In-situ Loading Device for Neutron Texture Diffractometer

Abstract

The texture of polycrystalline material is the preferred orientation distribution of its crystallites. As an intrinsic feature of metals, alloys, ceramics and polymers, texture strongly affects many properties of polycrystalline materials. It will make the material exhibit significant anisotropy in properties, consequently affecting its service performance. Therefore, texture is regarded as one of the essential parameters for describing a full microstructural characterization of polycrystalline materials. Texture determination is usually based on the pole figure measurements by X-ray, synchrotron radiation, electron back-scatter diffraction and neutron diffraction. Among these techniques, neutron diffraction offers many advantages in texture characterization due to the low absorption coefficient of neutrons. For example, it enables the use of sample environment devices to investigate texture evolution during in-situ high temperature or loading processes of materials. The first neutron texture diffractometer in China has been built at the China Advanced Research Reactor (CARR), due to strong demand for texture measurement with neutrons from the domestic user community. This instrument is mainly applied to study texture in commonly used industrial materials and engineering components. As the study of texture evolution during in-situ loading processes is extremely important for a deeper understanding of the deformation modes and performance evolution mechanisms of materials under various deformation processes and service environment. A specialized in-situ loading device was designed and developed based on the neutron texture diffractometer of CARR, capable of applying a maximum loading force of 10 kN, with a continuously adjustable loading rate ranging from 0.01 to 3 mm/min. In order to realize real-time measurement of the microstructure and bulk texture evolution in polycrystalline materials during in-situ tensile and compression processes, this loading device can be rotated around neutron texture diffractometer Euler cradle χ angle from 0° to 90° and along the tensile axis rotated from 0° to 360°. The texture evolution of hot-extruded Mg-1.2Al-0.3Ca-0.47Mn (MMK1) alloy during in-situ tensile process was studied using this device, and it was found that the intensity of the (0002) basal texture continuously increased with increasing of tensile displacement, indicating that the device’s capability to measure texture evolution of polycrystalline materials during in-situ loading processes. The design and development of this in-situ loading device at the CARR neutron texture diffractometer provide crucial technical support for investigating the relationship between microstructure and mechanical properties of polycrystalline materials, especially the laws and mechanisms of material structure evolution under external load condition.

Keywords

• china advanced research reactor
• neutron texture spectrometer
• in-situ loading device
• evolution of body texture
• extruded magnesium alloy