| Due to good biocompatibility, mechanical properties and corrosion resistance, Titanium and titanium alloys have achieved great success in clinical applications of bone replace. But mechanical properties (mainly elastic modulus) of titanium alloys don't match very well with that of bone, easy causing implants surrounding tissue stress shield is absorbed, and implants loose, eventually lead to implant failure. One way to solve the problem is to introduce pores into the surface of the implant or the whole implant, elastic modulus of the implant can even be tailored to closely match the modulus of the bone by controlling its porosity, thereby reducing the stress shielding, which induce the bone ingrowth. And the body fluids and nutrients can transport through the porous implant, accelerate healing process. Therefore, porous titanium and titanium alloys with good compatibility of biomechanics have been widely studied in recent years.The pure titanium and a new type of nearβbiomedical titanium alloy Ti-3Zr-2Sn-3Mo-25Nb (TLM) developed by the Northwest Institute of Nonferrous Metal Research have been researched. At first, the hydrogenation dehydrogenation process of titanium alloy TLM has been investigated; then porous titanium was prepared by powder metallurgy, and ammonium hydrogen carbonate was selected as pore former in this paper. The structure of powder was characterized by means of image size distribution system, the porousity and morphology of porous materials was characterized by means of electron analytical balance and scanning electron microscope(SEM), the mechanical properties of samples were measured by an instron universal testing machine, the specific surface area of porous tiantium was be measured by the specific surface area and porosity analyzer, and corrosion resistance was characterized by simulation testing fluid and electrochemical workstations. The main results are summarized as follows:(1) This paper has investigated the hydrogenation dehydrogenation process of titanium alloy TLM which process is simple and low cost. The TLM alloy powders was directly prepared with its alloy chip followed by the hydrogenation, grinding, dehydrogenation, which have irregular polyhedron shape, uniform chemical composition.(2) Through the powder particle size, content of hole material, powder mixing method, pressing process, drying and vacuum sintering system, the porosity of porous titanium and porous TLM alloy has been controlled successfully. Under certain conditions, the pores of porous materials have been in homogeneous distribution, connectivity well, rough internal surface of hole, homogeneous composition, whose size range from 50μm to 600μm.(3) During the 1100-1300℃, as the sintering temperature increased, pore shape is more regular and more uniform for pore size distribution, but it is not obvious that sintering temperature has influence on the mechanical properties of porous materials; compressive strength and elastic modulus is mainly effected by porosity, which will sharply decrease with the increase of porosity. In the same porosity, the finer the powder, the better the mechanical properties of porous material. Under the condition of same particle size and porosity, compared with the porous pure titanium, porous TLM alloy has more high strength and low elastic modulus.(4) Corrosion resistance of low porosity (about 30%) of the porous titanium and porous titanium alloy TLM is better than dense material, but the corrosion resistance of porous materials will decrease with the increasing of porosity, and the larger matrix metal powder size, the better the corrosion resistance of the porous material.(5) When the powder is about-400 in size and 50% in the porosity, the mechanical properties of porous TLM titanium alloy (compressive strength is 264Mpa. elasticity modulus is 6.4GPa) are close to chancellor's bone. Porous TLM titanium alloy has good corrosion resistance, and suitable as bone implant materials. |
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