Xu Pingguang, Harjo Stefanus, Ojima Mayumi, Suzuki Hiroshi, Ito Takayoshi, Gong Wu, Vogel Sven C, Inoue Junya, Tomota Yo, Aizawa Kazuya, Akita Koichi
Materials Sciences Research Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
J-PARC Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
J Appl Crystallogr. 2018 May 9;51(Pt 3):746-760. doi: 10.1107/S1600576718004004. eCollection 2018 Jun 1.
Neutron diffraction texture measurements provide bulk averaged textures with excellent grain orientation statistics, even for large-grained materials, owing to the probed volume being of the order of 1 cm. Furthermore, crystallographic parameters and other valuable microstructure information such as phase fraction, coherent crystallite size, root-mean-square microstrain, macroscopic or intergranular strain and stress, can be derived from neutron diffractograms. A procedure for combined high stereographic resolution texture and residual stress evaluation was established on the pulsed-neutron-source-based engineering materials diffractometer TAKUMI at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Center, through division of the neutron detector panel regions. Pole figure evaluation of a limestone standard sample with a well known texture suggested that the precision obtained for texture measurement is comparable to that of the established neutron beamlines utilized for texture measurement, such as the HIPPO diffractometer at the Los Alamos Neutron Science Center (New Mexico, USA) and the D20 angle-dispersive neutron diffractometer at the Institut Laue-Langevin (Grenoble, France). A high-strength martensite-austenite multilayered steel was employed for further verification of the reliability of simultaneous Rietveld analysis of multiphase textures and macro stress tensors. By using a texture-weighted geometric mean micromechanical (BulkPathGEO) model, a macro stress tensor analysis with a plane stress assumption showed a rolling direction-transverse direction (RD-TD) in-plane compressive stress (about -330 MPa) in the martensite layers and an RD-TD in-plane tensile stress (about 320 MPa) in the austenite layers. The phase stress partitioning was ascribed mainly to the additive effect of the volume expansion during martensite transformation and the linear contraction misfit between austenite layers and newly transformed martensite layers during the water quenching process.
中子衍射织构测量能够提供具有出色晶粒取向统计数据的体平均织构，即使对于大晶粒材料也是如此，这是因为所探测的体积约为1 cm³。此外，晶体学参数以及其他有价值的微观结构信息，如相分数、相干微晶尺寸、均方根微观应变、宏观或晶间应变与应力等，都可以从中子衍射图中推导出来。在日本质子加速器研究中心材料与生命科学实验设施的基于脉冲中子源的工程材料衍射仪TAKUMI上，通过划分中子探测器面板区域，建立了一种用于组合高立体分辨率织构和残余应力评估的程序。对具有已知织构的石灰岩标准样品进行极图评估表明，织构测量所获得的精度与用于织构测量的既定中子束线相当，例如美国新墨西哥州洛斯阿拉莫斯中子科学中心的HIPPO衍射仪以及法国格勒诺布尔劳厄 - 朗之万研究所的D20角度色散中子衍射仪。采用高强度马氏体 - 奥氏体多层钢进一步验证多相织构和宏观应力张量的同时Rietveld分析的可靠性。通过使用织构加权几何平均微机械（BulkPathGEO）模型，在平面应力假设下进行的宏观应力张量分析表明，马氏体层中存在轧制方向 - 横向（RD - TD）面内压应力（约 - 330 MPa），奥氏体层中存在RD - TD面内拉应力（约320 MPa）。相应力分配主要归因于马氏体转变过程中的体积膨胀以及水淬过程中奥氏体层与新转变的马氏体层之间的线性收缩失配的叠加效应。
