Verification of the manufacturing conditions for translucency ceramics are showed using powder forming and sintering method in order to establish the manufacturing technology for optical devices with arbitrary complex shape and shape retention, and high-optical excitation. However, this method is extremely difficult to obtain translucency ceramics because the combination of complex factors such as “the shape and particle size of the raw materials, forming conditions and sintering” adversely affect the translucency of the sintered material, which is caused by the transmitted light scattering of the sintered material. Therefore, we have succeeded in realizing translucent ceramics by examining these complicated factors (materials, molding, sintering conditions, crystallization) and specifying the amorphous sintering conditions and the densification-molding conditions necessary to eliminate the light scattering factors inherent in sintered materials. It is necessary to show the correlation of the volume change with respect to Tg-temperature and Tm-temperature, which are important regarding amorphization, considering the sintering treatment conditions that depend on the particle size of the raw material fine powder, and to specify the molding body-pressurization (pressure and time) conditions. These optimizations will make it possible to develop the expected high-functional-photoelectric optical devices with microstructures and, high-power laser light sources independent of materials.
Laser-Beam Powder Bed Fusion (PBF-LB), which is a type of AM technology, offers the advantage of fabricating complex shapes such as dies with conformal cooling channels. Recently, due to the optimization of process parameters, it has become possible to manufacture H13 tool steel products without cracks. On the other hand, in light of the fact that PBF-LB is time-consuming, there is a demand to improve building speed in order to increase productivity. In this research, to achieve high-speed PBF-LB process of alloy tool steel, the microstructures of specimens via PBF-LB using high power laser were evaluated and the possibility of achieving PBF-LB with high speed and high quality was studied. As a result, the optimum fabrication condition of high-speed PBF-LB using 1 kW multi-mode fiber laser was elucidated by studying a process map between laser power and scan speed on relative density. In addition, tempered specimens processed by the high-speed PBF-LB have achieved microstructures and mechanical properties equivalent to those processed by conventional PBF-LB.
20/0/20 vol% Al2O3/Mg laminated spark plasma sintering compacts (20/0/20 vol% laminated SPS compacts), which were fabricated by mechanical milling / SPS method, have proved to possess lightweight like that of general practical Mg alloys and higher surface hardness than them. Moreover, the “diffusion layer” formed at their 0/20 vol% layer interface has been found to exhibit high adhesion to the 20 and 0 vol% layers. The microstructures and the characteristics of “diffusion layer” were investigated using EPMA, XRD and so on. From the results of XRD, the constitutive phases were identified as αMg and MgO. From the results of microstructure observation and elemental analysis using EPMA at the cross section, the microstructures were presumed to be Al solid-solved αMg and needle-like Mg17Al12 generated along the grain boundary of αMg in the mesh-shaped MgO. The cross-sectional hardness was 145 to 155 HV and was higher than that of the AZ91D Mg alloys. The width grew almost linearly rather than parabolic with the passage of sintering time. It is considered that the solid-state reaction of Mg and Al2O3 was promoted with the passage of the sintering time, and the amount of Al dissolved from Al2O3 increased, so that the diffusion amount of Al increased.
Low magnetic zirconium-based alloys were developed to prevent artifact formation in magnetic resonance images. The processes of the optimization of composition, evaluation of powder properties, and manufacturing by laser powder bed fusion were introduced for Zr‒1Mo alloy. The gas atomized Zr-1Mo powder showed comparable powder properties to Ti‒6Al‒4V. The process map on the porosity were constructed and the different pore morphologies were observed depending on the energy density and laser scanning speed. Oxygen and nitrogen content in the build increased with increasing energy density and laser scan speed. Mechanical properties of as-built Zr‒1Mo were also different depending on the parameters, and showed higher values in the higher energy density and lower laser scanning speed. Although the elongation of the as-build Zr-1Mo was about half as low as that of Ti-6Al-4V ELI, the UTS and elongation were improved comparable to those of Ti-6Al-4V ELI by a post treatment.
In the field of the electronics, silver is widely used as a conductive material. In order to improve the electrical conductivity of the silver-containing conductive material, it is essential to form a network of the silver in it, which requires not only controlling the size and number of silver particles but also flake shape.
By pulverizing the silver particles in two stages, a bead mill and a microbead mill, flake-shaped particles with a thickness of 20 nm could be obtained, and the silver network of the conductive material could be strengthened. The conductive material using the ultra-thin flake-shaped Ag powder was superior in conductivity to that of the conventional flake-shaped Ag powder, and the conductivity was difficult to change even when deformed. These features are not only suitable for applications such as conductive paste and conductive ink, but are also expected to be applied to miniaturization and thinning required in the electronics field, contact sensors for robots, and bed leaving sensors used for nursing beds.
Electron beam processing has advantages over laser beam processing in terms of speed and quality when applied to metal melting due to its absorptivity into metal and vacuum process environment. Using the features of the electron beam, the newly developed EB/PBF 3D printer (Electron Beam Powder Bed Fusion 3D Printer) has one of the world’s largest build sizes and highest build speeds. This review provides a description of basic electron beam processing, the development of the electron beam gun, which can control a beam covering a large scan area with high speed and precise beam profile, the additional mold transfer system and basic technology required for powder recycle. A small-size EB/PBF 3D printer that applies the fruits of this development has been released.
This study examined the microstructures and mechanical properties of Al-Cu-TiB2 alloy fabricated by selective laser melting (SLM). The SLM specimens without solidification cracks were obtained by optimizing laser irradiation conditions, and the relative density was 99.8%. The SLM specimens had a fine solidification structure with equiaxed cells owing to the heterogeneous nucleation by TiB2 particles. The generation of the solidification cracks was thus suppressed due to dispersed shrinkage strain. The hardness of the SLM specimens increased by the solution treatment and subsequent artificial aging treatment. As a result of the precipitation of an Al2Cu phase by aging, the SLM specimens have exhibited excellent strength through precipitation hardening.
The packing density of powder bed is one of the critical parameters affecting the quality of the final parts fabricated via powder bed fusion additive manufacturing. In this study the packing density of the first layer of the powder bed was experimentally estimated from the packing densities of recoated powder with different number of layers. It is found that the packing density of the first layer is much lower than the apparent density of powder and the macro-scale packing density increases as the number of recoated layer increases. Furthermore, recoating simulation using discrete element method (DEM) was conducted to investigate the deposition mechanism of the powder at the particulate-scale. The simulation results showed the packing density of powder bed increases as the number of recoated layer increases, similar to the experimental results. This is caused by the rearrangement of the powder in the powder bed stimulated by the supplied powder. Also, the packing density of the powder bed was not uniform in the thickness direction, and the top surface layer which affects the quality of manufactured parts had almost the same packing density as that of the first recoated layer independently of the number of recoated layers.