In this study, we aim to address the dominant microstructural parameter of the high strength of Al-Fe alloy components additive-manufactured by the laser powder bed fusion (L-PBF) process. This study systematically investigated the compression response of single-crystal micropillars with a fixed diameter of approximately 3μm prepared on the surfaces of the L-PBF built Al-2.5%Fe binary alloy sample, and the subsequently heat-treated samples (300°C and 500°C), together with the slowly solidified Al-2.5%Fe alloy sample for comparison. The single-crystal micropillars of the L-PBF built sample exhibited a high yield strength of approximately 250 MPa and pronounced strain hardening. The compressed single-crystal specimens exhibited a uniform deformation indicating the activated multi-slip systems. Such a trend was observed in the 300°C heat-treated sample. However, the relatively low yield strength and strain hardening rate were found in single-crystal micropillars of the 500°C heat-treated sample as well as the slowly solidified sample. In the compressed micropillars, a single-slip system was dominantly activated. These results indicated that numerous nano-sized Al₆Fe-phase particles (contained in the specimens of the L-PBF built sample and the 300°C heat-treated sample) could contribute to high yield strength and the enhanced activation of multi-slip systems resulting in the pronounced strain hardening.

In Al-Zn-Mg alloy, hydrogen leads to degradation of mechanical properties. It is indispensable to suppress this phenomenon called hydrogen embrittlement (HE) for increasing the strength of Al-Zn-Mg alloy. Intergranular fracture (IGF) mainly occurs when HE affects this alloy. In order to suppress HE, we need to understand the initiation behavior of IGF. Heterogeneous distribution of stress, strain and hydrogen concentration in polycrystalline material have an influence on the IGF initiation. In the present study, distribution of stress, strain and hydrogen concentration in actual fractured regions were investigated by employing a crystal plasticity finite element method and hydrogen diffusion analysis using a 3D-image-based model. This model was created based on 3D polycrystalline microstructure data obtained from X-ray imaging technique. By combining in-situ observation of tensile test of the same sample by X-ray CT with the simulation, we compared distribution of stress, strain and hydrogen concentration with actual crack initiation behavior. Based on this, the condition for intergranular crack initiation were discussed. As a result, it is revealed that stress load perpendicular to grain boundary induced by crystal plasticity dominate intergranular crack initiation. In addition, accumulation of internal hydrogen induced by crystal plasticity had little impact on crack initiation.

Magnesium rechargeable batteries are attracting attention as next-generation rechargeable batteries because of their resource abundance, cost, safety, and high electrical capacity per volume compared to conventional lithium-ion rechargeable batteries. Our joint research team focused not only on the electrochemically active magnesium composition of ribbon for the negative electrode materials of magnesium rechargeable batteries but also on the production process, focused on the single roll type liquid quenching and rapid solidification method, which can be produced at a lower cost. In this study, the optimal processing conditions were examined by comparing CAE analysis with ribbon actually manufactured, with the aim of further improving manufacturing conditions using the same method, such as length discontinuities, thickness, and surface properties of ribbon. We specifically various process parameters such as injection pressure and roll peripheral speed for evaluation. As a result, several linear cracks were observed on the surface of the ribbon as the peripheral speed increased and as the Gap became wider, and the surface properties tended to deteriorate. Also, It was found that the dominant factor in the length of the ribbon was the peripheral speed. As the peripheral speed increased, the length of the ribbon tended to increase.