Development of eco-materials by using nano-structure analyses with neutron scattering

用中子散射法研究了不同碳含量(质量分数)达0.9%的拉拔钢丝的组织演变和强化机制。用本研究新发展的中子衍射仪分析了织构、晶间应力、晶粒度和位错密度。0.9C钢的晶粒度为几十纳米，这与透射电子显微镜的观察结果一致。利用中子衍射法的优点是可以获得与力学行为有很好联系的大量的微观因素的平均值。阐明了专利珠光体及其拉丝的微观组织和变形行为的多尺度非均质性，并用中子衍射仪原位研究了钢的相变行为。30Ni-0.2C钢在冷却和回火过程中无热马氏体相变过程中的原位衍射谱揭示了具有低温t…的bct马氏体c/a的变化。更具帝王气概。现场研究了加热过程中马氏体向奥氏体的扩散转变，奥氏体向铁素体和珠光体的转变，发现了富碳、晶格应变(内应变)、体积分数等。首次研究了中子衍射条件下的热机械控制过程。利用直接实验数据讨论了奥氏体形变对相变和晶粒细化的影响，并用小角散射法评价了几种含氮量的奥氏体不锈钢中的纳米氮有序区。对大角(Bragg)和小角中子衍射进行了原位中子散射，发现了晶间应力和短程有序的破坏。这些新的发现揭示了含氮钢高性能的机理，这些材料都是为了实现环保材料，并在目前结果的基础上开始了进一步的相关研究。较少

Microstructure evolution and strengthening mechanisms of severely drawn steel wires with various carbon concentrations up to 0.9 mass% were examined by means of neutron scattering. Texture, Intergranular stress, grain size and dislocation density were analyzed by a profile analysis for neutron diffraction, which was newly developed in this study. The grain size of 0.9C steel becomes several ten nanometers that is consistent with TEM observations. The merits to use neutron diffraction is to obtain bulky averages of micro-factors which are well connected with mechanical behavior. The mutli-scaled heterogeneity in microstructure as well as deformation behavior of as-patented pearlite and its drawn wires have been made clear.Phase transformation behaviors of steels were studied in situ by neutron diffraction. The in situ diffraction during athermal martensitic transformation in a 30Ni-0.2C steel during cooling and tempering reveals the change in c/a of bct martensite with low temperature t … More empering. Diffusional transformation from martensite to austenite upon heating and then austenite to ferrite and pearlite transformations was studied in situ and carbon enrichment, lattice strain (internal strain), volume fraction etc can be found. Thermo-mechanically controlled process was firstly investigated under neutron diffraction. The effect of austenite deformation on phase transformation and grain refinement are discussed by using direct experimental data.Nano-scaled nitrogen ordered zone was evaluated by small angle scattering in austenitic stainless steels with several amounts of nitrogen contents. In situ neutron scattering was performed for large angle (Bragg) and small angle neutron diffraction and the intergranular stress and destroy of short range ordering were found. These new findings have revealed the mechanisms of high performance in nitrogen bearing steels.These materials are all aimed at realizing ecomaterials and further related investigations have been started based on the present results. Less