17-4PH不锈钢纳米析出物的磁小角中子散射研究

本文充分发挥中子对磁灵敏、穿透力强等技术优势，利用加载磁场小角中子散射实验技术研究核电站实际服役14年的阀杆17 4PH不锈钢样品。结果表明，与不加磁场时相比，加载磁场条件下二维散射图谱呈明显各向异性，在散射矢量垂直于磁场方向上散射强度显著增强。利用多分散球模型对数据进行拟合，结合原子探针实验结果分析得出，衬度的增加降低了Cu析出物周围元素分布不均匀对散射的相对贡献，从而有助于更加准确地获得Cu纳米析出物的尺寸。

Magnetic Small-angle Neutron Scattering Study on Nano-precipitate of 17-4PH Stainless Steel

By taking advantage of neutron scattering technique, such as magnetic sensitivity and deep penetration, the magnetic small angle neutron scattering (SANS) technique was applied to investigate the 17 4PH stainless steel sample from the valve rod which has been served for around 14 years in nuclear power plants. The results show that, compared with no magnetic field, the two dimensional scattering pattern is obviously anisotropic when the magnetic field is loaded, and the scattering intensity is significantly enhanced when the scattering vector is perpendicular to the direction of the magnetic field. The scattering intensity where the scattering vector is perpendicular to the direction of the magnetic field is significantly higher. By analyzing the SANS data along two different directions using polydisperse sphere model, it is concluded that the increase of the contrast is helpful for accurately analyzing the size of the Cu nano precipitate. This is because that the relative contribution of the scattering from the fluctuations of the composition in the vicinity of Cu nano precipitate, which has been shown by previous atom probe tomography experiment, can be largely reduced by the magnetic scattering.