Effect of Milling Time on Pore Size and Distribution of Ti-Nb-Zr Biomaterials with Space Holder Consolidated by Spark Plasma Sintering

Abstract

Titanium and its alloys are useful for implant materials. In this study, porous Ti-Nb-Zr biomaterials were successfully synthesized by powder metallurgy using a <TEX>$NH_4HCO_3$</TEX> as space holder and <TEX>$TiH_2$</TEX> as foaming agent. Consolidation of powder was accomplished by spark plasma sintering process(SPS) at <TEX>$850^{\circ}C$</TEX> under 30 MPa condition. The effect of high energy milling time on pore size and distribution in Ti-Nb-Zr alloys with space holder(<TEX>$NH_4HCO_3$</TEX>) was investigated by optical microscope(OM), scanning electron microscope(SEM) & energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD). Microstructure observation revealed that, a lot of pores were uniformly distributed in the Ti-Nb-Zr alloys as size of about <TEX>$30-100{\mu}m$</TEX> using mixed powder and milled powders. In addition, the pore ratio was found to be about 5-20% by image analysis, using an image analyzer(Image Pro Plus). Furthermore, the physical properties of specimens were improved with increasing milling time as results of hardness, relative density, compressive strength and Young's modulus. Particularly Young's modulus of the sintered alloy using 4h milled powder reached 52 GPa which is similar to bone elastic modulus.