2020同步年報

084 ACTIVITY REPORT 2020 Specifically, additive manufacturing (AM) brings high degrees of geometric freedom to the production, but it raises a great challenge to control the microstructure het- erogeneity and anisotropic mechanical properties induced by localized rapid cooling and directional solidification. It is hence important to apply neutron diffraction measure- ments in situ to reveal the mechanical behavior of the AM materials. Under the Neutron Program of NSRRC, Huang showed that, through the generation of a transient phase using AM, the metals are strengthened. 3 The plastic anisot- ropy and deformation-induced phase transformation of additive-manufactured metals were revealed. Neutron dif- fraction in situ also unraveled the thermal history about the reversibility of the phase transformation of additive-manu- facturing metals. Using the advanced light sources at the NSRRC in Taiwan for the multi-scale characterizations, the team applied synchrotron-based high-resolution X-ray microcomputed tomography to microstructured images of the bulk im- plants surgically embedded in the iliac bones at TLS 01A1 . Transmission X-ray microscopy is also a non-destructive image microscopy technique, which enables the character- ization of high-resolution X-ray radiography in both two dimensions and the internal microstructure tomography in three dimensions at TLS 01B1 . The direct contacts of new bone, mature bone, and void areas were distinguished. The small- and wide-angle X-ray scattering techniques have been extensively carried out to identify the predominant orientation distribution, degree of crystalline arrangement, as well the shape and size of mineralized hydroxyapatite within the regenerating bone tissues at TLS 23A1 . The characterization in crystallographic textures of mineral crys- tallites acquired by X-ray diffraction is capable of evaluating the progress of bone remodeling and bone mineralization during bone healing process. To map the crystallization of the local bone growth, Huang’s group applied the nano X-ray Laue diffraction at TPS 21A for scanning across the boundary from the implants to the mature bone through the new-born bone and at TPS 23A for element mapping. Although AM enables the freedom for the fabrication, the concept of high-entropy alloys (HEA) opens new space for many further possibilities. To investigate the complicated HEA, in situ neutron diffraction experiments, which simul- taneously measure the bulk performance and the deforma- tion at the lattice level, 4 reveal great insight. For example, “a study of lattice elasticity from low entropy metals to medium and high entropy alloys”, 5 supported by the Neu- tron Program of NSRRC, is the first research revealing the The NSRRC Neutron Program supports Huang’s team for the neutron experiments at (a) Australian Nuclear Science and Technology Organisation; (b) Japan Proton Accelerator Research Complex; and (c) Spallation Neutron Source, Oak Ridge National Laboratory. [Photos courtesy of E-Wen Huang] (c) (b) (a)