Papers by Author: Shinsuke Suzuki

Abstract: Lotus-type porous aluminum with cylindrical pores oriented in one direction was deformed by Equal Channel Angular Extrusion (ECAE) through a 150° die with sequential 180° rotations, and the pore morphology and Vickers hardness after the extrusion were investigated. The Vickers hardness increases with increasing number of passes in the extrusions both parallel and perpendicular to the pore direction, accompanied by the decrease of porosity. The densification occurs more easily in the perpendicular extrusions than in the parallel extrusions, and the large deformation by the densification gives rise to the large increase in the Vickers hardness for the perpendicular extrusions.

Abstract: Lotus-type porous carbon steel (lotus carbon steel) plates were fabricated by continuous casting technique in a pressurized nitrogen atmosphere. The experiments were done both with adding 0.3wt% of NiO powder in molten carbon steel in a ceramic crucible and without NiO powder. The lotus carbon steel fabricated without NiO powder under nitrogen pressures of 0.1 and 0.5 MPa had single pores which grew independently. On the other hand, the lotus carbon steel fabricated with adding NiO powder had pores which coalesced each other and became in irregular shapes. Under nitrogen pressure of 2.5 MPa, the pores formed with adding NiO powder were smaller than that formed without NiO powder. The porosity increased by adding NiO powder in every pressurized nitrogen atmosphere. From these results, NiO powder in molten carbon steel is considered to act as nucleation sites for pores at the solid-liquid interface and to increase of the pore number.

Abstract: Porous Al-5mass%Ti alloys were fabricated using a continuous casting technique in a hydrogen atmosphere, and the effects of transfer velocity (V) and the peritectic solidification process on the pore morphology and matrix microstructure were examined. In the case of V = 0.5 mm/min, columnar microstructure and directional pores grow along the transfer direction. The Al3Ti phases are formed in localized regions of matrix part, and however, they do not suppress the growth of directional pores in the other regions. In the case of 5.0 mm/min, because needle-like Al3Ti phases grow along the transfer direction, directional pores can grow between them. On the other hand, in the case of 10.0 mm/min, spherical pores surrounded by equiaxed peritectic microstructure and homogeneously distributed Al3Ti phases are formed, because the primary α -Al and Al3Ti phases probably prevent the growth of directional pores.

Abstract: Although forming of porous metal is demanded for industrial applications, the deformation characteristics have not been investigated sufficiently. In this study, lotus-type porous copper is processed by multi-pass cold rolling. At the early stage of rolling, the elongation of the porous copper in the rolling direction is small, and the porosity decreases almost linearly with the total reduction in thickness. It is found that pass schedule with small rolls and with small reduction per pass is effective to suppress pore closure. Hardness of the porous copper increases almost linearly with total reduction. If the effective total reduction is considered, the hardness change is similar to that of a nonporous copper.

Abstract: Deformation behavior of lotus-type porous copper with long cylindrical pores aligned in one direction through equal-channel angular extrusion (ECAE) process was investigated using a die with channel angle of 150º. Although the density slightly increased after every pass, the porous structure remains in the process. The Vickers hardness and the compressive yield strength of lotus copper increased through the ECAE process. The compressive yield strength after 3 passes increased up to 10 times larger than that before processing. The deformation of lotus copper takes place by buckling and the shearing of the cell walls. The increase in hardness is considered to be caused by work hardening.