能需求等方面的发展历程。通过光学显微镜、扫描电子显微镜和电子背散射衍射仪(EBSD)表征中国百年来具有典型时期代表性的8种钢轨钢1904、1911、1953、1955、1994、2013、2018、2021的微观组织，讨论分析它们的微观组织演变规律。结果表明，这8种钢轨钢的基体组织由大量铁素体+珠光体，变化为网状铁素体+珠光体，再变化为全珠光体，这与钢轨钢中碳含量的增加密切相关(质量分数从0.15%增加到0.81%)。从1911年至2021年中国生产的钢轨钢的珠光体团平均晶粒尺寸逐渐减小，这使得钢轨钢的硬度、强度均有所提高。另外，对由EBSD分析获得的反极图+晶界分布图进行研究，可以发现这8种钢轨钢微观组织中的小角度晶界比例逐渐增大，晶界取向差分布更集中于小角度区间，降低了对位错滑移的阻碍作用和裂纹形核的概率。在局部取向差(KAM)+晶界分布图中，钢轨钢的珠光体组织比铁素体组织具有更高的KAM值，这表明珠光体组织比铁素体组织存在更高的缺陷密度，在变形过程中产生的应变越大。从施密特因子(SF)...

Microstructures of rail steels over a century in China

Reviewing the evolution of the microstructures of rail steels over a century,is better to understand the development of rail steels in terms of material design,production technology and application performance requirements. The microstructures of eight rail steels which are the representative of typical periods in China over a century,were characterized using a combination of optical microscopy,scanning electron microscopy and electron backscatter diffraction (EBSD),and the evolution of their microstructures was discussed. The results showed that the matrix of the eight rail steels changed from ferrite with a small amount of pearlite,to reticulated ferrite+pearlite,and then to full pearlite,which should be related to the carbon content increasing from 0.15% to 0.81%. Moreover,the average grain diameter of pearlite colony gradually decreased for the rail steels produced in 1911 to 2021,which indicated that the eight rail steels exhibited an increase in the hardness and strength. In addition,it was found that the proportion of low angle grain boundaries for the eight rail steels gradually increased,and the distribution of grain boundary misorientation was more concentrated in the low angle range based on the diagram of the diagram of Inverse Pole Figure plus Grain Boundary obtained by EBSD results. These changes could lower the hindrance of dislocation slip and the probability of crack nucleation. In the distribution diagram of Kernel Average Misorientation (KAM)+Grain Boundary,the pearlite microstructures hold a higher KAM value than the ferrite microstructures in the rail steels,which indicates that the geometrically necessary dislocation density of the pearlite microstructures is higher than that of ferrite microstructures,thus the higher strain should be generated during plastic deformation. From the distribution diagram of Schmidt factor (SF)+Grain Boundary,it is known that the higher SF value results in the higher probability that initiates the slip system {110}<111> and is easier to form {110}<111> textures.