Anistropic compressive properties of lotus-type porous NiAl fabricated by continuous zone melting technique

초록

Recently, many porous metals with long cylindrical pores(Lotus-structured metal) have been fabricated and studied and its superior mechanical property compared to conventional porous metal was proved from preceded investigation. In addition, NiAl is a potential high temperature structure material due to its high melting point, low density, high elastic modulus and excellent oxidation resistance. In this study, porous NiAl with long cylindrical pores aligned in one direction was fabricated by continuous zone melting technique in pressurized hydrogen and argon gas. The porosity of the specimens varied in the range 37-41% and the mean pore size was obtained 421μm. Compression specimens(7.5 long×5×5mm) were cut from ingots by using wire electro-discharged machine(EDM). Each specimens were homogenized in vacuum for 24hours at 1200℃. Compression tests were carried out on specimens with cylindrical pores orientated parallel and perpendicular to the compressive direction at room temperature, 400℃, 500℃, 600℃ with initial strain rates of 8.3×105/s. The compressive yield strength of porous NiAl whose pore axis is parallel to the compressive direction was higher than perpendicular to the compressive direction.