Fabrication, Mechanical and Physical Properties, and Its Application of Lotus-Type Porous Metals
This paper reviews recent development of fabrication methods, various mechanical and physical properties of lotus-type porous metals and its application. The porous metals are fabricated by unidirectional solidification in pressurized gas atmosphere such as hydrogen, nitrogen and oxygen. The elongated pores are evolved from insoluble gas when the melt dissolving gas is solidified. Three fabrication techniques — mold casting, continuous zone melting and continuous casting techniques — are introduced. The latter two techniques can control the solidification velocity and the last one possesses a merit of mass production. Anisotropy observed in mechanical and physical properties is resulted from anisotropic pore morphology. The anisotropic behavior of tensile, compressive and fatigue strength is explained in terms of stress concentration depending upon pore orientation, while that of thermal and electrical conductivities is interpreted by anisotropic electron scattering. The porous metals exhibit good sound absorption and vibration-damping properties. Several possible applications of heat sinks, golf putters, machine tools and dental implants are introduced. This Paper was Originally Published in Japanese in Materia Japan 58 (2019) 252–260.