Papers by Author: Masakazu Tane

Abstract: The tensile deformation of lotus-type porous copper with cylindrical pores oriented in one direction was investigated. Deformation was occured homogeneously in the copper matrix for loadings parallel to the orientation direction of pores (pore direction), while deformation was localized in the matrix around pores for loadings perpendicular to the pore direction. In the case of parallel loading the decrease in cross section of tensile specimen was smaller than that of nonporous copper, because of the constant-volume law (i.e. incompressibility condition) for deformation was not applicable to the deformation of pores. In the case of perpendicular loading, the deformed regions were disconnected and constant-volume law holds only in the matrix around the pores, and thus, the cross section hardly decreases during the tensile deformation.

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: Dynamic and quasi-static compression tests were conducted on lotus-type porous iron with porosity of about 50% using the split Hopkinson pressure bar method and universal testing machine, respectively.　In the dynamic compression parallel to the pore direction, a plateau stress region appears where deformation proceeds at nearly constant stress, while the plateau stress region does not appear in the quasi-static compression. The plateau stress region is probably caused by the buckling deformation of matrix iron which occurs only in the dynamic compression. In contrast, the compression perpendicular to the orientation direction of pores exhibits no plateau-stress regions in the both dynamic and quasi-static compression.

Abstract: Al foams whose matrix contains dispersed AlN particles (Al/AlN composite foams) were prepared by a melt foaming method, and the effect of foaming temperature on the pore morphology of the prepared foams was investigated. First, Al/AlN composites were prepared by non-compressive infiltration of Al powder compacts with molten Al alloy in nitrogen atmosphere. Next, the prepared composites were melted by induction heating and foamed at various temperatures using TiH2 powders as blowing agents. The porosity of prepared Al/AlN composite foams slightly decreases with increasing foaming temperature, and the pore morphology of the foam becomes homogeneous simultaneously. When the foaming temperature is 1123 K, homogeneous pores are formed in all over the ingot. This pore homogeneity is probably achieved by the stabilization of the foaming behavior due to the formation of Al3Ti particles in the melt and dispersion of AlN particles.

Abstract: The elastic and plastic deformation behaviors of lotus-type porous copper (lotus copper) with cylindrical pores oriented in one direction were investigated using two acoustic methods (resonant ultrasound spectroscopy and acoustic emission method). All the independent components of elastic stiffness were determined by resonant ultrasound spectroscopy combined with electromagnetic acoustic resonance method, which revealed that the Young’s modulus exhibits the anisotropy originating from the anisotropic porous structure and anisotropic matrix texture. The porosity dependence of the anisotropic Young’s modulus can be calculated by the micromechanics modeling based on effective-mean-field theory. The tensile deformation behavior of lotus copper was analyzed by acoustic emission method, which revealed that many burst acoustic emission signals are detected during the tensile deformation. This implies that many cracks are formed during the tensile deformation.

Abstract: We studied the fatigue strength of lotus-type porous magnesium with cylindrical pores aligned unidirectionally, which was fabricated through unidirectional solidification in pressurized hydrogen atmospheres. The fatigue strength shows anisotropy; the fatigue strength in the direction parallel to the longitudinal axis of pores is higher than that in the perpendicular direction. Not only anisotropic pores but also fiber texture grown along the pore direction contributes to the anisotropy in the fatigue strength.

Abstract: A porous Ti-48.0at.%Al (Ti-rich TiAl) crystal, in which lotus-type long cylindrical pores were aligned and (γ/α2) two-phase lamellar structure was simultaneously developed, was fabricated by floating zone method under the pressure of hydrogen and helium mixed gas. Plastic deformation behavior and microstructure of the Ti-rich TiAl crystal with lotus-type aligned pores were investigated by focusing on the elongated pore direction. The as-grown and annealed crystals show a well-developed lamellar structure and no texture accompanied by 52% porosity and a mean pore diameter of 380 μm. Yield stress strongly depends on the loading direction against the elongated pore. When loading directions are parallel and perpendicular to the pore direction, yield stresses obey K=1 and 2.5, respectively, in equation of σ=σ0(1-p)K, where σ is the yield stress with pores, σ0 is the yield stress without pores and p is porosity. This reflects macroscopically homogeneous and locally heterogeneous plastic deformation between pores, respectively.

Abstract: We investigated the pore morphology in lotus-type porous copper fabricated by continuous casting technique as a function of transference velocity range from 1 to 100 mm･min-1 under hydrogen gas pressure of 1.0 MPa. Lotus-type porous copper with long cylindrical pores aligned in one direction parallel to the transference direction was fabricated, which posses a sufficient uniformity of the porosity and pore size. The pores formed at transference velocity of 1 mm･min-1 were larger than other condition. Necks were observed in these pores, whose formation may be attributed to bubbling in the melt. The pore size decreased with increasing transference velocity, while the porosity was not varied much by transference velocity.

Abstract: Lotus-type porous NiAl and Ni3Al intermetallic compounds, possessing cylindrical pores aligned in the direction parallel to the solidification direction, were fabricated by using a unidirectional solidification technique in a pressurized hydrogen atmosphere of 2.5MPa. The porosity of lotus NiAl is 24.2 %, and the porosity of lotus Ni3Al is 3.2%; the porosity of the porous NiAl is larger than that of Ni3Al. This is because the solubility gap of hydrogen between liquid and solid phases of NiAl is larger than that of Ni3Al.

Abstract: Lotus-type porous metals with low thermal conductivity are fabricated by continuous zone melting technique, which possess directional elongated pores. The porous metals have been able to be fabricated through the conventional casting method by utilizing the solubility gap between solid and liquid in pressurized gas atmosphere. However, there is a shortcoming that the pores are coarsened in the part farther from the chill plate in the ingot. In order to overcome such a shortcoming, we developed the continuous zone melting technique and successfully produced the lotus-type porous metals with even low thermal conductivity such as stainless steel and superalloys. Furthermore, from the viewpoint of mass production with low cost, we invented novel ”continuous casting technique”. The molten metals dissolving gas are solidified continuously by passing through the mold cooled with chiller and thus, lotus-type porous metal plate as long as one meter was produced for short time. Sufficient uniformity of the porosity and pore size was obtained in such long porous ingots. This technique is prospective method for commercial mass production.