ABSTRACT Applications of neutron diffraction to microstructure evaluation of steel investigated by a project commissioned by the Innovative Structural Materials Association are summarized. The volume fraction of austenite (γ) for a 1.5Mn-1.5Si-0.2C steel was measured by various techniques including backscatter electron diffraction (EBSD) and X-ray diffraction. It is recommended to measure volume fraction and texture simultaneously using neutron diffraction. The γ reverse transformation was in situ monitored using dilatometry, EBSD, X-ray diffraction and neutron diffraction. The γ reversion kinetics showed excellent agreements between dilatometry and neutron diffraction, whereas the γ formation started at higher temperatures in EBSD and X-ray diffraction measurements. Such discrepancy is attributed to the change in chemical compositions at the specimen surface by heating; Mn and C concentrations were decreased with heating. Phase transformations from γ upon cooling were monitored, which enabled us to elucidate the changes in lattice parameters of ferrite (α) and γ affected by not only thermal contraction but also transformation strains, thermal misfit strains and carbon enrichment in γ in the above hypoeutectoid steel. Pearlitic transformation started after the carbon enrichment reached approximately 0.76 mass% and contributed to diffraction line broadening. Martensitic transformation with or without ausforming at 700°C was monitored for a medium carbon low alloyed steel. Dislocation density after ausforming was determined using the convolutional multiple whole profile fitting method for 10 s time-sliced data. The changes in γ and martensite lattice parameters upon quenching were tracked and new insights on internal stresses and the axial ratio of martensite were obtained. GRAPHIAL ABSTRACT

中文翻译：

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使用中子衍射对钢微观结构进行晶体学表征

摘要 总结了创新结构材料协会委托的一个项目研究的中子衍射在钢的微观结构评估中的应用。1.5Mn-1.5Si-0.2C 钢的奥氏体 (γ) 的体积分数通过各种技术测量，包括背散射电子衍射 (EBSD) 和 X 射线衍射。建议使用中子衍射同时测量体积分数和纹理。使用膨胀法、EBSD、X 射线衍射和中子衍射原位监测 γ 逆变换。γ 回复动力学显示了膨胀法和中子衍射之间的极好一致性，而在 EBSD 和 X 射线衍射测量中，γ 的形成开始于更高的温度。这种差异是由于加热后试样表面的化学成分发生了变化；Mn 和 C 的浓度随着加热而降低。监测冷却后 γ 的相变，这使我们能够阐明铁素体 (α) 和 γ 的晶格参数变化不仅受热收缩的影响，而且还受上述亚共析钢中 γ 中的相变应变、热失配应变和碳富集的影响. 碳富集达到约 0.76 质量％后开始珠光体转变，并有助于衍射线变宽。对中碳低合金钢在 700°C 下有或没有奥氏成形的马氏体转变进行了监测。使用卷积多重整体轮廓拟合方法对 10 s 时间切片数据确定 ausforming 后的位错密度。跟踪淬火时 γ 和马氏体晶格参数的变化，并获得了关于内应力和马氏体轴比的新见解。图形摘要